POF 2

Question 1

List the criteria for a maximum rate, minimum radius turn

Answer 1

• Max value of the product of: C_LMAX, speed and angle of bank (‘nibbling’ the stall buffet)
• Max rho (density) - sea level
• Min wing loading (min aircraft weight)

Question 2

Explain how ‘flap type’ controls work and what influences their effectiveness (x 4)

Answer 2

Flap-type controls work by changing the camber of a control surface to create an aerodynamic force that rotates the aircraft about each of its axes.

Primary controls are: elevator, ailerons and rudder.

Effectiveness of each control depends on:

1) The shape and size of the control surface
2) The amound the control surface is deflected
3) The aircraft’s speed
4) The moment arm ( distance from the CoG)

Question 3

Explain the principle of aerodynamic balance

Answer 3

Aerodynamic balance helps to overcome the apposing force on control surface movement due to control surface deflection - to make the pilots job less physically demanding!

Question 4

List and explain 4 methods of achieving aerodynamic balance

Answer 4

1) Inset hinge
2) Horn balance
3) Internal balance
4) Various balance tabs incl. geared tabs, servo tabs, spring tabs

Question 5

Explain the purpose of trim tabs

Answer 5

A Trim tab exerts a small downwards force at the TE of the elevator. The large moment arm is sufficient to balance the larger elevator force and its smaller moment arm.
2 types: Fixed tab, Trim tabs
Reduces pilot work load

Question 6

Explain mass balance

Answer 6

Reduces flutter by moving the CoG of the control surface closer to the hinge line.
Reduces fatigue

Question 7

Explain the purpose of spoilers

Answer 7

To reduce lift.

Question 8

List 5 other control features

Answer 8

1) Mass balance to remove flutter
2) Aero-elastic distortion - eliminated using stiffer wings
3) Airbrakes
4) Spoilers
5) Adverse Aileron yaw

Question 9

Explain adverse aileron yaw

Answer 9

Difference in drag between down-going and up-going wings creates yaw.

Question 10

How is adverse aileron yaw mitigated (x4)?

Answer 10

1) Differential Ailerons: For a given stick deflection the up-going aileron is deflected through a larger angle than the down-going aileron thus reducing the difference in drag and the adverse yaw.
2) Frise-type ailerons: The nose of the up-going aileron protudes into the air stream below to increase the drag on that wing.
3) Coupling of controls: Gear the rudder to the ailerons so that when the ailerons are deflected the rudder produces an appropriate yawing moment.
4) Spoilers: Increase drag on downgoing wing
(( Rudder: Manual correction by the pilot))

Question 11

Explain the difference between static and dynamic stability

Answer 11

An aircraft is disturbed from trimmed flight.
Its initial reaction after the disturbance is removed is termed static stability.
Its long term reaction is termed dynamic stability.

Question 12

What are positive, neutral and negative stability?

Answer 12

Positive - indicates a return towards the initial position
Neutral - indicates maintaining the new position
Negative - indicates continued divergence from the initial position

Question 13

What are the 3 components of stability and their axes?

Answer 13

Axis - Motion - Stability

Normal - Yaw - Direcetional
Lateral - Pitch - Longitudinal
Longitudinal - Roll - Lateral

Question 14

List the design features which enhance longitudinal stability?

Answer 14

tailplane and elevator

long moment arm

Question 15

List the design features which enhance directional stability?

Answer 15

fin and rudder

long moment arm

Question 16

List the design features which enhance lateral stability?

Answer 16

1) Dihedral (anhedral reduces lateral stability)
2) Wing position (high mounted wing)
3) Fin size (increased drag in sideslip induces roll)
4) Sweepback (low wing higher AR = more lift)

Question 17

What are the 3 types of Lateral Dynamic Stabilty?

Answer 17

Rolling motion
Spiral motion
Dutch Roll

Question 18

Explain Dutch Roll

Answer 18

An oscillation involving yaw, roll and sideslip.

