# Stirling school flight engineer course notes

### Title

Stirling school flight engineer course notes

### Description

Notes covering electrics, theory of flight, engineering science, supercharging, power, fuel consumption and engine use in various stages of flight.

### Creator

### Language

### Format

Thirty two page notebook with cover

### Publisher

### Rights

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 https://creativecommons.org/licenses/by-nc/4.0/ and https://ibccdigitalarchive.lincoln.ac.uk/omeka/legal.

### Identifier

MGouldAG1605203-160708-02

### Transcription

1605203

SGT GOULD A.G.

2 WORKSHOP

CLASS 3

Form 619.

ROYAL AIR FORCE.

[Underlined] Stirling [/underlined]

[Underlined] School [/underlined]

Notebook for use in Schools.

[Page break]

[Diagrams]

[Page break]

[Underlined] Electrics [/underlined]

For a current to flow in a circuit it is necessary to have (1) An electrical pressure or E.M.F.

(2) Conductive Material.

(3) Complete circuit.

E.M.F. is measured in Volts with a Volt Meter connected in Parallel with the circuit.

Current is measured in Amps by means of an Ammeter which is connected in Series with the circuit.

Resistance is measured in Ohms and depends upon length & gauge of wire.

[Underlined] Ohms Law. [/underlined]

Volts / Current = Resistance in Ohms.

Volts x Current x Resistance.

Volts / Resistance = Current.

[Diagram]

Change resistance of lamp so that amps are 2 2/5 amps = 6 1/2 ohms

Power – measured in Watts

1 Watt = Volts x Amps

[Page break]

746 Watts = 1 Horse Power

Connection in Series.

(1.) Cells [diagram] = 6v

(2.) Resistance [diagram] = 6 Ohms

Connections in Parallel.

(1). Cells [diagram] 2v

(2) Resistance [diagram] [calculations]

Magnetic Effect of a Current

Strength of a field depends on :-

(1.) Current.

(2) No of turns.

i.e. on the number of turns.

(3) Whether coil is wound on soft iron.

[Page break]

Points to be considered in wiring an aircraft.

(1.) Voltages required to operate the various components.

(2) Size of cables – weight involved.

(3.) Size of switches – space involved.

[Diagram]

[Underlined] Accumulators. [\underlined]

Lead Accumulator

Voltage per cell 2.2

2 Plates 1 of Lead Peroxide Composition Positive

1 of Lead Negative.

Diluted Sulphuric Acid.

Fully Charged Condition

Specific Gravity 1.35

Voltage 2.2 v

Finall [sic] Charge while Gassing 2.7v

Fully Discharged Condition.

Specific Gravity 1.18

Voltage 1.8

Discharge weakens acid & fords Lead Sulphate on plates.

[Page break]

Amp hour Efficiency must be 60% to be airworthy.

[Underlined] Capacity [/underlined] Measurement is Amp hours based on the 10hr Rate.

[Underlined] Efficiency [/underlined] is the Amp hours discharge/Amp hr charge Approx 80-90%

[Underlined] Generator Cuts Out. [/underlined] 27v to Cut In

7 amps to Cut Out (reverse current)

[Diagram]

[Diagram]

[Page break]

[Underlined] Relay Switch. [/underlined] (1) Handles the heavy current

(2) Wiring run is shortened (3) Volt drop in run is lowered.(4) Heavy cabling kept from cockpit.

[Underlined] Used [\underlined]

Landing Lamps, Undercart, & Heater.

[Underlined] Voltage Regulator [\underlined]

2 Parts Voltage Reg & Current Regulator terminators are connected in Parallel.

Shunt Generator.

Speed & Magnetic Field Control the Current of the Generator Controlled by the Carbon [indecipherable word].

Magnet works motor which spins Carbon [indecipherable word] [symbol] worked by coil connected across [indecipherable word] of Generator.

[Indecipherable word] prevents the motor from [indecipherable word]

[Diagram]

2. Voltmeter in Charging Circuit but no Magneto

[Page break]

[Blank Page]

[Page break]

Theory of Flight

Air Resistance (Drag). depends on :-

(1.) Shape & attitude

(2.) Frontal Area

(3.) Air density (.077lb [symbol] ft at sea level)

(4.) (Airspeed) 2

Types of Drag.

