Peter Webb's Engineering Notes



Peter Webb's Engineering Notes


A notebook used by Peter Webb to record lecture notes regarding engine systems, instruments and electrics.




40 page book with handwritten notes


This content is available under a CC BY-NC 4.0 International license (Creative Commons Attribution-NonCommercial 4.0). It has been published ‘as is’ and may contain inaccuracies or culturally inappropriate references that do not necessarily reflect the official policy or position of the University of Lincoln or the International Bomber Command Centre. For more information, visit and




[front cover Blank]

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Normal Flight :- 80lbs sq” at 70 ° C R.P.M. above 2,000
Min :- 70 “ “ “ “ “ “ “ “ “
Carburettor :- Claudel Hobson A.I.I. 132 M.C.
Ignition :- Double mags Rotax N.S.T. 14/1
B.T.H. C2 – 14/8
Simms F.S.T. 14/1
Firing order :- 1, 10, 5, 14, 9, 4, 13, 8, 3, 12, 7, 2, 11, 11, 6
Max : Perm : Cyl : Temperature :-
T.O.B. 230 ° C ab start
Climbing * 270 °C for 30 mins
Cruising * 270 °C
Emergency * 280 ° C
*Allowance of 20 °C for climatic conditions

To overcome the different angles of Cam rods the rods on the mags are set at different intervals.
The A.T.D.* is fully advanced at 800 R.P.M. giving a mag advance at 26°BTDC
Take off 14 °BTDC
Normal 16 ° “
Cruising Boost 19 ° BTDC
The ignition must be gradually retarded as boost increases as the pressure in the combustion grows so if the spark or mag was not retarded a backfire would be the outcome.
This is retarded by means of a spiral gear connected to the throttle lever.
The ATD* is worked of the Centrifugal force basis.
[small drawing]
[page break]
When retarding the mag the centrifugal force falls of a the spring loaded weights automatically retards.

Static & dynamic balance is used on the crank assembly to smooth out the vibration. (Saloman Damper)
Pistons must also be of the same weights.
Nos 4 & 11 cylinder house the Master Rods and the pistons are fitted with the special rings to assist in the lubrication.
The sleeves are of cast steel except the Master Sleeves which are forged.
[two drawings showing the sleeve ports relationship to the piston & cylinder on Induction and compression strokes]
[page break]
[blank page]
[page break]
Hercules VI
Front web is split & held by 2 Maniton bolts.
Rear web is split & held by 1 Maniton bolt.
The front web is held by two bolts because of the excessive load that is transmitted through it to the prop.
The rear webs are detachable and are “Nip” fitted with a 5 thou nip. The Maniton bolt itself stretches 12 thou.
The web is open by a special jack.
[page break]
[blank page]
Crankcase Vents & Supercharger vents.
Crankcase Vent is situated in the front cover & vents to atmosphere the Crank Case, Front Cover & Reduction Gear Cover. A gauze screened recess in the wall of the Reduction Gear Cover is connected to atmosphere by two external pipes. These are taken to a position where a pressure is always positive.
Front Supercharger Bearing.
A chamber is formed between Crankcase & Volute Casing in which is situated the front bearing. The vent is situated in the top chamber to atmosphere. A plug is fitted in the bottom to allow the oil to be drained after different periods set down in Station Routine Orders.
[page break]
Rear Supercharger Bearing
[?] the rear bearing & clutch housing. The vent is situated over the S/C 2 Speed Change over Valve. If the eye of the impellor was not vented the oil would enter the induction system instead of lubricating the bearing.
Rear Cover Vent
Is lead by a pipe to the hydraulic separator.
The fixed and driving bevel wheels of the reduction gear are conical sealed & self aligning. The thrust race in the Bevel Pinion is held down by a short nut & locked by a tab washer.
The sleeve drive shafts are driven off the crankshaft by a splined spur gear via 7 intermediate gears which in turn drive 2 gears on one shaft which drive front and rear sleeve drive shafts.
C.S.U. oil first travel to the end of the top of the reduction gear cover by an oil duct, it then enters the fixed bevel drive, into the “U” tube & then the crankshaft into the prop.
[page break]
[two drawings of Hercules VI 2 speed unit]
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[drawing of Pesco fuel pump]
[page break]
[drawing of AMAL fuel regulator]
To maintain a constant pressure of 2½lbs sq “ at all throttle openings, altitude & attitudes of the a/c. the fuel delivered wil be 3 gals per min.
The fuel enters the valve through drillings, through the valve and onto the carb. Should the pressure build up over the 2½ lbs sq “ it will close the valve & decrease it. As it drops below the set pressure the spring & atmosphere that is led into a chamber that is below the neoprene diaphragm will automatically open the valve bringing the pressure back to the pre-determined level.
