Happy-flier
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A340 Ailerons Drooping When Flaps Set

Sun Feb 17, 2008 4:15 am

I've seen lots of photos of A340 (and I suppose A330 as well) wings in takeoff and/or landing configuration where not only are the flaps down, but the outer aileron sections are as well. I'm sure aerophysicists knew what they were doing when designing these systems - but I can't quite place the sense of it in my mind: doesn't aileron deflection that far out on the wing basically just bend the wingtips up? Is there much significant lift gained by doing this? You certainly never saw this on the L1011, DC-10 or even the 767 (though the inner ailerons do droop down on the 767).

And, the other question: Can an A340 pilot elect to just use the flaps, and leave the ailerons in neutral position - or does the outer aileron drooping happen by default?
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longhauler
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RE: A340 Ailerons Drooping When Flaps Set

Sun Feb 17, 2008 4:17 am

Aileron droop, has been a feature of Airbus aircraft since the A300.
They still work as ailerons, just from a different datum.

No, the pilot has no control over aileron droop.
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CosmicCruiser
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RE: A340 Ailerons Drooping When Flaps Set

Sun Feb 17, 2008 10:44 am

The MD-11 has them as well but ours were disabled due to high maint issues.
 
FlyASAGuy2005
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RE: A340 Ailerons Drooping When Flaps Set

Sun Feb 17, 2008 11:29 am

This sounds interesting. Could you provide a link so I can see this in action?
What gets measured gets done.
 
planewasted
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RE: A340 Ailerons Drooping When Flaps Set

Sun Feb 17, 2008 11:39 am



Quoting CosmicCruiser (Reply 2):
The MD-11 has them as well but ours were disabled due to high maint issues.

Interesting. For the Airbus it probably means no extra maintenance because the Ailerons are controlled through the FBW systems.
 
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Starlionblue
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RE: A340 Ailerons Drooping When Flaps Set

Sun Feb 17, 2008 11:43 am

The 777 also has aileron droop, but since it's a Boeing the surfaces are referred to as flaperons.

Quoting PlaneWasted (Reply 4):
Interesting. For the Airbus it probably means no extra maintenance because the Ailerons are controlled through the FBW systems.

That doesn't follow. Maintenance is on the actuators, flap tracks and such. What initiates the droop seems irrelevant.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
planewasted
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RE: A340 Ailerons Drooping When Flaps Set

Sun Feb 17, 2008 12:59 pm

But the MD11 probably has some dedicated hardware for the droop, while the Airbus is just software. or..?
Just guessing here.
 
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seabosdca
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RE: A340 Ailerons Drooping When Flaps Set

Sun Feb 17, 2008 4:04 pm



Quoting FlyASAGuy2005 (Reply 3):
This sounds interesting. Could you provide a link so I can see this in action?


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Look around the database for photos of A330 and A340 aircraft in initial climb and on short final and you'll find quite a few more like these.
 
SlamClick
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RE: A340 Ailerons Drooping When Flaps Set

Sun Feb 17, 2008 4:20 pm

Airbus certainly didn't invent the concept.


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Quoting CosmicCruiser (Reply 2):
disabled due to high maint issues

Wonder if there is a performance penalty. They do contribute life.
Anyone have a CDL?
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Happy-flier
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RE: A340 Ailerons Drooping When Flaps Set

Sun Feb 17, 2008 8:27 pm

Another thought: Why didn't the 727 use a similar aileron-droop system? It had a clean wing with no engine appendages, so at the very least they could have used the inboard ailerons to augment short-field takeoffs.

Anyone know if the 727 could do that?
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OldAeroGuy
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RE: A340 Ailerons Drooping When Flaps Set

Sun Feb 17, 2008 9:06 pm



Quoting Starlionblue (Reply 5):
The 777 also has aileron droop, but since it's a Boeing the surfaces are referred to as flaperons.

The 777 flaperon (ie inboard aileron/flap) is different than a drooped aileron. When extended to act as a flap, it has both Fowler motion and opens a slot, becoming a single slotted flap. Dropped ailerons have no Fowler motion and don't open a slot as they articulate via a simple hinge.

