Chapter 9 - Angle of Attack and Stall Warning Systems

Question 1

What is the aircraft’s AOA system sometimes called?

Answer 1

Alpha system

Question 2

What systems might use AOA data?

Answer 2

• Stall warning and detection systems
• Autopilot system
• ADC
• AOA indicators

Question 3

What are the two ways of detecting AOA?

Answer 3

• AOA vane
• AOA probe

Question 4

What are the two types of AOA probe?

Answer 4

• Fixed
• Rotating

Question 5

How does a fixed AOA probe work?

Answer 5

Pressure inlet ports are located inline with the central axis of the probe vertically, but above and below each other

At different angles of attack a pressure difference directly related to the AOA is produced

Sensed by a transducer to measure the difference and present the data as required

Question 6

How does a rotating AOA probe work?

Answer 6

System monitors pressures in P1 and P2, and where a difference exists, a synchro motor will rotate the probe in the correct direction to equalise the pressure

Angle of rotation is the AOA

Question 7

What are the two types of stall warning system?

Answer 7

1. Pneumatic
2. Vane

Question 8

Describe a pneumatic stall system?

Answer 8

Inlet on the left wing leading edge which is ducted to a horn in the cockpit

Question 9

At what speed will a pneumatic stall system operate a warning?

Answer 9

5 to 10 knots above the stall

Question 10

What are the inputs to a stall warning computer?

Answer 10

• Slat position
• Flap position
• AOA
• ADC
• Air/ground switch

Question 11

What can be the outputs of a stall warning computer?

Answer 11

• Audio and visual warnings
• Automatic slat deployment to reduce stalling speed
• Stick shaker
• Stick push to lower the elevators

Question 12

How should dual stall warning systems be powered?

Answer 12

From separate systems

Question 13

What happens if one system senses stall conditions in a dual stall warning system?

Answer 13

Will trigger the other one to operate