The regulator itself is as near as possible to the carb & should not be more than 12 ins away. If it was any distance away the centrifugal force acting on the fuel while the a/c was doing acrobats would not give a constant pressure.
[page break]
[drawing of valve]
1 Maintain a steady oil temperature by controlling the oil through the cooler.
2 Prevent damage to the cooler.
3 Facilitate quick warm up.
On starting up oil trapped in the bellows chamber is cold and viscous & this cannot pass through the friction tubes thus assisting the 10 lb sq “ spring to keep the control valve on it’s seat. Pressure built up by the incoming oil lifts the 30 lbs sq “ relief valve and bypasses the oil to the tank.
As the oil gets warmer heat is transferred to the oil in the bellows chamber & this is able to pass through the friction tubes thus relieving the pressure in the control valve. Thus the control valve gradually opens & bye pass valve closes.
Both valves are open when the engine is running.
Relief valve.
The 40 lbs sq “ relief valve comes into operation when the pressure of over 40 lbs sq “ is built up in the carb heater spindle and the 80 lbs sq “ or over is built up by the carb heater jacket.
To overcome the sluggishness of the oil when starting up. The oil will be less viscous at this stage when diluted.
Dilution takes place after flying if the plane is not going up for 6 hours.
The engine is stopped & the oil allowed to cool off. When it is down to 40 °C or below the engine is then started up & with it at 1000 revs, the Oil dilution button is pressed. The button is kept pressed for two minutes & upon the weather conditions. The engine must be stopped before the dilution button is released to ensure the system is well diluted.
Should the aircraft be laid up & the effects of the dilution nullified owing to the length of time or by a mistake, oil dilution takes place by loading hot oil into the system from an external source. After this takes place the engine dilution can be brought in after the oil temp. reaches 20 °C.
No plane is taken up with diluted oil & the oil temp itself will not build to its correct temp.
[page break]
Working Principle.
When oil dilution takes place the current is switched on & a solenoid is magnetized. This solenoid is out of centre so it will centralise itself when energised & allow fuel to pass into a chamber down the piston to enter the oil.
[page break]
[blank page]
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[drawing of carburettor controls for Hobson A.I.I. 132]
The throttle lay shaft is moveable through a total of 80°
SR – CB 0° - 51° throttle opening.
CB – RB 51° - 67° throttle opening.
RB – 70B 67° - 80° throttle opening.
Interconnection between the throttle & mixture control is provided in the Pilots cockpit so that the weak mixture control can only be brought into action between 10° - 51° throttle layshaft operation.
The butterfly throttles & spindle are hollow to allow the oil from the scavenge pump to circulate oil around the butterfly & chokes. A relief valve at the starboard end of the butterfly spindle bypasses the oil to the main carb jacket to the outlet. If the oil pressure rises above 30 lbs sq “ due to the high viscosity after cold oil in the scavenge system.
[page break]
[drawing of carburettor]
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The boost bias & minimum power stops, are set very carefully & should rarely need adjustment.
Jet sizes
Main. 4,200 to 4,600 ccs (in 100 ccs)
Slow running 800 ccs
Power 2,200 ccs
Power bleed
Corrected 300 or 400 ccs
Enrichment 500 ccs
Fuel level 13 to 15 mm below the flange joint at 2½ lbs sq “ fuel inlet pressure.
Choke diameter 105 mm.
Magneto Timing
Timing engine on erection.
1 Find true TDC using PPI timing disc & pointer
2 Set No 4 Master cyl on compression stroke
3 Move crankshaft against direction of rotation about 50° & then tap forward until 19° BTC [sic]
4 Connect & adjust linkage rod between carb & Bendix variable drive to retard 7° from its advance position. Set layshaft to C/B position.
5 Set contract breaker points to .009 to .01 “
6 Insulate Primary winding.
7 Clip ATD to fully advanced position.
8 Set leading brush on correct segment with points just breaking & engage mag to engine.
9 Check with lamp & battery at a 19° BTDC at CB is 14° BTDC at TOB & carb 26° BTDC at slow running.
[page break]
10 Remove clip from ATD & check timing is now 9° BTDC at cruising boost & 16° BTDC at slow running.
11 Tighten and split pin the serrated drive couplings, connect and lock the primary winding.
12 Secure mag to engine.
13 Fit contact breaker & distributor covers.
14 Connect starter and earth lead.
15 Time second magneto & synchronise with first magneto.
[page break]
Halifax U/C consists of twin Messier oleos mounted in a light alloy casting. The U/C is raised by engine driven pump pressure & lowered by accumulator pressure. The accumulator is mounted on the rear face of the front spar in the retraction bay.
In the “up” position the U/c is locked hydraulically & by means of a manually operated mechanical lock remotely controlled from the Rest bay.
