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MSFS20 MSFS Aileron Control Reversal below 10,000 ft and above Mach 1.3. - SOLVED

T

TangoGolf

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unitedkingdom
Hi,

I seem to be experiencing aileron control reversal with my model when below 10,000 ft and above Mach 1.3.

Above 10,000 ft and between Mach 1.0 to Mach 2.0, aileron control sense is correct. Below 10,000 ft and below Mach 1.3, aileron control is also operating in the correct sense.

Anyone have any ideas?

Tyler
 
Control reversal is normal and what speed it happens is based on wing design. I don't have any more particulars regarding that. I have a really thick book on aerodynamics which probably goes into a seriously painful mathmatical description... but, not gonna open that today! No sir!

Seriously though... control reversal happens to any aircraft that exceeds it's aileron reversal speed.
 
Control reversal as described would prevent that airplane becoming certified or cleared for use as a fighter. Something similar nearly stopped the latest version of the F-18 entering service. It was fixed but caused a long delay.
Some aircraft like the F-4 had a kind of control reversal close to the stall, so you turned it with the rudders at low speeds. If you used ailerons the downgoing aileron could cause the airflow to stall which would give adverse roll and yaw. That did not happen at normal speeds.
It is not normal to find a released airplane with a flaw like control reversal.
Roy
 
Roy Holmes said:
Some aircraft like the F-4 had a kind of control reversal close to the stall, so you turned it with the rudders at low speeds. If you used ailerons the downgoing aileron could cause the airflow to stall which would give adverse roll and yaw. That did not happen at normal speeds.
Click to expand...
Was this the reason for the extreme dihedral in the tail?
 
The Bristol 188 was a supersonic research aircraft made from stainless steel, so the ailerons should have been fairly rigid. During my research I haven't come across anything that reported any observed control reversal.

I will have a look at the flight_model.cfg file and experiment with some changes to see if it reduces or eliminates the aileron control reversal.
 
TangoGolf said:
During my research I haven't come across anything that reported any observed control reversal.
Click to expand...
Really? Do you have access to Wikipedia? They have a whole article on "Control Reversal."

Your reply implies that your only possible understanding of control reversal, involves the actual control surfaces moving opposite of what is intended. The fact is that control reversal can occur even when the ailerons are functioning correctly.

Because I'd thought it had been common knowledge that large, swept wing bombers, could overcome wing stiffness with extreme aileron inputs, producing a net reversal and they tell us as much in the Wikipedia article. They go on to inform that the Wright Brothers already knew how to turn perfectly well when they invented the rudder specifically to combat control reversal, although it is understandable you did not research Wright developments.
 
"Was this the reason for the extreme dihedral in the tail?"
The tailplanes have anhedral, the opposite of dihedral, ie they slope down. The main reason for that was to get the surface down as far as possible to keep it below the wing induced flow at high AOA. The tail mounting structure was above the engines, so it was a bit high for a straight tail. The other oddity with the F-4 was the wingtips which did have dihedral. I think it was to overcome the fact that the wing was straight for strength and gear length reasons so it could not have enough dihedral. It was a very complex wing with blown leading and trailing edge flaps, that reduced the stall speed by about 20 knots. Sitting in close formation on an approach when the leads flaps were lowered it looked like the wing was folding on itself, very odd and a bit scary the first time you saw it.
Roy
 
=rk= said:
Really? Do you have access to Wikipedia? They have a whole article on "Control Reversal."

Your reply implies that your only possible understanding of control reversal, involves the actual control surfaces moving opposite of what is intended. The fact is that control reversal can occur even when the ailerons are functioning correctly.

Because I'd thought it had been common knowledge that large, swept wing bombers, could overcome wing stiffness with extreme aileron inputs, producing a net reversal and they tell us as much in the Wikipedia article. They go on to inform that the Wright Brothers already knew how to turn perfectly well when they invented the rudder specifically to combat control reversal, although it is understandable you did not research Wright developments.
Click to expand...

Thanks. My research was for the Bristol 188 and no aileron control reversal was reported by the test pilots during the 70 test flights and hence I did not want this unreported characteristic within the flight model of my aircraft model in MSFS.

For anyone that is interested, aileron control reversal can be adjusted and removed within the MSFS flight_model.cfg by editing the aileron_elasticity_table figures.
 