(1.) Form Drag – due to shape, reduced by streamlining

(2.) Skin Friction – reduced by polishing skin

Fineness Ratio = Length / Max Width which should be 1/3 back.

Skin Friction – due to nature of surface & air density.

(3) Induced drag – due to production of a/c – reduced by using high aspect ratio, tapering [indecipherable word].

Total Drag.

[Diagram]

[Page break]

Aerofoils.

Bernouilli’s [sic] Theory.

Total energy of a fluid = Constant

Kinetic Energy + Pressure Energy = Constant

Thus an increase in speed will cause a decrease in pressure & vice versa (Venturi Effect)

Production of Lift.

Angle of Attack

[Table]

[Page break]

Indicated Air Speed (I.A.S.) = Speed from A.S.I.

Rectified Air Speed (R.A.S.) = IAS [symbol] Instrument Error Corrections

[Symbol] Position Error Correction.

True Air Speed = R.A.S x Altitude Correction Factor

Position Error Correction at 65,000ft Load with Pressure Head on top of Fuselage.

[Table]

[Calculations]

The total drag of an a/c is least [indecipherable words] when flying at the Optimal angle of attack and the speed at this angle of attack is [indecipherable word] as the [indecipherable words] Cruising [indecipherable word] Moderated Stalling Speed for as a/c of given weight is the same for all attitudes, but the True Stalling Speed increases as the altitude increases.

[Page break]

(S.H.F.) Steady Horizontal Flight

Relationship between Airspeed & Angle of Attack

Economical Cruising Speed.

S.H.F. is Flight at Constant Height at a Constant Speed.

For an aircraft to be in S.H.F. the two following conditions must be satisfied:-

Lift = Weight of Aircraft

Thrust = Drag.

An aircraft may be in steady H.F. at different angles of attack and different air speeds.

For a given a/c at a given Weight, for each angle of attack there is one corresponding speed of horizontal Flight & 1 only.

Assume a Stirling weighing 65,000 lbs is in S.H.F. at 6° Angle of Attack & 165 miles an hour. Thus the same aircraft could be flown at a greater speed but the angle of attack would have to be less than 6° x Similarly it could be flown at a less speed but in this case the angle of attack would have to be more than 6°.

However, out of all these possible combinations of angle of attack & airspeed, only 1 angle of attack & thus only 1 corresponding airspeed will at the same time give minimum drag & hence maximum range.

The angle of attack is the optimum angle and the corresponding airspeed is Economical Cruising Speed

[Page break]

The effect of Weight of Aircraft on Cruising Speeds.

[Underlined] Example [/underlined]

Stirling.

Outward bound (Heavy)

Recommended I.A.S. = 165 m.p.h.

Homeward bound (Light)

Recommended I.A.S. = 160 m.p.h.

The reason for the above difference is the difference in weight carried on the two trips.

No matter what the weight of the same aircraft, for maximum range it must be flown at the Optimum Angle of Attack. Thus the less the weight of the aircraft, the Less Lift required, hence the Less Speed required to give the Lift.

[Page break]

[Blank Page]

[Page break]

[Underlined] Engineering Science. [/underlined]

Graphs of Hercules Economical Cruising Boost &[indecipherable word] & Altitude Corrective Factor.

For any particular power requirement with in the economical cruising range the best conditions are obtained by reducing the R.P.M. and keeping the boost up as long as it does not exceed + 1lb [symbol] “

[Underlined] Engine Operational Conditions [/underlined] [underlined] B.P. [/underlined]

Takeoff (3 mins) RPM 28,000 + 6 3/4

Max Climb (30 mins) RPM 25,000 + 3 1/2

Max for Continuous Cruising (Rich) 25,000 + 3 1/2

Max Cruising (Work) 25,000 + 1

Max All Out Level (5 mins) 28,000 + 6 3/4

[Page break]

[Blank Page]

[Page break]

Supercharging.

Volumetric Efficiency = Weight of charge forced in per [indecipherable word] stroke / Weight of Charge to Fill [indecipherable word] Vol at N.T.P.

Normal Temp = 15° 6.

