Night Hawk
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A330 Control Surfaces

Tue Apr 05, 2005 8:20 pm

I work at Perth Airport in Australia and one day I was driving past the back of one of Qantas's A330's and noticed all the control surfaces (aileron's & elevator's) were angle'd down, and the rudder fully deflected to the left. Im wondering what the story is with that? The aircraft was parked at the gate with the APU running if that means anything.

Greg
 
troubleshooter
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RE: A330 Control Surfaces

Tue Apr 05, 2005 10:12 pm

You´ll see that on all fly-by-wire aircraft. If there is no hydraulic pressure on the flight controls, the ailerons and elevators go down due to their own weight. The rudder is deflected by sidewinds. All actuators are dampened to prevent flutter in high wind conditions. As soon as hydraulics are on, all flight controls will move to their commanded position (they will center if there is no trim input).

Hope this helps.
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VC-10
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RE: A330 Control Surfaces

Tue Apr 05, 2005 10:52 pm

Quoting Troubleshooter (Reply 1):
You´ll see that on all fly-by-wire aircraft

You'll also see it on conventional airliners. Just look at the elevators & inbd ailerons on a 747 when the hyds aren't powered.
 
troubleshooter
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RE: A330 Control Surfaces

Wed Apr 06, 2005 1:03 am

VC-10,

thanks for your info on the 747. I don´t see them very often at our airport, so I didn´t know that. I just tried to point out that "hanging" flight control surfaces are a common finding on all FBW aircraft. Which doesn´t mean that this is not valid for conventional airliners, too.
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CCA
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RE: A330 Control Surfaces

Wed Apr 06, 2005 9:17 am

Quoting Troubleshooter (Reply 1):
the ailerons and elevators go down due to their own weight.

You'll find the 747 Outboard Ailerons and elevators rarely droop under their own weight as they are balanced. ie they have weights forward of the hinge equal to the weight aft of it.

Rgds CCA
P1 in A330, A340, A346, B742, B744, B748.
 
HorizonGirl
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RE: A330 Control Surfaces

Wed Apr 06, 2005 10:22 am

I have always wanted to answer this!
this will happen mostly on Fly-By-Wire aircraft.
As soon as there is no pressure, the Control surfaces will
"droop." and as VC-10 said, this will also sometimes happen on
other aircraft.

Devon
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Jetlagged
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RE: A330 Control Surfaces

Wed Apr 06, 2005 9:39 pm

I suppose you could say the 747 was fly-by-wire, in that the control signals are carried to the actuators by (mechanical) cables  Wink

Any aircraft with fully powered, irreversible flying controls will have suffer this kind of surface droop if the surface is not balanced.

On aircraft with manual or boosted controls, the surfaces may even go fully up, due to out of balance masses. Control locks are generally fitted on these aircraft to stop the surfaces being damaged, especially by tail winds, which can slam them between full down and full up.
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VC-10
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RE: A330 Control Surfaces

Thu Apr 07, 2005 1:31 am

Quoting CCA (Reply 4):
747 Outboard Ailerons.............. rarely droop under their own weight

With the flaps up the Otbd Ailerons are locked in the neutral postion. One of the first indications of a failed lock out mechanism is a drooping Otbd Aileron

And the elevators:


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[Edited 2005-04-06 18:37:11]
 
B747FE
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RE: A330 Control Surfaces

Thu Apr 07, 2005 2:46 am

Night Hawk

Regarding the A330 ailerons, they would droop to 10 as soon as the flaps are in 17 (ECAM indication 1+F). Not likely when the aircraft is at the gate, unless maintenance was inspecting it.


Quoting CCA (Reply 4):
747 Outboard Ailerons and elevators rarely droop under their own weight as they are balanced

Yes, they are balanced surfaces, but the lockout mechanism is activated when the leading edge flaps are retracted.

Regards,
B747FE.
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CCA
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RE: A330 Control Surfaces

Thu Apr 07, 2005 7:35 am

Quoting CCA (Reply 4):
747 Outboard Ailerons and elevators rarely droop under their own weight

Sorry what I should have added is under nil wind conditions, because if it's windy they could end up full up or down just like the rudder moves, balanced surfaces won't fall under their own weight.

Also the lockout has no effect it's mechanical and just prevents the outboard aileron inputs reaching the actuator so once hydraulic pressure is removed it may move after some time due to the wind.

Rgds CCA
P1 in A330, A340, A346, B742, B744, B748.

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