Aileron Reversal

[Genghis the Engineer]

I don't have a copy to hand, but Jeffrey Quill's fascinating book "Spitfire" describes the problem of aileron reversal being met on some marks of Spitfire, causing significant torsional stiffening of the wings to be required.

I've met one modernish light aeroplane (the CFM Shadow) which depending upon model can do this in a big way also.

However, can anybody refer me to any other aeroplanes that have had aileron reversal problems - ancient or modern?

G

[gruntie]

Hellcat, I think, maybe.

[BEagle]

At above 345 KIAS, the VC10 suffers partial aileron reversal. Thus symmetric spoiler extension as speedbrakes is inhibited above that speed to ensure that the spoilers can be used differentially for roll control.

Not usually a problem nowadays as Vmo has been reduced to 300KIAS....

[Evileyes]

P-47 Thunderbolt as I recall.

[treadigraph]

Think the Bearcat did as well.

[con-pilot]

Lear 23/24/25 during over Mach limit, usually followed by wing separation.

[Conan the Librarian]

McDonnell F3H Demon was one. Also had a bit of a problem with drop tanks. There was so much drag, that the aircraft range was reduced to less than a clean one :}

Conan

[ICT_SLB]

Believe the FW-190 suffered from it too - read somewhere that only thing that kept some Hurricane pilots alive was a low level turn at the last minute.

[innuendo]

Conan: "Also had a bit of a problem with drop tanks. There was so much drag, that the aircraft range was reduced to less than a clean one "
Guess you needed to have enough of them and the money for new ones to be able to actually drop them . Not too practical in peace time I suppose.:)

[Dan Winterland]

A lot of big Boeings. For example, the B747 has inboard and outboard ailerons to counter the problem. The outboards are only used at slower speeds, the inboards, because of their position cause very little torsion twisting so don't lead to aileron reversal. The Classic 747s outboards are used when the flaps are at 1 or more, the 747-400s are speed scheduled. 237 Knots rings a bell.

The 707 and 727 had inboards as well. Don't think the 737 does, and don't know about the 777. Airbusses don't.

[ancientaviator62]

If my fading memory serves me the crash of an RAF Argosy during a high speed low level run at El Adem ? was put down to either wing warping and/or airleron reversal. I believe the Argosy utilised the Avro Shackleton wing with minor mods, and thus not optimsed for speed.

[djpil]

P-47 Thunderbolt as I recall.
Page 131 of NACA Report 868, Summary of Lateral-Control Research:
For the P-41C-1-RE at 400 mph IAS, a 31% loss in aileron effectiveness. The aileron reversal speed is about 545 mph IAS.
Spitfire at 400 mph IAS, approx 65% loss in aileron effectiveness.
Get it at http://techreports.larc.nasa.gov/

[Tim Inder]

Not sure if the F-100 actually suffered from it, or was designed from the start with inboard ailerons?

[BEXIL160]

Now here's an interesting situation....

A320 Captains Side stick works in the opposite sense to the Co-Pilots... Read on:

http://www.cs.york.ac.uk/hise/safety-critical-archive/2001/0362.html

Rgds BEX

[sled dog]

Ancientaviator62

Is that the one that hit the water tower ?

[Saab Dastard]

Genghis,

It was only the very last marks - Griffon engined marks 21 and above - that were affected.

The torsional stiffness of the wings on the mark 21, 22 & 24 was increased by 47% over previous marks, raising the theoretical aileron reversal limit from 580 to 825 mph IAS.

Up to this point, aileron reversal had not been considered a problem, as the vne was lower than the theoretical AR speed for other reasons. But with the advent of ever more powerful engines, the designers felt that the margin was decreasing too rapidly between the attainable speed in normal operating conditions and the AR limit.

Apparently the Bristol Bagshot experienced the phenomenon in 1927, also the Lockheed C141 (somewhat later, obviously). The Mig. 29 had small vortex generators added each side of the nose to overcome an early tendency to aileron reversal at angles of attack above 25 degrees.

[Conan the Librarian]

Tim, the F-100 problems were legendary. Aileron reversal, Yaw coupling - take your pick. A very hard and painful lesson accelerated by the Korean war, but eventually they got it about right. Even the experienced, hardcore Sled drivers referred to a good landing, as a controlled (and flapless) crash.

The author of Jonathan Seagull, Richard Bach (and many other priceless tomes for those with a love of aviation - wonderful author) was an ex Sled jockey and I seem to remember him writing a superb piece about it.

Might start a thread on Richard Bach one day.... Inspirational...

Conan

[BEagle]

Saab Dastard - do you mean 'aileron reversal' or 'roll reversal'?

At high AoA, the F-4 Phantom suffered hugely from roll reversal if the control column was used to roll the a/c. So much so that the phrase "If it buffets, use your boots" was often heard. I recall quite clearly the 'High AoA' handling trip I had to do with the Sqn QFI - including a 360 deg 'rudder roll' maintaining 19(??) units AoA...

