F-22 Raptor speed

[bf-fly]

Therefore, the declaration of supercrising with the speed of 1,600 mph to 1,920 mph at the height of 40,000 to 70,000 fts

Who said that? I think were talking about 1300 mph. That is assuming of course, a standard atmosphere. I'm not the one postulating mach two, but you cannot assume it's not possible either.

[bf-fly]

I think I read eslewhere he actualy said 36 minutes (798nm)

[Scorpion1alpha]

Amazing at the speculations.

[asiatrails]

But we did the math and figured we could be there if we supercruised in about 25 or 30 minutes."

25 minutes = 1920 mph
30 minutes = 1600 mph

And that's prolly in the mid to high 40's. Above the commerical stuff. Take it to something 'round 50K to 60K (where the Mach is lower) and it may even be a touch faster!

Not that impossible, I was a FTE on the Concorde program back in the mid 70's and we supercrused at M2.2 60K for service profiles. One flight I was on we went out to M2.5 and there was still more to go. The flight restriction was the L/E temperature this was set for commercial service at 212 degrees C.

[Raptor_One]

Yes, but the Concord had 4 huge engines, variable geometry inlets, and an aerodynamic design with only one purpose... to go fast. The F-22's design is a very nice set of compromises. It's by no means optimized for Mach 2+ supercruise though. The Concord obviously was.

[sferrin]

double post

[sferrin]

So with all this rampant speculation about what he said, what he might have meant to say, what alt they were at, if he meant max supercruise over an 800 mile circuit, if he meant 800km or 800 miles, if he meant he would have saved 25-30 minutes ad nauseum.

It pretty much puts us right back where we were on page 1 when Raptor_One stated that trying to extrapolate the -22 supercruise speed based on one interview is silliness.

If you go back to what was actually said the pilot didn't state miles or kilometers at all. He said (AFTER he'd already flown the flight so he knew both how far he'd flown and how long it took him) that had they supercruised they could have done it in 25-30 minutes. Period. All the rest of the bullsh!t theories getting tossed around are people attempting to explain why it's impossible and that the pilot is either clueless or lying- when they don't have the slightest friggin' idea if it is or not. No doubt Raptor One will come back foaming at the mouth with his panties in a twist but those are the facts.

[Raptor_One]

The only reason I posted again in this thread was in response to someone whose comments are based on actual first-hand engineering knowledge. Asiatrails obviously knows his stuff. I don't mind debating with him whether the F-22 can do Mach 2.4-2.9 supercruise based on his first-hand knowledge of the Concord's performance capabilities. I didn't actually know the Concord could do Mach 2.5+ at 60,000 ft, but I'm not surprised. Do I think the F-22 can do the same thing? No. I have no problem debating that with someone who's obviously capable of intelligent scientific debate.

[asiatrails]

Yes, but the Concord had 4 huge engines, variable geometry inlets, and an aerodynamic design with only one purpose... to go fast. The F-22's design is a very nice set of compromises. It's by no means optimized for Mach 2+ supercruise though. The Concord obviously was.

Sorry. its purpose, which it did very well for 25 years, was to routinely carry about 100 people in the lap of luxury from one side of the ocean to the other and back again.

The four Olumpus 593-610 engines were straight turbojets with about 40,000 lbs of thrust, above M1.5 the intake was the key. the rest of the propulsion system worked hard to get it there. AB was used only on takeoff and to get from M0.98 to M1.2.

Although a pure commercial aircraft we had sufficent manoverability and power to simulate the filght profile of Backfire B (TU22M2) bombers.

This allowed us on runs down the North Sea from northern Norway to act as intercept targets for the RAF.

Now back to the Raptor, it is probably capable of the same performance and I would expect some more.

Edit to remove data.

[Raptor_One]

Sorry. its purpose, which it did very well for 25 years, was to routinely carry about 100 people in the lap of luxury from one side of the ocean to the other and back again.

That's like saying the SR-71's purpose was to conduct high altitude surveilance and signal intelligence. Not fair.

The four Olumpus 593-610 engines were straight turbojets with about 40,000 lbs of thrust, above M1.5 the intake was the key. the rest of the propulsion system worked hard to get it there. AB was used only on takeoff and to get from M0.98 to M1.2.

Like you say, the intake was key. How would the Concord have performed with a fixed intake that required taking flow around a bend to hide the engine fan blades?

Although a pure commercial aircraft we had sufficent manoverability and power to simulate the filght profile of Backfire B (TU22M2) bombers.

That's interesting. How many G could the Concord pull at supersonic speeds?

This allowed us on runs down the North Sea from northern Norway to act as intercept targets for the RAF.

How did the Concord fair?

Now back to the Raptor, it is probably capable of the same performance and I would expect some more.

Edit to remove data.

