Instrument course notebook



Instrument course notebook


166 pages of instrument course including notes with details and hand-drawn colour diagrams of aircraft instruments and gauges including pressure gauges, warning systems, clocks, compasses, bomb and gun sights, flight instruments and telecoms equipment.



IBCC Digital Archive


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Cover and 83 double pages





Spatial Coverage



18Y5 Volume 1 General Information of Aircaraft Insurments i.e. Installation etc.
18Y5 Volume 2 Modifications i.e. additions to Instruments or equipment etc.
Y00 Inspection Form (To be signed after each inspection)

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[underlined] AIRCRAFT MAINTENANCE [/underlined]

All RAF aircraft are inpeced periodically in accordance with specially drawn up schedules. These inspections are under three headings. 1) Daily Inspection
Carried out every day and the aircraft is serviceable for 24 hrs from time of the inspection.
2) Minor Inspection.
Carried out in accordance with U.M.O’s usually after every 300845 hrs.
3) Major inspection
Complete overhaul Is carried out at the end of a flying cycle usually 240 to 320 flying hours. The major cycle is divided into 6 or 8 minor periods, a minor inspection being carried out at the end of each. Thus a 240 major inspection sub-divided into 6 minor periods, would have one major and 5 minor inspections to the cycle. Some items do not require checking every minor inspection and where an item
requires checking every other minor a star is put against the assembly group number in the 17.1.R form. two stars would indicate every third minor and three stars every fourth. Major items are indicated by black capital letters as small letters underlined.

[underlined] FORM Y00 [/underlined]

This has two main sections.
1) Daily Inspection Sheet is used to record signature of airmen carrying out the (D. In) and aircraft cannot fly until the D.1 certificate has been completed
2) Change of Serviceability and Repair is used to record any change of state of an aircraft. When an aircraft is U/S for any reason that reason is stated in this log. Any members of ground or aircrew can put an aircraft U/S but [deleted] permen [/deleted] competent N.C.O or Officer can make it serviceable. All entries must be made in ink or copying ink pencil.

[page break]


Is used to record all work done on minor and major inspections. All items are listed separately, and [deleted] to [/deleted] as each one has been inspected and found satisfactory, the airmen records his initials in column “A”. Should a defect be discovered it is indicated by a cross in column “A” and when rectified is signed for in column “B”, by group 1 tradesman. If an airman is taken off an inspection before completion, he draws a double line below the last item inspected by him, in the appropriate column and signs on it. The airman continuing the inspection initials each following item if satisfactory.

[underlined] A.P. 12Y5 VOLUME 1 – 2 [/underlined]

Is the instrument manual of the Raf Details of all instruments are given with instructions on installation maintenance and calibration. Volume 2 is made up of amendment leaflets to Volume 1.

[underlined] DIRECT TYPE PRESSURE GAUGES [/underlined]
[drawing with annotation]

[underlined] BOURDON TUBE [/underlined]

Iis [sic] a ‘C’ shaped tube, with an elliptical cross-section. One end is fixed and left open, the other end is closed and free to move. Any pressure applied within the tube, will try to make the cross section circular, which will result in the tube straightening out and thus causing a movement of the free end

[underlined] BOURDON TUBE MECHANISM [/underlined]

Connected to the free end is a link, which in turn is connected to the tail of the

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quadrant gear. In mesh with the quadrant is a pinion to which is attached a pointer. A hair-spring is fitted on the pointer spindle to take up slackness

FUEL, OIL AND AIR [/underlined]

Air, oil and fuel is fed direct to the Bourdon tube causing movement. Gauges differ only in range, colour of bezel and strength of Bourdon Tube
[underlined] Fuel [/underlined] – Range 0-5 or 0-10 lbs per sq. inch
Colour of bezel – [underlined] Red [/underlined]
[underlined] Oil [/underlined] – Range 0-200lbs per sq. inch
Colour of bezel – [underlined] Yellow [/underlined]
[underlined] Air [/underlined] – Range 0-250 lbs per sq inch
Colour of bezel [underlined] Black [/underlined]

[drawing of spigot union]
[drawing of hydraulic choke]
[drawing of Nipple adaptor union]
[drawing of layout or brake pressure gauge]
[drawing of spherical union]
[drawing of transmitting gauge (suction)]

[page break]

[underlined] BRAKE PRESSURE GAUGE [/underlined] (Sec. 11 Chap 15)

Range of Instrument 0 – 300 lbs [square] “ Colour of Bezel – Black, three nipple adaptor unions at rear (See standard notes)

[underlined] SUCTION GAUGE [/underlined]

Has an edge-ways scale capsule type mechanism. Range 0 – 10” HG. Colour of Bezel. Black (see standard notes) Spherical type union

[underlined] HYDRAULIC PRESSURE GAUGE [/underlined] (SEC II CHAP 10)

(See standard notes)
Range 0 – 200 lbs [square] “. Colour of Bezel Black nipple adapter union

[underlined] HYDRAULIC CHOKE [/underlined]

Is fitted in the pipe connecting the gauge to the system in order to protect the gauge from damage sue to rapid action of pressure Instal [sic] with arrow in direction of flow when installing the pipe should be primed and the choke connected in
the correct manner The connections should be left slack and the two halves of the choke unscrewed half a turn. This allows the fluid to by-pass the restriction for the purpose of priming. With the gauge slackened fluid should now be forced through the system, until it is seen to be leaking at the gauge connection hand tighten the gauge connection followed by the choke and the lack with lacking-wire. The pipe line is now primed. The filter on the inlet side may be cleaned with clean petrol if the two parts of the choke are unscrewed. The choke sealing must not be adjusted. hipple [sic] adapter unions are used and the filter is cleaned on a minor


With the exception of the suction gauge, the above instruments are secured to the panel by means of 2 – 2 SA nuts and bolts

[page break]

and possibly distance pieces. The suction gauge is fitted from the [underlined] front [/underlined] of the panel and is secured by 2 HBA nuts and bolts and a clamping plate. When installing ensure the pipe-line does not exert a strain on the instrument.

[underlined] TRANSMITTING TYPE PRESSURE GAUGE [/underlined]

(See Standard notes) [underlined] FUEL ‘ OIL [/underlined] (SEC II CHPTS 2’8
The two instruments differ only in range and colour of bezel.
[underlined] Fuel [/underlined] Range 0 – 10 lbs [square]”. colour of bezel – Red
[underlined] Oil [/underlined] “ 0 – 300 lbs [square] “ “ “ Yellow
[underlined] Installation [/underlined]
Ensure that the instrument has the correct length of capillary by checking ref. no and test the instrument on the portable Pressure Gauge Callibrater [sic]
[underlined] Maintenance [/underlined]
Daily Inspection – inspect for visible defects and security – clean glass (VD-S,C.G)
Every Minor Inspection – Callibrate [sic] with
pressure gauge calibrator
Every second Minor Inspection – Examine capillaries for kinks, dents and damage
[annotated drawing]
(DEAD WEIGHT TESTER) [/underlined]
Is used to test accuracy of pressure gauge up to 200 lbs per [square]. The pressure of oil is used to support a weight and at the same time to give a reading on the gauge under test. To avoid weight and bulk, each weight is a fraction of its indicated value. The plunger disc

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weighs 2ozs and its surface area resting on the oil 1/8”, therefore, if 1/8” is taken as a basic, the plunger weighs in effect 1lb and this 8:1 ratio as maintained. Various weights are available to represent certain pressures. Direct type gauges are connected straight up, transmitting gauge by means of a hollow bolt adapter Use anti-freezing oil.

[underlined] FUEL PRESSURE WARNING LIGHTS [/underlined] MK 1A 0-10lbs MK 1C 10-20lbs
Is fitted to give the pilot warning by the illumination of a red lamp, when the pressure falls below a safe volume. Consists of a pressure unit, resistance unit, warning lamp, electric leads, fuse, and switch. The supply can be either 12 or 24 volt and is cut down by the resistance to the required 6volts for the lamp
[underlined] Installation. [/underlined] The lamp fits into a housing which is mounted on the
[annotated circuit diagram]
[annotated drawing of a pressure unit]
[underlined] PRESSURE UNIT [/underlined]

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instrument panel. The pressure unit must be adjusted to the correct volume for the particular type of engine.
[underlined] Adjusting proceedure [sic] [/underlined] [circled number] 1 [/circled number] ascertain from filter in change of aircraft [circled number] 2 [/circled number] Fit pressure unit onto calibrator [circled number] 3 [/circled number] Put required weights on and adjust until they are raised. [circled number] 4 [/circled number] Adjust pressure unit until the light just flickers on [circled number] 5 [/circled number] how if the pressure is increased the light should go out [circled number] 6 [/circled umber] If the pressure is decreased the light should come on [circled number] 7 [/circled number] Lock grub screw with lock nut or seal with shellac
[underlined] Maintenance [underlined]
Daily Inspection. Switch on the lamp should light that is with engines nit running See that the system is secure and connections are correct
Minor Inspection. Check wiring for security and fray
[annotated drawing]
PRINCIPAL [/underlined] VAPOUR PRESSURE [underlined] RANGE 40”C – 140”C OR 50”C – 150”C
[annotated drawing]
NOTE [/underlined] Bulb of Air Thermometer is 18ins long and is coppered

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(See Standard Notes)
Colour of bezel – Blue. Range 50 – 100oC or 40 – 140oC. Copper Capillary 1mm bore.
[underlined] Installation ]/underlined] As for other Capillary Instruments The instrument is secured to the panel by 2.2BA nuts and bolts and possibly distant pieces. Avoid passing the capillary over heated parts of engine or aircraft. Ensure the loop adjoining the bulb is held by the special clip and that the copper washer is in position when the bulb is fitted. Lock nuts with locking wire.
[underlined] Maintenance [/underlined]
Daily Inspection underlined VD.S.C.G
Minor Inspection Test function on ground test
Second Minor Inspection Check capillary for kinks, dents and security
(see Standard Notes)
Range – [underlined] Oil [/underlined] 0 – 100oC [underlined] Air [/underlined] – 35o – 0o – 55oC
Bore of Capillary is 006’
[height and air speed chart]
[underlined] COMPRESSIBILITY CORRECTOR CARD [/underlined]
[annotated drawing]
[underlined] MARK III AIR TEMP THERMOMETER [/underlined]
INSTALLATION [/underlined] Similar to other capillary instruments and ensure that the
capillary(steel) does not pass nearer

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than Y” to the compass
[underlined] Maintenance. [/underlined] Daily Inspection – VD.3.C.G should be temperature of the
[underlined] Minor Inspection [/underlined] – Check oil temperature for function on ground test
Second Minor Inspection – Check capillary for kinks, dents and security
For air temperature Mk II[/underlined]
Compression of air around the bulb in the sun shield causes an increased temperature. A card showing the required correction to be applied to the reading is mounted in the panel close to the instruments.

[underlined] AIR TEMPERATURE THEMOMETER [/underlined] MK III
Similar to MK II air temp but the bulb assembly is different Consisting of a 12” bulb made of copper plated steel, sweated through out it’s length to a base of Monel Metal. A then cover also of Monell Metal is fitted
closely over the bulb to increase the rate of transference of heat between base plate and bulb.
[underlined] Installation [/underlined] – Similar to MK II, except that the bulb assembly is flush mounted and recessed into the plane about 3/4”. It’s secured by 10 – 4BA fixing screws and insulated washers which hold the unit in position as well as insulating it from the A/C.
[underlined] Maintenance. [/underlined] As for MK II Air Temp
[underlined] ho [sic] [/underlined] correction card.

Range [/underlined] 0o – 220oC – [underlined] Scale [/underlined] – sub divided into 5oC [underlined] Late [/underlined] Ensure that the N.P.L. certificate accompanies the Thermometer
[underlined] Important [/underlined] – when not on use keep in still housing.

[page break]

[annotated drawing]

[underlined] THERMOMETER CALIBRATOR [/underlined]

[annotated drawing]

[underlined] MK I AIR TEMP THERMOMETER [/underlined]

[underlined] DIRECT READING AIR TEMP THERM MK I [/underlined]
Is of the liquid in glass type (Benzene) and is superceding [sic] other types on multi-engine aircraft. The glass bulb is best [sic] at right angles, so as to project through the side of the aircraft. The bulb is protected by a sun shield and the vertical part (cradle) fitted on the Observen’s [sic] panel is fitted with a scale – YO to 40oC
[underlined] Installation [/underlined] The backing plate rubber washer (for insulation purposes) and the sun shield should be attached to the aircraft skin and the thermometer placed so that the bulb projects aprox [sic] 1” through the skin The cradle is fastened to the cabin wall by bolts provided and distant pieces. The glass is marked with a datum line at 0oC The scale should be periodically checked against this point

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[annotated drawing]

[underlined] MECHANICAL ENGINE SPEED INDICTOR [/underlined]

[underlined] MECHANICAL ENGINE SPEED INDICTOR [/underlined]
(See Standard Notes) (Sec 1 Chpt 1)
[underlined] Installation [/underlined] – The instrument is secured to the panel by 3.2BA nuts and bolts and distant pieces. The drive should be placed along the shortest possible route, sharp bends less than 9” rad being avoided. Ensure that the oil escape hole is at the engine end. No part must pass within 11” of the compass. Support along the whole length at intervals and lock union nuts with lockingwire.
[underlined] Maintenance [/underlined] The flex drive should be periodical examined for wear and tear, and greased with heavy grease. The shaft may be withdrawn from the casing, after carefully removing one of the slip washers. No strand should be badly worn or broken, and the end connections should be secure. Gear boxes should be periodically examined for wear and greased with anti-freezing grease. The drive must have a 1/4” end play.

