15.1 - Fundamentals

Question 1

What is work?

Answer 1

Work is done when an object is moved over a distance.

Work = Force x Distance

e.g. Work = 600N x 30m = 18,000Nm

Question 2

What is Power?

Answer 2

Power is the rate of doing work

Power = Work/Time (W) 1W = 1Nm/s

e.g. Power = 600N x 30m = 1800W (1.8kW)
10s

Question 3

What can mechanical energy be divided into?

Answer 3

Potential energy (PE)
Kinetic energy (KE)

Question 4

How do you work out the Potential energy for an object?

Answer 4

PE = mgh Force (ma = mg) x Distance ( =m =h)

Question 5

How can kinetic energy be expressed?

Answer 5

KE = 1/2mV2

Question 6

What is Newton’s first law of motion?

Answer 6

Called the Law of inertia

A body at rest remains at rest and a body in motion continues to move at a constant velocity unless acted upon by an unbalanced force.

Question 7

What is Newton’s second law?

Answer 7

That the acceleration produced in a mass by a force acting on it is directly proportional to the force and inversely proportional to the mass.

Expressed as

Force = Mass x Acceleration
F = ma (N)

Question 8

How does Newtons second law relate to Gas Turbine Engines?

Answer 8

The thrust is proportional to the mass of the airflow through the engine multiplied by the acceleration of the air through the engine

Question 9

What is Newton’s third law?

Answer 9

Every action has an equal and opposite reaction. (KQ)

Question 10

How does Newton’s third law apply to Gas Turbine Engines?

Answer 10

The action in a turbojet engine is the exhaust as it rapidly leaves the engine. The reaction is the thrust propelling the aircraft forward.

Question 11

What is the working cycle of an engine?

Answer 11

1. Induction
2. Compression
3. Combustion
4. Exhaust

Question 12

What are the four ideal changes of state?

Answer 12

1. Isobaric
2. Isochoric
3. Isothermal
4. Isentropic

(For Gas Turbine Engines, only the Isobaric and the Isentropic changes of state are of importance)

Question 13

What is an Isobaric process?

Answer 13

A process carried out where p = constant

Question 14

What is an Isochoric process?

Answer 14

A process carried out where v = constant

Question 15

What is an Isothermal process?

Answer 15

A process carried out where t = constant

Question 16

What is an Isentropic process?

Answer 16

A process carried out in an adiabatic system (a system with boundaries impervious to heat), therefore,there is neither heat addition or rejection possible

Q = 0

Question 17

What are the functions of an aircraft engine?

Answer 17

1. Create the necessary movement of the aircraft (main function)
2. Supply hydraulic power
3. Supply electrical power
4. Supply bleed air for the pneumatic system

Question 18

What are the advantages of a piston engine over a gas turbine engine?

Answer 18

1. Simpler in design
2. More fuel efficient

Question 19

What are the disadvantages of a piston engine over gas turbine engines?

Answer 19

1. Performance decreases at higher altitudes
2. Can be to large for the aircraft due to the ratio of weight and power decreases with the size of the engine

Question 20

What are the different types of gas turbine engines?

Answer 20

1. Turbojet engines
2. Turbofan engines
3. Turboprop engines
4. Auxiliary Power Units