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lfo
6th Jun 2004, 20:13
hello everyone.
could someone explain to me what dynamic ailerons are?.
thank you very much:O

411A
8th Jun 2004, 01:55
Generally speaking, dynamic ailerons are designed so that when the aileron is deflected, the hinge line is not at the trailing edge, but some distance along the chord, which results in aerodynamic assist, if designed properly.
On US aircraft, first used extensively on Douglas and Lockheed 4-engine piston transports.
My understanding anyway.
Others may disagree...:rolleyes:

lfo
8th Jun 2004, 10:06
thanks for your answer.
i was told, it had something to do with new technology but i haven't found anything about it.
thanks again

Intruder
8th Jun 2004, 16:51
I don't know if it is the same concept, but "active ailerons" have been tried on a few airplanes (L-1011?) to re-distribute the wing load in flight and/or to help damp lateral oscilaltions. Current fly-by-wire fighter airplanes such as the F-16 and F/A-18 also have active ailerons.

forget
8th Jun 2004, 17:32
http://www.globalsecurity.org/military/systems/aircraft/c-5a.htm

411A
9th Jun 2004, 03:27
Intruder,

You are indeed quite correct.
The Lockheed L1011-500 series had active ailerons, which worked to relieve gust loads on the wing.
If, for any reason the system was unserviceable, the aircraft could still be dispatched under MEL, but with a rather severe weight penalty.

The system on the -500 was very reliable and worked good. :)

Ah...Lockheed.
Ask the folks who operated one...delightful.:D

conch
9th Jun 2004, 09:23
So I understand from your posts that dynamic ailerons are nothing else than active ailerons, or am I wrong?
Seems that somebody just renamed the whole thing...
Airbus has dynamic ailerons installed, is that correct?

Intruder
9th Jun 2004, 12:09
So I understand from your posts that dynamic ailerons are nothing else than active ailerons, or am I wrong?
Dunno...

You asked the question without giving any context. You will have to decide if these are the answers you are seeking, or give us more information.

lfo
9th Jun 2004, 21:36
i read on another post that it had something to do with new technology (Airbus), but i can't find anything at all about it. i don't know ir dynamic are the same as active ailerons.:confused:
thank you
cheers

idg
10th Jun 2004, 01:11
Ifo,

Indeed early A320s had 'active ailerons' in much the same way that 411A has described for the L1011-500.

In later models they were deleted, since I was told that the wing had been 'beefed' up. Certainly the 321s never had this system.

In Airbus 'speak' it was called LAF for 'load alleviation function' and worked very much as the L1011's sytem did by moving both ailerons together up or down when a gust was sensed to be loading the wing, effectively suppressing or damping out the bending moments on the wing and thus allowing a lighter weight structure to carry heavier weight.

Interestingly on the L1011, the CAA approach to the system was very different to that of the FAA.

During flight testing for CAA certification it was found that in a jet upset type scenario the ACS (as it was called on the tri-motor) would effectively be 'adding' to the elevator up and would cause the a/c to increase the pitch up and thus exacerbate the situation. This was a result of the very short fuselage for the -500 variant that put the extended wingtips almost at the same longitudinal position as the stabiliser.

The fix was to change the ACS schedule and also to fit an extra device called recovery speed brake (RSB) which sensed the onset of this phenomenon and deployed almost full speed brake to kill the lift on the wing....very dramatic!

:ok:

conch
10th Jun 2004, 09:43
Thank you for your explanation idg.
I think one question asked by Ifo still remains unanswered.
Are dynamic ailerons the same as active ailerons??
I know what active ailerons are but I have not heard the term 'dynamic' related to ailerons either so far.
Thanks

idg
10th Jun 2004, 10:10
Conch,
I haven't heard the term before either. I suspect that indeed they are one and the same thing.

While I think of it the ailerons also droop 5 degrees training edge down when flaps are deployed on the 320 to change the outer wing camber. Another active mode?

:ok:

CS-TMX
3rd Jul 2004, 06:06
During flight testing for CAA certification it was found that in a jet upset type scenario the ACS (as it was called on the tri-motor) would effectively be 'adding' to the elevator up and would cause the a/c to increase the pitch up and thus exacerbate the situation. This was a result of the very short fuselage for the -500 variant that put the extended wingtips almost at the same longitudinal position as the stabiliser.

And also to prevent jet upset all L1011 series used a stabilator or an "all flying stabiliser" as it was called.

Besides ACS it also had the Maneuvering Direct Lift Control wich was an extension of DLC/Autospoilers function which improved pitch control characteristics at high speed (above Mach 0.65) in function of positive accelerations.

The ACS and MDLC make the TriStar500 the smoothest plane to ride ever built and with great turbulence response. No modern aircraft can beat it.

Just to let you know, the neutral angle of active ailerons in flight cruise was 2 down!

As for DLC it worked during approaches (after flaps more than 30) to provide vertical speed control without significant changes in pitch attitude.
When flaps are more than 30, DLC makes the 4 inner spoilers raise to a new neutral position of 7. If you are are above your glidepath than the spoilers vary from 7 to 14 to "kill" lift. If you are under you glide path they vary between 7 and 3. And voila, you also have the smoothest and precise approach.

You can see DLC working on this video of a wingview approach:

http://www.tristar500.net/filmes/landing.wmv


More things could be said... Also it's the only commercial aircraft that do not re-circulate the cabin air. Instead, the total cabin air is renewed every 4 minutes!!! And you got a healthier flight!

A trully remarkable aircraft with some tech still ahead of OUR time.

It will be sorely missed!:ugh:

Best regards