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[underlined] Daily Inspection [/underlined] V.D.S.C.G.
[underlined] Minor Inspection [/underlined] Check, functioning on ground test
[underlined] Record Minor Inspection [/underlined] Examine flex drive

[underlined] AIRCRAFT CLOCKS
MK II [/underlined] luminous 8 – day movement. To wind rotate bezel. Centre second hand and dummy hand and minute hand are for time of trip (hour hand set by winding bezel clockwise, minute hand by rotating knob. Lever at top right corner [undecipherable word] up and bezel is rotated to set hands.
[underlined] MK IIC [/underlined] 8 – day movement has no second or dummy hand. Set hands by pulling out knob.
[underlined] MK IID [/underlined] 8 – day movement has centre second and dummy hour and minute hand operated by two smaller knobs in centre of glass. Push winding knob in to set hands.
[underlined] MK IIIA [/underlined] 8 day movement has time of trip dial and second hand Has coloured “tell tale” (red for recording, white for waiting) For recording time of trip, operate by knob at 4 o’clock, successive pressings of knob at 4 o’clock will [inserted] start [/inserted] stop and return to zero the time of trip hand and centre second hand. The knob at 8 o’clock is rotated for winding and by pulling out for setting.

[underlined] PSYCHROMETER. [/underlined]
This instrument is to enable to find the relative humidity of the air at various altitudes for the purpose of compiling weather reports. The pychrometer [sic] consists of the liquid and glass thermometers. The bulb of the air is kept dry whilst the other is left wet by a wick

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dipping into a tank of distilled water therefore under certain conditions the wet bulb (Thermometer) will give lower readings compared with the dry bulb due to the evaporation of the water on a dry day. This instrument is fitted on the strut of the starboard side with the dry bulb [underlined] forward [/underlined]

[underlined] COMPASSES
“P” TYPE [/underlined] :- consists of 1) Rotatable Grid Ring. 2) Fixed Rubber lie in fore & aft line of A/C. 3) Freely pivoted magnet system 4) Bowl completely filled with liquid and de-aerated 5) Aft marking and scale on securing – lug in 0o
[underlined] “O” TYPE [/underlined] :- consists of 1) Rotatable [underlined] Azermuth [sic] Circle [/underlined] 2) Fixed Rubber Line in Fore and Aft of A/C 3) Truly pivoted magnet system (Compass Card) 4) Bowl completely filled with liquid 5) Clamping device for securing in mounting (O5 – 0.5A STANDARDS)
[chart showing types, uses and A/C]

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[underlined] Reasons for using Alcohol – Distilled water [/underlined]
1) Low freezing point
2) Low viscosity
3) Helps to take weight off the pivots
4) Damps down movement of magnetic system

[underlined] Requirements of an A/C Compass [/underlined]
1) Must be apperiodic [sic] (dead beat)
2) Must have a large magnetic moment & a small moment of inertia
3) No liquid swirl
4) C.G. below pivoting point (1/20”)
5) Liquid to withstand the temperature change of -50oC & 50oC
6) Device for allowing 12% volume change
7) Must have anti vibrational device

[underlined] “P” TYPE COMPASS [/underlined]

[annotated drawing]

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Coefficient “A” [/underlined] – any error that is the same on all headings – corrected by rotation of compass
[underlined] Coefficient “B” [/underlined] is any deviation or variation from E – W – corrected by Connector Box
[underlined] Coefficient “C” [/underlined] is any deviation or variation from N – S – corrected by Connector Box. Any deviations or variation left over are noted on Corrector Card
[underlined] Installation [/underlined] [circled number] 1 [/circled number] Use only [underlined] Brass [/underlined] screws nuts & washers. [circled number] 2 [/circled number] All magnetic materials must be kept well away from compass [underlined] at least 18” away [/underlined]. [circled number] 3 [/circled number Ensure that it is in the Fore and Aft line of A/C
[underlined] Daily Inspection [/underlined] – Clean glass, Check for visual defects – check freedom locking of lined [sic] Ring & Azemuth [sic] Circle (Clean apties [sic]) – Check Corrector Box for security
[underlined] 40 hr [/underlined] – As D.I. & examine for [circled number] 1 [/circled number] [underlined] Discolouration [/underlined] [circled number] 2 [/circled number] [underlined] Functioning of A.V.M. [/underlined]
[underlined] 40 * hr [/underlined] As 40 hr & [circled number] [underlined] Pivot Fraction Test [/underlined] [circled number] 2 [/circled number] Damping Test
Corrector Box is fitted under mounting of “P” Type compasses and in 0.5 standard “O” Type.
[underlined] Pivot Fraction Test [/underlined] [circled number] 1 [/circled number] Bet N to N [circled number] 2 [/circled number] Deflect 10” and hold for 30 sec. [circled number] 3 [/circled number] Allow pointer to return [underlined] NOTE READING [/underlined] [circled number] 4 [/circled number] Deflect to 10” in oposite [sic] direction hold 3 sec [circled number] 5 [/circled number] Allow pointer to return [underlined] NOTE READING [/underlined] – Add the two readings together and [underlined] total should not exceed 2o [/underlined]
[underlined] Damping Test [/underlined] [circled number] 1 [/circled number] Bet N to N [circled number] 2 [/circled number] Deflect 90o and hold 30 seconds [circled number] 3 [/circled number] Allow to return – should take about 5 – 14 secs. [circled number] 4 [/circled number] Deflect 90o opposite direction [circled number] 5 [/circled number] Hold 30 secs and allow to return – time should be as before
[boxed list and times]

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[underlined] BOMB SIGHT MK IXC [/underlined]

[underlined] 1 [/underlined] Set Wind Speed – Zero } To pack into Case
[underlined] 4 [/underlined] “ Air Speed – Max } To pack into Case
[underlined] 5 [/underlined] “ Terminal Velocity [infinity symbol] } To pack into Case
[underlined] 6 [/underlined] “ Height 3500ft } To pack into Case
[underlined] 3 [/underlined] “ Direction 90o } To pack into Case
[underlined] 2 [/underlined] “ Enemy Speed Zero } To pack into Case
[underlined] 7 [/underlined] Fold height bar } To pack into Case

To remove from case :- If equipped with crass levelling bracket, remove this first To remove B/S Pull back small catch at rear front of B/S.
[underlined] Crass levelling Bracket [/underlined] – provides a mean of A.V.M. for the B/S.
[underlined] Azemuth Bracket [/underlined] – as crass levelling bracket but also incorporates a means of giving an indication to pilot as to how many 0o the aircraft has to be turned to bring target in the drift-wires & A/C Fore and Aft line.

[underlined] DRIFT RECORDER [/underlined]
[underlined] Purpose [/underlined] To indicate the drift of the A/C over the ground
[underlined] Construction [/underlined] Consists of a periscope type optical system – also movable chart an graticular [sic] on lens, fixed scale – with centre zero Max 30o – flag operates by movement of penal holder – Computer on top of folding cover
[underlined] Installation [/underlined] Drop plump line from nose and tail and connect with a long piece of string extending 30ft in front of A/C. make several marks on the ground in the sight of recorder choosing a mark which you require. Make mark opposite and describe two arcs and with another centre scribe two more arcs and were arcs intersect draw a line which will be at right-angles to the fore and aft line, line up intersecs [sic] to a parallel and set scale at zero by loosening the two side screws.

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[underlined] BOMB SIGHT MK IXC [/underlined]

[underlined] BACKLASH TEST [/underlined]
Air Speed 107 MPH or 120 MPH
Wind Speed 38.5 MPH or 60 MPH
Ground Speed 100.0 MPH or MAX
[underlined] DRIFT [/underlined] should read 21 & - 15’ or 30 & - 15’

[underlined] DISTANT READING COMPASS MK.1 [/underlined]
This compass introduced to do away with the errors of the ordinary magnetic compass. These errors are overcome by the pivotting [sic] of the magnet. It is regially [sic] pivotted [sic] in jewel bearings top and bottom and is a solid bar

The compass is also gyroscopically stable. This gyroscope is of unusual feature it is of the three phase squirrel cage induction motor. It is driven at 12 – 13,000 [inserted] per min [/inserted] revs. The A.C. current is derivided [sic] from a rotary converter and taken to the gyroscope As any toques to the gyro will cause precession to the outer ring which in turn will cause the inner frame to rotate due to the action of the frame motor. The system used in this compass is one of remote control, the master unit being in the tail of A/C and instruments in

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the case of A/C, this is bought about by means of repeater contacts and repeater motors. When the inner frame rotates, rotating with it is a large gear wheel is enmeshed with repeater contacts. Impulses are sent to the V.S.C from there they are distrubuted [sic] to the repeater motor by means of the two separate sets of 60 1 ratio gear
[underlined] Consists [/underlined] of Master Unit, VSC, Repeater, Suppressor Distributor Boxes

[underlined] PROCEEDURE FOR STARTING D.R.C. [/underlined]
1) Set the “on – off” switch to on and the normal setting switch to setting
2) Allow about 5 mins to elapse until oscillates about the constant heading
3) Set the normal setting switch to normal and the system should be ready for use

[underlined] Procedure for before Flight [/underlined]
1) As for starting above
2) Set V.S.C to zero
3) Check that all repeaters are synchronised correctly, that is, they should read the M.ll reading & and A error
4) Check the “hunt” on the scale of the M ll, should be between 1/8 and 3/4 of a degree
5) With the “normal setting switch” to setting till the M ll in an easterly direction, note that the readings – increase on easterly and decrease on westerly
6) Set local variations on V.S.C. if required by local orders
[underlined] Switch “on off switch” to on and normal setting switch to setting for D.I and above [/underlined]

[underlined] Functioning Test [/underlined]
1) As for Starting proceedure [sic].
2) Check the normal hunting 1/8 – 3/4 decree [sic]
3) Turn normal setting switch to setting and note that M ll reading is between 3 and 8 degree.
4) Set normal setting switch to normal

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and note M ll reading tilt M ll in an easterly direction and when the scale reading has changed by 5o return to the vertical and after 2 minutes note reading, repeat by tilting to the west. The two final readings should not differ by more than 2o. (The movement in this test is due to the Angle of Dip) – ([underlined ] PIVOT FRICTION [/underlined])
5) Switch the normal setting switch to setting and tilt the M ll to the east holding it to it’s limit of travel until the reading changes by 40o, switch back to normal and return M ll to the vertical allow to swing to and fro.
Time the M ll by its travels over the first 20o back to its original heading and note that at all times the M ll and repeaters are within 1o degree of each other.
6) Repeat the above in a westerly direction
7) The time intervals [inserted] of recordings [/inserted] by operations for 5 and 6 should not differ by more
than 3 minutes and neither should take more than 7mins to return ( - DAMPING TEST)
8) Set the V.S.C to zero and note repeater readings, Set V.S.C to 10o East and note the repeaters have changed by 9 – 11o, repeat the setting to 10o West and note the change of readings again
9) Repeat the above by holding knob of pilot’s repeater – there should be no change – [underlined] SWITCH OFF [/underlined]

[underlined] Synchronising Repeaters [/underlined]
1) Start D.R.C as before
2) Set V.S.C to zero
3) Set all repeaters as near as possible to M ll Reading (thought they can only move in 3o movements) plus the “A” error
4) Adjust V.S.C to final readings of repeaters, correct if neccessary [sic]
5) Loosen the two screws holding the scale and set lubber line to zero tighten screws. – [underlined] Switch off [/underlined]

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[2 annotated drawings]

[underlined] 1. INDICATOR [/underlined] [underlined] 2. INDICATORS [/underlined]
This is an electrical means of measuring the crank shaft speed of engine, when engine is situated some distance from the panel and a mechanic type would be impracticable
[underlined] Installation [/underlined] bolt securely to panel and fix into anti-vibration mounting. Care should be taken to ensure that cables are connected correctly, if instrument read backwards it is not necessary to unsolder the lead, but just to reverse the interior of the plug, this is done by unscrewing screw.
[underlined] Maintenance. [/underlined] grease the flex drive on all minor inspections. The brushes and commutators of generators are cleaned on minor inspections also. When indicators are suspected of under reading, check with voltmeter or
strobescope. Check calibrate as A.P. 1275 section I chapter II

[underlined] ENGINE CYLINDER THERMOMETER. [/underlined]

[annotated diagram]

[underlined] USED ONLY IN AIR COOLED ENGINE [/underlined]

[underlined] COMPENSATING LEADS MUST NOT BE CUT [/underlined]

[underlined] Installation – Instruments [/underlined]
Usually mounted in A.V.M. mounting held in by two screws only. The position of the thermo – couple is dependant [sic] upon the manufacturers of the engine. Remove the wire shorting the terminals at the back of the instrument, connect the compensating leads red to red blue to blue Allow to stand on open circuit with Master Thermometer by its side for 1/2 hr, then set the temperature of the day on the

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instrument by means of screw.
[underlined] Maintenance D.I. [/underlined] Ensure that the leads are secure and the instrument is reading the temperature of the day [underlined] Minor Inspections [/underlined] check functioning on ground run.