Control reversal is a fundamental consequence of aerodynamic development and controls that are impossible to reverse, like the rudder in the Titanic, or directional stabilizers on a locomotive, have deleterious effects on maneuverability. The more maneuverability a plane has, the less inherently stable it will be. If one must apply unrealistic values to their airplane structure, it implies the flight dynamics model is equally unrealistic.
 
Rick,
What is the point you are making? Are you saying that control reversal in inevitable? And what do you mean by unrealistic values?
Roy
 
I am saying that all aileron controls will reverse eventually, given sufficient speed. Going back to Wikipedia, I'll link the article, copy/paste the section of the Spitfire and strongly endorse everyone to bone up, it's short and describes several notable incidents.

Supermarine Spitfire​

Due to the high speeds at which the Supermarine Spitfire could dive, this problem of aileron reversal became apparent when it was wished to increase the lateral maneuverability (rate of roll) by increasing the aileron area. The aircraft had a wing designed originally for an aileron reversal airspeed of 580 mph, and any attempt to increase the aileron area would have resulted in the wing twisting when the larger ailerons were applied at high speed, the aircraft then rolling in the opposite direction to that intended by the pilot. The problem of increasing the rate of roll was temporarily alleviated with the introduction of "clipped" wing tips (to reduce the aerodynamic load on the tip area, allowing larger ailerons to be used) until a new, stiffer wing could be incorporated. This new wing was introduced in the Mk 21 and had a theoretical aileron reversal speed of 825 mph (1,328 km/h).

Control reversal - Wikipedia

en.wikipedia.org en.wikipedia.org

So we can see that despite not testing it, the engineers knew at exactly what speed to expect the Mk21 ailerons to reverse. Now, as to realism, I don't really want to drill into criticism, he is making his project to his own specifications. Can't fault it and I did pretty much the same thing to get my own Waverider flyable.

Now, with that said, the recent MSFS update was manifold in complexity, as usual and one of the proudly touted revisions was atmospherics, cross winds on the runway, windshear and such, the glider people have been very excited about this. If your aircraft was working before Asobo made the atmosphere more realistic, then arbitrarily changing the elasticity of a control surface to compensate, does not seem like an equivalent application of realism. Aileron reversal at transitional speeds, implies fundamental design issues. Most, or at least many real world aileron reversal situations are caused by too much leverage, in the intended direction, causing wing twist and deflection ultimately turning the plane, in the unintended direction. So presumably the OP made his ailerons more elastic?

Anyway, looking over the 188, it is pretty hard to imagine those boxy wings twisting off, although they are knife thin. The big problem was the engines and by all accounts, they'd eclipse any inherent handling issues, by starting their own with incessant surging. It looks like it was set up to go fast and straight and any tuning done to accomplish this, probably cannot detract from those engines.
 
Three points.
First, the most common cause of control reversal according to the God Wikipedia is human error.
Second, an article that quotes the Wright Brothers, Spitfire and B-47 is hardly basis for the statement "I am saying that all aileron controls will reverse eventually, given sufficient speed" . Just maybe designers consider control reversal and design it out.
Third, a practical point is that "sufficient speed" would probably be way higher than the airplanes limiting speed so it is irrelevant. The theoretical aileron reversal speed of 825 mph on the Spitfire is about 715 kts which is about Mach 1.1 at sea level. The max level speed of a Spitfire was about 320 kts. The highest speed ever recorded for a prop aircraft was a Spitfire which was diving at about 0.92 Mach when its prop came off.
Roy
 
Are we squaring off, or something? Because if we're going to start quoting the laws of physics, I'd prefer we defer to Ed's book, over Wikipedia.
WarpD said:
Control reversal is normal and what speed it happens is based on wing design. I don't have any more particulars regarding that. I have a really thick book on aerodynamics which probably goes into a seriously painful mathmatical description... but, not gonna open that today! No sir!

Seriously though... control reversal happens to any aircraft that exceeds it's aileron reversal speed.
Click to expand...
I apologize for using Wikipedia in the first place, I mean, I know it has a reputation for being hearsay, but I figured common knowledge hearsay about wing twist and Wright Brothers would make it seem less "rocket scientist" and just so you know, I never flew jets, only ever jiggled the yoke in a Cessna for that matter, never designed wings, but I did design airfoils. I built them, I sailed them, I tweaked, tuned and even dreadedly, experienced control lock and reversal with them.

It might have many causes, human error, bank turning a Phantom at low speed, placing my mast too close to my rudder, whatever. Declaring a software update that ostensibly improves the fidelity of the wind, to be the cause of aileron reversal, seems like a cop out. That's all I'm saying.
 
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