Ernie Twells' notebook



Ernie Twells' notebook


Notes written during Ernie Twells' engineering training. There are calculations, diagrams and notes.





One notebook of 38 pages handwritten notes


IBCC Digital Archive


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[inserted] LAC Twells [/inserted]

Form 714


Rough Notebook for use in Laboratories and Workshops.

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[inside cover]

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[3 pages calculations]

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Airscrew efficiency
Efficiency = Thrust HP [Horse Power] / Brake HP

Engine develops 1000 HP
Airscrew develops 800 HP

Airscrew efficiency = THP x 100% / BHP = 800 x 100% / 1000 = 80%

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[underlined] EMERGENCY AIR [/underlined]

[deleted] Compres [/deleted] Air bottle on rear of front spar filling point in the bomb compartment. Pressure 1,200 lbs / [symbol for square]” Works the U/C [undercarriage] when valve is turned on but not the flaps until selected control valve on starboard at font of port spar.

[diagram of emergency air / hydraulic system]

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[underlined] Hydraulic System [/underlined]

The Dowty gear type pumps fitted on inboard engines. Supply the light pressure oil nessesary [sic] for the following resource U/C & [indecipherable fragment] FLAPS Fuel jet Hot and Cold air for [indecipherable word] The following selector [deleted fragment] valves fitted in the system direct the light pressure oil independantly [sic] to each source on [underlined] 1 [/underlined] [underlined] U C [/underlined] control valve.
Fitted on right hand side of Pilots seat and has only two pos [positions] for lever,
up or down
2 [underlined] BOMB DOORS [/underlined] Fitted on left hand side of Pilot and is a simalar [sic] valve as U.C
3 [underlined] FLAPS [/underlined] Fitted in front of the [two indecipherable words] pedestal right hand side of pilots seat the plunger moves up or down for the opperation [sic] of flaps this valve however is provided with a neutral position which forms a hydraulic lock to both pressure and return lines of flaps so enabling flap to be set in any given angle.

[underlined] Hydraulic Accumulators [/underlined]

This is fitted in the system charges with an initial air pressure of 220 lbs/[symbol for square]” to absorb the increasing pressure caused by the opperation [sic] of either the Fuel jet or Hot and cold air and so prevent chattering of the valves in the A.C.O [automatic cut out]

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When the hydraulic is idling sufficient pressure (i.e 850 lbs [symbol for square]”) is stored in the [indecipherable word] to opperate [sic] the Hot and Cold fuel jetts [sic] with out the A.C.O cutting in. The [indecipherable word] will also maintain any small leak at the [deleted] system [/deleted] jacks or in the pipe line after the cut out To test internal air pressure make a selection of one of the resources so allowing the air in pressure to become slack and the air pressure will only register on the gauge

[underlined] Emergency Air System [/underlined]

Compressed air at a pressure of 12,000 lbs [symbol for square] is stored in a bottle [deleted fragment] fitted on the rear face of the front spar and controled [sic] from a valve on the starboard side of the spar will opperate [sic] [deleted word] the U/C. or [underlined] Flaps [/underlined] should the Hydraulic system fail.

[underlined] Lower U/C [/underlined] Open control valve the air will be directed to via the emergency air valve and non return valve [indecipherable word] the down side of the jacks as the air does not pass through the normal hydraulic lines or selector it is not necessary to select U.C down when using this system

[underlined] Flaps [/underlined] When lowering the flaps by this system a selection of the control valve must be made as the air enters the normal hydraulic pressure line before the control valve and is then directed along the normal lines to the jack

[underlined] Note [/underlined] When lowering the U/C the flap selector must be kept in neutral [underlined] Flaps to be opperated [sic] once [/underlined]

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[5 pages calculations]

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[underlined] STARTING AND TAKE OFF DRILL [/underlined]

[underlined] 1 [/underlined] Twist cross balance cock to be shut for normal use

[underlined] 2 [/underlined] Swich [sic] on Fuel controls gauge and leave on during flight

[underlined] 3 [/underlined] Test each emersed [sic] pump by ameter [sic] before starting reaching 2 to 4 amp [sic] otherwise pump US [unserviceable] leave immersed pump on, and 2 tanks on until after take off

[underlined] 4 [/underlined] Start engines on No 2 Tanks

[underlined] 5 [/underlined] Warm up run up and Take of [sic] on No 1 tanks

[underlined] 6 [/underlined] Wach [sic] for Fuel pressure warning lights during take off and if red light appears turn the appropriate tank selector cock to No 2 tanks an [sic] land as convenient

[underlined] 7 [/underlined] If take off is OK change over to No 2 tanks and swich [sic] off emmersed [sic] pump in No 1