Normal Pressure = 14.7 lbs [symbol] “

High Boost, Low Revs for maximum Range

Methods of increasing power

[Calculation]

I.H.P. may be increased by

(1.) Increasing C ([indecipherable word]) Limits, [indecipherable word] weight, drag

(2) LA ([indecipherable word] x area = ) Weight Volume Limit as before

(3.) Increase N (RPM It [deleted word] Power to Drive [indecipherable words] increase. Dynamic Stress x [Indecipherable words]

(4) Increase [indecipherable word] In this case the increase in power would be got without the [indecipherable word] involved in (3), thus it is best to Increase Pressure. To do this we apply a [indecipherable word], rather than using light

[Page break]

comparison ratio.

Boost Pressure (British Engines)

Pressure above + or below - (14.7 lb [symbol] “). Note Air Ministry on Boost of RPM for specified operational condition (See Handbook)

Climb

(1.) Atmospheric Pressure Decreases, Power falls off

(2) Temp decreases, This will tend to compensate for fall off in power to (1)

Combined effect of 1 & 2 gives us a fall in Power

Power Altitude Curve N.A. Engine

[Diagram]

Effect of Maintaining constant Indicated Pressure with S/C + ABC.

[Diagram]

[Page break]

The gain to full throttle Height is the (1) [indecipherable words]

(2) Better Economy, both at altitude.

Pressure Ratio of S/G = Outlet Pressure / Inlet Pressure

Comparison of M & S Gear

[Table]

(a) High Revs – Low Boost

(b) Low Revs – High Boost

(c) Both Revs + Boost lower.

(a) Charger absorbs power without much height, Engine & [indecipherable word] losses high. (More Oil)

(b) Power taken by Charger reduced, Engine Losses reduced

[Page break]

Max Available Cruising Power

[Diagram]

to fly @ 170 IAS

The power required to fly an aircraft at any given I.A.S. Increases steadily with altitude as Seen by the graph

The increase is due to the [indecipherable word] in I.A.S. while the drag remains constant.

The Altitude where the power required crosses the power available is the ceiling of the aircraft. This ceiling is not fixed because as the speed & load vary, the power required line varies if S gear is engaged at sea level the power available drops because of the higher temp of the S gear change + the extra power to drive S gear that due to the higher gear ratio the boost pressure can be maintained to a higher altitude.

S gear always requires more fuel per H.P. than M therefore whenever possible M gear must be used. When cruising engage S gear only if the speed required cannot be obtained in M.

[Page break]

Climbing

[Diagram]

Gear change when climbing.

The gear to use in a climb is always the one which is capable of giving the higher rate of climb. That is the one which gives the greater horsepower. From sealevel up to 9,000 ft M gear gives more HP than S despite the fact that at 9,000 ft the boost in M has dropped to +3 ½. From 9,000 ft on, S gear gives more H.P. than M. Therefore when climbing change to S gear at 9,000 ft or where the boost in M has dropped to +3 1/2.

Performance.

Range Flying – Big bomb load – smallest possible fuel load.

Range Flying.

This is the condition of Flight normally met in a Stirling, where the pilot is trying to obtain maximum miles per gallon. For this the petrol used per mile

[Page break]

must be best, and since each gallon of petrol is equal to a certain number of ft lb of work, the work done per mile must be best i.e. Drag must be a minimum. Since lift is fixed equal to weight, drag will be best when the lift drag ratio is greatest i.e. when flying at the optimum angle of attack.

In flight it is impossible to measure directly the angle of attack sufficiently accurately to make sure of flying at the optimum angle. At the average outward load of 66,000 lbs the optimum angle can only be obtained by flying at 160 IAS. And on the return journey where the load is reduced to 55,000 average, the speed must be reduced to 155 IAS to maintain the optimum angle. Therefore the speed given above is the most economical and will give maximum A.M.P.G.

[Diagram]

[Page break]

[Table]

[Calculations]

[Table] [Calculations]

[Page break]

[Calculation]

Trip 1200 Fuel required 1900 Fuel Taken 1946

[Calculations]

[Page break]

With the exception given below the range obtainable in a Stirling is independent of the altitude at which the aircraft is flying. The reason is that as altitude increases the pilot must maintain the same IAS to get maximum range and is therefore encountering the same drag.

Therefore the work done per mile is the same at all altitudes, and the range obtainable does not alter.

