F-22 Raptor speed

F-16ADF · by **F-16ADF** » 17 Aug 2017, 16:28

The F-15's top speed with GE F110-129 or PW F100-229 will probably be the same as the PW -220 powered jets. They are restricted because of the canopy starting to melt.

It says it in Col. Dildy's book: F-15 Eagle Engaged: The world's most successful jet fighter

disconnectedradical · by **disconnectedradical** » 17 Aug 2017, 20:49

mixelflick wrote:OK... does anyone know the top speed (clean) of an F-15 with those bigger, more powerful GE motors?

They all seem to be Strike Eagle derivatives, but assuming you take the FAST packs/CFT's and everything else off....? Any guesses vs. the Pratt and Whitney birds?

Believe it or not, according to the F-15E flight manual, the top speed with the -229 motors is actually lower at Mach 2.3 than with the -220 motors, which tops out at Mach 2.4 (the lighter single seat F-15C with the same motors go Mach 2.45). To be honest I'm not sure why this is the case. But the acceleration charts shows the -229 motors are much better though.

sprstdlyscottsmn · by **sprstdlyscottsmn** » 17 Aug 2017, 21:47

The -229 has better performance sub-Mach2.2 and much better altitude performance. That was my take away from the F-15E charts. Oh, but just look at the acceleration or envelope diagrams for 12 mk82s. That is where the -229 really shines, high weight and high drag configs.

phantasm · by **phantasm** » 17 Aug 2017, 23:44

tacf-x wrote:
alloycowboy wrote:High speed supersonic fghter airplanes were originally intended to intercept high speed supersonic bombers at short range on short notice but when all the supersonic bombers got cancelled in lieu of ICBM's the need for mach 3 bombers dissolved.

Also the amount of fuel required to do a mach two plus supersonic dash isn't really worth the effort since drag is the square of the velocity and thrust must equal or exceed the drag the fighter goes bingo fuel to fast to make it operationally useful. For instance the combat radius of the mig 25 was only 300 KM which when compared to some thing like the Patriot missile system is relatively comparable given the required mission.

With that being said it is easy to see why the USAF dropped the mach 2 requirement for the F-22 and F-35 as it just wasn't useful. Instead of a high ultimtate speed specification of mach 2 it was operationally realized that a high average speed in realm of mach 1.6 to mach 1.8 was more then adequate given the operational historical data of how fourth genration fighers were actually used in combat configuration.

Not only that but the Mig-25's engines were over-optimized strictly for high speed flight. The engines consisted of a low OPR single-spool turbine which meant fuel consumption at low speeds and altitudes was going to be crap as well. The reason why low compressor pressure ratios are desired for high-speed flight is because all you really need for compression at ~Mach 3 is the ram compression from the intake ramps, shockwaves and diffuser. The turbomachinery would only increase the likelihood of overtemping the turbine inlet at those speeds.

Likewise for the Blackbird....

So if the Raptor was optimized for high speed flight- it's efficiency would go up when doing that sort of work, and it would have a option that only Foxbats/Foxhounds have- outrunning enemy air to air missiles/fighters....

It'd be hell on the RAM....and that would be the next challenge- but it seems like that is a valuable option to have-

I can't imagine the havoc a even somewhat low-observable fighter could do while also operating for long periods of time at high speed...Not only hard to lock on-to ,but also moving a bit quickly to follow. keep an eye on. Of course, IRST's would be more valuable for such targets when tracking- but as far as getting to it- that would be difficult.

I also forsee a lot of cases that we can't perform- such as something operating at those speeds being able to cruise at 80,000 ft with ease at least- and if also low-observable, very hard for enemy fighters or bombers to evade. And the standoff weapon range would be vastly increased.

sferrin · by **sferrin** » 17 Aug 2017, 23:51

phantasm wrote:Likewise for the Blackbird....

Not so. The Mig-25 had a low pressure ratio engine because they didn't want it to melt at speed, when the inlet system was feeding it compressed air. All air entering the Tumanskys went through the turbine section. The J58 in the Blackbird got around this by piping the air AROUND the turbine section and dumping it into the afterburner. The J93 of the XB-70 was more like the Tumansky.

tacf-x · by **tacf-x** » 18 Aug 2017, 03:13

Sferrin is correct. The SR-71 basically just used its 6 bypass tubes with a favorable pressure delta between compressor and afterburner to force a lot of the air around most of the turbomachinery. There really is no point or desire for a Raptor to ever be able to reach the speed of the Blackbird. The aircraft just structurally can't handle it since aerothermodynamic effects increase with the square of the mach number.

mixelflick · by **mixelflick** » 18 Aug 2017, 15:21

sferrin wrote:
mixelflick wrote:OK... does anyone know the top speed (clean) of an F-15 with those bigger, more powerful GE motors?

