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Flapping Ailerons On Takeoff A340  
User currently offlineA300 American From United States of America, joined Jan 2000, 173 posts, RR: 1
Posted (8 years 8 months 5 days 16 hours ago) and read 5146 times:

Hello all,

Back in 2003, I was on LAN from Santiago to BUE, we were in LANs A340 and I noticed the ailerons "flapping" up and down just before takeoff. Is this done purposely by the computer or pilot? What purpose does it fill? Ok, thanks in advance for the answer. Take care

A300 American

19 replies: All unread, jump to last
 
User currently offlineJamie757 From , joined Dec 1969, posts, RR:
Reply 1, posted (8 years 8 months 5 days 15 hours ago) and read 5117 times:

I think this check is done by the pilots to ensure that control surfaces are free and able to move. A pilot will be able to elaborate on this.

Rgds.


User currently offlineDH106 From United Kingdom, joined Jun 2005, 626 posts, RR: 1
Reply 2, posted (8 years 8 months 5 days 15 hours ago) and read 5113 times:

Flapping for extra lift cos the A340 needs all it can get ?  Big grin

Just kiddin.  Silly



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User currently offlineGoldenshield From United States of America, joined Jan 2001, 6120 posts, RR: 14
Reply 3, posted (8 years 8 months 5 days 15 hours ago) and read 5099 times:

Was this done during the takeoff roll, or was this done prior to entering the runway?


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User currently offlineMatt72033 From United Kingdom, joined May 2005, 1617 posts, RR: 4
Reply 4, posted (8 years 8 months 5 days 15 hours ago) and read 5091 times:

Quoting Jamie757 (Reply 1):
I think this check is done by the pilots to ensure that control surfaces are free and able to move. A pilot will be able to elaborate on this.

yep, you'll see every aircraft do there full and free checks sometime after pushing from the gate and getting to the runway, just to make sure theres no jammed control surfaces


User currently offlineA300 American From United States of America, joined Jan 2000, 173 posts, RR: 1
Reply 5, posted (8 years 8 months 3 days 17 hours ago) and read 4815 times:

Hello All,

Yes, the flapping of the ailerons occured DURING the takeoff role, which is why it caught my attention. Testing of controlled surfaces it definately wasn`t, since this is performed when the aircraft is stationary or taxiing. Anyway, the flapping stopped right before the aircraft rotated.

Quoting DH106 (Reply 2):
Flapping for extra lift cos the A340 needs all it can get ?


Exactly what I was thinking !!!  bigthumbsup 


User currently offlinePihero From France, joined Jan 2005, 4679 posts, RR: 77
Reply 6, posted (8 years 8 months 3 days 14 hours ago) and read 4745 times:
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Quoting A300 American (Reply 5):
Exactly what I was thinking !!!

So why do you ask the question ?



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User currently offlineNeilfking From United Kingdom, joined Mar 2006, 6 posts, RR: 0
Reply 7, posted (8 years 8 months 3 days 12 hours ago) and read 4704 times:

Quoting Pihero (Reply 6):
So why do you ask the question ?

Pihero, I think you are annoyed by anti-AB thoughts here and I sympathise with your annoyance as this sort of thing has no place on the Tech/Ops forum.

However, as you are an AB pilot, I would be interested to know your view on the aileron "flapping" during the T/O roll question. Is it something to do with nosewheel inputs translating through to the ailerons, maybe???

Look forward to your reply. Thank you.

Neil


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17186 posts, RR: 66
Reply 8, posted (8 years 8 months 3 days 12 hours ago) and read 4691 times:

Goodness. 777 ailerons "flap" as well if you count their connection to the spoilers. But I haven't seen it on take-off. Just landing.


"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineCX flyboy From Hong Kong, joined exactly 15 years ago today! , 6642 posts, RR: 55
Reply 9, posted (8 years 8 months 3 days 7 hours ago) and read 4641 times:

I am not an airbus pilot, so really do not know for sure, but I am going to take a wild stab at it, probably to be shot down as rubbish, but still...


...from what I understand, in an Airbus, if you hold the sidestick to say wings level, then the aircraft will do just that. If a gust of wind picks up a wing, or turbulence occurs, the aircraft knows the pilot wants wings level, and will use the control surfaces automatically to compensate, and give the pilot wings level. The pilot does now have to move the sidestick to compensate.
In a Boeing, the pilot has to move the control column to fight unwanted pitch/angle of bank movements.

So, perhaps what you saw was the aircraft compensating for any wobbles caused by an uneven runway and/or gusts of wind trying to pick up a wing when the pilot was commanding wings level?

Any Airbus pilot willing to elaborate or completely shoot down my theory?


User currently offlineCCA From Hong Kong, joined Oct 2002, 846 posts, RR: 14
Reply 10, posted (8 years 8 months 3 days 4 hours ago) and read 4611 times:

Quoting CX flyboy (Reply 9):
Any Airbus pilot willing to elaborate or completely shoot down my theory?

Good attempt.

Not on the bus anymore, but it's in "Direct law" on the ground so there is no compensating, after lift off Normal law is blended with Direct law until all you have is Normal law.

You end up with Direct law again at 100' AGL when landing.