[Underlined] Exceptions. [/underlined]

At some altitudes the engine can get work out of petrol with greater efficiency than at others not therefore at the more efficient altitudes the range obtainable will increase. Above about 16,000 ft S gear must be engaged and below about 6,000 ft the engine is partly throttled, therefore at these particular altitudes engine efficiency drops and range is reduced.

[Page break]

[Table]

Duration Cruising (Endurance)

This condition is not very [indecipherable word] a Stirling It occurs when the pilot is trying to obtain Max Time in the air. The time is the air depends on the G.P.H. & will be the greatest when the G.P.H. is least i.e. when the H.P. is best. To reduce the H.P. Pilot must operate his revs & throttle and as he cuts the H.P. the speed will drop and the angle of attack will increase.

As this happens the amount of control over the a/c becomes smaller. Minimum galls per hour are obtained

[Page break]

when the H.P has been reduced just sufficiently to allow the pilot, reasonable control.

Range flying is minimum power.

Duration flying is minimum work.

For minimum control the pilot must maintain a certain I.A.S. and the power required to do this will increase steadily as altitude increases owing to the increase in TAS. Therefore gallons per hour will be best and duration greatest when flying at the lowest possible operational altitude.

Calculation

(1.) Enter Fuel Left.

(2) Switch Tanks

(3) Subtract Fuel

[Page break]

[Table]

[Calculations]

[Page break]

[Underlined] Climbing [\underlined]

During a climb the engines are working against 2 forces – Drag & Gravity & the rate of climb will depend on the amount of H.P. which can be used against Gravity. The H.P. used against drag increases steadily as forward speed increases but the thrust H.P available from the engines in a climb also increases as forward speed increases due to a steady rise in propellor [sic] efficiency. These 2 facts are shown by the 2 graphs – HP available & H.P. required against drag.

[Diagram]

From the graph is will be seen that the biggest margin of power available for climbing [indecipherable word] at about 160 IAS therefore this speed will give the highest rate of climb. To obtain this speed the engines are opened up to Max Climbing (2400 w +6) and speed reduced to 160 by adjusting the angle of climb.

[Page break]

[Blank page]

[Page break]

[Table]

[Page break]

[Blank Page]

[Diagram]

Stirling Circuit & Bumps

[Page break]

[Table]

[Calculations]

[Page break]

[Calculations]

SGT GOULD A.G.

2 WORKSHOP

CLASS 3

Form 619.

ROYAL AIR FORCE.

[Underlined] Stirling [/underlined]

[Underlined] School [/underlined]

Notebook for use in Schools.

[Page break]

[Diagrams]

[Page break]

[Underlined] Electrics [/underlined]

For a current to flow in a circuit it is necessary to have (1) An electrical pressure or E.M.F.

(2) Conductive Material.

(3) Complete circuit.

E.M.F. is measured in Volts with a Volt Meter connected in Parallel with the circuit.

Current is measured in Amps by means of an Ammeter which is connected in Series with the circuit.

Resistance is measured in Ohms and depends upon length & gauge of wire.

[Underlined] Ohms Law. [/underlined]

Volts / Current = Resistance in Ohms.

Volts x Current x Resistance.

Volts / Resistance = Current.

[Diagram]

Change resistance of lamp so that amps are 2 2/5 amps = 6 1/2 ohms

Power – measured in Watts

1 Watt = Volts x Amps

[Page break]

746 Watts = 1 Horse Power

Connection in Series.

(1.) Cells [diagram] = 6v

(2.) Resistance [diagram] = 6 Ohms

Connections in Parallel.

(1). Cells [diagram] 2v

(2) Resistance [diagram] [calculations]

Magnetic Effect of a Current

Strength of a field depends on :-

(1.) Current.

(2) No of turns.

i.e. on the number of turns.

(3) Whether coil is wound on soft iron.

[Page break]

Points to be considered in wiring an aircraft.

(1.) Voltages required to operate the various components.

(2) Size of cables – weight involved.

(3.) Size of switches – space involved.

[Diagram]

[Underlined] Accumulators. [\underlined]

Lead Accumulator

Voltage per cell 2.2

2 Plates 1 of Lead Peroxide Composition Positive

1 of Lead Negative.