In the “down “ position the U/C is locked with a (!) mechanical locking jack (2) Hydraulic Lock (3) Geometric Lock & an electrical solenoid lock prevents accidental selection of “up” position.
[drawing of Messier Shock Absorber]
[page break]
[drawing of Halifax fuselage layout]
Filling of Messier S/A Strut
To fill the Messier S/A Strut the weight off the a/c to be on the leg.
(1) connect to the charging valve. Pump in oil DTD 388 until a definite resistance is felt. When this occurs, cease pumping oil & inflate with air until leg extends approx 2 ins. Allow leg to stand for a short period in order that the oil emulsion may subside.
With pump disconnected open up charging valve & allow leg to collapse. On completion of collapsing, movement should be accompanied by an oily mist from the charging valve. If only air escapes insufficient oil is indicated. When the correct oil level has been obtained the leg should be inflated with air until the extension is 4.5 in +/- .2 in.
[drawing of Messier internal mechanical locking jack]
[page break]
[drawing of Halifax fuselage & wing showing sections]
Divided into four sections.
Front fuselage
Contains Bomb Aimer, Navigator, W/O, Pilots & F/E positions & carries the armour plated bulkhead.
Centre Section
Is built integral with centre section of Main plane. Extends a matter of 2 or 3 “ for & aft the spar of the Main Plane & is sometimes known as “The Covered Waggon”.
Rear fuselage
Extends from rear spar to position slightly aft of main entrance door & carries Mid Upper Turret, part of
[page break]
Bomb Bay & the Well.
Tail Bay
The Tail Bay carries the Rear Turret & Tails and retractable rear wheel.
Main Planes
Comprises of 5 sections. The Centre Section which is built into the Fuselage, contains leading edge, two no 2 tanks (ie Port & Stbd). It also contains 2 inboard engines and Retraction Bays.
Intermediate Section carry tanks 1,3 & 4 & in leading edges carry Double Oil tank.
Outboard Panel carry outboard engines, tanks 5 & 6 & in the port one the landing lamp will be found.
[page break]
Fuel System
The normal system comprises of 12 tanks fitted into the Main Planes & numbered Port & Starboard 1 – 6. No 6 tank has no cock & is connected directly to no 5 tank. Tanks 1,2, 3, 4, 5, have cocks operated from the Rest Position, by means of pulleys & cables. A main galley pipe line runs from Outboard engine to outboard engine & all tanks feed into the pipeline. It also feeds all 4 engines from behind the inboard line a tapping is taken for the main gallery pipe to which is connected a drain plug.
[drawing of fuel system]
Note. All tanks & pipes lines are self sealing with the exception of the pipelines of the Priming System.
[page break]
General rules for use Fuel System
1 No engine may be fed from more than one tank at a time.
2 All ways turn off tanks before turning on new ones.
3 All balance cocks must be turned off for take off, landing & whilst over target.
4 Fuel should be disposed of wisely with the object of ensuring that there will be no tank changes over the target area.
5 All tank changes will be carried out in collaboration with the Pilot.
6 Balance cocks may only be used with the “Skippers” express permission.
7 Fuel tank gauges must be switched off for Taxying, Take Off & Landing.
Fuel Emersion pumps are fitted in the Long Range Tanks only.
[page break]
Anti icing.
The leading edges of all the aerofoils are covered with a thin [?] layer of Kill Frost Paste. The props being treated with a special type which has been developed for its greater adhesive qualities which make it less susceptible to centrifugal force. The action of the paste is to exude a moisture with an extremely low freezing temperature. This moisture prevents the adhesion of ice. The Pilots windscreen & the Bomb Aimers clear vision panel are both treated with a spray of Anti freezing fluid (Glycol, Alcohol, distilled water) being supplied by two Rotax spring loaded pumps which draw their supply from a reservoir mounted immediately behind the Throttle Pedestal. The B/A pump is mounted on the starboard side of the junction of the fuselage & the Perspex nose.
Icing conditions
Occur between the temperature of +2 & -10C providing that the atmosphere contains sufficient moisture.
[drawing of Halifax front fuselage with anti icing system]
[page break]
Oxygen system consists of (19 bottles +2) 21 bottles. These bottles each contain 750 litres at a pressure of 1800 lbs sq “ & 15 of them are stowed beneath the F/E’s seat & 6 more immediately aft of the armour plate. The bottles are all interconnected by means of non return valves which isolate one if it is damaged.
[drawing of the Halifax oxygen system]
The oxygen supply gauge (right hand side of regulator) must read at least 7/8 full prior to take off. The left hand cock is adjustable & allows the left hand gauge to be set in any desired position including the position emergency, marked either E or 40 on the regulator. This emergency position causes the supply to be continuous & in excess of requirements instead of a series of puffs as in normal settings. One bottle without an economiser – one man 1¼ hrs at 20,000ft. with an economiser it will last him 2½ hrs plus increased endurance 100 percent.