Nothing to do with wing stiffness, this was purely an aerodynamic blanking effect. The F-4 used aielron and spoiler to roll; at high AoA the adverse yaw from the downgoing aileron was considerable and the upgoing spolier was blanked from the airflow...

Modern FBW takes care of such unpleasant quirks, leading to 'carefree handling' throughout the flight envelope which would have been totally impossible in older jets such as the F-4.

[ancientaviator62]

Sled dog I believe it was.

[BEagle]

In May 1968, XR133, the Whistling Tit to which you refer, hit a 45 gallon oil drum mounted on a wooden support 10 ft off the ground at Gat-el-Afrag desert strip in Libya during a low level high speed beat-up, euphemistically termed an 'undercarriage check'....:rolleyes:

In the collision, the a/c was in a right hand bank and lost the outer section of the starboard wing and the starboard aileron. Attempting to roll to port when the left wing is producing considerably more lift than the right could, I suppose be thought of as 'aileron reversal'...:uhoh:

However, the root cause of the accident was pretty obviously something else.

[ancientaviator62]

BEAgle,
thanks for the correction ref the 'Whistling Wheelbarrow ' accident, memory is a fallible thing.

[Kolibear]

For the slightly dense amongst us (me !) could someone explain what causes aileron reversal and what the effects are.

I'm assuming that its due to the wing twisting when the ailerons are deflected at high speed - the ailerons remain fixed in space and the wing twists.

Does this actually reverse the control input from the pilot ie a left bank rolls the a/c to the right, or does the term 'aileron reversal' refer purely to the structural effect.

[BEagle]

Partial aileron reversal means that the torisonal stiffness of the wing (resistance to twist) is inadequate at high IAS and that aileron deflexion will indeed twist the wing, reducing the effective roll rate due to the reduced AoA change over the section concerned.

Taken to extremes, it might become so twisted that the effective AoA would cause a rolling moment in the opposite direction to that intended by the pilot.

Torsional flutter problems can also occur when a wing is disturbed in turbulence and twists, it's the effect you hear when a venetian blind buzzes in a strong draught!

[Genghis the Engineer]

For the slightly dense amongst us (me !) could someone explain what causes aileron reversal and what the effects are.

I'm assuming that its due to the wing twisting when the ailerons are deflected at high speed - the ailerons remain fixed in space and the wing twists.

Does this actually reverse the control input from the pilot ie a left bank rolls the a/c to the right, or does the term 'aileron reversal' refer purely to the structural effect.

Yes and yes.

Generally what happens is that aileron effectiveness steadily reduces with increasing speed until the aileron reversal speed is reached (when actually you have no roll control at-all), above that the control works in the reverse sense.

G

[Mark 1]

Not strictly aileron reversal in the sense you describe, but Delmar Benjanin's replica GeeBee racer had some telling scrapes on the wing tip from the first time he tried to 3-point it onto the runway.
Apparently, in the 3-point attitude, the angle of attack was sufficient to stall a wing tip if any down-aileron was applied, with ensuing entertainment.

From then on it was wheelers only (at about 110mph).

[Wunper]

G
I understand aileron reversal was endemic at surprisingly low airspeeds in some vintage gliders of the 30's and was accommodated by their pilots through deft and positive footwork. A trawl though VGC might be worth the effort.
W

[Genghis the Engineer]

I think what's surprised me here (plus scouting around I found out a few other things - for example that the prototype C141 had a serious aileron reversal problem) is not that aileron reversal is there, but that it seems to have happened so much, on so many aeroplanes, and is apparently still cropping up.

I *thought* that the basic theory and solution had been cracked 40 years ago, but that wouldn't appear to be true. It also appears true from Wunper's post that it was known well before the Spitfire as well, which surprises me somewhat.

Interesting, very interesting.

G

N.B. Wunper, on the one aeroplane I've ever flown with a serious aileron reversal problem, a development of the CFM shadow that was eventually, and rightly, abandoned before certification, it was certainly true that heavy use of rudder was the only way to achieve anything resembling a useable roll rate at most speeds.

[Conan the Librarian]

Without scanning back, I think that some wise soul (maybe BEagle?) posted about the F-4, which apparently also needed heavy bootfuls of rudder to roll in certain regimes. I remember this being said by msny others, though I think it was more to do with AoA than anything.

Conan

[BEagle]

See reply No 18



.

[sailing]

Not quite aileron reversal, but....
Shortly after buying a DH82 I was interested to note that as the stick was moved to one side the appropriate ailerons would go up and down in the correct sense, but further movement caused the upgoing one to go further up, while the (previously) downgoing one would start to come back up. Close to full travel, one would be well up, the other back to neutral. At full travel, one was fully up, the other very slightly up! Believe this is normal behaviour for a Tiger, no doubt designed to reduce adverse yaw. Also no doubt contributes to the leisurely roll rate!

[treadigraph]

Sailing, think DH developed (and patented?) the differential aileron for the Moth family, as you say, to reduce adverse yaw. Never knew it was that extreme though!