777 outboard ailerons droop when flaps are extended and are referred to as (wait for it!) dropped ailerons.
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Jetlagged
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RE: A340 Ailerons Drooping When Flaps Set

Sun Feb 17, 2008 10:09 pm



Quoting SlamClick (Reply 8):
Airbus certainly didn't invent the concept.

Good to see you back in the forum.  thumbsup 

Quoting Happy-flier (Reply 9):
Anyone know if the 727 could do that?

No aileron droop on a 727. They probably had enough complication in that wing without that.
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Starlionblue
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RE: A340 Ailerons Drooping When Flaps Set

Sun Feb 17, 2008 11:06 pm



Quoting PlaneWasted (Reply 6):
But the MD11 probably has some dedicated hardware for the droop, while the Airbus is just software. or..?
Just guessing here.

Yeah maybe. But I don't really think the assemblies would be that different.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
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ThrottleHold
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RE: A340 Ailerons Drooping When Flaps Set

Sun Feb 17, 2008 11:27 pm

The 330/340 outboard ailerons droop by 5' when the flaps are deployed to enhance lift.
 
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RE: A340 Ailerons Drooping When Flaps Set

Mon Feb 18, 2008 12:16 am

I don't think there are any FBW airliners out there without some sort of aileron droop. And that includes all current production Airbusses from 318 to the 380. It's a quite simple addition to flight control software which boosts slow speed performance a little.

It does, however, give a serious adverse yaw tendency when operating the drooped ailerons as ailerons. But at least the Airbussses (don't know about B777 and MD-11) have automatic rudder compensation for adverse yaw. You simply don't touch the pedals in flight until you have to make a landing in sidewind.

As far as I know the MD-11 is the only non-FBW airliner with aileron droop.

My model aeroplanes also have aileron droop, which I can disable with a switch on the R/C transmitter. That's needed since I don't have automatic adverse yaw compensation.

Competition gliders have had fully mechanical aileron droop for decades, but in a slightly different way. The ailerons follow the flaps when only activated a few degrees for maximising cruise performance. When flaps are lowered beyond a certain angle, and becomes as much brakes as lift generators, then the ailerons go back to neutral again for improved roll control, and also to keep adverse yaw within sensible limits. Some gliders even give negative droop on the ailerons when flaps are fully extended, which makes all four control surfaces work as mainly very efficient air brakes.
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CosmicCruiser
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RE: A340 Ailerons Drooping When Flaps Set

Mon Feb 18, 2008 9:51 am



Quoting Starlionblue (Reply 5):
That doesn't follow. Maintenance is on the actuators, flap tracks and such. What initiates the droop seems irrelevant

That's what I meant, thanks for wording it better. The A/C status page of the FMS would show drooped ailerons so I'm sure it was FMC generated. I never experienced any yaw on T/O or cruise or any other unfavorable flight characteristics. If you didin't see it on the FMS it would transparent.

Quoting SlamClick (Reply 8):
Wonder if there is a performance penalty. They do contribute life.
Anyone have a CDL?

I believe it would have been fuel burn penalty but not enough to justify the maint. I just tried looking it up in the MD-11 CFM but it looks as it's been deleted from our books. If I were at home I have an older CFM that I could reference if anyone is interested let me know.
 
FlyASAGuy2005
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RE: A340 Ailerons Drooping When Flaps Set

Mon Feb 18, 2008 11:15 am

Still no pic?

Anyone? I won't know what to look for if I try to go through the database.
What gets measured gets done.
 
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Buyantukhaa
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RE: A340 Ailerons Drooping When Flaps Set

Mon Feb 18, 2008 11:30 am



Quoting Happy-flier (Thread starter):
but I can't quite place the sense of it in my mind: doesn't aileron deflection that far out on the wing basically just bend the wingtips up?

So what? It would still be a force acting on the plane as a whole, so even if it would bend the wings up it would not "disappear" .
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PhilSquares
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RE: A340 Ailerons Drooping When Flaps Set

Mon Feb 18, 2008 11:41 am



Quoting Prebennorholm (Reply 14):
It does, however, give a serious adverse yaw tendency when operating the drooped ailerons as ailerons. But at least the Airbussses (don't know about B777 and MD-11) have automatic rudder compensation for adverse yaw. You simply don't touch the pedals in flight until you have to make a landing in sidewind.