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8 Transfer fuel from No 3 tanks to No 2 as soon as space is available. swich [sic] of [sic] emmersed [sic] pump when No 3 tank is empty

[underlined] 9 [/underlined] Cross balance cock is for emmergancy [sic] use only when it is required to run all engines from one tank only. one tank is to be on when cross balance cock is open and emmersed [sic] for that tank must allso [sic] be on

[underlined] 10 [/underlined] If a prop has been feathered or and [sic] engine failed it [sic] master fuel cock must be [deleted] shut [/deleted] turned off

[diagram of fuel pump switches]

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Action to be taken if Damage to
[underlined] Fuel Tanks [/underlined]

Should slight damage be sustained the gauge should show a slow leak run all engines of [sic] leaking tank.

[underlined] 1 [/underlined] Swich [sic] on immers [sic] pumps in damage [sic] tank

[underlined] 2 [/underlined] Open cross balance cock

[underlined] 3 [/underlined] Turn appropriate selector cock to leaking tank

[underlined] 4 [/underlined] Turn the other tank selector cock off. When the leaking tank has been emptied run all engines [indecipherable word] off the same tank on opposite side in order to balance U/C


Indicated by needle dropping quickly and will not be possible to run all engines of leaking tank. To maintain balance of U/C however it will be nessesary [sic] to run the engines [deleted] on the [/deleted] off the same tank on the opposite side.

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[underlined] FUEL JETTISON SYSTEM [/underlined]

[diagram of fuel jettison system]

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[underlined] Fuel Jettison [/underlined]

2 valves are fitted in each No 1 tank for the purpose of jettisoning fuel they are Hydraulic opperated [sic] and controled [sic] by a rotary valve situated on the port side of pilot seat (RED HANDLE).
Opperation [sic] of the control allows Hyd. pressure to open the air vents and fuel jettesson [sic] valves Fuel is then jettessoned [sic] through a colaspable [sic] tube which extends when the jettesson [sic] valve opperates [sic]. When the required amount of fuel has been jettessoned [sic] the [inserted] CONTROL [/inserted] valves should be returned to its original position thus allowing the springs to return the valves to the closed position the oil displaced being directed to atmosphere
during the action of jettessoning the following instructions must be carried out speed reduced to 150 to 115 M.P.H and flaps lowered 15 [symbol for degrees] 20 degrees [symbol for degrees].

[inserted] [indecipherable word] [/inserted]
[double underlined] GRAVINER FIRE SYSTEM [/double underlined]

A 3 pint Grav Fire Est containing methyl bromide is mounted on the bulkhead behind the each engine when the Ext is opperated (sic) the methyl bromide is sprayed in the form of a gas around the spark plugs and into the chokes of carb. This gas has a smothering and cooling affect on the fire but has no dettremental [sic] affect on the engine.

[underlined] OPERATION [/underlined]

[underlined] 1 [/underlined] Push button on the starboard [underlined] of [/underlined] instrument panel. one per engine.

[underlined] 2 [/underlined] Flare [indeceipherable word] two of these switches mounted on each engine bulkhead if either of these switches ar [sic] subjected to a temp of 140 to 150 C the ext for that engine is opperated [sic
[underlined] INERTIA [/underlined] mounted on starboard side of nose of fuselarge [sic] this switch opperates [sic] the ext for all engines when the

[page break]

deceleration of A/C exceds [sic] 6G

[underlined] GRAVITY SWITCH [/underlined] Mounted on starboard side of nose of F.U opperates [sic] when A C is upside down or U/C is locked down.

[underlined] [/underlined]

[underlined] 1 [/underlined] Port side of Nose, 1/2 GALL
[underlined] 2 [/underlined] Port " of Pilot seat 1/2 GALL
3 Navigators Position Starboard side 1/2 GALL
4 Front Spar Starboard Side 1 GALL
[underlined] 5 [/underlined] Flare station Starboard side 1/2 GALL
[underlined] 6 [/underlined] Rear gunners station starboard side [underlined] 1/2 GALL [/underlined]
[underlined] [/underlined]

[underlined] ACTION TO BE TAKEN IN EVENT OF FIRE ON ENGINE [/underlined]

[underlined] 1 [/underlined] Turn off fuel [inserted] at t master [/inserted] on that engine open throtal [sic] fully. If fire does not go out switch of [sic] ignition feather the prop press button (deleted) [underlined] 2 [/underlined] [deleted] for fire extinguisher if onboard turn off cabin heating system. Do not atempt [sic] to restart engine.

