unstable or stable aerodynamic designs

[highlyflammable]

what do these terms mean, ive heard that unstable aircraft are better at maneouvring but im looking for an explanation, also, can wikipedia be trusted when it comes to aircraft?

[+Typhoid]

what do these terms mean, ive heard that unstable aircraft are better at maneouvring but im looking for an explanation, also, can wikipedia be trusted when it comes to aircraft?

 

unstable means if left alone (hands off the controls) it will deviate from its flight path. Stable means if left alone, it will stay in steady flight.

 

generally speaking; trainers, acrobatic and fighter types are unstable (to a degree) while general aviation and airliners are stable.

 

that is a VERY general description and there will be lots of exceptions and variations to that. I expect that many such examples will be posted here soon....

 

wikpedia is not a bad reference. Generally it is ok although on occasion it will get some details a little off.

[csb]

SF/WOV/etc aircraft are stable. Yah!?

[+SkippyBing]

Generally when people talk about unstable aerodynamics these days it's with reference to something like the Typhoon or Raptor where the flight control system deals with the unstable part of the problem and as far as the pilot is concerned it's perfectly stable. As an example if you can find the video footage of the Typhoon almost hitting the ground at RIAT after coming out of a loop look at the canards. The pilot was obviously pulling back on the stick as hard as he could, the canards however appear to be almost in negative pitch, this is because being unstable once the pull up had been initiated the airframe would just keep rotating in that direction. So to stop the thing stalling the canards were holding the nose down to the max AoA the wing could handle at that speed.

There's actually three types of stability, positive where when you let go of the controls it returns to level flight, neutral where when you let go it just keeps doing what it's doing and negative where it'll keep going in the direction you pushed it to go. As it'd be very tiring to fly a negatively stable aircraft for any length of time it's really only used in aircraft with electronic flight control systems (and I think the Wright Flyer), the advantage is they are much more agile and for airliners fuel efficient (the CoG and Centre of Lift are much closer together so there's less trim drag).

I hope that clears things up a bit! If I've confused anyone further let me know and I'll try and clarify.

[j33l]

Unstable Aerodynamics Means Those planes that will not fly without a computer. The most unstable plane is the F117 Nighthawk. It is shaped like a Diamond and dsnt like to fly. It is "KEPT" in the air by very powerful pc's It will not fly even if one of its computer fails.EF2000 Typhoon is also an unstable plane. other examples are F22 Raptor, YF23 Black Widow, B2 Spirit S37/Su47 Berkut. The most stable planes are the F16 Falcon , F18 Super Hornet, F15 Eagle etc

Hope that Explains it.

Edited February 18, 2007 by j33l

[+BUFF]

The most stable planes are the F16 Falcon , F18 Super Hornet, F15 Eagle etc

The F-16 is inherently unstable - without the computers it wouldn't fly.

I would think that the F-18 is the same but the F-15 probably isn't (being slightly older tech.).

[tank03]

The F-16 is inherently unstable - without the computers it wouldn't fly.

I would think that the F-18 is the same but the F-15 probably isn't (being slightly older tech.).

 

The F-16 is certainly unstable. There was a TV program a few weeks ago that detailed the develpoment of the F-16, apparently it's instability contributes to it's great manuverability, and at the time the air force was dubious of the computer technology to keep it in the air.

[j33l]

Hmm i have to refresh my knowledge

And yah Wikipedia is a best source for Plane infoand Janes book's If you dont have a Pc lying around.

Edited February 18, 2007 by j33l