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User currently offlineMytravel330 From United Kingdom, joined Aug 2005, 42 posts, RR: 0
Reply 11, posted (8 years 7 months 3 weeks 3 days 17 hours ago) and read 4309 times:

From what i can remember airbus aircraft are fitted with a system called aileron lockout,when the flaps are deployed for take off and landing both ailerons droop down to complete the trailing edge and aid lift/drag when this has to be reduced on one side of the aircraft the aileron on that side will raise slightly whilst the other one stays in line, as opposed to the conventional style of opposite deflection, remember that the force of the aircraft travelling down the runway is pretty substantial and it may just be caused by the force of it gaining momentum and is being forced up slightly more as the aircraft gains speed.

I'm sure i will be corrected if i am wrong but they employ this system in conjunction with the spoilers to turn the aircraft in the air as it reduces torsional twisting of the wing and to alleviate having the opposite effect to what you want if both ailerons are deflected to the same degree without spoilers.


User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 12, posted (8 years 7 months 3 weeks 3 days 16 hours ago) and read 4282 times:

I think they were signalling a turn.

Or having some kind of spasms.



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User currently offline2H4 From United States of America, joined Oct 2004, 8956 posts, RR: 60
Reply 13, posted (8 years 7 months 3 weeks 3 days 16 hours ago) and read 4271 times:
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Quoting SlamClick (Reply 12):
I think they were signalling a turn.

Exactly. That's why if you're turning left, the left aileron goes up, and vice-versa with the right.




2H4





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User currently offlineVC-10 From United Kingdom, joined Oct 1999, 3708 posts, RR: 34
Reply 14, posted (8 years 7 months 3 weeks 3 days 15 hours ago) and read 4249 times:
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Quoting Mytravel330 (Reply 11):
From what i can remember airbus aircraft are fitted with a system called aileron lockout

Aileron Lockout is when an a/c (e.g. B747) is fitted with both high speed & low speed ailerons. With the flaps retracted, the low speed ailerons are locked out i.e. locked in the neutral posn.

What you are referring to on the Airbus is Aileron Droop.


User currently offlineLH463 From United States of America, joined Apr 2006, 68 posts, RR: 0
Reply 15, posted (8 years 7 months 3 weeks 1 day 8 hours ago) and read 4068 times:

I think it was probably just a corsswind correction. When applying power for takeoff, pilots will turn the ailerons into the wind for correction. The greater the corsswind, the more aileron deflection there will be. As the aircraft gains speed and lift over the wing, the ailerons become more responsive, less and less aileron deflection is needed. Finally when the aircraft rotates and becomes airborne the aileron deflection should be very slight, or virtually none at all. As the climbout continues the pilots establish a crab to maintain the "imaginary" runway centerline.

My 2 cents,
LH463



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User currently offlineLTU932 From Germany, joined Jan 2006, 13864 posts, RR: 50
Reply 16, posted (8 years 7 months 3 weeks 1 day 5 hours ago) and read 4039 times:

Quoting Neilfking (Reply 7):
Is it something to do with nosewheel inputs translating through to the ailerons, maybe???

The nosewheel I believe isn't handled through the sidestick or a yoke. It's controlled through the wheel tiller.

Don't the ailerons move all the time to maintain the aircraft steady, not only on T/O but also in flight? I've seen this video of an SR MD-11 on FL350.com and it clearly showed that the inboard aileron was moving a little bit in flight.


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17186 posts, RR: 66
Reply 17, posted (8 years 7 months 3 weeks 1 day 2 hours ago) and read 3995 times:

Quoting LTU932 (Reply 16):
Quoting Neilfking (Reply 7):
Is it something to do with nosewheel inputs translating through to the ailerons, maybe???

The nosewheel I believe isn't handled through the sidestick or a yoke. It's controlled through the wheel tiller.

The nosewheel is indeed handled through the tiller, but also has limited movement range with pedal input. So if you move the pedals, you get nosewheel and rudder movement (no aileron movement). This nosewheel movement is locked out off the ground and above a certain speed (on certain aircraft).



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineZeke From Hong Kong, joined Dec 2006, 9240 posts, RR: 76
Reply 18, posted (8 years 7 months 3 weeks 20 hours ago) and read 3935 times:

Quoting A300 American (Thread starter):
Back in 2003, I was on LAN from Santiago to BUE, we were in LANs A340 and I noticed the ailerons "flapping" up and down just before takeoff. Is this done purposely by the computer or pilot? What purpose does it fill? Ok, thanks in advance for the answer. Take care

I think it would be a cross wind takeoff, if you apply too much roll input you will have spoiler deployment.



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User currently offlineWing From Turkey, joined Oct 2000, 1575 posts, RR: 23
Reply 19, posted (8 years 7 months 3 weeks 14 hours ago) and read 3879 times:

Flapping ailerons as you described for a crosswind take off it certainly not the correct technic for Airbus flyby wire airplanes.If lateral side stick input is necessary for strong crosswind take off it shouldn't be large enough to cause the spoiler deployment.
The aircraft will tend to turn into the wind and causing increase in drag.And as the airplane lifts off the wing will drop to the side jeopardising an engine or even a wing strike on the runway.

The inside wing will be pressed more to the wheels therefore reducing the tail clearence and its a major problem as the airplane you are flying gets longer(ie A321)



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