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Action in the event of Fire in Fuselare [sic] Warn the rest of crew on intercon [sic] to wear oxygen masks turn oxygen to counteract methyl bromide fumes atack [sic] fire with extinguishers with as many of the crew as are avalble [sic] When fire is extinguished open windows to clear fumes.
[underlined] [/underlined]
[Anti icing diagram]

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[double underlined] OXYGEN [/double underlined]

[diagram of pressure gauges]

PRESURE [sic] 18,00 [deleted] 0 [/deleted] square "

Ground test when flow indicator is not fitted. Sel regulator to 30 place end of thick rubber [deleted] pipe [/deleted] tube near ear when if economiser is working normally [underlined] slow [/underlined] puffs of oxygen will be fell [sic] and heard at 5 to 9 puff per minute.

[underlined] FLOW INDICATOR FITTED [underlined]

Sel regulator to 30 connect up mask and breathe slowly flow indicator needle should flick across with each breath as bag empties If you suspect lack of oxygen turn to emergency

[underlined] [/underlined]


7 em A/C supply last 10 mins Amount indicated on gauge


20,000 4 HRS
30000 2 1/2 HRS

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[double underlined] PYROTECHNICS [/double underlined] [underlined] A.P. 1661 [/underlined]

[underlined] FLAME FLOAT [/underlined] YELLOW AND RED
[deleted] BLACK [/deleted] SILVER WITH YELLOW BAND
[deleted] MARINE DISTRESS [indecipherable word] [/deleted]
[underlined] MARINE DISTRESS SIGNAL [/underlined}
[underlined] 1 1/4 INCENDIARY BOMB {/underlined]
[underlined] [/underlined]

[underlined] Flame Float [/underlined] rec outer body painted red inner body on float yellow punch attached to laib vane ring uses Nav by night at sea airsea rescue work immergency [sic] flare path when ditching Seting [sic] and launching Pirces [sic] sealing disc with punch and remove remove safty pin and noze [sic] cap launch tail forst [sic] Precaushing [sic] must be launch if sealing disc is moved

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[underlined] Smoke float [underlined]

body green tail ring and fins yellow half inch round nose. pistol adapther [sic] secured in tail uses Nav aid by day at sea air sea rescue work seting [sic] and lawnching [sic] remove saftey [sic] pin and launch tail first precautions ensure that arming vane is free to rotate replace pin if not used.

[underlined] [/underlined]

Aluminium sea marker MARK IV
Streamline in shape painted aluminium and half inch red band round nose uses to mark position at sea and provide a target for bombing at sea seting [sic] and launching remove transport pin and launch tail first replace pin if not used
MARK V [deleted] send [/deleted] round in shape teliscopic [sic] and painted [deleted] all [deleted] aluminium uses same as MK IV

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Extend fully and launch nose first, colapse [sic] if not used 14lb [underlined] destructor incendiary [/underlined] painted red with instructions on the side
Uses For the destruction of A/C down in enemy localloy [sic] Take off [deleted] ad [/deleted] Tape and remove cap and strike hard dispose of bomb as soon as nose is struck
[underlined] Signal Cartridges [/underlined] 1 1/2"
[underlined] reconition [sic] classified in 5 [/underlined] groups
[underlined] A [/underlined] double star identified by two coloured tryangles [sic] on case
[underlined] B [/underlined] Changing [deleted] coill coller [/deleted] coullor [sic] bands on cartridge case
3 Single [deleted] coullr [/deleted] coloured identified by single coloured band on cartridge case cartridge case [deleted] on [/deleted] has a milled band in the case of a red signal

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[underlined] D [/underlined] Smoke puffs identified by a coloured serpentine on cartridge case

[underlined] E [/underlined] Illuminating case longer than other groups. wide white band round cartridge case uses Signaling [sic] and [deleted] recon] [/deleted] [deleted] recoggnition [/deleted] recognition
[underlined] [/underlined]
[underlined] MK 1 TO 4 RECCO FLARE WITH MK II 42 FUSE [/underlined]
[underlined] [/underlined]
[table detailing fuse usage]
Mark 1 to 5 black case with 1/2" red band four fins around body at tail.
[underlined] [/underlined]

Not to be droped [sic] below 5,000 ft Fuse Capsule marked in numbers
[table detailing fuse usage]
To launch [deleted] fit [/deleted] conect [sic] static line to cable on fuse and launch tail first Mark V has the words delay on side uses for lighting up target area for th [sic] purpose of identification by night in No 42, MK 2 Fuse is secured into nose and the appropate [sic]

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delay capsule inserted With MK V Flares a delay capsule normaly [sic] for use at an altitude [deleted] 2000 feet [/deleted] a capsule 2000 feet less is used launching as for photo flash. precautions as for photo flash.