Not on the 320. If you have an engine failure prior to engaging the autopilot, you will have to use rudder just like a conventional aircraft. Once the autopilot is engaged, it will compensate for adverse yaw.
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Jetlagged
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RE: A340 Ailerons Drooping When Flaps Set

Mon Feb 18, 2008 11:53 am



Quoting Prebennorholm (Reply 14):
As far as I know the MD-11 is the only non-FBW airliner with aileron droop.

The Airbus A300, A310 and A300-600 all have aileron droop. The Boeing 767 has inboard aileron droop.
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RE: A340 Ailerons Drooping When Flaps Set

Mon Feb 18, 2008 12:19 pm



Quoting BuyantUkhaa (Reply 17):
Quoting Happy-flier (Thread starter):
but I can't quite place the sense of it in my mind: doesn't aileron deflection that far out on the wing basically just bend the wingtips up?

So what? It would still be a force acting on the plane as a whole, so even if it would bend the wings up it would not "disappear" .

Actually wing bending does have an effect. Say the right aileron goes down and the left goes up (roll left). If the wings bend enough, the effect does "disappear". The wing bend acts as a control force in the opposite direction. So on the right wing, the aileron goes down, but the up bent and twisted wing acts like an aileron going up.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
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Jetlagged
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RE: A340 Ailerons Drooping When Flaps Set

Mon Feb 18, 2008 12:38 pm



Quoting PhilSquares (Reply 18):
Not on the 320. If you have an engine failure prior to engaging the autopilot, you will have to use rudder just like a conventional aircraft. Once the autopilot is engaged, it will compensate for adverse yaw.

Same for the A330 and A340. The flight control system computes a beta target, it's up to the pilot to follow it if autopilot is not engaged.
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David L
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RE: A340 Ailerons Drooping When Flaps Set

Mon Feb 18, 2008 12:55 pm



Quoting Starlionblue (Reply 20):
Actually wing bending does have an effect. Say the right aileron goes down and the left goes up (roll left). If the wings bend enough, the effect does "disappear". The wing bend acts as a control force in the opposite direction. So on the right wing, the aileron goes down, but the up bent and twisted wing acts like an aileron going up.

Hence the reason that outboard ailerons are often locked out at higher speeds, if fitted at all. However, can we assume that at those speeds where the flaps are deployed, the wing twist isn't a significant factor?
 
CanadianNorth
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RE: A340 Ailerons Drooping When Flaps Set

Mon Feb 18, 2008 2:05 pm



Quoting Prebennorholm (Reply 14):
As far as I know the MD-11 is the only non-FBW airliner with aileron droop.



Quoting SlamClick (Reply 8):
SlamClick

...


CanadianNorth
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David L
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RE: A340 Ailerons Drooping When Flaps Set

Mon Feb 18, 2008 2:49 pm



Quoting CanadianNorth (Reply 23):
Quoting SlamClick (Reply 8):
SlamClick

Does the Beaver count as an airliner?  Smile

Incidentally...

Quoting Jetlagged (Reply 11):
Good to see you back in the forum.

 checkmark  Ditto.
 
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SEPilot
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RE: A340 Ailerons Drooping When Flaps Set

Mon Feb 18, 2008 2:51 pm



Quoting Jetlagged (Reply 11):

No aileron droop on a 727.

The 727, having totally mechanical flight controls, would have a much more difficult time implementing it than would FBW planes. Boeing probably figured at the time the mechanical complexity added risk of failure and would not have been worth the risk. But as SlamClick pointed out, the concept has been around for a long time. There is a conversion kit available for Cessnas that adds it.

Quoting Starlionblue (Reply 20):

Actually wing bending does have an effect. Say the right aileron goes down and the left goes up (roll left). If the wings bend enough, the effect does "disappear". The wing bend acts as a control force in the opposite direction. So on the right wing, the aileron goes down, but the up bent and twisted wing acts like an aileron going up.

