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BTC 3/24 - ACFT > ACFT - Aircraft Engines > Flashcards

ACFT - Aircraft Engines Flashcards

1
Q

Three differences of Piston Engines? (3)

A
  1. Air cooled
  2. Dual Ignition Systems
  3. Fuel / Air Mix
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2
Q

How many Operations take place in a Four Stroke engine? (1)

A

Five

  1. Induction
  2. Compression
  3. Ignition + Power
  4. Exhaust
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3
Q

The 4-stroke cycle is sometimes referred to
simply as: (4)

A

Suck
Squeeze
Bang
Blow

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4
Q

What is a Carburettor? (1)

A

A device which provides a suitable mixture of fuel and air to the cylinder for ignition

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5
Q

When air is flowing, the Carburettor draws fuel from a reservoir. This is called? (1)

A

Venturi tube

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6
Q

How is air passed through the Venturi section? (3)

A
  1. The air accelerates
  2. There is a drop in air pressure (Bernoulli’s principle)
  3. This causes fuel to be drawn through the main jet where it mixes with air in the Venturi

The fuel/air mixture is then fed to each cylinder in turn

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7
Q

What are the 2 main reasons for Carburettor icing? (2)

A
  1. Pressure
  2. Temperature

Fuel changes from liquid to Vapour = Latent Heat is required (“DOUBLE COOLING”)

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8
Q

How do Pilots avoid Carburettor icing? (2)

A
  1. Avoid areas where moisture is present & icing likely
  2. Regular application of Carburettor heat
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9
Q

What is Propellor Pitch? (1)

A

Defined as the angle made by the chord of the blade and its plane of rotation

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10
Q

What are the 3 types of Propellor pitch? (3)

A
  1. Coarse pitch
  2. Fine pitch
  3. Standard pitch
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11
Q

What is Coarse pitch? (1)

A

When the blade angle is Great (Bigger bite of the air)

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12
Q

When is Fine pitch useful? (1)

A

Take off & Climb

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13
Q

When is Coarse pitch useful? (1)

A

Cruising altitude

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14
Q

Why may Standard pitch be used? (1)

A

Gives efficiency over a range of power settings (Best of both pitches)

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15
Q

What is Feathering? (1)

A

Variable pitch propellers are rotated to be parallel to airflow to reduce drag if the engine fails, or is deliberately shut down

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16
Q

What are the Advantages of the Piston engine & Propellor? (5)

A
  1. Simpler design reduces manufacturing and maintenance cost
  2. More efficient at low speeds and low altitude
  3. Faster initial acceleration than jet engine
  4. Immediate reaction to pilot input
  5. Propwash over wings generates lift at low speeds, which reduces take-off run and aids controllability
17
Q

What is the Disadvantages of the Piston engine & Propellor? (2)

A
  1. Power output limitation
  2. Propellor performance limitation
18
Q

What are the differences between Propellor & Jet engines? (2)

A
  1. A propeller accelerates a large volume of air by a small amount
  2. A jet engine accelerates a small volume of air by a large amount
19
Q

What is the equation of Newton’s Second Law? (1)

A

F= M x A

Force = Mass x Acceleration

20
Q

What are the basic parts of a Jet Engine? (5)

A
  1. Air Intake
  2. Combustion Stage/s
  3. Combustion Chamber/s
  4. Turbine Stage/s
  5. Exhaust
21
Q

What types of Jet Engine are there? (7)

A
  1. Turbojet
  2. Low Bypass Turbofan
  3. High Bypass Turbofan
  4. Turboprop
  5. Ramjet
  6. Scramjet
  7. Turboshaft (Helicopters)
22
Q

What are the 2 types of Jet Engine Compressors? (2)

A
  1. Centrifugal flow
  2. Axial flow
23
Q

What is a Centrifugal flow Compressor? (2)

A
  • Uses an impeller to accelerate the air, and a diffuser to produce the required pressure rise
  • Air leaves the centrifugal compressor at 90° to the flight direction and it must be turned back towards the combustion chamber, resulting in a drop in efficiency
24
Q

What is a Axial flow Compressor? (1)

A

Employs alternate rows of rotating (rotor)
blades, to accelerate the air, and stationary (stator) vanes to diffuse the air, until the required pressure rise is obtained

25
Q

What is a Turbofan Bypass Engine? (2)

A

Developed in order to increase fuel efficiency and to reduce noise, bypass engines use a fan to draw air both through, and around a core.

By surrounding the fast-moving exhaust jet with a stream of slower moving air, which by-passes the central core of the engine, noise is reduced considerably

26
Q

What is an Afterburner? (3)

A
  • Axial flow and low-bypass turbofan engines can generate additional thrust by injecting fuel directly into the hot exhaust gas stream
  • Up to 70% extra power
  • Very fuel inefficient & noisy
27
Q

What is a High bypass ratio engine? (1)

A

Modern high-bypass ratio engines draw air in at a rate of over a tonne per second, achieve an overall pressure ratio of up to 1:50 and typically generate 60-80 000 lbs thrust

28
Q

What are the Advantages of the Turbofan engine? (4)

A
  1. Efficient
  2. More power than a piston engine
  3. High speed ability
  4. Afterburner > additional thrust
29
Q

What are the Disadvantages of the Turbofan engine? (3)

A
  1. Complex design
  2. High costs
  3. Slow response from Pilot input
30
Q

What is a Turboprop? (4)

A
  • Is a jet engine, which drives a propeller > turbine at the back is turned by the hot gases and this turns a shaft that drives the propeller via a gearbox
  • Ratio in reduction gearing: 5-20:1
  • Has better propulsion efficiency up to 500mph
  • Found on smaller, shorter range, commercial aircraft.
31
Q

What are the Advantages of the Turbo prop engine? (5)

A
  1. In dense air
  2. Can operate on shorter runways
  3. “Feathering” > minimise drag with engine failure
  4. Mechanically reliable > Lesser moving parts
  5. Lightweight
32
Q

What are the Disadvantages of the Turbo prop engine? (4)

A
  1. Propellers lose efficiency at high altitudes
  2. Vibration and noise levels can cause passenger discomfort
  3. Lower cruising levels can be susceptible to icing and turbulence
  4. Lower cruising speeds can cause sequencing problems for ATC when mixed with jet operations

BTC 3/24 - ACFT (17 decks)

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