Airbus redundancy controls

[Gravox]

Got asked at an interview last year about what sort of redundancy control does the Airbus340 have. I struggled with an answer, and was told that I'll have to do more research into that for my next interview. After walking out i felt a little silly cos the :mad: thing is fly by wire. So is there any redundancy in the control surfaces?

What about The RAT (Ram Air Turbine), what does it power?

That next interview is just around the corner and thought I had better make an effort in finding out some answers, btw it was with Cathay.

[vapilot2004]

All A340 flight control surfaces are electrically controlled and hydraulically actuated. There are 3 Primary flight computers & 2 secondary units. Any one computer can control the aircraft.

Loss of Electrical Control and subsequent manual reversion:
Stabilizer trim and rudder have mechanical backup. Stab
requires B or Y hydraulics to operate.

The RAT supplies pressure to the Green Hydraulic system and green
can operate an emergency generator. With RAT in operation 15-45% of normal pressure (depending on airspeed) is available. The actuation of elevators, ailerons and spoilers occurs at a reduced rate.

Green system supplies:

High Priority
Normal brakes
Flaps
Slats
Flaps WTB (wing tip brake)
Slats WTB
Yaw damper 1
#1 & #5 Spoilers
Inboard outboard ailerons
L & RH Elevator
Rudder
#1 & #4 Reversers

Low Priority
Emergency Generator
Nose Wheel Steering
Landing Gear

Many of the computer/hydraulic failure scenarios have the A340 systems doing some pretty fancy stuff. I will not attempt to describe.

[FlapsOne]

Why would anyone need to know that unless they were qualified on type?

There are some dull interview questions floating round!!

[Dan Winterland]

I think this is a fly by wire question. Simply described as follows:

The Airbus FBW aircraft have four levels of redundancy. Firstly, Normal Law is all computers working, with all systems and protections normal. Lose a couple of computers, then you're in Alternate Law where everything works, but you lose some protections. Lose a bit more, then you go to Direct Law where the control movement is proportional to stick movement. In otherwords, it's now a Boeing! (Taking cover at this point :ooh: ). If it's really not your day and you've lost all the computers tou are now in maunual backup and the rudders control yaw (and consequently roll) and the stab trim contols pitch. Sounds drastic, but still flyable.