What ever happened to decoupled flight controls and manouvering?

Afternoon, (well it is here..) dont know if this has been covered in previous threads, if so spank me!

Those of us on ATS who remember the 1970's and 80's (if you dont, ask your mum who David Lee Roth was ) will recall a series of programs that explored the concept of decoupled flight systems. Such programs as the US CCV and F-16AFTI sought to gain new ways of controling aircraft in combat by seperating the roll, pitch & yaw axis. This allowed previously impossible manouvers like flying along a bearing and slewing the nose to one side to take a shot, all without moving off that original lateral bearing. That is the aircraft effectively flew sideways keeping its nose pointed at the target.

The program results showed great promise for future aircraft development and tactics, but as far as I know the idea seemed to have died out. If anyone is aware of its incorporation into new aircraft programs please enlighten me. Given the explosion in UCAV development it seems like a logical way of fully utillising these airframes when they dont have flesh on board limiting there G envelope.

[edit on 1-3-2007 by thebozeian]

Originally posted by thebozeian
Given the explosion in UCAV development it seems like a logical way of fully utillising these airframes when they dont have flesh on board limiting there G envelope.

The airframe still has a g envelope as well.


For instance, high lateral g's will load oil inside the engines different, will load the wing box different, will load the vertical fins different.


There is more to g limiting than just the pilot

Fair point kilcoo316, although my quip about using axis decoupling for UCAV's wasnt really my thrust(I clouded my point it seems) .

Of course I was aware any airframe has G limits, with or without a "flesh bag" on board. After all this was the reason Rolls Royce developed "Miss Shilling's orifice" for the Merlin engine around the start of WWII.(Interesting true story)

The fact of the matter is they sucessfully demonstrated it on an existing manned platform (F-16 AFTI), so it is logical to assume that the generally greater practical & theoretical flight envelope of UCAV's could fully exploit said method.

Having said that about unmanned platforms it would be just as usefull on manned fighters, so I guess my original question remains valid.

LEE.

They didn't go to waste, the F-16CCV, F-15ACTIVE and HiMAT (plus several others) all played a part in the F-22 development, elsewhere the ACT Jaguar and F-104CCV led to the Typhoon via the EAP and the Mitsubishi F-1CCV was utilised in developing the F-2. All three fighters use decoupled control characteristics, as well as the later 'three surface' Flanker models, its just that designers found a less obvious way of achieving the same results through use of more normal looking aerodynamic controls and clever manipulation through FBW.

just a nice piccy;


[edit on 2-3-2007 by waynos]

Ahhh thank you again waynos. You have been helpfull to me twice in one day.

So my suspicion was correct, they did incorporate it in modern FCS's. I forgot about the F-15ACTIVE program and good old HiMAT. The ACT Jaguar was run by DERA was it not? I barely remember the F-104CCV, and cant place the Mitsubishi effort in my memory banks. There was a time as an 80's teenager I could have rattled all this off in a second. Thats what you get when your just shy of 37 I guess

BTW, I checked out the link to the fastest piston engine fighter thread you gave me. Your top 5 fastest made for an interesting mix, Thanks for the advice and help mate

Look forward to more conversing in the future,

LEE.

Just thinking about this - I suppose the ultimate expression of this concept would be current AAMs - it manouvres irrespective of its axis to the dynamic motion.


Although, there are research programs for missiles that may change that somewhat, for instance a protruding pin affecting pressure distributions on the rear fins, to minimise energy bleed, it may be the case that the missile is rotated/rolled to optimise pitch/yaw control.

Hadn't thought about the AAM analogy. I guess the late model Python family is a good example.

Interesting research on pressure distribution changes, I gather the "pin's" would be placed forward and in line with each (fixed?) control fin. Trying to picture the effect in my "internal wind tunnel"... Nope its to late in the evening and the last beer just kicked in. Let me have a think about it and I'll get back to it tomorrow maybe.

LEE.

What ever happened to decoupled flight controls and manouvering?

Simply said - new generation short range AA missiles combined with HMS made them irrelevant. No matter how agile your plane is, today there's no chance to escape/outmaneuvre missile. You also no longer need to turn the plane nose to the enemy - with HMS you simply turn your head. Today more emephasis is put into stealth, speed and radar/avionics.

Originally posted by thebozeian
Interesting research on pressure distribution changes, I gather the "pin's" would be placed forward and in line with each (fixed?) control fin.

No, 2 pins, either side of the fin a distance away from the fin itself, about 1/4 chord location on the fin.

They are normally kept flush to the surface, when you want to turn, extend one and the resulting shock interactions change the pressure distribution over the fin and result in moments upon the missile.

Originally posted by longbow
What ever happened to decoupled flight controls and manouvering?

Simply said - new generation short range AA missiles combined with HMS made them irrelevant. No matter how agile your plane is, today there's no chance to escape/outmaneuvre missile.

I think the rule of thumb is the missile has to have at least 4 times the agility to turn inside a hard manouvering target (aircraft).

So, for a 40g missile a 9g capable aircraft is very hard to hit, for a 60g missile its easier, but if airframe/pilot limits were raised to 13/14g, that would put it all back on the line again.

Most recent missiles like Python for example can make 80-100Gs and it is is much more easier to make more manuvrable missile than plane. Future highly maneuvrable UCAVs might change that, but there are not even proposals to make some (X-45/47 is not manuvrable at all).

Originally posted by longbow
Most recent missiles like Python for example can make 80-100Gs and it is is much more easier to make more manuvrable missile than plane. Future highly maneuvrable UCAVs might change that, but there are not even proposals to make some (X-45/47 is not manuvrable at all).

Yeah, your probably right.

The future of missile "evasion" is going to be frying the sensors in it with directed energy.