Forum: F-22A Raptor

I've been studying this video of the official F-22 demo and have a few questions to those who knows:

http://www.f22-raptor.com/media/video_gallery/videos/F22_AirShow_Langley.wmv

If you study the tail surfaces you see them moving radically in each direction when the Raptor is falling, while maintaining a horizontal, seemingly stable attitude, which I believe causes the pitch change in the same way as a falling leaf twist around while it falls from the tree. The problem then is what is the thrust vectoring doing while this is going on?

1. Does the thrust vectoring participate in the roll motion, i.e. one goes up and the other goes down to amplify the a roll rate?

2. If 1 is true, can the pilot disconnect the trust vectoring from the roll channel when he wants to with a paddle switch or similar easy to reach switch?

3. If 1 is true and 2 not true how come it is not rolling while it is falling?

4. if 1 is not true how is he able to force a roll motion while standing nearly still in the air, nose vertical?

Would not think this is classified stuff, so hoping for a good discussion on this.

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Elite Joined: Jul 20, 2005 Posts: 1021 Status: Offline

Hmmm...Well while doing the pedal turn, its performed with the rudders. There are no maneuvers like the one you described where a roll is commanded while standing still in the air with the nose vertical. As far as details about the thrust vectoring system...sharing those would be a no-no.

I thought the TVC nozzles cannot act independently, i.e one up one down, both must pitch in the same direction at the same time...

lamoey wrote:

1. Does the thrust vectoring participate in the roll motion, i.e. one goes up and the other goes down to amplify the a roll rate?

2. If 1 is true, can the pilot disconnect the trust vectoring from the roll channel when he wants to with a paddle switch or similar easy to reach switch?

3. If 1 is true and 2 not true how come it is not rolling while it is falling?

4. if 1 is not true how is he able to force a roll motion while standing nearly still in the air, nose vertical?

1) No - nozzles are only used symetrically, in pitch.
2) n/a, but even if they were, he would not be given such control.
3) Let's clarify - it may look like it's 'falling', but it's really still flying. It's not rolling because it's not a leaf. The combination of aerodynamics and FLCS create a stable system in all axes.
4) He can't. Unlike the pitch axis (due to tv) at pure zero airspeed there is no control of the lateral/directional axis. The only possibility is for the pilot to squeeze a little yaw control from differential thrust (different power settings left vs right). Obviously, this only directly affects yaw, not roll, but does have some limited utility. In the 'helicopter' turns, there is enough total airspeed to give the control surface effectiveness required to perform the manuever (obviously).

And to clarify, the pilot does still use the rudder pedals (for the turn), but the actual rudders are blanked and really don't do anything. The horizontal tails are deflected differentially to generate the yaw motion (as you can see in the video).

Ok, so no asymmetric thrust vectoring. Impressive that the flight control system allows, and stays in control during all the seemingly impossible flight situations the Raptor shows compared to a Viper in the same attitudes and speeds. I'm curious - does the pilots head buzz from all the alarms he's getting trying to tell him he's about to stall, land or crash?

lamoey wrote:

Ok, so no asymmetric thrust vectoring. Impressive that the flight control system allows, and stays in control during all the seemingly impossible flight situations the Raptor shows compared to a Viper in the same attitudes and speeds. I'm curious - does the pilots head buzz from all the alarms he's getting trying to tell him he's about to stall, land or crash?

They're probably going off, but he's tuned them out because he's constantly cross checking his altitude and airspeed with his ground spotter(s). There's a video floating around of part of the demo with HUD info and pilot communications on it. You can see and hear during every maneuver, but especially the slow speed/falling ones his cross checks.

Elite Joined: Oct 21, 2005 Posts: 744 Status: Offline

Maybe you're referring to this one at ASB:

http://www.airshowbuzz.com/videos/view.php?v=b512534b

All releasable stuff.

Nice!

Quote:

Recovering from the tail slide when he hits 50 knots of NEGATIVE airspeed

How does he know his negative airspeed. From the inertial, pitot tubes in the rare, or those new AOA probes that senses all?

Newbie Joined: Jul 16, 2007 Posts: 6 Status: Offline

lamoey wrote:

Nice!

Quote:

Recovering from the tail slide when he hits 50 knots of NEGATIVE airspeed

How does he know his negative airspeed. From the inertial, pitot tubes in the rare, or those new AOA probes that senses all?

Most likely it is inertial derived.

What ever happened to the P51 "Risky Business" maneuverability fly-off against an F-22?

Elite Joined: Jul 22, 2005 Posts: 915 Status: Offline

F16JOAT wrote:

What ever happened to the P51 "Risky Business" maneuverability fly-off against an F-22?

What would be the point? The P-51 would win then we'd have POGO and Ricionni screaming about how worthless the F-22 is. Rolling Eyes

You got a point. Same reason they won't want to stick a GE-AVEN engine in an F-16 and WOW them as well.
Like you said, POGO and Ricionni are famous at the upper levels where the $$$$ is freelance.

Forum: F-22A Raptor

F-22 Thrust Vectoring and Roll Control