AS 03 - Propulsion

Question 1

Define Thrust in terms of energy

Answer 1

Fuel is fed to an engine, this chemical energy is changed into thermal energy then converted into mechanical work in propelling an aircraft against the drag.

Question 2

What are the types of engines and the different type of propeller options?

Answer 2

Combustion and turbine engine
Fixed pitch and variable pitch propeller

Question 3

Old and well-tried system, gives a small acceleration to a large amount of air and driven by a combustion or turbine engine describes what type of propulsion?

Answer 3

Engine/ propeller propulsion

Question 4

What is a piston frequently referred to as? what is its product?

Answer 4

Referred to as a powerplant and its product is power.

Question 5

PLAN/3000 gives what calculation?

Answer 5

The amount of power a combustion engine can produce.

Question 6

The following equation explains what: T = m▲V?

Answer 6

The amount of thrust provided equals the rate at which momentum is given to the air

Question 7

What’s the difference between turbo-prop and a turbo-jet/ fan means of propulsion?

Answer 7

A turbo-prop gives a large mass of air a small acceleration
A turbo-jet/ fan gives a small mass of air a large acceleration

Question 8

What is the function of a propeller?

Answer 8

To convert the torque given by the engine’s power into a straight forward push or pull, called thrust, for forward speed.

Question 9

How does a propeller operate? (Think motion and forces)

Answer 9

Moves forward in a corkscrew motion
Pushes air backward to create thrust
As it rotates, it produces lift and drag
Forces are designated as thrust and torque

Question 10

The tip of the propeller spins faster than the base, how is uniform thrust maintained throughout most of the propeller diameter?

Answer 10

The propeller is “twisted” so that the angle of attack is less near the tip than the base.

Question 11

Define pitch (WRT propellers)

Answer 11

It is the distance in feet a propeller travels forward in one revolution.

Question 12

What are the main types of pitch?

Answer 12

Coarse and fine

Question 13

What governs the pitch?

Answer 13

The angle at which the blade is set

Question 14

What is the difference between coarse and fine pitch?

Answer 14

Coarse pitch: Blade set to a large angle, blade will travel a greater distance forward per revolution
Fine: Propeller will revolve around its own axis at a higher speed, enabling the engine to generate more power

Question 15

What is the trade-off for a fixed pitch propeller?

Answer 15

The angle is set by the manufacturer, you either have better take-off or cruising performance.

Question 16

“Engine and propeller always work at maximum efficiency” describes what pitch type?

Answer 16

Variable pitch

Question 17

True or false

A variable pitch propeller is manually adjusted and the propeller revolves at different rates depending on pitch.

Answer 17

False, the pitch is automatically adjusted and the prop maintains a constant rpm, with different pitches.

Question 18

What are the mechanisms for varying pitch?

Answer 18

Mechanical, hydraulic and electrical

Question 19

What are some difficulties of making propellers work well at high speeds?

Answer 19

Rotational speeds: Prop moves through air faster than speed of sound well before the aircraft
Supersonic flow: (PPT doesn’t go into much detail about this one)

Question 20

What kind of engine is used in the Dash 8?

Answer 20

Two Pratt & Whitney of Canada (PW120A)

Question 21

Which engine type only has a small amount of exhaust gases used as jet thrust?

Answer 21

Turbo-prop, the engine exhaust gases are used to drive the compressor and engine. Afterwards, exhaust gases are used as jet thrust.

Question 22

Describe the engine specs of a PW 120A and its propeller.

Answer 22

Each engine can produce 1800 SHP, with possible up trim to 2000 SHP in event of engine failure.
The propeller is a 13 ft diameter, four blade, constant speed, hydraulically controlled propeller.

Question 23

Where is the propeller connected to in a “Free Turbine” system?

Answer 23

Connected to what is referred to as a power turbine which “floats” in the high pressure exhaust gases in the turbine section.

Question 24

Review Questions

Name four common types of jet engines.

Answer 24

Ram-jet, turbo-jet, turbo-fan and engine/ propeller combination

Question 25

Review Questions

Which type of engine gives a large mass of air a small acceleration?

Answer 25

Turbo-prop

Question 26

Review Questions

What is the coarse pitch setting used for?

Answer 26

Cruise

Question 27

What is the SHP of the PW-120A?

Answer 27

1800 SHP, can up trim to 2000 SHP in the event of an engine failure.