How To - AoA Mode

[mattY]

What is AoA mode?

AoA mode is an AT mode designed to maintain a minimum safe angle of attack and varies depending on its activation condition.

AoA mode is engaged automatically under any of the following conditions:

• TO
• GA
• Fully configured for landing
  • Flaps deployed to 33 degrees
  • Landing gear down
• In flight if speed drops below the minimum speed

If AoA is uncommanded (in flight below safe speed) - the speed target by the AT system will be 1.3 x current stall speed (Vs). This is to ensure the aircraft is able to maintain a safe angle of attack, somewhat similar in concept to the Airbus A.FLOOR. If it engages in flight and you use the AT mode to maintain this speed - when you are in a more stable flying condition you must toggle off AT to disable the AoA protection.

If AoA is commanded by TO or GA modes the target speed becomes 1.25Vs and will become inactive when an AP is selected on, or a vertical AFCS mode is selected.

If AoA is commanded by landing configuration, the speed target is a bit more involved. Rather than being a function of Vs, it becomes a function of Vthreshold (Vth) - the speed at which you should cross the runway threshold. Landing AoA speed is: Vth + %CG additive (nominal 6 kts, moving towards 10 kts for forward %CG and 3 kts for aft %CG) + wind compensation. Note that dependant on your weight (for example, loaded for a TATL flight and having to make a return) this speed may well exceed the common 160 kts to 4 DME instructed by ATC. If heavy, its recommended to advise "unable", rather than disable AT and try and hold slower than safe speeds.

Note: the AoA mode WILL NOT respect the speed set in the speed window.