Why would you expect more? That's an honest question. I wouldn't expect it to do more for two main reasons: 1) fixed inlets and 2) an aerodynamic design that had to meet stringent stealth and combat-related requirements. For example, the Concord was famous for its complex variable geometry nose section. How fast would the Concord go without a streamlined nose section? For example, what if it had a bubble canopy like the F-22. That's my whole point about the Concord being designed for Mach 2+ supercruise. There are so many compromises on the F-22, yet it still has amazing performance. I wouldn't expect it to do better than the Concord that didn't really make any compromises. I mean... there's really no single design point for the F-22. The F-22 is all about off-design performance. The Concord, if I'm not mistaken (which I might be), is about on-design performance.

Finally... some good debate.

[sferrin]

Why would you expect more? That's an honest question. I wouldn't expect it to do more for two main reasons: 1) fixed inlets and

The whole "fixed inlet" arguement has been shredded so many times it almost doesn't bare repeating. Just for your enlightenment though:

Oh this is rich! You'd think you'd have learned the first time since it was you the guy was replying to:

"Wow, some of you guys need to learn about modern technology inlets.

Modern inlet systems do not have to change geometry to provide optimum pressure recovery for the engine. Traditional supersonic inlets have moving ramps, cones or other devices to capture the normal shock in the inlet throat. The F-22 inlet system does the same thing without traditional moving parts. No moving parts makes RAM treatments inside the inlets more durable and reduces RCS.

Like old technology inlets, each F-22 inlet is spaced away from the forward fuselage to form a boundary layer diverter. This prevents low energy turbulent air from entering.

The upper inboard corner of the inlet lip creates an oblique shock. Air is slowed by passing through that shock and is compressed in an external compression ramp before entering the inlet throat.

In the inlet throat, a sophisticated porous plate bleed system traps a normal shock where airflow becomes subsonic. The bleed system dumps overboard through the parallelogram-shaped door on top of the fuselage about 3 feet behind the upper inlet lip.

Airflow pressure increases as it passes through a gradually diverging duct with a 6:1 length-to-engine face diameter ratio that assures uniform airflow quality at the engine face.

Any excess airflow is dumped overboard through a hexagonal grid on top of the fuselage near the wing root."


Add to that the engines are about 30 years newer. There has been an improvement or two in engine technology and performance in those years you know.

2) an aerodynamic design that had to meet stringent stealth and combat-related requirements.

Until recently this was the excuse given for the Raptor not being able to do a Cobra There is no physical law that states "if you're a stealth aircraft it's physically impossible for you to exceed Mach 1.72 without afterburners".

For example, the Concord was famous for its complex variable geometry nose section. How fast would the Concord go without a streamlined nose section? For example, what if it had a bubble canopy like the F-22. That's my whole point about the Concord being designed for Mach 2+ supercruise. There are so many compromises on the F-22, yet it still has amazing performance. I wouldn't expect it to do better than the Concord that didn't really make any compromises. I mean... there's really no single design point for the F-22. The F-22 is all about off-design performance. The Concord, if I'm not mistaken (which I might be), is about on-design performance.

The XFU-8-3 (Crusader III) was good for well over Mach 2 speed with a fixed intake and didn't have the Concord's low-drag aerodynamics. In fact the test pilots estimated it would have likely reached Mach 2.9 and possibly Mach 3.

Finally... some good debate.

It would be nice if you could deliver what you demand of others but all you seem to be good at is bluster and attempts at ridicule.

[Raptor_One]

I'm not arguing with you on this one. It's obvious that your intent is not intelligent debate. You and some others have some strange desire to prove the F-22 is faster and faster and faster. If it's not speed, it's probably something else. The only problem with this is your use of silly "evidence". If you want to have a debate about variable geometry vs. fixed geometry inlets, that's fine. Just make sure you actually understand the basic science behind oblique shockwaves, normal shock waves, and so on. Look up stagnation pressure loss. Find out how it is reduced through the use of multiple oblique shocks. It's rather hard to get really good supersonic performance without the use of variable geometry intakes. Why do you think Concord used them? Why do you think the F-15 uses them? Why do you think any aircraft that has them uses them? Do you think it was just some fad? It's not as important as stealth these days, and there are more powerful engines now too.

By the way... what kind of shock system developed in the XFU-8-3 intake at Mach 2+? I somehow doubt it was a normal shock. And as for boundary layer diverters, this is nothing new either. I don't know why you think the F-22 is special because it has them. So does the F-16 and F-18 (fixed inlet fighters). What of it? It's also a bit amusing when you talk about how the normal shock is trapped in the F-22's intake. You act as though this is a special feature of the F-22. Any aircraft with a conventional jet engine needs to pass the airflow through a normal shock at supersonic speeds before it hits the engine face. Jet engines don't like supersonic airflow. You pass air through a set of oblique shocks at high Mach to slow the air down efficiently before passing it through a final normal shock to get the flow subsonic. That's just how things work. The faster you pass the air through a normal shock, the higher the stagnation pressure losses. That's why oblique shock systems are used via variable geometry intakes.