[underlined] ELECTRICAL FUEL CONTENTS GAUGE. [/underlined]

[circuit diagram]

[underlined] SIMPLIFIED CIRCUIT [/underlined]

[circuit diagram]

[underlined] CIRCUIT FOR 5 TANK SYSTEM [/underlined]

[page break]

[underlined] Installation [/underlined] Unslacken screw on arclip [sic] remove arclip [sic] and instal [sic] instrument from front of panel, place arclip [sic] back over instrument, clamp arclip [sic] to instrument and the you tighten screws, which forces arclip [sic] on instrument. See that rubber ring is between instrument and panel. Work on 12 volt system only.

[underlined] PRESSURE HEAD [/underlined]


[underlined] LAYOUT OF PRESSURE HEAD [/underlined]
[underlined] Inspection [/underlined] switch on pressure head circuit for [underlined] not more than [/underlined] 5 mins, test head by feeling for warmth which will ensure that element is working correctly. Mouth of tube and static slots should be kept clean and free from dirt on 40hr. Inspection also check for security.
[underlined] For Insulation Test see Bridge Megger [/underlined]

[underlined] REFLECTOR GUNSIGHT [/underlined] MK. IIIA

[3 drawings]

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[underlined] GUNSIGHT [/underlined] (CONT) This is a typical example of reflector gunsights, which are clamped with special fittings to various guns, to be found mounted in A/C and consists of the following parts 1) Case to which is attached the optical unit, dimmer switch and lamp 2) The optical unit comprising of a translucent ring, and bead graticule [sic] and lens system 3) The reflector and hood complete with dimmer screen 4) The dimmer switch and lamp
[underlined] Maintenance [/underlined] Check electrical circuit for continuity and also check the insulation resistance to earth. When a new lamp is fitted, care must be taken to ensure that the lamp is positioned correctly, a line, a white mark on the lamp, with a corresponding mark on the holder. Care must be taken not to disturb the harmonization of the sight
[underlined] Before Flight Inspection [/underlined]
1.) Ensure sight is secure in it’s mounting
2.) Ensure that the clamping nuts are secure and tight
3) Ensure that the lens and reflector and dimming screen are clean. [underlined] Use Selvit on all lens [/underlined]
4) Ensure that the electrical system is functioning
5) Ensure that there are spare bulbs in the rack and all are serviceable

[underlined] ELECTRICAL TESTING APPARATUS [/underlined]
[underlined] Continuity Tester [/underlined] Consists of case, switch or push-button, battery and bulb. Used for testing low resistant circuits


[underlined] BRIDGE MEGGER [/underlined] Correct to .01 ohms Range to 100MO – accurately
[underlined] WEE MEGGER [/underlined] Correct to 10,000 ohms Range to 20MO – roughly

[underlined] WEE MEGGER [/underlined]

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[underlined] Wee Megger [/underlined] Used for high resistant circuits
1) Continuity of circuit test – reading should be zero – [underlined] For Resistances of over 10,000 ohms. [/underlined]
2) Earthing test – reading should be infinity
3) Insulation test reading should be infinity

Used for insulating and earth testing
A) Reading Infinity equals perfect insulation
B) Reading Zero shorting or bad insulation or good continuity
C) Reading M.O. equals value of insulation

[underlined] Insulation Test [/underlined] – connect line and earth to cable cord – reading should be infinity or a minium [sic] of 3 m.o. If climate is damp 1/2 m.o
[underlined] Earthing Test[/underlined] = connect line to cable cord and earth to airframe or casing of instrument on test
[underlined] Bridge Megger [/underlined] – can be used as the Wee megger but is designed primarily for
measuring unknown resistances accurately from 1/10 ohms to 100 m.o. Also for Darley [sic] Testing (not used in R.A.F.)
[underlined] Insulation Test on Pressure Head [/underlined] (40hr & 40*) Try must head hot reading should be 1/2 mo and cold 3 m.o.

[underlined] SIMMONDS FUEL CONTENTS GAUGE MK IIIA. [/underlined]

[annotated drawing]

(SIMMONDS) [underlined] Free Float Fuel Contents Gauge MKIIIA [/underlined]
Consists of three main parts 1.) [underlined] Tank unit [/underlined] This consists of a long resistance wire

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against which a light, hollow nickel silver ball is kept lightly pressed by means of a spring loaded plate. At the top of the tank unit is a small solenoid which operates the spring loaded damping plate. On depressing the push switch the circuit to the solenoid is made. The clamping plate is attracted by the solenoid releasing the hollow ball which will float or drop to the surface of the fuel
2) [underlined ] Indicator [/underlined] is a moving coil ohmmeter connected electrically to the tank unit. The current flowing in the circuit depends on the position of the ball on the resistance. This is regulated by the amount of fuel
3) [underlined] Push Switch [/underlined] – a wo position three contact switch controlling the clamping plate and indicators. In the half depressed position contacts 1 and 2 are made. In the fully depressed
position contacts 2 and 3 are made. Contacts 1 and 2 release ball to level of fuel, contacts 2 and 3 camp ball and complete indicator circuit
[underlined] Mk IIIB Simmonds Fuel Contents Gauge [/underlined]
Differs from Mk IIIA in that [circled number] 1 [/circled number] Hinged in opposite direction so that ball is normally free
[circled number] 2 [/circled number] Two position switch “in and out” When connecting switch use two terminals on opposite side. As soon as switch is depressed both circuits are completed (Solenoid and Indicator) The solenoid attracts the hinged bar which clamp the ball and gives a reading.
[underlined] Maintenance – Daily Inspection [/underlined] W.D & S. check reading and functioning. [underlined] 30HR , 30*HR [/underlined] – Examine all leads and connections. Check cork sealing washer on tank unit for serviceability

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[underlined] THE DESSYN SYSTEM [/underlined] – MK IV [underlined] FUEL CONTENTS GAUGE [/underlined]

[annotated drawing]

[underlined] Fuel Contents Gauge Mk IV [/underlined] (Dessyn)
Its an electrical means of measuring fuel contents and consisting of – [circled number] 1 [/circled number] Tank unit [circled number] 2 [/circled number] Electrical leads [circled number] 3 [/circled number] Indicators
[underlined] 1. Tank Unit [/underlined] is similar in construction to the Mk II except that a completely circular resistance is employed and five terminals are used.
[underlined] 2. Electrical Leads [/underlined] – from transmitter to indicator five core cable is used, from A/C supply to indicator two core cable is used
[underlined] 3 Indicator [/underlined] is similar in design to an electric motor, the armature being a permanent magnetic to which the pointer is attracted. The instrument is so designed that the armature of the indicator (and so the pointer too) will alway [sic] follow the same
position as the brush on the transmitter. The dial has a scale of nearly 300o giving clear reading with accuracy. There are seven connections to the indicator 1, 2 & 3 are the phase connections, 4 & 5 are the supply from the accumulator 6 & 7 are the limiting resistance terminals. The tank unit is identical except that terminals 4 & 5 are missing 6 & 7 being supply. The limiting resistances reduce the working current to avoid danger of short circuit to the tank. The leads and terminals are numbered to reduce the possibility of wrongly connected circuits. When switched off the indicator pointer will always assume a vertical position [underlined] and not zero [/underlined]
[underlined] Maintenance [/underlined] – Daily Inspection W D & B test for correct functioning when switching on
[underlined] 30HR [/underlined] [circled number] 1 [/circled number] Check all electrical connections for tightness. [circled number] 2 [/circled number] Ensure that the cork sealing washer fitted under the tank unit is petrol tight. Presence of petrol leak will show a light grey deposit around the poterntioometer [sic], If a leak is found remove the tank unit and replace cork washer, sealing with HERMITE.

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[underlined] TELEGONS [/underlined]

[annotated drawing]

[underlined] TELEGON TESTING LAYOUT [/underlined]

[annotated drawing]

[underlined] TELEGONS [/underlined]

The telegon system is American, and is used to transmit a mechanical movement electrically, the electrical construction of transmitted and indicator are identical.
The transmitter is magnetically coupled to an instrument mechanism, which will vary with the nature of the instrument. Engine instrument transmitters are situated in an anti-vibrational breeze box in the engine nacelle. Connections to the indicator are made by five core cable in the breeze wiring system.
The telegon system operates on 2HV [sic] aircraft accumulator supply through a dynamotor. This supply is 110V single phase A C at 400 cycles. This system may be applied to almost any type of instrument the mast usual being [circled number] 1 [/circled number] Oil is Fuel Pressure. [circled number] 2 [/circled number] Oil & Caburetter [sic] intake temperature [circled number] 3 [/circled number] Fuel & Oil contents [circled number] 4 [/circled number] Flap and under-carriage positions [circled number] 5 [/circled number] Manifold (Boast

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[underlined] Telegon Four Dial Indicators [/circled number] – the most usual type being [circled number] 1 [/circled number] Engine Indicators [circled letter] A [/circled letter] Oil pressure [circled letter] B [/circled letter] Fuel pressure [circled letter] C [/circled letter] Oil temperature [circled letter] D [/circled letter] Caburretter [sic] air temperature [circled number] 2 [/circled number] Position indicator [circled letter] A [/circled letter] Flaps [circled letter] B [/circled letter] Port wheel [circled letter] C [/circled letter] base wheel [circled letter] D [/circled letter] Starboard wheel
[underlined] Telegon Testing [/circled number] – for single dial indicators and transmitters.
[circled number] 1 [/circled number] Set up avometer [sic] for testing resistance values up to 10,000 ohms.
[circled number] 2 [/circled number] Check avometer [sic] zero.
[circled number] 3 [/circled number] Connect single leads on telegon – tester to avometer [sic] terminals
[circled number] 4 [/circled number] Connect socket no.1 to indicator and tester
[circled number] 5 [/circled number] Connect plug no.1 to breeze socket and test transmitter through its wiring
[circled number] 6 [/circled number] Set following number and letters on tester

[box chart showing switch numbers and resistance]

