Forum: General F-22A Raptor forum

Hello, lurked for awhile but was unable to post because there was something wrong with my browser before I wiped.

Anyways, I was wondering when the overpressure doors on top of the Raptor open?

Now, I'm no aerospace engineer (I'm mechanical), but am I correct in assuming they open when there is too much pressure for the compressor to handle? If so I'd assume they'd open at low altitudes going fast.

Thanks in advance!

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I'm a computer engineer (in the making) so I wouldn't know for sure either. But I'm guessing it's what you said. Maybe they also function when the engines need more air in high alpha??? I'm not sure. They sure are the most kick-a$$ looking overpressure doors I've seen!

I've seen pics of the Raptor at various speeds and power settings, but I've never seen those open. I only have 1 pic of a supersonic Raptor, but it's from a low aspect, so you can't see if those doors are open.

Are these overpressure doors open on this F-18 taking off?

Tinito_16 wrote:

Are these overpressure doors open on this F-18 taking off?

Those are ducts for additional electronics cooling on the Block 2 Superhornets.

Seems no one knows for sure what those doors on the Raptor do...

To me it looks like the doors that cover the refueling recepticle. -Adrian

Not that... he means the serrated vents (opening aft) on either side of it.

Some kind of venting for the weapons bays perhaps? (wild guess)

Elite 1K Joined: May 26, 2005 - 08:39 PM Posts: 1496

shep1978 wrote:

Some kind of venting for the weapons bays perhaps? (wild guess)

I don't think so, they're right over the engine ducts, I'm sure the OP is right, they've got something to do with managing incoming air to the engines.

They remind me of the two vents on the back of an F-14... and I seem to remember that those served a dual purpose (aux air intake at low speeds, overpressure vent at high speed). Could also be an exhaust for a boundary-layer management system in the inlet?

Anyone have video of Raptor going supersonic? I can't find any.

Tinito_16 wrote:

Seems no one knows for sure what those doors on the Raptor do...

Not true at all. They're just what many have been saying - they spill excess air overboard. Several aircraft have had the same, they're just not as obvious. XF8U-3 had 'em as did the F-14 Tomcat. Blackbird had them too.

This is WAY out there, but has anyone thought about "directing" the excess air during supersonic flight to reduce the sonic boom. I don't know if it would even be possible or useful. Has this ever been proposed. I know they have thought about other ways to minimize sonic boom in concept aircraft. It would be cool, an F-22 silently doing 1.5 1500 feet off the ground. Question

tank_top wrote:

This is WAY out there, but has anyone thought about "directing" the excess air during supersonic flight to reduce the sonic boom. I don't know if it would even be possible or useful. Has this ever been proposed. I know they have thought about other ways to minimize sonic boom in concept aircraft. It would be cool, an F-22 silently doing 1.5 1500 feet off the ground. Question

I don't think it'll help. Let's assume that you have a bunch of bleed air you can dump anywhere you want from the airframe, I don't see how that can be used make the sonic boom less pronounced.

Sonic booms occur because pressure fronts leaving aircraft -- including sound and compression fronts -- travel at the speed of sound through air. When you are travelling at the speed of sound or faster, these stack up into a shock front or cone. The so called "quiet" SST technologies focuses on shaping the airframe such that a larger number of weaker shock fronts are generated instead of a few strong ones. Vent air really doesn't help with the problem.

Forum: General F-22A Raptor forum

Overpressure doors