Tech Prep - PoF

Question 1

Critical engine

Answer 1

The engine most affect handling performance:
PAST:
P factor (left yaw)
Accelerated slip stream (roll left)
Spiraling slipstream (yaw)
Torque (roll left)

Question 2

Swept wing:
advantages
disadwantages

Answer 2

High mach cruise speed: Mcrit delayed to M/cos(sweep)
stability in turbulence (poor lift qualities)

Disadvantages:
poor lift qualities (high lift devices)
speed instability at lower speeds
wing tip stalling tendency

Question 3

High lift devices

Answer 3

Increase CL and CD (more drag than lift) by increasing wing surface or camber, slotted flaps/slats re-energise the boundary layer

Question 4

Critical Mach number

Answer 4

lowest speed at which the airflow over some point of the aircraft reaches the LSS

Question 5

Mach tuck

Answer 5

aerodynamic effect of downward nose pitch as the airflow reaches supersonic speeds.
The effect increases significantly above M1

Question 6

Coffin corner

Answer 6

its the altitude at which stall speed = critical mach number (Vs = Mcrit)

Question 7

Stall

Answer 7

sudden reduction in lift when the critical angle of attack reached or exceeded

Question 8

Deep stall

Answer 8

A stall that results in significant loss of elevator authority, making normal recovery actions ineffective.
Rudder effectiveness is greatly reduced as well.
If the engines are in the stall wake as well, engine stall can also occur, further increasing the danger.
T-tail aircraft are most susceptible for deep stalls

Question 9

Dutch roll

Answer 9

A combination of roll, yaw and slip, a dynamic oscillation movement that occurs when lateral stability (dihedral effect) is stronger than directional stability

Question 10

Centre of pressure

Answer 10

The average location of all of the pressure acting upon a body moving through a fluid.
Changes with varying AoA
The total aerodynamic force can be considered to act through the centre of pressure and can be resolved into its two components, lift and drag.

Question 11

Why does a heavier aircraft descend slower?

Answer 11

Because for the same rate of descent it would need to maintain a higher airspeed (i.e because of the higher weight it needs more lift, and therefore more speed)