[underlined] Testing [/circled number] – for four dial indicators
[circled number] 1 [/circled number] Set up avometer [sic] for testing resistance values 10,000 ohms.
[circled number] 2 [/circled number] Check avometer [sic] zero.
[circled number] 3 [/circled number] Connect single leads on telegon – tester to avometer [sic] terminals
[circled number] 4 [/circled number] Connect socket no.1 on tester to plug No.1 on indicator
[circled number] 5 [/circled number] connect socket No.2 on tester to plug No.2 on indicator
[circled number] 6 [/circled number] Set following number and letters on Tester
[underlined] Maintenance [/underlined] – same as for ordinary English instruments but with additional testing resistance of coils – continuity and insulation tests
[underlined] Daily Inspection [/underlined] – switch on main supply and all that dynamotor operates. Check readings of all dials, S, D & B and switch off. [underlined] Rate [/underlined] above readings on DI applicable only when engines have not been run. On engine run-up pointers
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Should travel smoothly over dials.
[table of transmitter readings]
[underlined] BREEZE BOX [/underlined] (Transmitting Box)
[drawing of breeze box]
The Breeze Box provides an anti-vibrational mounting for the Telegon engine transmitter. It is mounted in the rear of the engine nacelles
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[underlined] BREEZE WIRING [/underlined]
Consists of the following [circled 1] Flexible consolidated conduit system assembled in sections. [circled 2] Mautiple [sic] plugs sockets and junction boxes. Circuits are identified by code lettering detailed in the reference hand book. Leads and mouldings are numbered or lettered for assembly purposes. Sections or single leads are replaceable. Spray-proof screened conduits are used and the system is waterproof.
[underlined] Maintenance [/underlined] [circled 1] Examine all conduits for damage and junction box for security [circled 2] Blacken coupling nuts before fixing or removing any sockets using a strap wrench [circled 3] Grease threads with D.T.D. 143 (an animal grease) or lanoline [circled 4] Fault finding carried out with a Wee Megger and Continuity Tester
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[underlined] TESTMETER TYPE “D” OR AVOMETER [/underlined]
[diagram of testmeter] [underlined] ANTI-PARALLAX MIRROR [underlined]
[underlined] D.C. SWITCH [/underlined] [amp & volt tables]
The type “D” Tester provides a mean of measuring a wide range of A6 & D6 volts & current as well as resistance values in one instrument.
[underlined] Explanation of Control [circled 1] A6 & D6 switches
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Are used for setting of various voltage, current and resistance values (for range of scales and controls see below
[circled 2] K1 & K2 multiplies switch.
[circled 3] P. adjustment for zero on Ohm’s scale 10,000 [symbol] range.
[circled 4] R. as above at 1,000 [symbol] range
[circled 5] Z. for zero adjustment of volts and amps scale
[underlined] Operation [/underlined] Instrument should always be laid on flat surface.
[circled 1] To measure volts and amps & set pointer to zero by Z. If measuring D6, turn A6 switch to D6 all adjustments are to be made with D.6. switch, if measuring A.6. turn D6 switch to A.6. all adjustments made with A6 switch. If voltage and amperage values are not known set range switches to highest value, use K.2. Readings on switch may then be decreased as necessary, until correct range is obtained. Multipliers switch (K1 & K2)
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will give multiplication in every case except A. 6. 300 volts where the readings will be doubled and quadrupled ie K.1 will give twice full scale deflection on 300 volts K. 2 will give four-times full scale deflection on 600 volts.
[circled 2] To measure resistance values – connect ends of leads together with A. 6 switch to D.6, set D.6 switch to 10,000 [symbol] multipliers to K. 2 adjust knob “P” until pointer reads zero D 6 switch to 1000 [symbol] adjust on knob “R” until zero is obtained, repeat this until pointer is balanced at zero on both 1000 [symbol] and 10000 [symbol] ranges. If balance cannot be obtained replace internal Avometer cell.
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[underlined] AUTO-SYN [/underlined]
[diagram of transmitter]
Provides for a means of electrical transmission for the following instrument mechanisms
[circled 1] Tachometer (E.B.I.) [circled 2] Oil Pressure Gauge [circled 3] Fuel Pressure Gauge [circled 4] Oil Thermometer [circled 5] Manifold Pressure (Boost Gauge) [circled 6] Fuel Contents Gauge [circled 7] Fuel Flow Indicator [circled 8] Wheels. Flaps etc indicators. The Auto-syn system consists of [circled 1] [underlined] Transmitter [/underlined] – is mounted on an anti-vibrational panel, similar to the Breeze Box, as near as possible to the attachment position. The Transmitter consists of a gauge
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mechanism, having a quadrant in mesh with the motor spindle of the Auto-syn motors
[circled 2] [underlined] Indicators [/underlined] (single) – has a mechanism similar to the transmitter, except that instead of a pinion a pointer is attached to the shaft which operates over a suitable dial
[circled 3] [underlined] Indicators [/underlined] (dual) – consists of two Auto-syn motors mounted in line. The shaft of the foremast being hollow. The spindle from the rear motor passing through it. The pointers are marked 1 & 2 and 3 & 4. The Auto-syn system operates on 24 volts. A/c accumulator supply through a dynomotor, this supplies A. 6 at 26 volts – 400 cycles at 52 volts – 800 cycles as required.
[underlined] Transmitter Mechanisms [/underlined] – fitted with quadrant coupling [circled 1] Oil Pressure simple Bourdon tube [circled 2] Fuel Pressure – diaphragm type [circled 3] Manifold Pressure – diaphragm type in a pressure tight housing with linkage [circled 4] Tachometer centrefugal mechanism driven by a short flexible drive [circled 5] Oil Temperature – simple
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Bourdon tube having a bulb and short capillary working on the vapour pressure principle – no bends in the capillary are to be less than 4” rad [underlined] [indecipherable word] [/underlined]. Fuel, Oil and Manifold pressure gauges have direct type connections. All the above mechanisms are fitted on the anti-vibration mounting on the engine.
[underlined] Transmitting Mechanisms [/underlined] – operating through a magnetic coupling. [circled 1] Fuel contents fitted on fuel tank. It has a flack operated gear system. The Auto-syn motor is completely separate from the gear mechanism. This ensures fuel does not enter the Auto-syn motor. [circled 2] Fuel Flow has a vane mechanism operated by fuel flow
[underlined] Transmitter Mechanism [/underlined operated by special linkage. Position a gear and sector mechanism operated by Flaps, wheels, and Bomb doors etc.
[underlined] Transmitter Wiring Chart [/underlined]
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[Terminal connection Table]
[underlined] DUAL INDICATOR WIRING CHART [/underlined]
[ Rear and front Motor Table of wiring]
nos 1 & 2 are the motor leads, nos 3, 4 & 5 are status leads
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[underlined] Recognition [/underlined] [circled 1] Type of instrument shown on small plate attached to transmitter unit.
[circled 2] By colour coding
[circled 3] By code numbering indicator and transmitter
[circled 4] Type of connection to transmitter
[underlined] Maintenance [/underlined] As for Telegons
This instrument operates on 3 phase. A. 6, in contrast to the MK II & III Engine Speed Indicator which are D. 6 operated. There are two main parts [circled 1] Generator [circled 2] Indicator
[underlined] Generator [/underlined] – is drawn from the engine by a flex-drive and is mounted on the engine bolt-head. A gear Box to step up the revs of the flex-drive is built in the generator casing. Connection to the Indicator is made by three core cable from terminals 1-2-3 on the generator.
[underlined] Indicator [/underlined] – is a synchronous motor designed
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To run at the same speed as the generator. The motor drives a magnet attracting a copper drum to which the pointers indicating hundreds and thousands of R.P.M are geared. The indicator is connected to the supply from the generator by three terminals 1, 2 & 3 on the rear of the case.
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For clock-wise rotation of the generator, connect red to T1, blue to T2, and green to T3. For anti-clockwise rotation of generator connect red to T1, green to T2, blue to T3.
[underlined] Maintenance Dial [underlined] S. D & B If pointers are not on zero and engines [underlined] not [/underlined] running, slight tapping of the glass should return the pointers.
[underlined] 30HR [/underlined] , [underlined] 30HR [/underlined] [symbol] – [circled 1] Examine flex-drive for signs of excessive wear. [circled 2] Remove inner cable and lubricate with anti-freezing grease (stores ref. 34A/49). [circled 3] Replace, ensuring that locking nuts are secure and locked with locking wire. [circled 4] Examine gear-box on generator for wear, then lubricate with grease high-smelting point (stores ref 3HA/84 & 89) [circled 5] Examine all electrical connections for security
[underlined] Calibration [/underlined] – carried out against a Stroboscope.
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[underlined] OXYGEN [/underlined]
[diagram of valve]
[underlined] OXYGEN EQUIPMENT [/underlined]
Oxygen equipment is installed in all A/C through out the R.A.F. with increase of altitude the air density decreases with a resultant decrease of O2 available for the aircrew. Exhaustion and fatigue would soon follow if an additional supply was not available. The apparatus allows adjustment for the varied heights.
Each A/C will need the following
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equipment [circled 1] Banks of cylinders for storage of oxygen. [circled 2] 1 or more regulators [circled 3] High pressure and low pressure pipe lines with various connecting pieces and fittings [circled 4] Bayonet plugs and sockets. [circled 5] Oxygen masks with flexible tubing
In addition an a/c may have flow readers, line valves, and portable sets. Recent changes in installation for the larger type of a/c are the modific to facilitate the changing of O2 bubbles in the aircraft. This is known as insitu installation
[underlined] Cylinders [/underlined] Mk V & Vc – both filled to a pressure 1800 lbs [symbol] Made of seamless steel capacity 750 litres. A brass collar around the neck is marked with the date of last test for pressure, if more than 2 years of age return to stores. Mk Vc bottle differs from the Mk V in that it is bound with wire to prevent fragmentation of bottle when struck by canon shell etc.
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[diagram of layout if MK VIIIB pilots and crew]
[underlined] LAYOUT OF MK VIIIB PILOTS & CREW [/underlined]
Each bottle is fitted with Mk VIIA [symbol] valve or a Mk V three-way connecting piece.
[underlined] Mk [/underlined] VA or VB [underlined] Cylinder [/underlined] these are portable cylinders. Capacity 75 litres – pressure 1800 lbs [symbol] These are used on portable sets Mk I or IA and are fitted with a Mk IX A [symbol] regulator. [underlined] Mk [/underlined] VII & VII A [underlined] Transport Cylinders [/underlined] – these are used for transit of O2 from the manufact to the unit. It is fitted with a standard valve for which a key is used, when
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changing open very slowly – capacity 1600 litres at 3600 lbs [symbol] weight 240-290 lbs.
[underlined] Cylinder Valve Mk [/underlined] VII A [symbol] – fitted to cylinder in normal systems where these are taken out for charging. When using always open fully to prevent leaking over gland. Oil as grease must not be used as a lubricant if too stiff strip and lubricate with special fluid graphite.
[underlined] Line Valve Mk [/underlined] VIII – this valve is used as a means of cutting off the whole supply when not required. It is especially useful in the insitu installations also when cylinder valves are not easily accessible, similar internally to Mk VII but has an inlet and outlet union for fitting in pipe lines also a base plate for installation.
When installing ensure that the lower inlet union is onto the cylinder as the other connection allows oxygen to leak over the glands. The
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valve is also used on the charging line. Again the lower connection is towards the bank of cylinders.
[underlined] High Pressure Tubing [/underlined] – used between cylinders and regulators 1/4 or 3/16 O.D. copper tubing. With soft soldered spherical nipple. Unions are made with two, three or four-way connection pieces Mk III III A or IV.
[underlined] Mk [/underlined] III [underlined] Connecting Pieces [/underlined] – 2, 3 or 4-way – Plain connection pieces for junctions in H.P pipe line – Core 3/32” approx.
[underlined] Mk [/underlined] IV [underlined] Connecting Pieces [/underlined] 2, 3 or 4-way. Used for junctions in H.P pipe-lines where a non-return is needed in one or more of the junctions. It is similar to the Mk III but the bore is screwed to take a captive ball type N.R.V in one or more of the ways.
[underlined] Mk [/underlined] III A [underlined] Connecting Pieces [/underlined] 23, 3 or 4-way, similar in design and supercedes Mk III and IV connecting pieces. The bore is 1/4 seam approx.
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so that a filter unit or a Mk I N.R.V. can be fitted. Can be fitted into any way required. The filter unit is normally fitted in a two-way piece between the line-valve and the regulator and before changing line-valve (insitu) Always indicate where N.R.V or filters are fitted by attaching labels to pipe-line.
[drawings of MK III, IV and V connecting pipes]
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[underlined] Mk [/underlined] V [underlined] Three-way Connecting Piece [/underlined]
This replaces the Mk VII A valve in the cylinders in insitu installations. One way contains a Mk I ball type NRV. held in by the nipple of the pipe connection of the charging pipe line. The other end is open to the supply pipe line an arrow indicates direction of flow.
[underlined] Mk [/underlined] VIII A [underlined] Regulator [/underlined] – Contains all the necessary controls and indicating apparatus. The oxygen enters the high-pressure inlet passing through a filter Here a pipe is T’d off to the supply indicator (line carries choke) which is a Bourdon tube type pressure gauge calibrated in a full bottle in 1/8th diversion. The oxygen then passes through to the reducing chamber where the high [inserted] pressure [/inserted] is reduced to 35 lbs [symbol] In case the pressure builds up there is a safety valve fitted blowing off at 80-100 lbs [symbol] The rate of flow. from the chamber is controlled by the regulator valve. When this valve is closed it has
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a slight leak which will give a reading of 5,000 ft. After leaving the regulator valve the oxygen passes through to the delivery indicator which has a moving vane type of mechanism. Dials calibrated in multiples of 5,000 ft from 0-40,000 ft when the control valve is adjusted and the pointer reads say 15,000 ft, the resultant flow will be equivalent to the requirement of 15,000 ft.
The flow leaves the regulator through a filter and then by the low pressure pipe line to the bayonet unit
[underlined] Mk VIIIA [/underlined] [symbol] For Pilot (No Economises)
[underlined] Mk VIII A [/underlined] For Crew (“ “)
[underlined] Mk VIII [/underlined] For Pilot (with Economises)
[underlined] Mk VIII [/underlined] For Crew (“ “)
[underlined] Low Pressure Safety Valve Mk I [/underlined]
Fitted so that when the arrangement is such that the pressure may build up in L.P pipe-line it would “blow-off” at about 35 lbs [symbol] chief use, when used in two
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[diagrams of Mk II Economiser]
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positions with economisers and 1 regulator MK VIIID
