F/A-22 top speed

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shocktroop

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Unread post23 May 2005, 10:19

All the sources that I have found about the F/A-22 say that the Raptor has a top speed of Mach 1.8 and can reach a speed of Mach 2 with afterburner.

The F-15C, which the Raptor is supposed to replace, has a top speed of Mach 2.5. Even the F-4E, which entered service in August 1962 has a top speed of Mach 2.17. The F/A-22 Raptor uses more powerful engines, so they should give him a top speed close to that of the F-15C.

The F/A-22 is heavier than the F-15C and the F-4E, but does this difference in weight effect the top speed that much?

Weights empty:
  • F/A-22: 34,000 lb.
  • F-15C: 28,600 lb.
  • F-4E: 30,328 lb.
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allenperos

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Unread post23 May 2005, 10:45

Here's what I have on top speed only, weight has little to do with top speed but does have to do absolute/combat ceiling, 50'/min rate of climb and 100'/min rate of climb, respectively,

Top speed - at FL 530, 1350 mph, or Mach 2.08, sonic velocity = 574 knts @ FL 360 where the temperature stabilizes but pressure continues to decrease.

Source: <a href="http://www.amazon.com/exec/obidos/ASIN/ 007109282X/threefournineA">"Introduction to Flight", by John D. Anderson</a>, and NACA Standard Atmosphere
Last edited by allenperos on 23 May 2005, 21:44, edited 1 time in total.
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Polaris

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Unread post23 May 2005, 20:09

The main problem, from what I've heard, for the F/A-22's top speed is not so much that the engines aren't powerful enough, but the fact that the skin starts melting somewhat significantly over Mach 2. I'm not 100% sure if that's correct, but please correct me if I'm not. Another thing I've heard is that to keep the inlet stealthy, they had to sacrifice Mach 2 performance. Again, if I'm wrong, please do correct me.
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calhoun

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Unread post23 May 2005, 20:25

The skin is fine past Mach 2. The inlets get more than enough air for mah 2. Its ratied at mach 2"+", meaning it will do well past 2, they just dont want to tell us how far past.
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agilefalcon16

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Unread post23 May 2005, 21:52

Polaris wrote:The main problem, from what I've heard, for the F/A-22's top speed is not so much that the engines aren't powerful enough, but the fact that the skin starts melting somewhat significantly over Mach 2. I'm not 100% sure if that's correct, but please correct me if I'm not. Another thing I've heard is that to keep the inlet stealthy, they had to sacrifice Mach 2 performance. Again, if I'm wrong, please do correct me.


Wasn't there a problem with the Raptor's engines overheating at speeds over Mach 2, or something like that?
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allenperos

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Unread post23 May 2005, 22:01

Shouldn't be, I haven't heard of it? Overheating? Perhaps nozzles. Engine rotates at Mil Pwr, intake, sure it'll heat up, the heat will dissipate as it would in any other aircraft traveling at sonic velocity. Where did you hear of this engine over heating?

Remember afterburner is separate from the engine, doesn't have anything to do with it
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calhoun

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Unread post23 May 2005, 23:52

Nope. Engines work great. No overheating that I've heard through DT, OT, or IOC.
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allenperos

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Unread post24 May 2005, 00:07

That's what I thought. Thanks for verifying calhoun. Agilefalcon16, does that answer your questions about overheating engines?
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TC

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Unread post24 May 2005, 00:11

It will beat the Eagle in a foot race and I'll leave it at that.

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Obi_Offiah

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Unread post24 May 2005, 00:31

The F-22 has none variable inlets, is this a factor?.

Obi
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VPRGUY

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Unread post24 May 2005, 00:59

TC wrote:It will beat the Eagle in a foot race and I'll leave it at that.

Beers and MiGs were made to be pounded!


It'll smoke the viper too. When the -22 came to eglin for the climatic lab they did a few locals as well- it was sobering to see the F-16 chase plane in the pattern as the -22 took off. The -22 would start its roll as the F-16 came alongside in the pattern; the -16 would light burner, the -22 would do a mil takoff (full mil, I assume), and the -22 would be accelerating past the F-16 by the other end of the runway. That things got balls.
Remember that a lone amateur built the Ark. A large group of professionals built the Titanic.
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allenperos

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Unread post24 May 2005, 02:33

Obi - It is not always necessary to have a variable inlet geometry type situation so long as the shock wave does not enter the inlet, however, it is possible to have compressible flow enter and go through a process called diffusion, where the pressure increases, temperature decreases, and velocity decreases. This situation can occur and allow the engine to run optimally, (normally).

Classic case, F-16, if you notice the upper lip of the inlet, the shock wave will form around that lip and keep the shock wave from entering the inlet, first stage and subsequent stages of the compressor. It is a give and take situation, an aircraft engine, is a "comprimise" of circumstances as Roscoe says in the construction of an aircraft. It's not perfect, but rather a negotiation of many factors.

You'll notice that a jet engine is a series of airfoils, as is an airframe. In the case of the F-22, I have seen compressible flow enter the intakes, what happens from there, well, probably diffusion. I mentioned earlier about variable inlet guide vanes and variable stator vanes between compressor stages, reversing in angle of attack, thereby diffusing the airflow, "Bernoulli's" principal of compressible flow. After doing some research after this post in several areas of compressibility, you can guarentee yourself that if the aircraft is traveling supersonic, the molecular flow of air going through the engine is and has to be subsonic, that is less than the speed of sound. Otherwise you will get that "compressor stall" or reverse flow of air through the engine. A good reference book and worthy of purchase is [Aerodynamics For Naval Aviators], by the United States Navy.

Prior to the engine, we have a variable geometry intake and then a variable geometry inlet. It doesn't necessarily have to be variable, it can be a fixed geometry inlet.
Last edited by allenperos on 26 May 2005, 00:06, edited 2 times in total.
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Polaris

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Unread post25 May 2005, 22:19

Ah, ok. I stand corrected then. So, Allen and calhoun, you both are saying that the F/A-22 can go past Mach 2 significantly?
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VPRGUY

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Unread post25 May 2005, 22:28

That's probably not something they can freely say :(
Remember that a lone amateur built the Ark. A large group of professionals built the Titanic.
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falconfixer860261

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Unread post25 May 2005, 22:30

Doesn't take long to hit bingo in most fighters once the burners are lit
Last edited by falconfixer860261 on 28 Jun 2005, 14:58, edited 1 time in total.
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