The Weird and Wonderful Logic

A318/A319/A320/A321
Professional
The Weird and Wonderful Logic
Vol
8
8-03-5
10 July 2018
• BANK ANGLE PROTECTION: another things your passengers will not like is to look out of the
window and stare directly at the ground. Also at high bank angles you will lose a lot of lift and
speed and G-loads will increase rapidly. That’s why the Airbus systems will prevent a very steep
bank. It will let you bank up to 67° and when you let go of the stick will return to 33°.
ALPHA FLOOR PROTECTION
A good example (and perhaps the most important) of the protections is the alpha floor protection. It’s
something every airbus pilot has to demonstrate on check flights and you can do the same. It’s safe and its
fun.
1. Disengage Auto-Pilot and Auto-Thrust Lever
2. Switch off the Flight Director
3. Retard Thrust Lever and let the speed go down to ‘green dot’ (the lowest safe speed at that
moment).
4. Now imagine an aircraft popping up and you have to avoid hitting it. Initiate a move UP and RIGHT
(forcefully!) to avoid a midair collision and observe what happens.
Clearly the aircraft will rapidly run out of airspeed and something needs to happen. Thankfully the Airbus
systems will detect this problem and it will initiate the alpha floor protection. The trust will go into TOGA
(the maximum available) mode and will stay there until the pilot tells it otherwise. The other protection
will prevent you from starting a loop or a roll. Although very close to the edge of the flight envelope the
aircraft will stay controllable during the whole procedure!
Oh, you want to know how to get back to stabilized flight?
1. Push forwards on the stick to reduce the angle of attack
2. Level the wings and let the aircraft ‘fly out of’ the problem. But you are about to face a new
problem as speed will increase rapidly and you could go from too slow to too fast in seconds!
3. Disengage Auto-thrust again by pushing the side button on the Thrust lever.
4. Select a safe speed on the FCU (for example 250 Knots).
5. Select both Flight Directors on again.
6. Re-engage Auto-thrust with the FCU A/THR button.
7. Set Thrust lever in CLIMB detent.
8. Re-engage Auto-pilot and establish normal flight.
9. Might not be a bad idea to talk to the passengers and to tell the cabin crew to distribute drinks for
the adults and toys for the kids.