This effect was discovered during the wind tunnel tests of the 707. It was found that at high speed the wing deflected so much with conventional ailerons that roll control was completely lost; which is why the flaperons were introduced. At high speed the ailerons were locked and the flaperons used; at low speed the flaperons did not have enough control authority and so the ailerons were used.
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Jetlagged
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RE: A340 Ailerons Drooping When Flaps Set

Mon Feb 18, 2008 3:12 pm



Quoting SEPilot (Reply 25):
The 727, having totally mechanical flight controls, would have a much more difficult time implementing it than would FBW planes.

FBW only affects how the controls are signalled, not how they are actuated. Aileron droop is used in many non FBW aircraft, see posts above. The 727 has powered controls, so aileron droop could be added by offsetting the servo valves. However the fact that Boeing had chosen to install triple slotted flaps meant that drooping ailerons were not needed, if they were even ever considered.
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Buyantukhaa
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RE: A340 Ailerons Drooping When Flaps Set

Mon Feb 18, 2008 3:54 pm



Quoting Starlionblue (Reply 20):
Actually wing bending does have an effect. Say the right aileron goes down and the left goes up (roll left). If the wings bend enough, the effect does "disappear". The wing bend acts as a control force in the opposite direction. So on the right wing, the aileron goes down, but the up bent and twisted wing acts like an aileron going up.

Well I was thinking in the context of drooped ailerons, meaning that the situation is symmetrical, and wing bending would not have much of an effect. The upward force would increase due to the drooping of the ailerons, and the downward force would still be the weight of the plane (assuming the plane has no major pitch up or down attitude).

Of course if the wings would bend 45 degrees then your upward force would only be cos(45deg)=0,7 of the original, but the deflections are small enough for this not to be a significant factor, me thinks.
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Starlionblue
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RE: A340 Ailerons Drooping When Flaps Set

Mon Feb 18, 2008 4:04 pm



Quoting BuyantUkhaa (Reply 27):

Well I was thinking in the context of drooped ailerons, meaning that the situation is symmetrical, and wing bending would not have much of an effect. The upward force would increase due to the drooping of the ailerons, and the downward force would still be the weight of the plane (assuming the plane has no major pitch up or down attitude).

Yes I see.
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2H4
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RE: A340 Ailerons Drooping When Flaps Set

Mon Feb 18, 2008 4:19 pm



Quoting SEPilot (Reply 25):
There is a conversion kit available for Cessnas that adds it.

Wren, for example:





2H4
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OldAeroGuy
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RE: A340 Ailerons Drooping When Flaps Set

Mon Feb 18, 2008 4:23 pm



Quoting SEPilot (Reply 25):
This effect was discovered during the wind tunnel tests of the 707. It was found that at high speed the wing deflected so much with conventional ailerons that roll control was completely lost; which is why the flaperons were introduced. At high speed the ailerons were locked and the flaperons used; at low speed the flaperons did not have enough control authority and so the ailerons were used.

The effect was demonstrated in flight on the B-47 long before the advent of the 707. Control was not just lost, at high speeds it was reversed. If you turned the wheel to the right, the airplane rolled left. This led to the inboard aka high speed aileron (not flaperon) on the KC-135 and 707 and the addition of spoilers for roll control.
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FlyASAGuy2005
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RE: A340 Ailerons Drooping When Flaps Set

Mon Feb 18, 2008 4:28 pm



Quoting 2H4 (Reply 29):
Wren, for example:

Ok now I finally know what you guys are talking about!

Thanks for indirectly helping me out 2H4
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DeltaGuy
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RE: A340 Ailerons Drooping When Flaps Set

Mon Feb 18, 2008 4:32 pm

The F/A-18 Hornet's ailerons droop as well.

DeltaGuy
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SEPilot
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RE: A340 Ailerons Drooping When Flaps Set

Mon Feb 18, 2008 4:40 pm



Quoting OldAeroGuy (Reply 30):

The effect was demonstrated in flight on the B-47 long before the advent of the 707. Control was not just lost, at high speeds it was reversed. If you turned the wheel to the right, the airplane rolled left. This led to the inboard aka high speed aileron (not flaperon) on the KC-135 and 707 and the addition of spoilers for roll control.