[underlined] Bayonet Sockets [/underlined]
These provide a quick means of attachment and release for the bayonet union plug attached to the flexible tubing the mask
[underlined] Mk [/underlined] III A plain bayonet socket without valve used when regulator controls supply to one socket only
[underlined] Mk [/underlined] III B. Bayonet socket with a valve (N.R.V.) Oxygen will only flow when the plug is attached. It is used when two sockets are available from one regulator. Oxygen will not leak when the other is in use. A slight leak is incorporated to prevent a pressure build-up in L.P. tubing when neither socket is in use
[underlined] Mk [/underlined] III c – similar to Mk III B but without calibrated leak. On the Mk X system use Mk III A on pilot’s position so that the pressure will not build up in
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L.P. system Use a Mk III B or III a sockets in all Mk X systems, other than the pilot’s.
[underlined] Mk [/underlined] IV – used on the end of the flexible tubing from Economisers and is fixed on the tubing by a [indecipherable word]. Will only fit the Mk IV plug as on the end of type E, E[symbol] & G
[underlined] Mask Type “D” [/underlined] – arranged for use with flying helmet and microphone it has rubber tubing connection from Mk III B [symbol] plug.
[underlined] Mask Type ‘E’ & ‘E [symbol]’[/underlined] – is similar to type D but it is used with Economiser. It has an inspiratory and exspiratory [sic] valve to enable it to be used with Economisers. It has Mk IV bayonet plug to fit into Mk IV socket on the Economiser flexible tubing. Type ‘E’ has a single need valve for inspiration and expiration. Type ‘E [symbol]’ has a separate inspiratory valve embodied. Must be airtight and fit closely to face
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[underlined] Mask Type ‘[indecipherable letter]’ [/underlined] similar to type E [symbol] but has a disc type respiratory valve
[underlined] Cut-off Valve Mk I [/underlined] – fitted in LP pipe line between regulator and economiser. It prevents damage to economiser and subsequent waste of oxygen by cutting of the flow when the Mk IV bayonet socket is pushed inti the clip. It is spring loaded, the spring being covered to prevent inginees of [indecipherable word]. Seals are affected by means of rubber washers on the plunger in both on and off positions
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[diagram of oxygen layout Mk X A]
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Mark X Regulator [/underlined] – this is the latest type used in aircraft oxygen installations where only one regulator is required this is controlled by the pilot:
This regulator controls the flow for the entire crew. It is similar in principal to the Mk VIII series but has a modified reduction chamber and is fitted with filters and drain plugs.
The oxygen supply is carried to the “On Off” valve which is rendered leak proof by means of bellows that are fitted round the operating spindle. It is fitted with a drain plug.
When the valve is open, the supply flow to the reduction chamber via a filter and also to supply indicator. The spring control of the reduction chamber is adjustable by means of the Flow as Regulator knob. The high pressure is reduced to medium pressure the valve of which is dependant upon the spring
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tension. Both high pressure and low pressure are fitted with drain plugs. The reduced pressure leaves the reduction chamber by a filter and lubricating box. This box is fitted with a safety valve operating pressure 80-100 lbs [symbol] and three outlet leads. One goes to the delivery indicator which is a Bourdon Tube pressure gauge and has a small scale similar to the Mk VIII. The other two feed the manifolds with 1/4” copper or light alloy medium pressure tubing. The system can [indecipherable word] 8 men without Economisers or 20 men with Economisers. The Mk X A is calibrated for use with economisers.
[underlined] Medium Pressure Tubing [/underlined]
Use from [indecipherable word] box to manifolds. Copper or light alloy 1/4" tubing (O.D) If pipe connections are necessary use a Mk VI three-way connecting piece.
[underlined] Manifolds [/underlined]
Each manifold has a filtered
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inlet and four outlets, one to each member of the crew (blank-off those not required) In each of the outlets is a metered jet. When the flow control knob on the regulator is set to give a pressure in the reducing chamber equivalent to a given altitude, the jet will pass sufficient oxygen for each man at that altitude.
Mk I manifolds used where no economisers are installed. Mk I A used where economisers are installed, the difference is in the size if the jets. The Mk I being the larger. In an installation using economisers the turret position may have a bayonet socket and no economisers. In this case a Mk I is fitted to the manifold outlet, feeding the turret and the Mk clearly indicated at the connection.
[underlined] Low Pressure Tubing [/underlined]
This is used from manifolds to bayonet sockets, and economisers and
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from Mk VIII regulators and economisers 5/16” O.D. aluminium tubing, connections being made with L.P. Unions. Sealing is made by the compression of the rubber washer against the tubing and union body by means of the union nut. To seal tighten union finger-tight and then 1/2 a turn with the spanner.
[underlined] Economisers [/underlined] – This has been slowed to reduce consumption and improve conditions at high altitude as when working high. It will be fitted in due course to all installations and will save approx. 50% oxygen.
Inlet connection is from Mk I cut-off valve by means of low pressure tubing and is adjustable. Outlet is adjustable in flow positions and has a length of flex-tubing (fixed by Aerobix clips) to a Mk IV Bayonet socket. The oxygen flows from the low pressure pipe line into a rubberised canvas bag, which is
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spring loaded. From here it passes through a filter through a mica disc valve to the Mk types E E [symbol] or G mask when the wearer of the mask inhales the valve opens and she will fill up his lungs with air. As he breathes out the pressure closes the two valves and opens a respiratory valve through which the used air passes to atmosphere. During this breathing out period the bag is filling up from the R.P. pipe line.
[underlined] To Check [/underlined] [circled 1] Remove encom. [sic] from a/c and set up flat on bench [circled 2] Connect L.P of spare regulator to the inlet.
[circled 3] Turn on oxygen supply & set flow meter to 5 litres per min [underlined] MK VIIIA [symbol] or VIIIB [/underlined] 22-25,000 ft [underlined] MK VIII C or D [/underlined] or [underlined] MK VIIIA [symbol] or VIIIB (with calibrated mask [indecipherable word]). 30,000ft. [underlined] MKX [/underlined] with 1A manifold 40,000ft [underlined] MK XA with manifold [inserted] Emergency [/inserted] 40
[underlined] MK T [/underlined] A [underlined] Flow Meter [/underlined]
Is used where two bayonet sockets are needed for on Mk VIII regulator and one is a good distance away from the regulator – the flow meter is fitted in the pipe-line prior to the bayonet sockets so that the one can know the
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amount of flow at the farthest point.
[underlined] Flow Inidicator Mk II and III [/underlined]
Used in the Mk X system for each point so that each member of crew can see if he is getting oxygen supply. Similar toi Mk I A [symbol] meter but it is not calibrated.
Mk II infos crew fuselage fitting, Mk III for pilot – panel fitting.
[underlined] Portable Sets [/underlined] Mk I, IA : I B
For use by a member of the crew who cannot remain at one supply point. Consists of a 75 litre cylinder Mk V or VB with a Mk IXA [symbol] regulator fitting; this regulator has the following [circled 1] Charging connection [circled 2]”On Off” valve [circled 3] A pressure gauge calibrated and marked in terms of minutes 0-10 [circled 4] A reducing valve which reduces high pressure to approx 50 lbs [symbol] [circled 5] A bayonet socket is for a Mk 3B [symbol] or Mk I or Mk IA as the Mk IV socket and flex tube on Mk Io. The delivery will be
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controlled by a jet and vary with the altitude.
[underlined] Portable Set Changing Procedure [/underlined]
[circled 1] Turn on off valve off
[circled 2] Remove blanking nut and connect charging connector to charging regulator with Mk II H.P. flexible hose
[circled 3] Ensure all joints are leak-proof
[circled 4] Turn on charging regulator valve and
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then the portable set valve.
[circled 5] Allow to charge until indicator reachs [sic] or passes the 10 min mark (1950 lbs [symbol] on charging gauge
[circled 6] Turn off portable set valve and then the charging regulator valve.
[circled 7] Disconnect from charging set first replacing blanking nut
[underlined] Rack Charging Procedure for A/c Cylinders [/underlined]
Before charging a blast of hip Oxygen should be allowed through the rack to clear piping of moisture etc, also open cylinder valves and check for same defects. Inspect cylinder for state of last list and test contents for [indecipherable word] and serviceability of valve.
[circled 1] Connect up transpoint cylinder and open its valve with a key until regulator pressure gauge reads 3,600 lbs [symbol] [circled 3] Open valve 1/4 – 1/2 a turn watching to
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see that low pressure is correct
[circled 4] Shut valve when pressure reaches a steady 1800 lbs [symbol] this should take approx. 20 mins.
[circled 5] Allow to cool for 20 mins when pressure will have fallen. Open valve again and top up to 1,800 lbs [symbol]
[circled 6] Close cylinder valves and disconnect.
[underlined] In Situ Charging [/underlined]
The charging regulator is mounted on a truck and connected to a charging point in the a/c with high pressure hose, before connecting up send blast through pipe-line to remove foreign matter. Charge up to 1900 lbs [symbol] to allow for lose in cooling. Close line valve before closing charging regulator valve. Disconnect and [indecipherable word] for leaks at charging point (glass tube.)
[underlined] Installation [/underlined]
[circled 1] Keep system free from oil and grease
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[circled 2] Test for leaks with soap solution [indecipherable word] off after testing.
[circled 3] H.P/ tubing where connected to cylinders should have a loop of at least 4” Diam to prevent hardening and cracking with constant disconnecting and connecting of unions low pressure unions should be tight and leak-proof. Examine rubber washers.
[circled 4] New tubing should be washed through with Trichoethylene and dried with blast of hot air.
[underlined] Boldering nipples [/underlined]
[circled 1] Clean off and square end of tubing
[circled 2] Use soft solder and killed spirits (soldering solution)
[circled 3] Tin end of copper tubing and use blow lamp and see that solder runs well down inside of nipple
[circled 4] See that end of nipple is clear of solder
[circled 5] Wash out with 1% hydrochloric Acid solution (to get rid of the flux) and
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then wash out in boiling water
[circled 6] Test new pipe line. Cover ends with linen if not to be used immediately
[underlined] Regulator Tests [/underlined]
[circled 1] Connect one full cylinder to each regulator and ensure all H.P and L.P unions are tight
[circled 2] See that pointers are at zero
[circled 3] Turn on cylinder valve and adjust delivery to 5,000 ft. Supply indicators should not read less than 7/8 Test H.P Unions for leaks
[circled 4] Adjust delivery to 35,000 ft. Test L P connections including bezel of Delivery Indicators and gland of Control Valve.
[circled 5] Turn off cylinder valve and note that delivery does not drop below 25,000 ft until Supply is below 1/16th
[circled 6] Read Supply accurately and allow regulator to stand for one hour with cylinder valve open and control valve closed. Fall in reading should be about 1/8th
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[underlined] Daily Inspection [/underlined]
[circled 1] Check contents of cylinder. Change if less than 7/8th: In case of replacement test the following
a) Cylinder valve gland nut
b) Cylinder valve spindle outlet
c) Recess in top of valve handle
d) Joint between cylinder valve and hip tubing
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[underlined] THE ATMOSPHERE. [/underlined]
The earth is surrounded by a belt of air about 200 miles deep and consists of a mixture of gases which have a definite weight. 1 su. ft at sea level weighs approx .08 lbs. Air therefore exerts a pressure on everything it surrounds which is about 14.71 lbs per square inch at sea level and it is obvious that this pressure will decrease with an increase of height. The pressure about 3 1/2 miles up is almost half owing to the fact that air is compressible. Atmosphere pressure varies from day to day at any given point due to temperature and humidity. The unit of absolute pressure is the ‘Bar’ which is equal to 1 megadyne per sq. cm. The practical unit is the millibar which is 1/1000th part of the bar. From this name is derived ‘Barometer’ which is the name given to the standard instrument for measuring atmosphere pressure
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[underlined] Portable Barometer Mk I [/underlined] is an instrument that makes use of the fact that atmospheric pressure will support a column of H G and has a scale of contracted inches which require no setting when taking a reading. It is designed to read inches of pressure and is also used in conjunction with Altimeter calibration. For a given pressure changes of temperature and the force of gravity (change in latitude), varing [sic] headings will be given and thus definite conditions must be laid down for these two factors. Kew Type Barometer
[temperature table]
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[underlined] The Fortin Barometer [/underlined] differs slightly in construction in the fact that it measures to three decimal places, using a special Dennier scale which is in true inches. Before reading, the adjustable reservoir must be adjusted to bring mercury to its Feducial Point.
[underlined] The Newman Barometer [\underlined] again is of different construction and has a true inch scale which must be adjusted before taking a reading.
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[underlined] ALTIMETER [/underlined]
Are designed to register changes in atmosphere of an evacuated capsule whose position is controlled by a flat leaf spring. Any changes in atmosphere pressure on the capsule means that the spring has a movement which is transmitted by means of a suitable system of links and levers to a pointer which rotates over a scale marked in terms of height i.e. thousands of feet, Arrangement is usually made up for setting pointer to a zero position
[diagram of altimeter]
[underlined] SIMPLE ALTIMETER [/underlined]
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[underlined] Calibration Lanes. [/underlined] Altimeters may be calibrated under two lanes
[underlined] 1 Isothermal lane [/underlined] – assumes that the pressure is 1013.2 mbs and that the temperature at all places and heights is 10%. This lane requires large correction at high altitudes
[underlined 2 I.C.A.K Lane [/underlined] – assumes the pressure on the ground to be 1013.2 mbs and the temperature falls at a rate of 1.98o C for every 1000 feet from 15o on ground to -56.5o C at 36,000 ft after which it remains constant [underlined] Mk [/underlined] XIII [underlined] Altimeter [/underlined] – Range from 0.20, 0.30 0-40,000 ft. Has a simple altimeter mechanism enclosed in a moulded airtight case, there is a nipple at the rear of case for connection to a static line. Has an adjusting knob which usually rotates the main scale, and there is a small hole in the dial with lines engraved on each side, when these lines are coincident with a line seen below the hole and
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brought about by rotating the knob the altimeter should read zero, providing the pressure of the day is 1013.2 mbs. Is calibrated to the isothermal low