[page break]
Above 20,000ft percentage increase in endurance is greater with corresponding drop below 20,000ft.
The a/c is also fitted with a number of portable bottles situated in various stations in the machine. The bottles contain sufficient oxygen to last approx. 10 minutes. They are fitted with a gauge showing contents as supply left in minutes. The bottle is also fitted with an aneroid type reduction valve.
An oxygen bottle should never be allowed to get empty as if it did so condensation would occur & it would become musty & the person who uses the bottle after it has been refilled is liable to be sick.
[page break]
Graviner (Fire extinguishers)
All a/c engines are fitted with Graviner type A automatic fire extinguishers. These bottles contain 6½ lbs of liquid metal [sic] bromide which vaporizes as soon as it is released. The remaining content of bottles being charged with nitrogen to a pressure of 60 lbs sq “. The bottle is fitted with a gravity valve to ensure that the contents are ejected by the nitrogen and not the nitrogen escaping into the atmosphere and leaving the metal [sic] bromide behind.
[drawing of fire bottle installation]
A/C is fitted with a number of portable fire extinguishers of which there are two types. The large type which is operated by striking the knob on the deck, & the smaller one is operated by unscrewing the large wing nut fitted at the top. A great advantage of the smaller type is that it may be turned off should the fire be extinguished before the bottle is empty.
Before using a bromide extinguisher inside
[page break]
it is essential that all air crew members are warned & that oxygen is turned up to emergency supply. After using the extinguisher in the fuselage all available hatches should be opened to ensure that the a/c is thoroughly ventilated.
[page break]
[drawing of Typical Block tube control, (Halifax III Rudder Control)]
Truing Controls
1 Jig the lever at the main control chassis.
2 With the adjustable control disconnected, set the rudder in line with the fin extension plate. Adjust control & reconnect.
3 Use adjuster behind F/E compartment to set servo motor neutral. Ie Datum mark on pulley to be in line with greaser nipple on body.
4 Use the adjuster in the F/E’s compartment to set squared rod evenly about the trimming tab control gear box.
5 Adjust on last adjustable control rod until rudder bar is neutral.
6 Adjust stop to ensure full range of movement.
[page break]
Trimming tab controls
For ease of remembering the reaction & action of trimming tab control, imagine the trimming tab to be attached to the tab control , directly & not indirectly. So that when the control wheel is rotated in a given direction the attached tab must obviously move in the same direction.
[drawing of trim tab system]
[page break]

Forms & Publications
Form 700
Is the day to day listing of the a/c over a period of limited time. In it is recorded the different signatures of the different trades who have participated in the Daily Inspection. The signature of the N.C.O. I/C Trades, refuelling logs, re-arming log, the change of serviceability certificate & pilots acceptance certificate (of a/c). If a/c is not flown the D/I may be waved for 6 days but must be carried out on the seventh regardless of any other consideration.
Daily Inspection
Makes the a/c serviceable for a period of 24 hrs unless:-
A A defect is discovered during the inspection.
B A defect is discovered [?] between flight inspection.
C Heavy landing & bumpy taxying causes damage to be suspected.
D Night flying is anticipated when complete or partial DI will be carried out at flight commanders discretion.
Between Flight Inspection
Certain items are inspected between flight & then is known as Between Flight Inspections.
No signature is recorded for B.F.I.
[page break]
Relevant Air Publications
[drawing showing Air Publication structure]
A.P. 1464
The R.A.F. Engineering Manual.
A.P. 1574
Aircraft Maintenance Regulations
A.P. 1086
Stores vocabulary
Form 700A
Is used should the aircraft be stationed temporarily away from it’s own station. It is a duplicate of the 700 into which is entered every detail when the kite returns a summary of the flying hours
[page break]
[blank page]
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Hydraulics & Pneumatics
[drawing of the pneumatic system]
[page break]
Pneumatic System
Heywood compressor. Supplys [sic] the system when the engines are running.
External charging valve. System is filled by this when engines are stopped.
Heywood regulator valve. To provide idling circuit, safety valve & N.R.V.
Oil & Water trap. Consists of a gauze filter. Drained every D.I.
Air bottles. Drained about every 200 hr inspection.
Air filter. Drys [sic] & cleans the air. Drain plug in the bottom.
Dual Relay valve. Adjusts the increase & decrease pressure in the differential units. Uneven pressure counter – acted by progressive rudder controls. Should the pressure be on when “Off” selected the Bowden cable will be too taut.
Brake Unit. If expansion tubes & segments are US, new sets must be installed. If only one segment is renewed a burst will be the outcome.