Another thing I find funny is how you coo over the dumping of excess airflow. Again, this is nothing new. The F-15 does this along with a bunch of other aircraft. Bleed air doors... wow... amazaing! Been around for a long time, dude! I don't think you actually understand what stagnation pressure losses are, which is why you probably think variable geometry inlets are useless. An inlet's job is to slow the airflow down to subsonic speeds. You can do this in a variety of ways. Some are more efficient than others. The measure of this efficiency is the stagnation pressure ratio of the inlet for any given Mach number. Air comes in at supersonic speeds and gets decelerated to subsonic speeds through one or more shockwaves. This is just what happens. All this other stuff you're talking about does not negate the stagnation pressure losses that occur when passing through one or more shockwaves. If the F-22 has a single oblique shock followed by a normal shock, that's not very good for Mach 2+. It's better than a single normal shock, but not optimal. The F-15 uses 3 normal shocks at Mach 2+ before the normal shock. That is optimal for those speeds. This is just fact, okay? Textbook stuff. All this other stuff you're on about is fluff.

Did I say I wasn't going to argue with you? Damn, I lied.

[Person]

Not that impossible, I was a FTE on the Concorde program back in the mid 70's and we supercrused at M2.2 60K for service profiles. One flight I was on we went out to M2.5 and there was still more to go. The flight restriction was the L/E temperature this was set for commercial service at 212 degrees C.

Concordes didn't/don't supercruise. They use their ABs for supersonic flight.

[Raptor_One]

Not that impossible, I was a FTE on the Concorde program back in the mid 70's and we supercrused at M2.2 60K for service profiles. One flight I was on we went out to M2.5 and there was still more to go. The flight restriction was the L/E temperature this was set for commercial service at 212 degrees C.

Concordes didn't/don't supercruise. They use their ABs for supersonic flight.

That is not true. Like Asiatrails said, the Concord used afterburners for take-off and to break through the transonic regime. Do a little research and you'll find out all about the Concord's supercruise capabilities.

[Raptor_claw]

2) an aerodynamic design that had to meet stringent stealth and combat-related requirements.

Until recently this was the excuse given for the Raptor not being able to do a Cobra There is no physical law that states "if you're a stealth aircraft it's physically impossible for you to exceed Mach 1.72 without afterburners".

(First - a little off topic - maybe should be in another thread) Interesting comment about the (former) perception (of the Raptor not being able to do a Cobra.) I was unaware that this perception was out there (granted I'm new to these boards (but hardly new to the subject...)). High AOA capability (of which the Cobra is but a small part) was demonstrated with F-16 MATV way back in the 80's. The F-16 was hardly designed with post-stall flight in mind (it does have a fairly restrictive limiter, after all). I would have expected that anyone who happened to notice the vectored nozzles way back on the YF-22 would have been surprised if a Cobra-type maneuver was not possible. Of course, an astute observer will say, "Ahh, but MATV had multi-axis vectoring, allowing it to use thrust to control both pitch and yaw, whereas F-22's vectoring is limited to pitch." True. True. But consider this - if there was no high AOA capability in mind, why have vectoring at all, it really doesn't buy you all that much for an AOA limited aircraft. So, 'someone' must have known that the stealthy shape was not incompatible with high AOA lateral/directional control.

Anyway, back 'on topic'
While all these debates about supersonic inlets and engine performance and shape-designed-for-stealth are interesting and more or less accurate, they proceed from the assumption that the top speed of the F-22 is limited solely by engine thrust vs aerodynamic drag. This assumption may not necessarily be valid. As others have pointed out, there might be (speaking theoretically, of course) other factors that could potentially be the speed limiters. It would only take one such factor to leave some amount of otherwise attainable speed capability unrealized. Could any and all other such potential factors be someday removed, remedied, or otherwise disregarded for a simple, flat out speed demonstration (ala Streak Eagle)??? Theoretically - sure. Would it cost a bunch of money and not really prove anything. Yup.

While this is all interesting debate, it is more interesting to me to see that people are so fervently debating the issue itself. What is getting lost seems to be the realization that top speed is not nearly the issue it used to be. For an air-superiority fighter, whose primary role is to go into a defended airspace, remove airborne threats and a few key high value targets, (paving the way for the F-35's, etc) does it really matter if it tops out at 2.0 as opposed to 2.2, or maybe 2.3 instead of 2.6??? If you are SECAF, how much money do you spend to get those extra knots, when you could put those dollars somewhere else (additional weapons clearance, avionics upgrades, etc)? Look at it this way - would you rather have Airplane X, which has a top speed of Mach 2.0 and the radar signature (and avionics suite) of an F-22, or Airplane Y, with tops out at Mach 2.5 but has an F-15's signature and radar?
I guess my point is simply that using top speed as a measuring stick for comparing fighter aircraft is a not nearly as valid as it used to be. Still, I understand the fun of the debate and the hypothesizing.

(For the record, I think Dozer was either speaking in hyperbole, was misquoted, or missed a decimal point somewhere....)