[underlined] Mk [/underlined] XIV [underlined] Altimeter [/underlined] – working range 0-40,000 ft Works on same principal as Mk XIII but mechanism is on a very different kind of construction. Has a moulded airtight case and nippled at the rear. Three pointers geared and indicates 100, 1000 & 10,000 ft. An adjustable barometric scale is also provided. This instrument is calibrated to the I.C.A.K Lane. The pointer and subsidary [sic] scale are so related that if zero height is indicated, the subsidary [sic] scale should indicate barometric pressure of the day at that particular time and place. A permissable [sic] error is allowed of plus or minus 50 ft. If the knob is rotated both pointers and subsidary [sic] scale move but during normal use as an altimeter only pointer move, the above relationship
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means 1). If height scale is at zero, subsidary [sic] scale will read pressure of the day at that particular time 2) If pointers are set to the height of the aerdrome [sic] above sea level, subsidary [sic] should read barometric pressure at sea level at that time. 3) If a pilot is landing at another aerdrome [sic] he can find by wireless barometric pressure at that aerdrome [sic] and set this on subsidary [sic] scale, and upon landing, his pointer should read zero.
[underlined] Altimeter Leak Tests [/underlined]
[underlined] Mk [/underlined] XIII – Apply a suction [underlined] carefully [/underlined] till pointer indicates 4,000 ft. Trap suction, pointer should not drop to below the 1000 ft mark in less than one minute (3,000 ft in one min)
[underlined] Mk [/underlined] XIV – Apply suction carefully till pointers indicate 1,000 ft, trap suction, pointers should not drop below the 950 ft mark in less than one minute (50 ft in one min.)
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[underlined] BOOST GAUGES [/underlined]
[diagram of boost gauges]
To indicate pressure of the fuel mixture in the induction system of a super-charged engine relative ti normal atmospheric pressure. The mechanism is similar in principle to a simple altimeter and is contained in an airtight case, [inserted] (MK III TYPE ONLY) [/inserted] at the back of which is a threaded nipple to connect a copper pipe, between the instrument and the induction system is a fuel trap situated usually at the lowest point of the pipe line. The instrument nipple contains a removable filter and it is so constructed that
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between the instrument and filter there is a choke to prevent damage which would be caused by an engine backfire. The pointer indicates at the positive and negative boost lbs per [symbol] relative to normal atmospheric pressure and is therefore only at zero when pressure in induction system is 14.71 lbs per [symbol] or 1013.2 mbs. When engine is stopped, pointer will read slightly above zero if barometric pressure is above normal and slightly below zero is barometric pressure is below normal.
[underlined] Types of Boost Gauges Used [/underlined] – are as follows.
Mk III c - -4- + 8 lbs, Mk III G – 4 + 16 lbs, Mk III e [symbol] -4- + 8 lbs. Mk III c [symbol] -4- + 16 lbs
[underlined] Mk [/underlined] III [symbol] type differ slightly in construction, which allows a none airtight case, but principle remains the same, (no filter).
[underlined] To Check Zero Reading [/underlined]
Method [circled 1] Draw a graph from figures given in a 1875 Sect II Chapter [underlined] 6 [/underlined] Table 1
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MK III [symbol] TYPE
Obtain barometric pressure of day in mbs, correct reading can be fixed by checking on graph.
Method [circled 2] a). 1 lb pressure is equal to a difference of level of 2.04 inches of h.g.
b) With a pressure of 29.44 inches h.g gauge should read zero
c) Therefore if amount of days pressure above or below 20.99 is divided by 2.04 (for practical purposes can be 1/2 ) the result will be correct boost gauge reading
[underlined] Leak Test [/underlined]
Carried out, [circled 1] Before a new gauge is installed.
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[circled 2] When a reserve aircraft is being fitted for flight
[circled 3] Before gauge is calibrated at a major inspection
[circled 4] When accuracy of gauge is suspected
[underlined] Test as follows [/underlined]
[circled 1] Remove wire locking bezel, slacken lubber mark locking screw [inserted] and tighten bezel hand tight. [/inserted]
[circled 2] Connect boost gauge to calibrating apparatus apply pressure to give reading of + 7 lbs per [symbol]
[circled 3] The time taken for pointer to fall 1/2 lb should not be less than one minute
[circled 4] If leak is outside this limit a new sealing washer must be fitted and the instruments re-tested
[underlined] AIR SPEED INDICATORS [/underlined]
This instrument indicates the speed of the aircraft relative to the air, but [underlined] not [/underlined] relative to the ground. It is a differential pressure gauge, whose pointer moves a certain distance which depends
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on the difference in pressure between still and moving air at any height. The dial is calibrated in M.P.H in and planes and knots in seaplanes and flying boats There are two L.P supplies at the back of a moulded airtight case which are mark Static (S) and Pressure (P), which are connected by 5/16 aluminium tubing and L.P unions to their respective connections ion the Pressure-head – Air Speed Indicators are filled in the Pilots, Navigators and Bomb-airmens instrument panels.
[underlined] Leak Test [/underlined] (Instrument only)
Apply suction carefully to static connection till pointer indicates 150 M.P.H and trap suction pointer should not drop more than [inserted] (13 KNOTS) [/inserted] 15 M.P.H in less than 10 secs
[underlined] Pressure Head [/underlined]
Consists of a pressure tube with an open end facing direction of travel and a static tube closed at the end, but with holes or slats cut in at right
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angles to the airflow of aircraft. In the Mk VII these tubes are set parallel with the static above the pressure. There is a special trapsion thin tube (pressure) to prevent dent entering and ice forming. In the Mk VIII the pressure tube is fitted inside the static – tube and the pressure-head is electrically heated.
[underlined] RATE OF CLIMB INDICATORS [/underlined]
[underlined] Mk [/underlined] IB – range +- 4000 ft per min – this indicator is a type of differential pressure head, it’s pointer indicating the difference of pressure
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between the inside of a capsule and the outer case in one type, and between a small chamber with a diaphram [sic] and the instrument case in the other type. A nipple at the back of the moulded airtight case, leads atmospheric at any height into the interior and the two parts of the instrument are divided by chokes. which allow pressure to leak between one part and the other at a definite rate. Thus if the chokes are suitably designed the pointer will indicate the rate of change of altitude and so the scale or dial can be marked off in 1000 ft per min. climbs or dives. There is usually incorporated a zero adjusting screw, situated at the bottom right-hand corner of the case.
[underlined] Leak Test [/underlined]
[circled 1] Connect instrument to a U. tube of water and a ‘T’ piece.
[circled 2] Apply a pressure [underlined] carefully [/underlined] to give a difference in level of water of 11.4 inches
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[circled 3] Trap pressure and water should not fall faster than 1” in 10 secs
[diagram of Leak Test Layout for Rate of Climb]
[underlined] BLIND FLYING PANEL [/underlined]
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[underlined] TURN AND BANK INDICATOR [/underlined]
[underlined] Turn Indicator [/underlined] – Object to aid the pilot to maintain straight and laterally level flights. Instrument has two pointers. The top one operated by a pendulum weight and indicates side clip. The lower pointer indicates rate of turn, and is operated by an air-driven gyroscope. A union att he rear of the air-tight case is connected to a vacuum supply, which causes the outside air to pass through a filter and jet, impinges on the rotor. The angle of tilt of the inner ring is controlled by a spring which is attached to it. The instrument should be mounted with the top points at zero when aircraft is laterally level.
[underlined] BLIND FLYING PANEL [/underlined]
Has been adopted to standardise the grouping and types of instruments used. Holds six instruments [circled 1] A.S.I top left.
[circled 2] Mk XIV Alt bottom left.) [circled 3] Art, Horizon top centre [circled 4] Direct. Ind. Bottom centre [circled 5] T & S Ind. bottom right. These instruments
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have been chosen so that if one becomes u/s there always remains an alternative by which blind flying can be completed. The B.F.P is supported in three places by anti-vibrational mountings which use both rubber buffer and metal spring to prevent excessive vibration from effecting [sic] the instruments.
[underlined] PIPE LINE SYSTEM [/underlined]
[underlined] Installation [/underlined]
The following precautions should be taken when fitting low-pressure tubing in the system. [circled 1] The pressure head must always be facing head forward and horizontal with a/c in flying position.
[circled 2] The static holes should always be kept clean and free from burns.
[circled 3] When fitting L.P unions, the aluminium tubing should be filed off square, and pushed intio union as far as it will go.
[circled 4] A new rubber ring should be
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fitted every time union is broken.
[circled 5] When fitting unions nuts should be done up finger tight, then a extra half turn with a spanner.
[circled 6] There should be no sharp bends but elbow unions should be used.
[circled 7] Drain traps for both static and pressure lines should be fitted at lowest point of installation.
[circled 8] System should be tested for leaks at frequent intervals.
[underlined] Installation Leak Test [/underlined]
a) [underlined] Pressure line. [/underlined] Disconnect from first L.P joint behind pressure head and attach rubber tubing and apply a pressure till A.S.I reads 150 miles per hr and trap pressure pointer should not drop below the 135 mark in less time than is given by following formula. 5/8 [indecipherable word] Y = length of pipe-line.
b) [underlined] Static Line [/underlined] Disconnect from first L.P joint behind pressure head, attach tubing and apply suction till A.S.I reads 150 MPH
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trap suction, pointer should not drop to 135 mark in less time than as given by the following formula 1/2 x 1/16 (N + 1/16) secs L = length of pipe N = no of instruments
[underlined] PESCO SUCTION PUMP [/underlined]
[underlined] Venture Head [/underlined] – Depends for it’s action on the increase of velocity of moving air due to the conical shape of the head. This increase of velocity causes a partial vacuum in an annular groove over which the air passes, so causing the
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air to be drawn out of the pipe-line
[underlined] Maintenance [/underlined] Ensure that groove is clean and the head secure and properly aligned.
[underlined] Pesco Vacuum Pipe [/underlined] Consists of a rotor out of centre with the case, with 30 blades passing through it at right-angles to each other. Air is drawn out of the pipe-lines and discharged, thus creating a partial vacuum in the pipe-line and instrument connected to it. The pump is engine driven and is supplied with oil under pressure for a) Lubrication b) Cooling c) Sealing. The pump can be driven in either direction
[diagram of relief valve]
[underlined] A.M RELIEF VALVE [/underlined] (VENTURE HEAD)
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[underlined] PESCO RELIEF VALVE [/underlined]
[underlined] CHANGE OVER COCK [/underlined]
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[underlined] Change Over Cock [/underlined] – To enable the pilot to use either the Pesco Pump or the Venture when fitted as to change over from one pump to another on other than single-engine a/c. Consists of a metal body containing four ports over which can be rotated an inner drum covering air opening the necessary ports. The cock incorporates two filters (see diagram)
[underlined] Aircraft Inspections [/underlined]. All aircraft inspections are laid down in the appropriate maintenance schedule, this is the only official guide for any particular a/c and should always be consulted. The first item on daily inspection of any instrument or piece of apparatus is check for D.D./a. This will of course be interperated [sic] differently for different instruments. When any particular inspection is carried out all groups of previous inspections must also be done.
[Table showing instrument inspections]
[Page break]
[Continuation of table showing instrument inspections]
[Page break]
[Continuation of table showing instrument inspections]
[underlined] SPERRY GYRO PILOT [underlined]
[underlined] Sperrys rule of Preccession [sic] [/underlined]
This is used to determine the direction in which a gyroscope will process if a torque is applied to it as follows :- Transfer the torque from the ring to the rim of the rotor then carry it around 90o in the direction of the spin. A push at that point will indicate the direction of the preccess [sic]. Two things govern the rate of the preccession [sic]. [cirlcled 1] The strength of the torque which if increased will increase the rate of preccessions [sic] [circled 2] The rotor speed which if decreased will result in an increase rate
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of preccession [sic]
[underlined] Space Gyro [/underlined]
Maintains its axis of spin relative to space always pointing towards the same fixed star.
[underlined] Earth Gyro [/underlined] This gyroscope preccesses [sic] at the same rate as the earth’s rotation and
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therefore maintains its axis of spin relative to earth.
[underlined] Directional Gyro [/underlined]
[underlined] Purpose :- [/underlined] To indicate to the pilot the course of a/c in[one decipherable word]. It is independent of acceleration error and northly [sic] turning error, to which the magnetic compass is subjected.
[underlined] Description :- [/underlined] Consists essentially of a control free gyro, having its axis of spin horizontal. The outer ring is pivotted [sic] about a vertical axis, and is used to carry a compass card, marked off in degrees and read in relation to the lubber line on the front of the case. A union at the rear of the case is connected to the suction system 31/2” H G. giving a rotor speed of 10,000 R.P.M.) Air passes into the case through a filter at the bottom and thence through the outer ring to two parallel jets impinging on the rotor. A caging knot on the front of the case is used [circled 1] To work
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the gyro for take off and landing [circled 2] To set the compass card coincident with magnetic compass [circled 3] To work the gyro when manoeuvres outside the 60o limit of climbs, dives, and rolls are executed.
[underlined] Installation [/underlined] Mounted on the B.F.P it has four alternative unions for connection to the suction system. These connections are made by means of an olive and nut, and special pieces of tubing to a distributor on the panel. For lengths up to twelve feet 3/8’ O.D. tubing is used, lengths 12’-25’ 7/16” O.D. tubing is required. A test flight is necessary after installation.
[underlined] Maintenance [/underlined] - [underlined] D.J. [/underlined] [indecipherable letters] check caging device and leave caged.
[underlined] 30 & 30* Inspection [/underlined] Clean filter by removing gauge discs. Clean discs in petrol and renew tissue part.
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[underlined] ARTIFICIAL HORIZON [/underlined]
[underlined] Purpose [/underlined] - to indicate to the pilot the altitude of the A/c in pitch and roll in relation to the horizon, also when night flying or conditions in which the true horizon is not visible.