[sketch of brake segment & drum]
[drawing of control valve]
[page break]
[drawings of Heywood compressor and pressure regulator valve]
Oil from the compressor passes through the N.R.V. to the system & when it builds up to a pressure of approx. 240 lbs sq in it is felt in the aneroid chamber. This pressure begins to overcome the spring of the regulator & at about 300 lbs sq in the regulator is in operation & the N.R.V. is on its seals, shutting off the system. Should the regulator fail to operate the safety valve will operate at 360 lbs sq in.
[page break]
Position of components.
Heywood compressor. Port inner engine.
Ex charging valve. Just forward of the entrance, port side of fuselage. (Original) (Modified) Rear of port inner engine bulkhead.
Pressure regulator. (Original) beneath air bottles. (Modified) Rear of port inner engine bulkhead.
Oil & water trap. Rear of port inner engine bulkhead.
Air bottle. Behind F/E’s armour plating port side of fuselage.
Air filter. Above & slightly to the rear of the air bottle.
Hot & cold air control valve. Forward of front spar. Port side of fuselage.
Dual relay valve. Forward of rudder bar. Pilots floor.
Triple indicator. On second pilots dashboard.
[page break]
[drawings of principle of Messier hydraulics and a/c power circuit]
[page break]
[drawing of U/C and flap circuits]
[page break]
U/C circuit
If by any chance your accumulators are punctured, do not select down for your bomb doors & flaps as the pressure built up, (if a restriction is in the return line) will unlock the mechanical hydraulic locks giving you a reversed selection.
Flap circuits
The isolation cock is fitted to isolate the accumulator from the jacks in flight. Should the E.D.P. line be damaged & the accumulator not isolated the flaps will be extended too for by the accum. & would be impossible to get them back.
If the flaps are not retracted when in flight, the pressure on the flaps will cause the jacks to retract & a depression will be felt behind the jacks. This will cause the valve to come of its seat in the distributor and allow fluid from the return line to hold the jacks in position.
[drawing of bomb door circuit]
[page break]
[drawing of principle of l/lamp & rad shutter circuit]
[drawing of U/C door circuit]
[page break]
Position of components
1. Main & aux. tanks. Front spar – port retraction bay.
2. Vokes filter. Rear of port inner engine bulkhead.
3. E.D.P. Port inner engine.
4. Automatic cut out . Rear of port inner engine bulkhead.
5. Cut out acc. Rear of port inner engine bulkhead.
6. Gauge relay valve. Front face front spar, port side of fuselage.
7. Main gauge. Above front spar, port side of fuselage.
8. Normal hand pump. Front face of front spar, port side of fuselage.
9. Pressure limiting valve. “ “ “ “ “ “ “
10. Emergency tank. “ “ “ “ Starboard retraction bay.
11. Emergency hand pump. “ “ “ “ starboard side of fuselage.
12. U/C & U/C door acc. Rear face of front spar, port & stbd retraction bays.
13. Bomb door acc. Just rear of front spar, port side of fuselage.
14. Flap acc. Rear of rear spar, port & stbd side of fuselage.
15. Flap isolation cock. Rear face of rear spar, centre of fuselage.
16. Bomb door isol cock. Beneath bomb door accumulator.
17. B/door & u/c em. cocks. Front face of front spar, centre of fuselage.
18. B/door selection cock. Starboard corner of F/E compartment.
19. B/door & u/c & flap distributors. Front starboard corner of F/E compartment.
20. U/C & b/door lever. Stbd side of Pilots seat.
21. U/C indicator light. Pilots panel.
22. Flap indicator. “ “
23. Bomb door lights. 2nd “ “
24. U/C warning horn. Port side of cockpit.
25. Landing light distributor. Port side of throttle controls.
26. Rad. Shutter distributor. Starboard lower corner of F/E compartment.
[page break]
When topping up system ensure that the following are in their correct positions.
U/C down.
Flaps down.
B/doors open.
L/L down.
R/S closed.
Cut out accumulator (1850 lbs sq in)
The fluid should be allowed to just touch the underside of the filter.
To bleed system of air select flaps up, operate hand pump, slacken off joints at high points. Keep the tank topped up & when bleeding is finished test controls to check.
U/C doors
1. Deflate accumulators.
2. Disconnect jacks from door & retract.
3. Pump in an amount of fluid ( enough to fill jacks, pipe lines to jacks & clearance volume in accumulator.)
4. Inflate to 50 lbs sq in & blow off excess fluid.
5. Reconnect jacks to the doors.
6. Inflate to 400 lb sq in.
U/C doors
1. Deflate accumulators.
2. Disconnect jacks & retract.
3. Pump in an amount of fluid (Enough to fill jacks, pipe lines to jacks & clearance volume in accumulators)
4. Inflate to 50 lbs sq in & blow off excess fluid.
5. Reconnect jacks to the doors.
6. inflate to 400 lbs sq in.
