Ch 15 - Stall Warning, Recovery And Regulations

Question 1

2 types of stall warner

Answer 1

Natural (buffet)

Artificial (flapper switch, audio warning system)

Question 2

Recognising the stall

Answer 2

Relatively low airspeed
Sluggish slow responses
Unresponsive
High nose attitude

(An accelerated stall may show no signs)

Question 3

Rectangular wing stall Symptoms

Answer 3

Increased buffet
Possible wing drop
Abrupt nose down pitch
Loss of altitude

Question 4

Swept wing stall warning

Answer 4

Artificial stall warners (audio, visual)
Stall prevention systems

Tip stall first (rapid roll rates)
Movement of CoP fwd which leads to a pitch up, combined with tailplane downforce = very unstable stall

Question 5

Fwd swept wings

Answer 5

Good stalling characteristics, likened to a rectangular wing

But hard to manufacture the structural stiffness required

Question 6

Canard Design in regards to stalling

Answer 6

Much more efficient aerodynamically

But the canard will stall first which will then send dirty air over the main wing which decreases the efficiency of the main wing and flaps

Question 7

Artificial Stall Warning Systems

Answer 7

All aircraft with limited aerodynamic stall warners will be fitted

Audio buzzer/alarm
Lights
Visual (PFD)
Stick shakers
Stick pushers

Question 8

The AoA Vane

Answer 8

Orientates itself in to the relative air flow and calculates how far it is from the longitudinal axis giving you your AoA

Question 9

AoA Probes

Answer 9

A little thing with two channels where RAF flows into, compares the difference between the two and is calibrated to then give you your AoA

Usually more than one used

Question 10

Restoring Probe

Answer 10

Motors move around the probe until the pressure difference between the two channels = 0

Again call I rated to then give the AoA

Small amount of lag

Question 11

Stick Shaker

Answer 11

Quite violent and will start either 5 degrees or 5kts (which ever is larger) above stalling speed

Question 12

Stick Pusher

Answer 12

Cannot be overridden by human (for exam)

Operates at 2kts or 2 degrees over stalling speed (which ever is larger)

Question 13

Stall recovery

Answer 13

First indication:
Reduce AoA
INcrease power to a safe speed
Use small and gentle aileron and rudder inputs to put AC into safe attitude

Disconnect autopilot if engaged

And be careful increasing thrust with underslung engines as it will create a pitch up moment

Question 14

What to do when stick pusher activates

Answer 14

Apply thrust
Disconnect autopilot
Trim
Allow for airspeed to increase and avoid rudder inputs
Once stick shaker deactivates, pitch up smoothly to regain lost altitude

Question 15

Recovery at the stall

Answer 15

Smoothly pitch nose down, slowly apply thrust

Once airspeed has increased to a safe margin above stall speed, pitch up to regain lost height

Question 16

Stall margins above the stall (EASA) for small and large aircraft

Answer 16

Small aircraft: CS23
Vs1 Vs0
- Worst CG
- Power off
- Mas Mass 

Larger Ac: CS25
Vsr (Vs1g) Vs (=0.94xVs1g)

Landing: TO:

1. 30 Vs0 (SA). -10 1.20Vs1
2. 23Vsr0 (LA). -10 1.13Vsr1

Question 17

Stall Warnings Requirements

Answer 17

Stall margin is the greater of 5kts or 5% and is Vsw