Mach speed control surfaces and wings.

[Zatnikitelman]

I've got a question about controling a vehicle at mach speed and about the wings.
I've read that at mach speeds, traditional "partial-deflection" control surfaces couldn't control a winged aircraft through mach-speed flight and that "full-deflection" control surfaces where the entire surface deflects had to be used. This is on a traditional aircraft with the wings separate from the vertical stabilizer.
What about with a Delta wing? Obviously the space shuttle and concord fly fine without deflecting the entire wing! (that'd look odd, but be hilarious :rofl so is it with computer adjustment, or would it work without fly-by-wire?
I'm working on a new spaceplane thing and need to know how to set up the control surfaces.
Thanks,
Zat

 

[Agra Barecasco]

low air pressure

maybe conventional wings can't work in mach speed because the control surface are subjected to very low air pressure right behind the "mach cone" or the high pressure "wall" that created in the front surface of the wing..
so air deflection in that area contributes small force to turn the vessel,

for a vessel like concorde, the long distance from front to back of the wings creates distance from the "wall" to the control surfaces, so air pressure is recovered enough in that area, and air deflection will works fine to turn the vessel..

 

[Stripe]

I'm remember something about this from a documentary on the television some years ago. They talked about the Me 163 and how beyond a certain speed it would go into what was called a 'graveyard dive'. There was no way out of it, it was such a tuck under dive, that it was inevitably a fatal crash.

Another plane had the same 'flaw' the DeHavilland Swallow, 3 were built and all three of them fell out of the skies killing their pilots.

http://en.wikipedia.org/wiki/De_Havilland_DH_108

From what I can remember (can't really read the wiki article as i'm at work) it was how a wing behaves as it approaches the speed of sound.

As shock waves ( or was it vortexes ? ) built up on the wing as the aircraft started to approach mach speeds the control surfaces were 'locked' into place, or even worse, the control surfaces would 'flail about' like a flag in a breeze. Once through the sound barrier of course, they started to work again.

It was found that if the wing was thinner, then these vortexes could be reduced somewhat until the aircraft got through the sound barrier, just that a thinner wing resulted in a lesser amount of lift.

Before fly by wire came into existence, there were aircraft who could go supersonic, the F-104 Starfighter, even the Bell X-1 I don't believe had fly by wire!

http://en.wikipedia.org/wiki/F-104_Starfighter
http://en.wikipedia.org/wiki/Bell_X-1

If you do a bit more research perhaps into what were the losses from the Swallow and how aircraft before fly by wire were able to get supersonic you might find what you're after ?

 

[JamesG]

Agra had it right. The shape of the leading edge of the nose, fuselage, and wings have to be carefully chosen for their trans and supersonic airflow character. One of the reasons that early supersonic AC had nose intakes and delta wings was that the supersonic shock wave and dynamics of those shapes are fairly simple. It was only after experience with the behavior and computer modeling allowed more complex shapes to be used.

 

[T.Neo]

I didn't know F-15s flew through wormholes. :rofl:

 

[Urwumpe]

I didn't know F-15s flew through wormholes. :rofl:

This is a more modern F/A-18, these can do that.

 

[pattersoncr]

I'm remember something about this from a documentary on the television some years ago. They talked about the Me 163 and how beyond a certain speed it would go into what was called a 'graveyard dive'. There was no way out of it, it was such a tuck under dive, that it was inevitably a fatal crash.

Another plane had the same 'flaw' the DeHavilland Swallow, 3 were built and all three of them fell out of the skies killing their pilots.

http://en.wikipedia.org/wiki/De_Havilland_DH_108

From what I can remember (can't really read the wiki article as i'm at work) it was how a wing behaves as it approaches the speed of sound.

As shock waves ( or was it vortexes ? ) built up on the wing as the aircraft started to approach mach speeds the control surfaces were 'locked' into place, or even worse, the control surfaces would 'flail about' like a flag in a breeze. Once through the sound barrier of course, they started to work again.

It was found that if the wing was thinner, then these vortexes could be reduced somewhat until the aircraft got through the sound barrier, just that a thinner wing resulted in a lesser amount of lift.

Before fly by wire came into existence, there were aircraft who could go supersonic, the F-104 Starfighter, even the Bell X-1 I don't believe had fly by wire!

http://en.wikipedia.org/wiki/F-104_Starfighter
http://en.wikipedia.org/wiki/Bell_X-1

If you do a bit more research perhaps into what were the losses from the Swallow and how aircraft before fly by wire were able to get supersonic you might find what you're after ?

The Lockheed P-38 was the first aircraft to run into this problem. They refered to it at the tim as "compressability". If I remember correctly, the vorticies created by the wings actually reversed the lift vecto from the tailplane. Past a certain speed, the nose would begin to tuck under. The harder the pilot pulled back on the yoke, the more the plane tucked under until eventually, the vortices ripped the tails of. Once the Germans realized that P-38 pilots were reluctant to enter a steep, high speed dive, it gave them a tremendous advantage, if they ever got in i situation they didn't like, they just pointed the nose at the grouns and were quickly out of the fight. Dive brakes installed on the underside of the wing eventually solved the problem.

 

[Urwumpe]

Once the Germans realized that P-38 pilots were reluctant to enter a steep, high speed dive, it gave them a tremendous advantage, if they ever got in i situation they didn't like, they just pointed the nose at the grouns and were quickly out of the fight.

Actually, this steep dive was a standard tactics of Germans, they used it against Spitfires already during the Battle of England, as the Spitfire initially had a carburetor, which required positive Gs, forcing the spitfire to roll while diving. The German planes had injection.

Later Merlin engines fixed that disadvantage.

 

[Linguofreak]

I've got a question about controling a vehicle at mach speed and about the wings.
I've read that at mach speeds, traditional "partial-deflection" control surfaces couldn't control a winged aircraft through mach-speed flight and that "full-deflection" control surfaces where the entire surface deflects had to be used. This is on a traditional aircraft with the wings separate from the vertical stabilizer.
What about with a Delta wing? Obviously the space shuttle and concord fly fine without deflecting the entire wing! (that'd look odd, but be hilarious :rofl so is it with computer adjustment, or would it work without fly-by-wire?
I'm working on a new spaceplane thing and need to know how to set up the control surfaces.
Thanks,
Zat

Conventional control surfaces fail on a normal tail because a shock wave ends up forming at the hinge. I'm not sure how deltas avoid this.

 

[Kozak]

Conventional control surfaces fail on a normal tail because a shock wave ends up forming at the hinge. I'm not sure how deltas avoid this.

Nope. The problem with control surfaces is due to the wing being twisted with the forces induced by ailerons - "aileron inversion". On some speed this effect will invert bank control, this moment is called "inversion speed", for modern fighters about 1500-1600kph IAS. Delta-wings (e.g. shuttle) just have more resistance to rotational forces.

 

[Linguofreak]

Nope. The problem with control surfaces is due to the wing being twisted with the forces induced by ailerons - "aileron inversion". On some speed this effect will invert bank control, this moment is called "inversion speed", for modern fighters about 1500-1600kph IAS. Delta-wings (e.g. shuttle) just have more resistance to rotational forces.

That is in fact a factor on some aircraft, and can be one at any speed, depending on the design of the aircraft, but there are other factors that affect controlability, many of which are Mach-dependant. Critical Mach effects and shockwaves at control hinges are among these.

 

[-Pv-]

Notice the three most successful high mach craft in discussion use elevons rather than tail planes for pitch and roll and delta wings (strength and efficiency.) Shuttle, Concorde, SR-71.
-Pv-