Forum: General F-22A Raptor forum

Any shots of the F-22 flying with four tanks yet?

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I'm sure I had a pic or two of the 4-tank flight but I cannot find them as of yet...If these have been posted before, accept my appologies.

-Check

One more.

sferrin wrote:

Any shots of the F-22 flying with four tanks yet?

Four tanks!? Why would the Raptor need four tanks!? It must be because it's a short-legged fighter that can only go 20 miles unrefueled! And I'm sure it wouldn't break 55 mph with wing tanks! What a waste! Bring back the Phantom! The F-22 sucks! Rolling Eyes

checksixx wrote:

One more.

Is it me or, judging from these and other pictures and videos, does the Raptor always fly nose-high in level flight?

In those photo's it is flying at a relatively low speed.

-Check

Elite 1K Joined: Aug 19, 2004 - 09:19 AM Posts: 1092

idesof wrote:

checksixx wrote:

One more.

Is it me or, judging from these and other pictures and videos, does the Raptor always fly nose-high in level flight?

That would mean it's always flying at a high AoA in level flight. This simply won't be the case at moderate to high calibrated arispeeds (i.e. at moderate to high dynamic pressure values).

One thing I've noticed in almost all pictures is that it's flying with flaps partially deployed. I wonder what speed it has to be at for them to be all the way up?

Elite 1K Joined: Aug 19, 2004 - 09:19 AM Posts: 1092

I started a thread a little while back about the F-22's use of flaps and its relation to the mission adaptive wing concept pioneered on the AFTI/F-111 project. They're not quite the same thing, but the general idea is similar in my opinion. The F-111's MAW was used all the way up to Mach 0.9 to improve the shape of the drag polar (i.e. better lift to drag ratio). I don't believe it was used at supersonic speeds though. I would expect this to be the same for the F-22's leading and trailing edge flaps, but I have no clue really.

Raptor_One wrote:

I started a thread a little while back about the F-22's use of flaps and its relation to the mission adaptive wing concept pioneered on the AFTI/F-111 project. They're not quite the same thing, but the general idea is similar in my opinion. The F-111's MAW was used all the way up to Mach 0.9 to improve the shape of the drag polar (i.e. better lift to drag ratio). I don't believe it was used at supersonic speeds though. I would expect this to be the same for the F-22's leading and trailing edge flaps, but I have no clue really.

On a similar topic one thing I've read they'd been working on in the past was something like "adaptivly configuring flight controls". Basically if you get a control surface shot up the system figures out what it's got left to work with and reconfigures the control "laws" to allow the pilot to get out of harm's way and back to base. As I recall it was the Israeli F-15 losing a wing and making it back to base that made them go "hmmm" initially. Then you had the case of the DC-10 pilots making a safe landing with only engine throttling to work with. Between the two -in theory- you should be able to lose quite a bit and continue on. Particularly with thrust vectoring. Anybody know if this got incorporated into the F-22s software? At times I wonder if this didn't hurt the F-23 a little bit as losing a tail on it would be quite a bit more dire than losing one on the F-22.

Elite 1K Joined: Aug 19, 2004 - 09:19 AM Posts: 1092

All that sort of information is probably pretty hush hush. I don't know if it's company confidential or classified or what. You could try searching for technical reports on the subject and see if the F-22 is mentioned. Smile

sferrin wrote:

On a similar topic one thing I've read they'd been working on in the past was something like "adaptivly configuring flight controls". Basically if you get a control surface shot up the system figures out what it's got left to work with and reconfigures the control "laws" to allow the pilot to get out of harm's way and back to base. As I recall it was the Israeli F-15 losing a wing and making it back to base that made them go "hmmm" initially. Then you had the case of the DC-10 pilots making a safe landing with only engine throttling to work with. Between the two -in theory- you should be able to lose quite a bit and continue on. Particularly with thrust vectoring. Anybody know if this got incorporated into the F-22s software? At times I wonder if this didn't hurt the F-23 a little bit as losing a tail on it would be quite a bit more dire than losing one on the F-22.

Without going into too many gory details, the control laws do reconfigure for any control surface failure (or failures). As an example, the (horizontal) tails are nominally used both symetrically (for pitch) and asymetrically (for roll). If either tail is flagged as failed the roll commands to the tails are zeroed, so that the remaining tail is used only for pitch control (obviously one surface can't do two things). Similar reconfiguration is done for all the surface pairs.
Obviously, the flcs can only respond to what it knows about. I guess it's conceivable that a surface could be shot up with bullet holes, but still be 'working'. As long as it wasn't spewing fluid, or jammed, I don't think flcs would get a failure flag. As far as getting half a wing shot off - there is no failure flag for that - specifically anyway. It would come down to exactly what hydraulic system lines were affected - in all likelihood the flcs would just think that the control surfaces (on the 'missing' wing) were just not working, and reconfigure appropriately.

