Aircraft Characteristics and Performance

Question 1

What are the motions of an aircraft called and around which axis does the motion take place?

Answer 1

Yaw - Around the vertical or normal axis
Roll - Around the Longitudinal Axis
Pitch - Around the lateral axis

Question 2

Which control surfaces affect the motion of an aircraft?

Answer 2

Ailerons - Roll
Rudder - Yaw
Elevators - Pitch

Question 3

What are the 2 types of drag called?

Answer 3

Profile drag - caused by the shape of the aircraft

Induced drag - Caused by the wings generating lift

Question 4

What happens to each type of drag as airspeed increases?

Answer 4

Profile drag increases

Induced drag decreases

Question 5

How does Bernoulli’s Principle relate to an aerofoil?

Answer 5

The top curved surface forces the air to travel faster over the top of the wing compared to the air underneath the wing. This leads to an increase in the dynamic pressure and a reduction in the static pressure on the top of the wing. High pressure moves towards low pressure causing the wing to rise.

Question 6

What is a chord line?

Answer 6

It is a straight line joining the leading edge and the trailing edge of a wing

Question 7

What is a chord line used for?

Answer 7

To calculate the angle of attack between the wing and the relative airflow

Question 8

What is a flap?

Answer 8

It is a trailing edge high lift device

Question 9

How does a flap work?

Answer 9

Increases lift by increasing the curvature of the wing

Question 10

What is a slat?

Answer 10

A leading edge high lift device

Question 11

What is a slot?

Answer 11

The space between the slat and the wing. It helps direct air over the wing when the wing is operating at particularly high angles of attack

Question 12

What does an elevator trim tab do and how does it work?

Answer 12

Removes excess force from the control wheel. It operates in the opposite direction to the elevator. For example, if the elevator is needed to be held up, the trim tab would be down.

Question 13

How does reaction propulsion work?

Answer 13

Either a small acceleration to a small amount of air or a large acceleration to a small amount of air

Question 14

What are the stages of an internal combustion engine?

Answer 14

Intake, compression, combustion, exhaust

Question 15

Name 3 advantages to a piston engine

Answer 15

i) More robust and easier to maintain
ii) |Lower temperatures and pressure so more fail safe
iii) Cheaper to manufacture

Question 16

Name 3 disadvantages to a piston engine

Answer 16

i) Relatively expensive fuel
ii) Lower ceiling
iii) More wear and tear due to vibration

Question 17

What is a propeller?

Answer 17

A means of converting engine power into propulsive force

Question 18

What happens to a blade pitch and why?

Answer 18

Blade pitch increases as you move closer to the hub. This is because the tips are moving faster than the propeller closer to the hub. Increased blade pitch results in a constant amount of lift along the whole length of the blade.

Question 19

What does the turbine in a gas turbine engine do?

Answer 19

Only drives the other parts of the engine. Does not produce any propulsive force

Question 20

Name 3 advantages to a gas turbine engine

Answer 20

i) Faster
ii) Relatively light engine with few moving parts
iii) Better climb performance

Question 21

Name 3 disadvantages to a gas turbine engine

Answer 21

i) High initial cost
ii) Less manoeuvrable at low level
iii) Delay in engine take up time (spool time)

Question 22

How does a jet engine work?

Answer 22

Air is taken in through the air intake and compressed in the compressor. The compressed fuel/air mixture is burned and the hot air is expelled through the turbine causing it to turn. The exhaust causes an equal and opposite reaction forwards

Question 23

What turbo prop configurations are there?

Answer 23

i) Direct drive turbine
ii) Free turbine
iii) Two spool (compound) turbine

Question 24

Name 3 advantages to a turboprop

Answer 24

i) More manoeuvrable at low speeds
ii) Quicker transition from approach to overshoot
iii) Quiet

Question 25

Name 3 disadvantages to a turboprop

Answer 25

i) Lower cruising level than jet engines
ii) Relatively higher initial build cost
iii) Greater frontal area causes more drag

Question 26

What thrust reverse systems are available?

Answer 26

Hot Stream - Post turbine

Cold Stream - Post compressor

Question 27

What is the artificial horizon?

Answer 27

A gyroscope instrument that indicates the attitude of the aircraft. Used when flying in poor visibility, over expanses of water or at night.

Question 28

What kind of gyro is fitted to an artificial horizon?

Answer 28

An Earth gyro (A free gyro which is aligned to the Earth with a pendulum)

Question 29

What is gyroscopic progression?

Answer 29

Any force which is applied to a gyro causes a change of direction of axis but at 90 degrees in the direction of rotation