Thanks for the correction. My memory was somewhat hazy and I was recounting what I thought I recalled. Your post jogged my memory and you, as usual, are correct.  thumbsup 
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prebennorholm
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RE: A340 Ailerons Drooping When Flaps Set

Mon Feb 18, 2008 6:52 pm



Quoting Jetlagged (Reply 19):
The Airbus A300, A310 and A300-600 all have aileron droop. The Boeing 767 has inboard aileron droop.

Thanks Jetlagged, I didn't know that also the A300/310 have aileron droop.

The B767, isn't that somewhat different, and in fact identical to even the B707 and DC-8? At slow speed, when flaps are extended, then aileron control is transferred from inboard to outboard ailerons. And the inboard ailerons are put fully down - drooped. But when drooped they do not work as ailerons any more. Roll control is fully in the hands of the outboard ailerons which do not droop.

Am I right?
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Jetlagged
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RE: A340 Ailerons Drooping When Flaps Set

Mon Feb 18, 2008 8:34 pm



Quoting Prebennorholm (Reply 34):
The B767, isn't that somewhat different, and in fact identical to even the B707 and DC-8? At slow speed, when flaps are extended, then aileron control is transferred from inboard to outboard ailerons. And the inboard ailerons are put fully down - drooped. But when drooped they do not work as ailerons any more. Roll control is fully in the hands of the outboard ailerons which do not droop.

No, and I don't think that's correct for the 707 or DC-8 either. Inboard ailerons always function as ailerons. The outboard ailerons are not so much taking over as supplementing the inboards, largely because of the increased roll damping with flaps extended but also because at higher speeds they would introduce excessive wing twist.

767 outboard ailerons are unlocked at low speeds and altitudes. The inboard ailerons droop at Flap 5 and more. Not sure by how much but it is no more than a few degrees. Thes photos show the droop is quite small.

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Arrow
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RE: A340 Ailerons Drooping When Flaps Set

Tue Feb 19, 2008 1:45 am



Quoting David L (Reply 24):
Does the Beaver count as an airliner?

Absolutely. I've been a paying passenger on many a Beaver flight, as well as Otters, Twin Otters. I'm pretty sure they all have flaperons, and in the Beaver's case it was designed in the 1940s.

Interestingly, the idea of a drooped aileron on the Beaver came about because the designer (Dick Hiscocks) thought the Beaver was going to be somewhat underpowered with a Gipsy Queen engine putting out 330 hp max. Without the drooped ailerons Hiscocks figured the float-version would never get off the water. When the Beaver was reconfigured to take the 450 hp P&W Wasp -- that fancy wing with all its gimmicks suddenly made the Beaver a world-beater in its class -- and it remains so today.
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David L
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RE: A340 Ailerons Drooping When Flaps Set

Tue Feb 19, 2008 10:47 pm



Quoting Arrow (Reply 36):

Quoting David L (Reply 24):
Does the Beaver count as an airliner?

Absolutely.

OK, let me rephrase: did Prebennorholm mean to include aircraft such as the Beaver in his comment?  Smile
 
2H4
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RE: A340 Ailerons Drooping When Flaps Set

Tue Feb 19, 2008 11:00 pm

I'm still in awe that a designer with a name like that wound up working on an airplane called the "Beaver".

As if there weren't enough innuendo possibilities as it was...  biggrin 

2H4
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MD11Engineer
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RE: A340 Ailerons Drooping When Flaps Set

Wed Feb 20, 2008 1:00 am



Quoting SEPilot (Reply 25):
The 727, having totally mechanical flight controls, would have a much more difficult time implementing it than would FBW planes. Boeing probably figured at the time the mechanical complexity added risk of failure and would not have been worth the risk. But as SlamClick pointed out, the concept has been around for a long time. There is a conversion kit available for Cessnas that adds it.

On the MD-11 the mechanism is actually quite simple:
The rods connecting the outboard aileron bell cranks to the ailerons contain a screwjack and a small electric motor. All that happens is that the rod becomes a little bit longer on T/O flap settings.

Jan
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9VSIO
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RE: A340 Ailerons Drooping When Flaps Set

Sat Feb 23, 2008 4:30 pm

The airbus ailerons don't just droop, they also deflect upwards on landing  Smile
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Jetlagged
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RE: A340 Ailerons Drooping When Flaps Set

Sat Feb 23, 2008 4:54 pm



Quoting 9VSIO (Reply 40):
The airbus ailerons don't just droop, they also deflect upwards on landing

The only way they will deflect upwards is from a roll input.
The glass isn't half empty, or half full, it's twice as big as it needs to be.
 