The requirements are written in terms of probability of failure, which primarily comes down things like hydraulic system and actuator reliability. Up to some 'remoteness' (can't remember the exact number, 1 in 10^6, or something like that) the airplane has to be able to recover to controlled flight and AR and land. So, most studies were done with different types of hydraulic failures, with associated surfaces failed or reduced in capability. And yes, the airplane is quite robust.
Other kinds of failure modes that had to be flyable and landable included engine and/or nozzle failures. The most 'exciting' though (in simulation only, of course) were probably the combination fuel system and 'hung store' failure modes that resulted in insane (for other aircraft, of course) center-of-gravity locations.

Raptor_claw wrote:

sferrin wrote:

On a similar topic one thing I've read they'd been working on in the past was something like "adaptivly configuring flight controls". Basically if you get a control surface shot up the system figures out what it's got left to work with and reconfigures the control "laws" to allow the pilot to get out of harm's way and back to base. As I recall it was the Israeli F-15 losing a wing and making it back to base that made them go "hmmm" initially. Then you had the case of the DC-10 pilots making a safe landing with only engine throttling to work with. Between the two -in theory- you should be able to lose quite a bit and continue on. Particularly with thrust vectoring. Anybody know if this got incorporated into the F-22s software? At times I wonder if this didn't hurt the F-23 a little bit as losing a tail on it would be quite a bit more dire than losing one on the F-22.

Without going into too many gory details, the control laws do reconfigure for any control surface failure (or failures). As an example, the (horizontal) tails are nominally used both symetrically (for pitch) and asymetrically (for roll). If either tail is flagged as failed the roll commands to the tails are zeroed, so that the remaining tail is used only for pitch control (obviously one surface can't do two things). Similar reconfiguration is done for all the surface pairs.
Obviously, the flcs can only respond to what it knows about.

I was wondering if they do anything more complex/creative. For instance if by some miracle the vertical tails got cleaned off without destroying the aircraft would it know to use flaps and ailerons as drag rudders like the B-2 in conjunction with differential throttle control for yaw control (I have no idea how much authority something like the would have admittedly).

A little off topic but there was a lot of work done thru` the eighties and nineties with the NASA F-15 HIDEC test bed. Amongst the work investigated was PCAS- Propulsion Controlled Aircraft System, The F-15 had digital engine and flight controls and used ONLY the engines to control turn, climb and descent using differential thrust and varying power settings. They even managed a landing in 1993.

There was also a -Self repairing and Self diagnostic Flight control system testbed. This was used to identify the failure of a control surface and reconfigure commands to other control devices such as ailerons, rudders, elevators, and flaps to continue the aircraft's mission or allow it to be landed safely.

I am sure things have moved along nicely since then...

sferrin wrote:

On a similar topic one thing I've read they'd been working on in the past was something like "adaptivly configuring flight controls". Basically if you get a control surface shot up the system figures out what it's got left to work with and reconfigures the control "laws" to allow the pilot to get out of harm's way and back to base. As I recall it was the Israeli F-15 losing a wing and making it back to base that made them go "hmmm" initially. Then you had the case of the DC-10 pilots making a safe landing with only engine throttling to work with. Between the two -in theory- you should be able to lose quite a bit and continue on. Particularly with thrust vectoring. Anybody know if this got incorporated into the F-22s software? At times I wonder if this didn't hurt the F-23 a little bit as losing a tail on it would be quite a bit more dire than losing one on the F-22.

Forgive me if I don't go looking for the exact source but I do remember reading that the Raptor's FCS is designed to work precisely as you have described. Same goes for the F-35.

Regarding that DC-10 incident to which you referred, just FYI but the pilots hardly landed that plane "safely". Have you seen the video? Huge f-ing fireball, the plane doing cartwheels down the runway. Amazingly, most of the crew and passengers survived, but dozens also died. Also, they did not make it back on one engine. What they lost was the middle engine and lost flight controls after a fan disk ejected from the aircraft and severed hydraulics in the process. They maintained a measure of control through differential thrust employed on the remaining left and right engines.