Diluted Sulphuric Acid.

Fully Charged Condition

Specific Gravity 1.35

Voltage 2.2 v

Finall [sic] Charge while Gassing 2.7v

Fully Discharged Condition.

Specific Gravity 1.18

Voltage 1.8

Discharge weakens acid & fords Lead Sulphate on plates.

[Page break]

Amp hour Efficiency must be 60% to be airworthy.

[Underlined] Capacity [/underlined] Measurement is Amp hours based on the 10hr Rate.

[Underlined] Efficiency [/underlined] is the Amp hours discharge/Amp hr charge Approx 80-90%

[Underlined] Generator Cuts Out. [/underlined] 27v to Cut In

7 amps to Cut Out (reverse current)

[Diagram]

[Diagram]

[Page break]

[Underlined] Relay Switch. [/underlined] (1) Handles the heavy current

(2) Wiring run is shortened (3) Volt drop in run is lowered.(4) Heavy cabling kept from cockpit.

[Underlined] Used [\underlined]

Landing Lamps, Undercart, & Heater.

[Underlined] Voltage Regulator [\underlined]

2 Parts Voltage Reg & Current Regulator terminators are connected in Parallel.

Shunt Generator.

Speed & Magnetic Field Control the Current of the Generator Controlled by the Carbon [indecipherable word].

Magnet works motor which spins Carbon [indecipherable word] [symbol] worked by coil connected across [indecipherable word] of Generator.

[Indecipherable word] prevents the motor from [indecipherable word]

[Diagram]

2. Voltmeter in Charging Circuit but no Magneto

[Page break]

[Blank Page]

[Page break]

Theory of Flight

Air Resistance (Drag). depends on :-

(1.) Shape & attitude

(2.) Frontal Area

(3.) Air density (.077lb [symbol] ft at sea level)

(4.) (Airspeed) 2

Types of Drag.

(1.) Form Drag – due to shape, reduced by streamlining

(2.) Skin Friction – reduced by polishing skin

Fineness Ratio = Length / Max Width which should be 1/3 back.

Skin Friction – due to nature of surface & air density.

(3) Induced drag – due to production of a/c – reduced by using high aspect ratio, tapering [indecipherable word].

Total Drag.

[Diagram]

[Page break]

Aerofoils.

Bernouilli’s [sic] Theory.

Total energy of a fluid = Constant

Kinetic Energy + Pressure Energy = Constant

Thus an increase in speed will cause a decrease in pressure & vice versa (Venturi Effect)

Production of Lift.

Angle of Attack

[Table]

[Page break]

Indicated Air Speed (I.A.S.) = Speed from A.S.I.

Rectified Air Speed (R.A.S.) = IAS [symbol] Instrument Error Corrections

[Symbol] Position Error Correction.

True Air Speed = R.A.S x Altitude Correction Factor

Position Error Correction at 65,000ft Load with Pressure Head on top of Fuselage.

[Table]

[Calculations]

The total drag of an a/c is least [indecipherable words] when flying at the Optimal angle of attack and the speed at this angle of attack is [indecipherable word] as the [indecipherable words] Cruising [indecipherable word] Moderated Stalling Speed for as a/c of given weight is the same for all attitudes, but the True Stalling Speed increases as the altitude increases.

[Page break]

(S.H.F.) Steady Horizontal Flight

Relationship between Airspeed & Angle of Attack

Economical Cruising Speed.

S.H.F. is Flight at Constant Height at a Constant Speed.

For an aircraft to be in S.H.F. the two following conditions must be satisfied:-

Lift = Weight of Aircraft

Thrust = Drag.

An aircraft may be in steady H.F. at different angles of attack and different air speeds.

For a given a/c at a given Weight, for each angle of attack there is one corresponding speed of horizontal Flight & 1 only.

Assume a Stirling weighing 65,000 lbs is in S.H.F. at 6° Angle of Attack & 165 miles an hour. Thus the same aircraft could be flown at a greater speed but the angle of attack would have to be less than 6° x Similarly it could be flown at a less speed but in this case the angle of attack would have to be more than 6°.

However, out of all these possible combinations of angle of attack & airspeed, only 1 angle of attack & thus only 1 corresponding airspeed will at the same time give minimum drag & hence maximum range.

