Reversed Flight Questions....

I know it is possible to fly backwards. The reason I love seeing Russian fighters do Kulbits is to see them flying in one direction and pointing the opposite way! It's such an amusing trick.

But the questions I have pertain to sustained horizontal rearward flight.

The first of them is- how long can one aircraft sustain such flight while retaining a horizontal vector? I understand this is dependant on the aircraft. Let us assume it is... say... I dunno. A TVC Su-35 Super Flanker. If one was to fly at the maximum speed for the inversion maneuver (We're assuming that the aircraft pitches up to reverse heading), how long could on retain the backward velocity? The maximum speed I have managed to attain a stable inversion at is 250 kts on Flight Sim 2002 but there is no real TVC (I have only tweaked the aircraft to simulate it as best I can), I am not sure about the real stats with actual TVC. I shall repeat the question- How long could one sustain rearward flight after such a maneuver?

The second question I have is- could a thrust reverser be constructed on an aircraft to increase the amount of time spent in rearward flight after the maneuver?

Image Of Maneuver

[edit on 8/20/2006 by Darkpr0]

When you have air going up the tailpipe like that you are running the risk of a compressor stall. If that happens you can damage the engine. That's why when you're going to do an engine run, you always run with the nose pointed into the wind. With the exception of a VTOL you're talking a SEVERELY limited time going backwards. Probably somewhere in the order of a second or two max.

Would there be any way to make a retractable shield for the jet outlet, similar to a reverser a la MD-80? (I think the MD-80 uses that method...)

It's a reverse thruster. The MD-80 family and many of the older and small palnes use a "clamshell" type like that. You can use it on the ground, and some airports actually do to back out of the gate, but if you deploy it in flight you risk a serious controllability issue. If I remember right there were a couple of accidents or near accidents from a thrust reverser deploying in flight. The other issue with putting them on fighters is weight. You want to be as light as you can be with a fighter and not put anything you don't HAVE to put on to save on weight.

Hmm.... So there's no real feasible way to allow an aircraft to fly backwards for a longer amount of time?

Only something like the Harrier, F-35, or another VTOL type really can. Flying backwards really just isn't feasable with modern jet engines.

Alright, so now the real question- what would it take to make it work, realistic or not?

reversible engines and reversible variable camber wings probably, ouch, what a technical nightmare!

When planes are flying backwards now it is either pure momentum (Flanker etc) or modest movement while supported on a column of efflux (Harrier etc), there is no real 'flying' going on.

[edit on 21-8-2006 by waynos]

I'm just thinking of the tactical advantages of being able to fly backwards for a short period of time, but longer than a couple seconds. I'm thinking somewhere in the 7-10 second range, so I believe that this is within the realm of momentum-maintained rearward flight (I only use the word "flight" because I can't immediately think of anything that works better ).

If an enemy plane were pursuing you at missile range and you were able to conduct the maneuver, you might be able to get a tone and launch the missile before having to revert. I imagine the reversion to normal flight would be otherwise identical to the maneuver used to put oneself in rearward flight, using momentum of course.

Reversible engines aren't new- but the reversibly cariably camber.... That's a nightmare. And it's not even figuring out how to do that, really. A few hydaulics inside the wing to push or pull the top part up or down, using wing deformation to get that new camber. But if you tried it on an F-15 or something, just the shape of the wing would probably screw it up. And then there's the control surface problem.

I guess my idea here is- how can we stop the airflow from damaging the engines while using momentum to fly (I still need a better verb) backwards?

Originally posted by Zaphod58
When you have air going up the tailpipe like that you are running the risk of a compressor stall. If that happens you can damage the engine. That's why when you're going to do an engine run, you always run with the nose pointed into the wind. With the exception of a VTOL you're talking a SEVERELY limited time going backwards. Probably somewhere in the order of a second or two max.

Uhm... well.


It depends on the speed of course, but on afterburner a typical nozzle pressure ratio is something like 8 or more maybe 12+ - its obviously choked (sonic). That means the flow upstream, that is, within the engine is not aware of the conditions beyond the nozzle.


Of course, if the aircraft is reversing fast enough, the dynamic pressure head will eventually mean the nozzle pressure ratio is less than 1, however, current aircraft don't have the manouverability to get into a reversing position at such speeds, nor are they close to it.


Bottom line is, if the aircraft enters the manouvre already in afterburner, it will not stall by back pressure through the nozzle. It may stall through local distortions on the compressor faces - indeed, thats much more likely.


edit: Of course, you won't reverse very far with the aircraft engines pushing the opposite direction.

[edit on 21-8-2006 by kilcoo316]

Originally posted by Darkpr0
I'm just thinking of the tactical advantages of being able to fly backwards for a short period of time, but longer than a couple seconds. I'm thinking somewhere in the 7-10 second range, so I believe that this is within the realm of momentum-maintained rearward flight (I only use the word "flight" because I can't immediately think of anything that works better

).

If an enemy plane were pursuing you at missile range and you were able to conduct the maneuver, you might be able to get a tone and launch the missile before having to revert. I imagine the reversion to normal flight would be otherwise identical to the maneuver used to put oneself in rearward flight, using momentum of course.

You could always pull the maneuver that they show in "Top Gun". Dump the throttle, deploy speed brakes (if you have them) and even lower your landing gear. This should drop your forward airspeed and should cause your enemy to overshoot. Of course this leaves you hanging in the air with mimimal airspeed so you better make that missile shot count and pray he doesn't have a wingman. Otherwise you're toast.

Originally posted by JIMC5499
You could always pull the maneuver that they show in "Top Gun". Dump the throttle, deploy speed brakes (if you have them) and even lower your landing gear. This should drop your forward airspeed and should cause your enemy to overshoot. Of course this leaves you hanging in the air with mimimal airspeed so you better make that missile shot count and pray he doesn't have a wingman. Otherwise you're toast.

You forgot the crucial bit that comes after....



YYEEEEEEE HHHAAAAAWWWWW

JESTER'S DEAD

And hope your landing gear doesn't fall off .

The thing on Top-Gun is that he deployed the variable geometries, which would increase the left. He woulda gone up too fast to get off a clean shot I think.