• Perdiodic time usually fairly short
• short peroid causes more problems
• often caused by too much lateral stability

Question 19

Explain coarse and fine pitch

Answer 19

To maintain the most efficient AoA of the prop (4 degrees) the blade angle can be varried depending on the speed of the aircraft.
Fine pitch - good acceleration at low speed, limited high speed, used for take off
Coarse pitch - poor acceleration at low speed, good high speed, used for flight cruise
Variable pitch maintains efficiency across flight range

Question 20

Explain why propeller thrust decreases with increasing TAS

Answer 20

As speed increases, the AoA of the blade decreases and this will mean a decrease in thrust.

Question 21

Explain why a propeller driven aircraft swings on take off

Answer 21

3 causes:

1) Slipstream effect - prop rotating clockwise imparts a rotation in the slipstream in the same sense. Asymmetric flow over rudder/fin creates yaw to the left.
2) Torque reaction - torque in opposite direction to prop rotation. E.g prop clockwise, torque rolls aircraft left, more weight port wheel, aircraft tends to swing left.
3) Crosswind effect - directional stability causes swing in the direction of the wind.

Question 22

Explain the factors that affect the take off run

Answer 22

TO Flap - reduces TO run
Wind - head wind decreases TO run
Runway gradient - uphill increases TO run
Slush/wet snow - increases TO run
Aircraft weight - increases TO run
Airfield elevation - increases TO run
Air temperature - high temps increase TO run

Aircraft attitude - excessive high nose increases TO run
Thrust - increased thrust reduces TO run

Question 23

Explain the factors that affect the landing run

Answer 23

Landing Flap - decreases landing run
Wind - head wind decreases landing run
Runway gradient - down hill increases landing run
Slush/Snow - increases landing run
Aircraft weight - increases landing run
Airfield elevation - increases landing run
Air temperature - increases landing run

Question 24

What are reverse thrust and feathering used for?

Answer 24

Reverse thrust: mainly used on landing for slowing an aircraft
Feathering: Used following an engine failure to reduce drag

Question 25

Explain the causes of wake turbulence

Answer 25

wing tip vortices generated by lift

forms at wing tips and decays over time

Question 26

State the factors affecting the intensity of wake turbulence

Answer 26

depends on lift generated
most intense/severe:
-heavy aircraft
-low speed
-high AoA/manouvre

calm wind may cause the vortex to persist several miles behind a large aircraft

Question 27

State the action recommended for avoiding wake turbulence

Answer 27

Maintain safe time separation minima
Fly above the flight path
Be aware

Question 28

State the hazards associated with aquaplaning

Answer 28

1) loss of braking and directional control
2) scalding of tyres and possible puncture
3) if brakes applied during aquaplaning and remain applied, tyre burn results as aquaplaning ceases.

Question 29

State the recommended method of landing on a wet runway in order to minimise the risk of aquaplaning

Answer 29

Land Firmly
Reverse thrust
Gentle braking below aquaplaning speed

Question 30

State the actions to take when the aircraft aquaplanes

Answer 30

Do not use wheel brakes until well below aquaplaning speed

Question 31

Explain how an aircraft’s life is conserved - how to reduce fatigue

Answer 31

1) fly only with serviceable fatigue meter
2) keep high g mavouvres to a minimum
3) do not exceed aircraft limits
4) fly smoothly
5) reduce the fuel load if possible
6) avoid turbulence
7) low fly only when task requires it
8) minimise roller landings
9) keep taxying speeds low (walking pace)

Question 32

Explain how aircraft engine life is monitored

Answer 32

1) optical inspections using fibre optics
2) magnetic particle detection
3) filter inspection
4) spectrometric oil inspection
5) vibration analysis
6) in flight performance both by pilot and electronics

Question 33

How to maintian good engine handling?

Answer 33

1) Move throttle smoothly
2) Ts&Ps monitored
3) Engine limits adhered to
4) Avoid icing