The angle of attack is the optimum angle and the corresponding airspeed is Economical Cruising Speed

[Page break]

The effect of Weight of Aircraft on Cruising Speeds.

[Underlined] Example [/underlined]

Stirling.

Outward bound (Heavy)

Recommended I.A.S. = 165 m.p.h.

Homeward bound (Light)

Recommended I.A.S. = 160 m.p.h.

The reason for the above difference is the difference in weight carried on the two trips.

No matter what the weight of the same aircraft, for maximum range it must be flown at the Optimum Angle of Attack. Thus the less the weight of the aircraft, the Less Lift required, hence the Less Speed required to give the Lift.

[Page break]

[Blank Page]

[Page break]

[Underlined] Engineering Science. [/underlined]

Graphs of Hercules Economical Cruising Boost &[indecipherable word] & Altitude Corrective Factor.

For any particular power requirement with in the economical cruising range the best conditions are obtained by reducing the R.P.M. and keeping the boost up as long as it does not exceed + 1lb [symbol] “

[Underlined] Engine Operational Conditions [/underlined] [underlined] B.P. [/underlined]

Takeoff (3 mins) RPM 28,000 + 6 3/4

Max Climb (30 mins) RPM 25,000 + 3 1/2

Max for Continuous Cruising (Rich) 25,000 + 3 1/2

Max Cruising (Work) 25,000 + 1

Max All Out Level (5 mins) 28,000 + 6 3/4

[Page break]

[Blank Page]

[Page break]

Supercharging.

Volumetric Efficiency = Weight of charge forced in per [indecipherable word] stroke / Weight of Charge to Fill [indecipherable word] Vol at N.T.P.

Normal Temp = 15° 6.

Normal Pressure = 14.7 lbs [symbol] “

High Boost, Low Revs for maximum Range

Methods of increasing power

[Calculation]

I.H.P. may be increased by

(1.) Increasing C ([indecipherable word]) Limits, [indecipherable word] weight, drag

(2) LA ([indecipherable word] x area = ) Weight Volume Limit as before

(3.) Increase N (RPM It [deleted word] Power to Drive [indecipherable words] increase. Dynamic Stress x [Indecipherable words]

(4) Increase [indecipherable word] In this case the increase in power would be got without the [indecipherable word] involved in (3), thus it is best to Increase Pressure. To do this we apply a [indecipherable word], rather than using light

[Page break]

comparison ratio.

Boost Pressure (British Engines)

Pressure above + or below - (14.7 lb [symbol] “). Note Air Ministry on Boost of RPM for specified operational condition (See Handbook)

Climb

(1.) Atmospheric Pressure Decreases, Power falls off

(2) Temp decreases, This will tend to compensate for fall off in power to (1)

Combined effect of 1 & 2 gives us a fall in Power

Power Altitude Curve N.A. Engine

[Diagram]

Effect of Maintaining constant Indicated Pressure with S/C + ABC.

[Diagram]

[Page break]

The gain to full throttle Height is the (1) [indecipherable words]

(2) Better Economy, both at altitude.

Pressure Ratio of S/G = Outlet Pressure / Inlet Pressure

Comparison of M & S Gear

[Table]

(a) High Revs – Low Boost

(b) Low Revs – High Boost

(c) Both Revs + Boost lower.

(a) Charger absorbs power without much height, Engine & [indecipherable word] losses high. (More Oil)

(b) Power taken by Charger reduced, Engine Losses reduced

[Page break]

Max Available Cruising Power

[Diagram]

to fly @ 170 IAS

The power required to fly an aircraft at any given I.A.S. Increases steadily with altitude as Seen by the graph

The increase is due to the [indecipherable word] in I.A.S. while the drag remains constant.

The Altitude where the power required crosses the power available is the ceiling of the aircraft. This ceiling is not fixed because as the speed & load vary, the power required line varies if S gear is engaged at sea level the power available drops because of the higher temp of the S gear change + the extra power to drive S gear that due to the higher gear ratio the boost pressure can be maintained to a higher altitude.

S gear always requires more fuel per H.P. than M therefore whenever possible M gear must be used. When cruising engage S gear only if the speed required cannot be obtained in M.