[underlined] Description [/underlined] consists of a gravity controlled earth gyro having its axis of spin vertical and enclosed in a case pivotted [sic] [one unknown word], and which form the inner most ring. The horizon bar is pivotted [sic] at the rear of the outer [inserted] ring [/inserted] and engages with a pin on the inner ring, moving in a curved slot in the outer ring. This bar indicates the pitch altitude of the a/c in relation to a model a/c attached to the case. A curved dome is secured to the outer ring, a small extension of it in the form of a pointer registering against a scale of 90o - 0o – 90o on the case, thus indicating the Bank angle of the a/c. In a bank or roll the gyro and horizon bar maintain their position,
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while the case and model a/c move with the a/c. The rotor is spun by similar means to the D.G. air entering through a filter at the rear of the case. The preccession [sic] housing forms an erecting device to maintain the axis of spin vertical and thus ensure that the inner ring conforms to the curvature of the earth.
[underlined] Installation [/underlined] Exactly the same as for the D.G. After installation, the locking screw must be removed, and the blanking screw and washer put in its place. It is found in a canvas bag on the instrument. The locking screw must be re-inserted in the instrument on packing the instrument for transit.
[underlined] Maintenance. D.I.[/underlined] [set of initials]
[underlined] 1st 2nd Minor [/underlined – D, I and clean filter as for D.G.
[page break]
[Diagram of Artificial Horizon]
[page break]
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[underlined] SPERRY GYRO PILOT [underlined]
[underlined] Purpose [/underlined] To maintain a/c on true course, level fore and aft and laterally.
To increase the accuracy of bombing and aerial photography, and to increase the safety factor when flying in poor conditions.
To relieve pilot of strain and stress on long flights.
The Sperry Gyro Pilot employs a modified version of the sperry D.G. and Artificial Horizon as the control units Both units are housed in a mounting unit fitted in front of the Pilot where the B.F.P. is usually placed. The D.G. unit controls ‘course’ and rudders, while the Bank and Climb unit controls ‘pitch’ and elevators and ‘roll’ actions.
[underlined[ Method of Establishing Control [underlined]
Attached to the respective rings of the gyro are ‘D’ shaped knife edges. Placed adjacent to the knife edges and attached to the units are the pick off tubes, so arranged that the slots in the pick offs
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are half covered by the knife edged discs. The two components detect movement of the a/c relative to the gyro. The pick offs are connected to each side of an air relay on the mounting unit, and flow of air passes through the air relay unit into the units via the pick offs. The diaphram [sic] of the air relay is connected by a spindle to the piston of the B.O.V. toward air relay transmits control. The B.O.V. transmits oil pressure down to the servo motors which are the means of operating the a/c control.
[underlined] Action [/underlined] When the a/c is disturbed the gyro and knife edge discs maintain their position but the pick offs moving with the a/c pass over the knife edge discs. This unbalances the pressure in the air relay, therefore the diaphragm will move, this in turn will move the piston of the B.O.V. Thus oil is allowed to flow down to one side of the servo motor and the building
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up of pressure causes the piston of the servo motor to move, control is then applied to check the disturbance. In order to limit the control to an amount proportional to the disturbance the pick offs are geared and connected by a follow up cable to the servo-motor which centralise the pick offs to the knife edge discs.
[underlined] Bank and Climb Unit [/underlined]
Consists of a gravity controlled earth gyroscope having its axis of spin vertical. The inner ring is pivotted [sic][one indecipherable word] and controls the elevator. A vertical bale ring is also pivotted [sic] [one indecipherable word] in the case and moves identically with the inner ring. It serves to detect movement of the aircraft in pitch and has mounted at the right hand [one indecipherable word] pivot a baffle plate and knife edge disc, while the elevator pick off is attached to the unit. Also attached to the bale ring is the
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model aircraft, which in relation to the longer bar indicates the pitch altitude of the aircraft. The outer ring is pivotted [sic] fore and aft and controls the a/c totally [one indecipherable word in brackets]. The baffle plate and knife edge discs are attached to the rear pivot of the outer ring, with the pick off at the rear of the case. Rolling is indicated on the dial by movement of the model a/c in relation to the longer bar on the outer ring. Follow up is arranged by gearing the pick offs to the p/up pulley on the mounting unit, which is connected to the servo motors by cable. The follow up [one decipherable word] indicate the relative position of pick offs and knife edged plate. A [one decipherable word] gauge is fitted on the front of the unit (range 0.8 HG) also fitted are elevator and [one indecipherable word] control knobs. Level flight control knob and caging knob. At the rear of the unit are Grommet connections to the air – relays, main suction and electrical circuit
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A large filter at the base allows air into the unit there are also two spring loaded follow up clutches which contact the follow up pulleys in the mounting unit.
[underlined] Pesso Suction Relief Valve [/underlined]
[underlined] Purpose [/underlined] Is the means to adjusting the suction in the system.
1. Prevents excessive operation of the Sperry Relief Valve.
2. To protect the air system pipe lines and fittings against excessive suction . It is always fitted close to the Pesco Pump, where the suction is a maximum, approx 7”H.G. It should be used for course adjustment, which is effected by releasing the lock nut and turning the adjusting screw anti-clockwise to increase. The filter cap should be removed to enable the filter to be cleaned with petrol (filter cleaned on the 1st & 2nd minor inspection)
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[underlined] Directional Gyro Unit. [/underlined]
This unit embodies a free gyro having its axis of spin horizontal. The outer ring is pivotted [sic] vertically and controls the rudder. The knife edge plate is attached to the top pivot of the outer ring while the pick off is on the top of the unit. The directional compass card is also attached to the outer ring being used in relation to a lubber line on the case. The follow up index card is attached to the pick offs and is placed above the compass card, and indicates to the pilot the relative position of pick offs and knife edge plates. [one indecipherable word] wander is not compensated for and gyro is reset every 15 mins. A deliberate course change knob and crass level indicator are fitted in the front of the case, the latter consisting of a curved glass tube, alcohol filled and containing a steel ball. At the back of the unit are to be found the spring – loaded F/U discs electrical,
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connect, grommet connections to the air relay and main suction. The unit is secured to the mounting unit by two bolts.
[underlined] Sperry Suction Relief Valve [/underlined]
To enable a fine asyustment [sic] to be made for the suction in the system and allows for difference of suction between the two extreme ends of the suction pipe line. It is bolted to either end of the mounting unit in one of six alternative positions. The four unions are marked P for pressure, H for Bank & Climb Unit. G for directional gyro and T for Turn and Bank Indio [sic] when fitted. To adjust the suction remove the cap and turn adjusting screw clockwise to increase suction and tighten up the locking nut.
[underlined] Check Valve [/underlined]
This is fitted in the suction pipe line to protect the gyro unit against back pressure of air in the system should the Pesco Pump reverse its direction of rotation
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[Diagram of Balanced Oil Valve]
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[underlined] Air Relay Valve [/underlined]
[underlined] Purpose [/underlined] To transmit the control from the gyro to the B.O.V.
[underlined] Description [/underlined] Consists of two alloys castings bolted together and having a rendered skin diaphragm between them. The diaphragm by two metal discs and has a spindle attached to the centre which connects with the B.O.V. System. Air is drawn in through a filter at each side and then passes to the pick off in the unit. Normally the slots are half covered and the pressures in the air relay are equal. If the aircraft is disturbed then the movement of the pick offs over the knife edged plate causes the pressures to be unbalanced in the air relay. The diaphragm is deflected and causes a movement of the B.O.V. piston which allows oil to flow to one side of the servo motor. To test the A.R.V. hold it horizontal with the spindle upper most then with the [one indecipherable word]
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lightly push the spindle up release and it should fall back to its original position.
[underlined] The Oil System [/underlined]
[underlined] The Sump [/underlined]
To supply the system with oil and to collect drainage oil from the system.
Is simply a narrow container having a number of unions, filter plug, drain plug and an inspection window. Normally in most a/c a sump will be fitted which supplies oil for the operation of the hydraulic system and in this case the Sperry system may be connected to the same sump. Where such a system does not exist, the Sperry sump must be fitted below the level of the mounting unit in order to provide gravity drainage into the sump. It should be maintained 3/4 full in the daily inspection.
[underlined] The Pump [/underlined]
To provide a note of flow of oil
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throughout the system.
[underlined] Description [/underlined] Consists of an alloy casing having a phaspho [sic] bronze lining in which are two gears meshing with each other. One gear is an idler gear the other is connected to the engine crank shaft. The inlet union is the side of the pump, where the gears move away from each other. The oil is drawn in at this point and carried round by the gears and forced out at the outlet union, 180o opposite. The unions are not inter-changeable to do so would affect the lubrication system of the pump. Care must be taken therefore to ensure that the rotation of the pump coincides with the direction of the engine, to the effect there is an arrow on the back of the casing. A drain plug at the rear allows drainage of engine oil which has leaked along the driving shaft.
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[underlined] Oil Pressure Regulator [/underlined]
[underlined] Purpose [/underlined] To regulate the pressure in the system to within + or – 10lbs □” of the working pressure.
[underlined] Description [/underlined] Consists of an alloy casting having three unions leading to the pump gyro pilot and sump. Down the centre of the regulator is a hollow spring loaded plunger which covers the outlet to the pump. As the outlet to the gyro pilot is smaller than the inlet union pressure is built up when at a predetermined figure, lifts the plunger off its sitting and allows excess oil back to the pump. A channel is cut from behind the plunger to a by pass connection in the casting, whose entrance is covered by a spring loaded ball valve. This channel allows oil which has leaked passed the plunger to return into the sump outlet and thus prevents build up of pressure inside the plunger. To prevent leakage of oil passed the adjusting screw a gland consisting of
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two dural [sic]washers and asbestos yarn soaked in tallow and graphite is placed around the spindle and kept in place by a gland nut. To increase the pressure the adjusting screw should be turned clockwise.
[underlined] Oil Filter [/underlined]
[underlined] Purpose [/underlined] To ensure that the oil is clean before passing to the B.O.V.
[underlined] Description [/underlined] Consists of an alloy casting having a filter element (old type maltese [sic]cross new type wire mesh) mounted on a spindle each staggered 1/8th of a turn, this forms a number of spaces thro’ which the oil can pass. The collar securing the filter has eight bolts through which the oil passes through before going out the outlet union. The casting should be mounted with the unions at the top so that dirt which has collected in the chamber comes out when the filter is removed for cleaning on a 1st & 2nd minor inspection.
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[underlined] Two Way Back [/underlined] This is fitted between the oil filter and the mounting unit and provides a means of by-passing the oil back to the sump when carrying out any repairs or inspections in the mounting unit side of the circuit where air might enter the system. Also to enable the pilot either direct or by remote control to by pass oil back to the sump, in case of leaked of oil during flight.
[underlined] Mounting Unit [/underlined] Consists of a frame supported on the four ‘load’ type. A V.M in the cockpit in place of the B.T.P. The two units slide into this cradle and are secured by two bolts. Attached to the unit are three air relays, 3 B.O.V’s electrical connections, main suction connection drain and pressure manifolds. At one end is placed the Sperry Relief Valve and all pipe lines leading from the B.O.V.’s and mounting unit must be flexible hose.
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[underlined] Balanced Oil Valve [/underlined]
[underlined] Purpose [/underlined] To transmit oil pressure to the servo motors in order to apply control.
[underlined] Description [/underlined] The valve is operated by the air relay to which the piston is attached. The valve consists of a six load piston moving inside a valve casing on the mounting unit, and has an inlet union connected to the servo motors. In addition an exhaust union leads away the exhaust oil from the side of the servo motor opposite the side under pressure, to the sump via the speed control valve and a drain union leads away oil which has leaked over the lands of the piston back to the sump on the drain manifold. The piston is spring loaded in order to assist centralisation of the air relay and to avoid all end play on the B.O.V. piston.
[underlined] Assembly of Piston [/underlined] On to the piston fit,
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a collar, spring and second collar, ensuring that the collar of the washer engages the spring. Then fit on the small bush and the sleeve and onto the end screw the clamp. Adjust by the clamp unfit the assembly is held securely without any tension on the spring, then lock the clamp from the opposite end of the piston, fit on the large bush, screwing it on to the small bush until the two collars and spring are held between the two bushes without tension of the spring, then tighten lock nut on the small bush. There must be no compression of the spring and no end play in the assembly otherwise lagging and restricted movement of the control surfaces or oscillation of the control surfaces will occur.
[underlined] Centralisation of Piston [/underlined] Screw the piston assembly right into the casting and after starting the engines put engaging lever on and the servo motor will move over its
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full travel. Unscrew the piston assembly until servo-motor just starts to move mark datiums [sic] on casting and screws. Screw piston assembly in again until servomotor just starts to move in opposite direction. Mark a second datium [sic] on the casting coincident with datium [sic] already on screw. Mark central position between the two datiums [sic] and unscrew piston assembly until datiums [sic] on screw and casting are coincident. The lock nut should then be tightened up with a ‘C’ spanner.