U/C, bomb doors & flaps
As for U/C door omitting items 2 & 5.
Undercarriage charge to 150 lbs sq in.
Cut out accumulator.
Operate one of the jacks to get rid of oil pressure in the accumulator this will ensure that the separator is on stop. Then fill up with air to 1850 lbs sq in.
[page break]
[drawing of fuel pressure warning light]
When the fuel pressure is safe the diaphragm operates a pin that keeps the contacts apart (red light out). When pressure drops to danger level – diaphragm drops and contact is made and the light goes on.
[sketch of pressure switch attachment]
[drawing of boost gauge MkIII]
[page break]
[drawing of boost gauge Mk IIIC*]
1. Normal boost indication. The boost exerts a negative or positive pressure on the operating diaphragm and the movement is conveyed to the pointer mechanism via a link & conveyor diaphragm.
2. Compensating action. If atmospheric pressure decreases it will cause a movement of the conveyor diaphragm & consequently a pointer reading. To prevent this the pointer mechanism is mounted on a compensating diaphragm so that when the conveyor diaphragm is moved the mechanism will also move an equal distance keeping the angle between the pin & L shaped lever unchanged. Consequently there will be no pointer movement due to change in atmospheric pressure.
[page break]
[drawing of a Desyn fuel contents gauge]
[page break]
Desyn fuel contents gauge (continued)
The movement of the float rotates via bevel gear two spring brushes over a circular resistance. The position of the brushes varies the amount & direction of the current to the stator coil of the indicator.
The strength & direction of the magnetic field in those coils is therefore varied & the rotor on the spindle of which the pointer is attached will align itself in the resultant magnetic field.
Note. A weak permanent magnet returns the pointer to the six o’clock position on the dial.
The pointer is returned to this position, so that even if the tank was empty we should always have a pointer movement when the gauge is switched on.
[page break]
[drawing of a cylinder head temp gauge]
This instrument is designed on the thermo couple principle. That is if two dissimilar metals (eg copper & constantin) are joined at both ends & one end is heated, then an EMF will be generated. In the case of cylinder head temperature gauge this EMF is measured on a milli – volt meter, the scale of which is graduated in degrees cent.
Action. The hot cylinder causes an EMF to be generated which will vary with the temperature of the cylinder. The EMF is let into a light moving coil via hair spring. The coil becomes [?] & will attempt to align itself in the permanent magnet. Its success depending on the induced poles which is proportional to the cyl. temp.
[page break]
[drawing of oil pressure gauge]
[page break]
[drawing of oil temperature gauge]
[page break]
[drawing of electrical engine speed indicator]
[page break]
To prevent whipping & wear the drive short & straight as possible & geared down 4:1 from the engine.
There is a 2;1 step up gear between flex & rotor so that the rotor rotates at ½ engine speed but the current is generated at engine speed. The generator produces 50 cycles AC per second at 3,000 R.P.M.
Indicator the AC (alternating current) from the generator produces a rotating magnetic field in the indicator stator & induces a field in the Rotor causing it to rotate synchronously.
A four pole perm magnet fixed on the same shaft as the rotor also rotates at engine speed. The copper drum fitted closely over the magnet but does not touch it. This drum is attracted around by the magnet but its motion is controlled by a large hair spring. When the drum is held the pointer indicates the speed of the engine.
[page break]
The current in a circuit is directly proportional to the EMF & inversely proportional to the resistance.
Expressed as V = I X R
The current varies inversely with the resistance providing the voltage remains the same. The current will be directly proportional to the voltage providing the resistance remains the same.
W = V X R 746 Ws = 1 HP or 33000ft lbs. 1KW = 1,000 Watts or BTU
[sketch and calculations for parallel resistance]
A commutator changes AC to DC or Vice – Versa. Dynamo supplies DC. Alternator supplies AC. DC is needed to charge a battery.
[page break]
[sketch of circuit demonstrating Ohms Law]
[drawing of shunt generator]
[page break]
[drawing of generator control circuit]
[page break]
Drawing of generator control circuit]
[page break]
[drawing of starter feathering circuit]
[drawing of U/C indicator circuit]
[page break]
D.H. Hydromatic Airscrews
1. Press feather button.
2. Throttle back.
3. When engine stops turn off fuel cock.
4. Switch off mags.
1. Turn on fuel.
2. Set R.P.M. lever to minimum R.P.M.
3. Throttle to half open.
4. Press feathering button & hold in.
5. Switch on mags.
6. Remove finger from button at 1,500 R.P.M.
7. Synchronise engine with others.
[page break]
Starting Running & Stopping Radial engines
Preliminary checks
1. See that chocks are in position.
2. Turn engine six revs. Note. A check for hydraulicing prior to every start except when motor has been stopped for less than a period of one hour.