[Page break]

Climbing

[Diagram]

Gear change when climbing.

The gear to use in a climb is always the one which is capable of giving the higher rate of climb. That is the one which gives the greater horsepower. From sealevel up to 9,000 ft M gear gives more HP than S despite the fact that at 9,000 ft the boost in M has dropped to +3 ½. From 9,000 ft on, S gear gives more H.P. than M. Therefore when climbing change to S gear at 9,000 ft or where the boost in M has dropped to +3 1/2.

Performance.

Range Flying – Big bomb load – smallest possible fuel load.

Range Flying.

This is the condition of Flight normally met in a Stirling, where the pilot is trying to obtain maximum miles per gallon. For this the petrol used per mile

[Page break]

must be best, and since each gallon of petrol is equal to a certain number of ft lb of work, the work done per mile must be best i.e. Drag must be a minimum. Since lift is fixed equal to weight, drag will be best when the lift drag ratio is greatest i.e. when flying at the optimum angle of attack.

In flight it is impossible to measure directly the angle of attack sufficiently accurately to make sure of flying at the optimum angle. At the average outward load of 66,000 lbs the optimum angle can only be obtained by flying at 160 IAS. And on the return journey where the load is reduced to 55,000 average, the speed must be reduced to 155 IAS to maintain the optimum angle. Therefore the speed given above is the most economical and will give maximum A.M.P.G.

[Diagram]

[Page break]

[Table]

[Calculations]

[Table] [Calculations]

[Page break]

[Calculation]

Trip 1200 Fuel required 1900 Fuel Taken 1946

[Calculations]

[Page break]

With the exception given below the range obtainable in a Stirling is independent of the altitude at which the aircraft is flying. The reason is that as altitude increases the pilot must maintain the same IAS to get maximum range and is therefore encountering the same drag.

Therefore the work done per mile is the same at all altitudes, and the range obtainable does not alter.

[Underlined] Exceptions. [/underlined]

At some altitudes the engine can get work out of petrol with greater efficiency than at others not therefore at the more efficient altitudes the range obtainable will increase. Above about 16,000 ft S gear must be engaged and below about 6,000 ft the engine is partly throttled, therefore at these particular altitudes engine efficiency drops and range is reduced.

[Page break]

[Table]

Duration Cruising (Endurance)

This condition is not very [indecipherable word] a Stirling It occurs when the pilot is trying to obtain Max Time in the air. The time is the air depends on the G.P.H. & will be the greatest when the G.P.H. is least i.e. when the H.P. is best. To reduce the H.P. Pilot must operate his revs & throttle and as he cuts the H.P. the speed will drop and the angle of attack will increase.

As this happens the amount of control over the a/c becomes smaller. Minimum galls per hour are obtained

[Page break]

when the H.P has been reduced just sufficiently to allow the pilot, reasonable control.

Range flying is minimum power.

Duration flying is minimum work.

For minimum control the pilot must maintain a certain I.A.S. and the power required to do this will increase steadily as altitude increases owing to the increase in TAS. Therefore gallons per hour will be best and duration greatest when flying at the lowest possible operational altitude.

Calculation

(1.) Enter Fuel Left.

(2) Switch Tanks

(3) Subtract Fuel

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[Underlined] Climbing [\underlined]

During a climb the engines are working against 2 forces – Drag & Gravity & the rate of climb will depend on the amount of H.P. which can be used against Gravity. The H.P. used against drag increases steadily as forward speed increases but the thrust H.P available from the engines in a climb also increases as forward speed increases due to a steady rise in propellor [sic] efficiency. These 2 facts are shown by the 2 graphs – HP available & H.P. required against drag.

[Diagram]

From the graph is will be seen that the biggest margin of power available for climbing [indecipherable word] at about 160 IAS therefore this speed will give the highest rate of climb. To obtain this speed the engines are opened up to Max Climbing (2400 w +6) and speed reduced to 160 by adjusting the angle of climb.

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[Diagram]

Stirling Circuit & Bumps

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### Collection

### Citation

A Gould, “Stirling school flight engineer course notes,”

*IBCC Digital Archive*, accessed September 30, 2023, https://ibccdigitalarchive.lincoln.ac.uk/omeka/collections/document/28703.## Item Relations

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