[underlined] Servo Motor [/underlined]
[underlined] Purpose [/underlined] To operate the control surfaces and follow up system.
[underlined] Description [/underlined] The three servo-motors are set in one block but each is a self-contained unit. They consists of a cylinder in which the pistons are a loose fit, compression being obtained by an assembly consisting of two cup shaped washers
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(leather), supported by the metal washers and held in position on the central sleeve by two nuts which should be drilled through and secured by two tapered pins. To make the cylinders oil tight, a gland is provided at each end consisting of dural [sic] and metal washers, held in place by a spring in the gland nut. So that manual control is possible, a by pass channel has been cut between the two ends of the servo cylinders and in the centre of this a simple on and off switch, connected to the engaging lever in the cockpit. With the lever on the sides of the servo motor are isolated from each other and movement of the B.O.V causes servo-action. With the lever off any movement of the manual controls causes the oil to flow around the by-pass. Incorporated in each is a relief or override valve which enables the pilot to regain manual control in an emergency
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without using the engaging lever to disengage the auto control. These valves are spring controlled to lift at 25lbs □ “ above the normal working pressure of 150lbs □ “. For installations with pressure above 150lbs □ “ the valve is screwed in fully until the spring is fully compressed.
[underlined] Testing Override Valves [/underlined]
1. Connect two direct-type pressure gauges to the manifold block or servo motor union.
2. Start up a/c engine and put engaging lever on.
3 .Apply manuel [sic] control until gauge reads 25lbs □ “ above working pressure, when the valve concerned should blow off.
4. Repeat by testing in the opposite direction adjusting by the grub screws if neccessary [sic].
[underlined] Manifold Block [/underlined] This is fitted close to the mounting unit and has two purposes.
1. It forms a junction between the flexible
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base from the B.O.V. and the ridged metal pipes from the servo motors.
2. By tapping in the two pressure gauges at the side unions access is obtained to each servo motor pipe line for testing the override valve. This gauge indicates to the pilot the working pressure of the system. It is of the direct Bourdon Tube type and is connected into the main supply line at the pressure manifold, bung inserted on a small panel on the mounting unit.
[underlined] Drain Trap [/underlined]
[underlined] Purpose [/underlined] to provide gravity drainage from the drain manifold when the mounting unit is below the level of the sump and to prevent air being drawn into the system.
[underlined] Description [/underlined] It consists of a copper float carrying a needle valve which is normally kept closed by a spring bearing down on the top of the flow. Two ounces of oil always remain in the trap, [one indecipherable word]
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when this quantity has increased by the flow of oil by the drip tray and manifold the float is raised and the valve opened. This allows oil to flow back to the sump, the float falling and the valve closing as the oil drains off. As the valve closes before all the oil is drawn off, air cannot be drawn into the system. The drain trap should always be fitted below the level of the drain manifold but not more than 5ft below the level of the pump. The outlet union at the base is connected to the sump pipe-line.
[underlined] Non Return Valve [/underlined]
This is fitted in the return pipe line from the drain trap to the pump. It’s purpose is to prevent any Blow back of oil into the drain trap should the pump reverse due to engine back fire. This will only happen if there is sufficient oil in the trap to lift the float at the time of the blow back.
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[Diagram of Servo Motor]
[underlined] Speed Control Valve [underlined]
[underlined] Purpose [/underlined] To provide the pilot with a variable rate of control depending upon varying weather conditions and different types of a/c. The same rate of control is obtained irrespective of the working pressure.
[underlined] Description [/underlined] Consist of an alloy casting having three inlet unions connected to the exhausts of the B.O.V.’s and one outlet union connected to the sump. The valve screws into the casting and terminates into a slotted shank which regulates the flow
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of oil to the sump. Behind the shank is a spring loaded plunger the land of which covers and uncovers the inlet from the B.O.Vs and thus allows oil to pass through the valve. Should the pressure build up in the system, the plunger is forced back and the land blanks off the inlet union, thus stopping the flow of oil except for a small quantity allowed to flow over the two dampers on the land. Thus prevents stoppage of the control. The dual setting 0-6, indicates the amount by which the valve is open. The return channels permit drainage oil to return into the sump outlet and a gland of leather and dural washers prevents leakage of oil passed the adjusting spindle. On a D.I. the valves should be set to the figure laid down of if unknown to 3 & 4. They are fitted below the mounting unit.
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[underlined] Daily Inspection [/underlined]
1. Check oil level in sump – 3 /4 full.
2. Check for air in servo motors as follows :- set a/c controls central and put engaging lever [underlined] on [/underlined]. Apply light pressure to controls each way and they should act as though locked. If there is any servo action it will be accompanied with movement of F/U indices and there is air in the servo motors which [underlined] must [/underlined] be removed during the engine run up.
But the engaging lever “off” and start up engine. Move each control to the extremity of its travel, holding it for 30 secs at each end to allow oil to wash the air along the pipelines to the sump. Repeat the operation with control in the opposite direction. In the initial check do not confuse springiness of the control with the resilient action of air in the servo.
3. Check the vacuum it should 3 HG
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at 1000 REM and 5” HG at maximum ground [one indecipherable word].
4. Check oil pressure, it should be ± 10lbs per □” of working pressure.
5. Uncage Bank and Climb Unit – if a/c not level the gyro should slowly move towards an indication of the a/c’s altitude.
6. Set and uncage Directional Gyro to coincide with the compass card.
7. Open Speed Control Valve to the figure laid down.
8. Using the control knobs set the F/U indices to match the gyro indications.
9. Set level Flight Control knob to “Off”.
10. Engage gyro pilot “O”. Test operation by moving Control knobs and noting that controls move in the correct direction at approx equal speed way and do not oscillate or hunt, but come to rest immediately. It is possible the elevators will move faster down then up owing
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to the state of balance.
11. Disengage Gyro Pilot.
[underlined] 1st Minor Inspection [/underlined]
1. Inspect all piping and fittings including flexible. Tighten and replace all pipe and oil fittings where necessary to stop leaks. Replace any flexible hose showing signs of seepage at joints or connections or pimples on the surface. Tighten the servo motor packing glands if leakage is observed.
2. Inspect all cables all connections and pulleys should be free and no sign of fraying should be visible.
3. Check follow up pulleys on mounting unit with both units removed. If necessary add a few drops of anti freezing oil to the F/U springs.
[underlined] 2nd Minor Inspection [/underlined]
1. Clean or change all filters.
2. Drain, rinse out and refill sump.
3. Inspect all the AVMs on the mounting
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unit for deterioration of rubber – replace if necessary.
4. Check override valves for blow-off pressure.
[underlined] Filters [/underlined]
[Description of Air and Oil Filters]
Oil Sump
[underlined] Follow Up [/underlined]
[underlined] Purpose [/underlined] To limit the amount of control so that it is proportional to the amount as the aircraft assumes its original position.
[underlined] Description [/underlined]
When the aircraft a disturbance the action between the pick-offs and
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cut off discs causes servo action in which the piston would move through its full range and apply full control irrespective of the amount of the disturbance. In order to limit the servo motor action it is necessary to return pick off central with the cut off disc. This is done by mounting the pick off on a quadrant which is geared through a differential and clutch drive to a F/U pulley on the mounting unit which is connected by cable to one end of the servo-motor piston. Hence when the servo-motor moves the quadrant causes the pick-off to centralise over the cut-off thus limiting the flow of oil to the servo-action and the amount of control applied.
[underlined] Installation of Follow-Up Cable [/underlined]
Fit the follow-up pulley on to the axle of the serrated disc taking care that the clutch pin engages and that
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change by 9-11o – repeat to [underlined] West [/underlined] and note change of readings.
9. Repeat above holding knob on pilot’s repeates [sic] – there should be no change in readings.
10. [underlined] Switch-off [/underlined[]
[underlined] SYNCHRONISING REPEATERS [/underlined]
1. As for starting.
2. Set V.S.C. to zero.
3. Set repeaters as near as possible to M.U. readings plus “A” error (note repeaters can only move in 3o movements.
4. Adjust V.S.C. to final readings of repeaters.
5. Loosen the two screws holding scale and set rubber line to zero – tighten screws and [underlined] switch-off [/underlined].
7. [underlined] Switch-off [/underlined].
[underlined] FUNCTIONING TEST [/underlined]
1 .As for starting.
2. [Indecipherable sentence.]
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[Blank page]
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[underlined] DIRECT READING COMPASS [/underlined]
[underlined] Starting [/underlined] “On and off” switch to [underlined] “On” [/underlined]
Normal Setting Switch to [underlined] Setting [/underlined]
[underlined] Allow to run for 5 mins [/underlined] (until M.U. has a comparative steady reading)
Normal setting switch to [underlined] Normal [/underlined]
System should be then ready for use.
[underlined] DAILY INSPECTION [/underlined]
1 .As for starting
2. Set V.S.C to Zero
3. Check repeaters – should be synchronised with M.U. – i.e. should be M.U. reading plus “A” error
4. Check the “hunt” on M.U. scale - i.e. should be between 1/8 and 3/4 of a degree.
5. Switch to [underlined] “setting” [/underlined] – tilt M.U. to [underlined] East [/underlined] – readings should increase – repeat to the West – readings should decrease.
6. Set for local variations on V.S.C. if required.
7. [underlined] Switch-off [/underlined]
[underlined] FUNCTIONING TEST [ /underlined]
1. As for starting.
2. [Indecipherable sentence]
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3. Switch to [underlined] “setting” [/underlined] – M.U. should then “hunt” between 3-8 degrees.
4. Switch to [underlined] “normal” [/underlined] - note M.U. reading – tilt M.U. to [underlined] East [/underlined] until scale has changed by 5o – return to vertical – after 2 minutes rate reading – repeat to [underlined] west [/underlined] – difference between final readings should not differ by more than 2o (Angle of Dep.)
5. Switch to [underlined] “setting” [/underlined] – tilt M.U. to East to limit of its travel until reading changes by 40o – switch to [underlined] “normal” [/underlined] and allow M.U. to return to vertical swinging to and fro time M.U. over the first 20o back to original heading – note M.U. reading and repeater readings should not differ by more than 1o.
6. Repeat to the [underlined] West [/underlined].
7. Time intervals of 5-6 should not differ by more than 3 mins and neither should take more than 7 min to return.
8. Set V.S.C to zero – note repeater reading, set V.S.C. 10o East – repeaters should
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[underlined] Inspections [/underlined]
[underlined] Between Flights [/underlined]
1. Set Clutch Lever “IN”. Ensure correct engagement by full movement of control column.
2. Set Main Control back to “OUT” position.
3. Set steering Lever central.
4. Set Altitude Control to zero.
5. See Test Lock is locked at “Flying” position. [circled number 6] Check oil level in Resevoir [sic].
[underlined] Daily Inspection [/underlined]
[underlined] R.E Plate [/underlined]
Remove cover. De-centralise and test motor for freedom. Inner ring must not have excessive end play. Play of .005” is permissible on outer ring. Oil all moving parts with one drop of anti-freezing oil. Check cork washer for deterioration. Examine all Bawden Cables – ensuring that they do not foul when the plate is rotated. Remove any surplus oil from the cover and replace. When re-centralising, there should not be any [one indecipherable word] in gimbal system.
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[underlined] Aitenon Plate [/underlined]
Remove cover and centralise cap. Fit centralise clip and decentralise. Test motor for freedom. Both rings should be free and without play. All weights must be secure. Apply one drop of anti-freezing oil to each moving part. Remove centraliser clip ensuring that the centralises lock the system. Remove surplus oil from cover and replace.
[underlined] Compressor [/underlined]
Examine for leaks and security of pipes. Ensure unions are locked.
[underlined] Oil Cooler [/underlined] [underlined] Automatic Valve [/underlined]
Test for security Examine for security.
[underlined] Oil Reservoir [/underlined]
Check level of oil top up if necessary. Check security of all unions! If Mk V lock tops on gauge.
[underlined] Chemical Air Drier [/underlined]
Change as necessary, but just before a flight.
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[underlined] Main Control Lock [/underlined]
Test for freedom of movement and leave in OUT position.
[underlined] Automatic Test Lock [/underlined]
Leave Mk IV locked in FLYING position. MkIV ensure that BakeliteBlanking cap is fitted Test for security and visable [sic] defects.
[underlined] Air Intake Throttle [/underlined]
Examine for security and visible defects.
[underlined] Steering Lever & Steering Control [/underlined]
Test for freedom and leave in central position.
[underlined] Pitch Altitude Control [/underlined]
Test for functioning and leave in zero position.
[underlined] Pressure Gauge [/underlined]
V.D. & B.
[underlined] Turn Regulator [/underlined]
Remove cover, test [one indecipherable word] for freedom and [two inserted words] on valve [/inserted] with one drop if necessary. Make the contact switch and decentralise the gimbal system. Ensure correct operation
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[underlined] Servo Motors [/underlined]
Test for freedom of movement by movement of control column. Check for security and visible defects.
[underlined] Clutches [/underlined]
Set to IN, ensuring that they are correctly engaged, set to Out and make sure of clearance (on clutch tongues) at 40/1000. Leave at IN.
[underlined] [one indecipherable word] Inspection [/underlined]
[circled 1] Clean all main filters with petrol and watchmakers brush.
[circled 2] Apply one drop of oil to pitch altitude control.
[circled 3] Test clearance on clutch tongues should be 50/1000.
[circled 4] Flush out automatic valve, oil cooler and oil pipe lines.
[circled 5] Flush all main valves with 40% anti-freezing oil and 60% petrol. Connect rubber tubing to inlet and with valve central force solution through also with controls at other two extremes



George Bubb, “Instrument course notebook,” IBCC Digital Archive, accessed April 20, 2021,

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