3. Turn Ground/flight switch to Flight and connect accumulator. Switch on D.R. compass & main contents gauge switch.
4. Check the following controls;-
a. U/C lever Down, lights green.
b. Brakes On, 80 lbs in each wheel.
c. Flaps Neutral
d. Main balance cock Off
e. Booster cut out Normal
f. Mixture control Normal, rich
g. Supercharger M gear
h. Air intake Cold
i. Prop control Max. R.P.M.
j. Throttle ½ in open
k. Cowling gills Open
Gills will be open for all Ground running & Taxying unless air temp. is below 0° C when gills will be left closed for starting & opened when cylinder head temp is 100° C. Use external battery for operating gills.
5. Turn Ground/flight switch to ground.
6. Turn on the appropriate fuel tank cocks & pilots master cocks.
7. Give order to ground crew ‘Ready for starting’, with ground crew reply ‘Ready’
[page break
8. Switch on main mags. & booster coil or hand starter mag.
9. Give order ‘contact’ & press starter button.
Turning period not to exceed 10 seconds with 30 sec interval between attempts. Whilst turning ground crew prime engine will require number of strokes. In cold weather it may be necessary to continue priming till engine has picked up.
Warming up & Checking
2. Switch off booster coil and hand starting mag. Ground crew turn off priming cock & screw down pump.
3. Warm up at 800-900 R.P.M. to 15° C & 100° C Cylinder head temp. Gills fully open.
4. Check ‘Dead Mag.@
5. Exercise the prop at least 2” in the constant speed range (1800-2500)
6. Test the C.S.U.
In constant speeding range move prop lever down to get approx. 200 R.P.M. drop. Open & close throttle to obtain a rise & fall in boost of 1 lb sq in, R.P.M. should remain constant.
7. Return prop lever to max. R.P.M., boost should remain constant A.B.C. working correctly.
8. Check Mags. At the appropriate boost with prop fully fine.
9. Check supercharger. Change into ‘S’ gear & note slight drop in R.P.M. & slight rise in boost pressure. Change back to ‘M’ gear, original position will be restored.
[page break]
10. throttle slowly back to 1,000 R.P.M. Snap throttle closed, check slow running.
Stopping engine
1. run at approx. 900 R.P.M. for 2 mins. To allow engine to cool down.
2. open up to -2lbs boost for 5 secs. Bring throttle lever slowly back to occupying about 5 secs.
3. when slow running position is reached open carb cut out & switch off mags when engine has come to rest.
4. Switch off fuel.
[drawing of Halifax III fuel system]
[page break]
[drawing of Halifax III engine panel]
[page break]
Running faults
A. ignition. Engine fails to start.
1. Isolate spark gap;-
a. Oil insulating contacts.
b. Cracked sleeve.
2. Defective switch or switch lead:- Earthing.
3. Defective hand starter mag. or booster coil.
4. Lead to main mag. broken or earthing to braiding.
5. Wrongly fitted C.B. cover.
6. Faulty brush.
7. C.B. arm stuck open or closed.
8. Dirty C.B. points.
9. Contact breaker spring broken.
10. Hand starter mag. sprocket sheared.
11. Condenser U.S.
B Priming
1. engine under or over primed.
2. Faulty priming.
3. Broken or leaking pipe.
4. Blocked filter or atomizer.
C. Engine starts but fails to pick up.
1. Incorrect throttle opening.
2. Insufficient fuel pressure, carb fuel starved.
3. Air lock or leak on the suction side of engine pump.
4. Slow running jet blocked.
5. Water or dirt in jet wells. (Causes previous defect).
6. Blocked tank vents. (Drop in fuel pressure).
[page break]
Incorrect oil pressure:-
A. High oil pressure.
1. Low (very) temperature of oil.
2. Faulty setting of compound relief valve.
3. Faulty pressure gauge.
B. Low oil pressure.
1. worn bearings.
2. Relief valve stuck open.
3. Incorrect settings of relief scrawl valve.
4. dirt on the seating of the relief valve.
5. Leak on the pressure side of the pump.
6. Faulty pressure gauge.
7. Overheating of the oil.
Incorrect Oil Temp
A. High temp.
1.Insufficient oil in the tank.
2. Engine overheating.
3. Cooler sludged.
4. Clarkes viscosity valve U.S.
5. Faulty oil temp gauge.
B. Low temp.
1. Incorrect gauge.
2. Rad flaps open.
3. Clarkes viscosity valve U.S.

Excessive cylinder head temp.
1. Damaged cylinder cooling fins (also dirty).
2.Misplaced baffle.
