Forum: General F-22A Raptor forum

I have seen several clear photos where both rudders are split independently away from each other while flying level and/or slight turning. They are split enough to cause noticeable contrails from their 'drag'. Is this a stability thing, a speedbraking thing, or something else. TIA.

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darkvarkguy wrote:

I have seen several clear photos where both rudders are split independently away from each other while flying level and/or slight turning. They are split enough to cause noticeable contrails from their 'drag'. Is this a stability thing, a speedbraking thing, or something else. TIA.

The F-22 (as well as the SuperBug, and very likely the F-35) employs a "virtual" speedbrake instead of a conventional, dedicated panel brake.

The flaps and ailerons are also used (both flaps down + both ailerons up). The FLCS allows for regular control inputs while braking is engaged.

I recall reading somewhere (I think it was in that Kopp interview with Paul Metz) that the deceleration imparted by such a system was more effective at slowing down the plane than the large panel brake used on the F-15.

Does anyone have photos of the F-22 or the SuperBug landing with full air-brakes deployed?

This technique was first used that I know of on the YF-23.

Again, hats off to the FCS guys, for working their magic.

Here is a great shot someone posted of a maneuvering/braking Raptor

Just an interesting addition. Because of the location of the speed brakes on the hornet (the rudders as mentioned), they use it for takeoffs from carriers as well (also for ground takeoffs as well), as it creates a nose-up pitch.

BTW, the hornet's speed brake works the other way around (the rudders move inwards instead of the outwards movement on the raptor).

photos:
http://www.airliners.net/photo/Switzerl ... 1214752/L/
http://www.airliners.net/photo/USA---Na ... 0431091/L/

Last edited by LinkF16SimDude on Dec 06, 2009 - 11:26 PM; edited 1 time in total

Not sure anyone noticed but in em745's pic it looks like the TE flight control surfaces on both wings also play a role in braking.

another F-22 speed brake shot

YF-23 speed brake shots

Thanks to all for clearing that up for me!!

Seems like a smart solution. Using existing control surfaces to brake instead of building separate, dedicated speedbrakes should be the less expensive (and lighter) way to deal with the issue.

Kryptid wrote:

Seems like a smart solution. Using existing control surfaces to brake instead of building separate, dedicated speedbrakes should be the less expensive (and lighter) way to deal with the issue.

Less expensive to build but the cost of software isn't free. The programming that runs the flight controls (and the fire control system) can be very expensive. Certainly less parts means lighter which is always a good thing.
fisk

Last edited by em745 on Dec 08, 2009 - 04:51 AM; edited 1 time in total

Kryptid wrote:

Seems like a smart solution. Using existing control surfaces to brake instead of building separate, dedicated speedbrakes should be the less expensive (and lighter) way to deal with the issue.

VLO requirements probably played into it also. Seems pretty nonsensical (IMO) to use a big ol' radar reflector as a brake on a VLO platform.

strykerxo wrote:

Again, hats off to the FCS guys, for working their magic.

Indeed. Writing up the code for the braking action while still retaining normal control laws/functions couldn't have been a cakewalk.

BTW, here's a couple other braking shots:

One of these jets is not like the others,
One of these jets just doesn't belong,
Can you tell which jet is not like the others
By the time I finish my song?

Razz

em745,

Good photos, thanks for posting. In the top photo, looks to me like the engines are in afterburner, so why the speedbrake use?

If speedbrake is needed, VLO is probably not an issue. Also, deflected control surfaces increase RCS similar to deflected speedbrake.

The flight control software issue may be even more complex than you think. I you have separate speedbrakes, they are useable independently of airplane maneuvering because they don't generally result in any additional structural load on the wings or tails. But if control surfaces are used as speedbrakes, they drastically alter the distribution and magnitude of load on wings and tails. So the flight control wizards have to work with the structures wizards modify the speedbrake functions when the wings and tails are heavily loaded from hard maneuvering. Or, structures has to increase the weight and cost of the wings and tails to handle to higher loads from combined maneuvering and speedbrake use.

johnwill wrote:

em745,
In the top photo, looks to me like the engines are in afterburner, so why the speedbrake use?

That photo may have been snapped a millisecond before some kick a$$ maneuver took place?

If i can remember correctly the YF-22 featured a dorsal air-brake. So LM probably considered them useless wheight.

In the Raptor for the speed brake function, the rudders flare outwards, the flaperons move TED and the ailerons move TEU. This is the same for the Super Hornet. However I beileve there are portions of the flight envelope where the rudders will flare slightly, even without the speedbrake function being issued. Part of the reason could be to ease the load on the vertical tails at high speed.
There is video/photo somewhere in which the Raptor rolls left with standard aileron and flaperon deflections, but with the left rudder deflected far more to the left than the right rudder is to the right.

Forum: General F-22A Raptor forum

F-22 rudder(s) movement