2H4
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RE: A340 Ailerons Drooping When Flaps Set

Sat Feb 23, 2008 5:24 pm

Ailerons and elevators aren't the only control surfaces that can deflect upward. Certain Maules and gliders have a negative seven degree flap setting.

2H4
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soon7x7
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RE: A340 Ailerons Drooping When Flaps Set

Sun Feb 24, 2008 3:07 am

A340 Ailerons also double as spoilers, dumping lift upon runway contact...In fist photo of D-AIHO in a long decent, in stable air, you can see the constant downward aileron deflection,...on FINAL, the ailerons rate of deflection and travel is incredible...looked like it was out of control...the second image clearly shows same surface in lift dump configuration...
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9VSIO
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RE: A340 Ailerons Drooping When Flaps Set

Sun Feb 24, 2008 10:45 pm



Quoting Jetlagged (Reply 41):

The only way they will deflect upwards is from a roll input.

Nope. There is a very clear "lift dump" mode  Smile

Quoting Soon7x7 (Reply 43):

Yeah, that's what I've been told by big bus drivers and I doubt that the a/c had a large roll input on the ground, I suppose I should have been more specific when talking about "Airbus" as I'm not sure abt the baby busses. There's prob documentation on smartcockpit on this.
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Jetlagged
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RE: A340 Ailerons Drooping When Flaps Set

Mon Feb 25, 2008 11:33 am



Quoting 9VSIO (Reply 44):
Nope. There is a very clear "lift dump" mode

Certainly not on the A320, and I can find no reference to this in A340/A330 manuals. Are you not confusing this with ground spoilers? After all once the ground spoilers are deflected up, airflow over the ailerons is going to be almost completely ineffective.
The glass isn't half empty, or half full, it's twice as big as it needs to be.
 
David L
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Joined: Tue May 18, 1999 2:26 am

RE: A340 Ailerons Drooping When Flaps Set

Mon Feb 25, 2008 11:51 am

Not much evidence of lift-dumping ailerons here:

320: http://www.youtube.com/watch?v=xhCbfdrA1HE
330: http://www.youtube.com/watch?v=3aRLHIFTANA
340: http://www.youtube.com/watch?v=_U0Of2MZB4U

But... the aileron does seem to match the spoilers from deployment to stowage here:

380: http://www.youtube.com/watch?v=hvs256uR_Q0
 
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Jetlagged
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RE: A340 Ailerons Drooping When Flaps Set

Mon Feb 25, 2008 3:10 pm

You learn something new every day! There are no spoilers in front of the ailerons so I guess Airbus decided additional braking and liftdumping from the ailerons was worthwhile for the newer models like the A380.

It also appears to be a feature of the A340-600:

http://www.youtube.com/watch?v=ntscvqhGwqA

and the A340-500:

http://www.youtube.com/watch?v=_i7-KQqBBjI

Thanks for helping clear that up, David. Apologies to 9VSIO for assuming no Airbuses had this feature just because the older ones don't.  Smile
The glass isn't half empty, or half full, it's twice as big as it needs to be.
 
David L
Posts: 8552
Joined: Tue May 18, 1999 2:26 am

RE: A340 Ailerons Drooping When Flaps Set

Mon Feb 25, 2008 4:25 pm



Quoting Jetlagged (Reply 47):
Thanks for helping clear that up, David. Apologies to 9VSIO for assuming no Airbuses had this feature just because the older ones don't.

I confess I went searching for the videos whilst in Bollocks Mode, myself.  duck 

I didn't think to check the 345/346 separately, though.
 
soon7x7
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RE: A340 Ailerons Drooping When Flaps Set

Mon Feb 25, 2008 5:25 pm



Quoting Jetlagged (Reply 41):

While Photographing these two configurations, both sides were in view and I was able to qualify symetry on both sides during two shots as I had never seen this before...I have seen similar behavior on high speed ailerons on 767's and 777's.
I have never seen this on outboards before...j

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