[double underlined] Photo Flash [/underlined]

Round in shape with four fins at tail body black fins and tail red half inch band round nose and the word flash in white. [underlined] Uses [/underlined] lighting up of target for night photo.

Seting [sic] and launching An 848 fuse is screwed into the nose and an appropate [sic] capsule inserted all capsules prefice [sic] with the letter P Place photo flash on flare chute tail first and suspend by means of bag provided on the release mech. atatch [sic] static line to arming vane cover and remove safty [sic] pin launch by triping [sic] mech on either manuly [sic] or elect [underlined] Precautions [/underlined] ensure that the nesserary [sic] capsule is in position prior to launching asetain [sic] that release mech is cocked before placing flash in position replace safty [sic] pin and disconect [sic] static line before removing from chute.

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[deleted] HYDRAULIC SYSTEM [/deleted]
[underlined ELECTRICS [/underlined]

FUSES [underlined] 40.60 [/underlined]
R = POWER (IY46Gw = 1HP) Sizes of [1 indecipherable word]
Fuses on Lancaster are [deleted] are [/deleted] all in bottom of Electrical Panel just downwards of front space

Battery are 12 volts 40 ampers [sic] The lead acid Accum situated behind the rear [deleted] spar. [/deleted] of front spar [underlined] 10 hour [/underlined] rate the rate that you can discharge accum with eff to test Accum with voltmeter swich [sic] [deleted] on [/deleted] at the 10 hour rate (8 amp) for 5 mins then take reading if voltage is [deleted] ft [/deleted] below 24 volts should be charced. [sic]
Two generators fitted to inner engines start round 29 1500 W.

[circuit diagram]

[page break]

[hydraulic diagram]

[underlined] DOWTY AUTOMATIC CUT OUT [/underlined]

[hydraulic diagram]

[page break]

[pressure theorem]
[Density theorem]
[underlined] [/underlined]
[specific gravity theorem]

[underlined] LAWS OF FLUID PRESSURE [/underlined]
[underlined] 1 [/underlined] PRESSURE TRANSMITTED [2 indecipherable words] EQUALLY IN ALL DIRECTIONS
[underlined] 2 [/underlined] PRESSURE IS ALWAYS AT RIGHT ANGELS [sic] TO SURFACE
[underlined] 3 [/underlined] PRESSURE AT A POINT IN A FLUID = [theorem]


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[double underlined] PNEUMATICS [/double underlined]
[schematic diagram of pneumatics in an aircraft]
[page break]
[underlined] AEROFOILS [/underlined]

[underlined] BENOULLIS [sic] THEOREM [/underlined]

The total energy of a fluid is constant, Thus once this is principally Kinetic energy and pressure energy then an increase in speed will cause a decrease in pressure and vice versa (Venturie Effect)

[diagram and chart illustrating Bernoulli's Theorem]

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Depends on [underlined] 1 [/underlined] Shape and altitude
[underlined] 2 [/underlined] Frontal area [underlined] 3 [underlined] Air density (.077 lb square " at sea level) 4 (Air speed) [underlined] 2 [/underlined]
[underlined] Typs [sic] of drag [/underlined] (Eddy resistance) [deleted] reduce [/deleted] reduced by Form drag - due to shape (streaming
Foneness Ratio = Length
Max width
Best at 4 or 3 [indecipherable word]
[underlined] 2 [/underlined] [underlined] Skin Friction [/underlined]
Due to nature of surface
air viscosity = reduced by polishing and flash riviting [sic] ect [sic]
[underlined] [/underlined]
[underlined] 3 [/underlined] Induced drag - due to production of lift reduced [indecipherable word] by using high aspect ratio tapering ect [sic]
[underlined] [/underlined]
[diagram showing total drag]

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[circuit diagram]
[underlined] [/underlined]
[circuit diagram entitled PARALELS]
[underlined] [/underlined]
[circuit diagram entitled MAGNETIC RELAYS]
[electrical diagram]
To save length and weight of cable [indecipherable word] and voltage drop and to keep [underlined] the cockpit clear of heavy cable [/underlined]

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The unit of EMF is the volt measured with a volt meter connected in paralel [sic] with the [indeceipherable word] circuit, Current is measured in Amps by means of an ammeter connected in series with the circuit [underlined] Unit [/underlined] of res [underlined] is the Ohm [/underlined] and depends upon length and gauge
[underlined] OHMS LAW [/underlined]
[circuit diagram]

For a current to flow in a circuit it is nessery [sic] to have 1 EMF 2 CONDUCTIVE MATERIAL COMPLETE CIRCUIT
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Ernie Twells, “Ernie Twells' notebook,” IBCC Digital Archive, accessed June 27, 2022,

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