3. Misplaced cylinder head deflector pads.
4. Weak mixture.
5. Tail to wind.
6. Engine cowlings must not be removed for ground runs.
7. Burnt out copper asbestos joint ring.
8. High boost at low revs.
9. Incorrect spark plugs.
[page break]
Excessive oil consumption
1. Excessive blue smoke from the exhaust due to too large a working gap in piston rings. Note. When sleeve or cylinder is worn it takes an oval shape allowing the oil to seep through.
2. Scored cylinders.
3. Broken rings.
4. Seizing up of cylinder piston rings.
5. Contraction ring of sleeve broken or seized.
6. Carb spindle gland leaking.
7. Scavenge pump in front cover. Note. Should the pump shear excessive oil will build up in the front cover & flood the [?] & it will be blown out through the breather.
Ignition Faults.
Rough running.
1. Loss of power, popping back in carb due to A.T.D. working incorrectly.
2. Dirty plugs, cracked insulation in plug or ignition harness, loose connections on plugs.
3. Mag. insulation cracked. Dampness in mag.
4. Weak spring.
5. Dirty C/B points(Set up a resistance in primary) Same symptom as Hand starter mag.
Engine vibration
1. Damaged prop or blade out of track.
2. Incorrect assembly.
3. Badly mounted or pitted or dirty cones. (Cones airscrew split collets.)
[page break]
Engine vibration.
1. Loose mounting bolts or loose bearer bolts.
2. Any ignition faults.
Low boost pressure.
1. Any leak in line from S/C to boost gauge.
2. Damaged gauge.
3. incorrect setting of layshaft in relationship to the throttle.
4. Slipping in S/C clutch drive.
5. Sticking piston (ABC)
High boost pressure.
1. Sticky pressure (ABC)
2. Punctured aneroid.
3. Any restriction in the line from aneroid & S/C will allow the aneroid to expand as the throttle will open.
4. Drop in oil pressure to servo piston. Piston will allow the spring to force its opening the throttle.
5. Seized or jammed servo valves allow oil to be directed in one direction only.
Low R.P.M.
1. Incorrectly adjusted C.S.U. spring.
2. Oil or dampness in the generator (R.P.M. indicator).
3. Ignition trouble.
4. Running engine in ‘S’ gear.
[page break]
Defect reports
Everything normal until.
02.20 hrs in level flight PI oil pressure fell slowly from 90 lbs sq in to 85 lbs sq in. Oil temp normal at 65 °C.
02.40 hrs PI oil pressure down to 80 lbs sq in, temp 70° C Cylinder head temp normal at 230° C. Capt warned.
02.45 hrs PI oil pressure down to 70 lbs sq in, temp 73° C cyl head 250° C. Capt. warned.
02.55 hrs PI oil pressure 60 lbs sq in temp 80° C cyl head 270° C, engine vibration. Advised capt. to feather engine. Engine switched off & feathered.
Suspect Main bearing failure.
Signed L.P. Webb Sgt F/E
[page break]
Air publications
The Engineering Manual of the R.A.F. A.P. 1464
Divided into 2 Vols (AP 1464 A & B vols I & II)
AP 1464A Vol 1 Is Manual of technical engineering & information relating to general engineering principles & W/S methods
AP 1464B Vol 1 deals with the use, construction & operation of individual items.
Vol II Consists of miscellaneous leaflets describing amendments or additions to the subject matter.
Form 700
Aircraft Serving Form
1. Particulars of the engines & inspections etc
2. Daily inspection certificates.
3. Refuelling certificates.
4. Oil coolant & armament certificates (Pilot signs).
5. Change of serviceability & repair log. (A/F)
6. Change of serviceability log (Engine)
7. Pilots acceptance & flying log (Pilot signs)
F700 A
Is a smaller addition of the F700 & is carried with the A/C on detachment etc & on return of A/C from detachments all particulars are transferred from the F700 A to the ‘pukka’ F700, but the F700A is kept filed with the with F700 when completed.
[page break]
Table of inspections.
50 Flying hours all minor items. Unstarred items
100 “ “ “ “ “ + 1 starred items.
150 “ “ “ “ “ + 2 “ “
200 “ “ “ “ “ + 1 & 3 “ “
250 “ “ “ “ “ Unstarred items.
300 “ “ “ “ “ + 1 & 2 Starred items
350 “ “ “ “ “ Unstarred items
400 “ “ “ “ “ + all starred & Major.
Any minor inspections may be anticipated or delayed. Any major servicing may be anticipated or delayed.
Should there be the amount of hours will be underlined in red ink.
[table of fire extinguishers]
[page break]
[blank page]



Peter Webb, “Peter Webb's Engineering Notes,” IBCC Digital Archive, accessed June 21, 2024,

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