The P&W -229s are as powerful as the F110s. (I'd think they'd do even better at high altitude/speed.)

Right, but those are Strike Eagles correct? And not F-15C's...

sprstdlyscottsmn · by **sprstdlyscottsmn** » 18 Aug 2017, 20:08

To get an idea of that look at the HAF F-16 -1 and you can see how -229 and -129 differ in the same airframe. You can then look at the F-15E-1 to see how the eagle planform does with -229 and make a guess that the -129 should have similar differences as it does in the F-16.

Areas that may cause this to fall apart completely are the fact that the F-16 has a fixed inlet and the Eagle doesn't. If the -129 is "4" better than the -229 in the F-16, but the -229 in the F-15 is "3" better than the -229 in the F-16 while the -129 is only "1" better than it would be in the F-16 then the -129 in the F-15 would only be "2" better than the -229 in the F-15. Or vice versa. If that made sense.

sferrin · by **sferrin** » 18 Aug 2017, 20:40

mixelflick wrote:
sferrin wrote:
mixelflick wrote:OK... does anyone know the top speed (clean) of an F-15 with those bigger, more powerful GE motors?

The P&W -229s are as powerful as the F110s. (I'd think they'd do even better at high altitude/speed.)

Right, but those are Strike Eagles correct? And not F-15C's...

There are no F-15Cs with bigger motors. They're all variants of the F-15E.

sprstdlyscottsmn · by **sprstdlyscottsmn** » 18 Aug 2017, 21:32

sferrin wrote:
mixelflick wrote:
Right, but those are Strike Eagles correct? And not F-15C's...

There are no F-15Cs with bigger motors. They're all variants of the F-15E.

Yes, and a 44,000lb "Clean AC" F-15E is not dissimilar to an F-15C save the larger canopy.

phantasm · by **phantasm** » 24 Aug 2017, 23:23

tacf-x wrote:Sferrin is correct. The SR-71 basically just used its 6 bypass tubes with a favorable pressure delta between compressor and afterburner to force a lot of the air around most of the turbomachinery. There really is no point or desire for a Raptor to ever be able to reach the speed of the Blackbird. The aircraft just structurally can't handle it since aerothermodynamic effects increase with the square of the mach number.

Funny, I just mentioned this, and it happened to make a note in the news

https://www.rt.com/news/400687-russian- ... tor-space/

I know it's rt, and between the laser stuff and the rest of stuff coming out on it now proclaiming it a space fighter... It's a little boastful.

But, it does bring up the fact they are working on a Mach 4 plane, and that will be an issue... Unless the still-in SR-72 gets an anti air missile capability, or we resurrect the Phoenix from the dead, we'll be using Raptors (or Eagles) slinging AMRAAMS, and the velocity boost from the fighter won't last long, leaving it at eventual terminal speed of Mach 4 against a 4- 4.3 plane.

Since we will be facing planes like this...
Doing something along the lines of 'buffing' the Raptor will be a cheaper option than a lot of other ideas to handle Mach 4+planes

On a unrelated note, I saw something that indicated the Mig 25 had more in common with the A5 than the Eagle does with the Mig, despite having a similar planform..

sferrin · by **sferrin** » 24 Aug 2017, 23:54

phantasm wrote:On a unrelated note, I saw something that indicated the Mig 25 had more in common with the A5 than the Eagle does with the Mig, despite having a similar planform..

Wut?

phantasm · by **phantasm** » 25 Aug 2017, 00:39

sferrin wrote:
phantasm wrote:On a unrelated note, I saw something that indicated the Mig 25 had more in common with the A5 than the Eagle does with the Mig, despite having a similar planform..

Wut?

gGs7Ml5.jpg

The comment I saw was in terms of design inspiration - and reflecting on how many Eastern and Western planes to take a few cues from planes before them - and was reflecting on how the designing of the Eagle may not have been as directly influenced by the Mig -25 as is thought.

Now, conversely, I feel there's little chance the T-50/SU-57 isn't more-than-other-planes inspired from the Raptor

F-16ADF · by **F-16ADF** » 25 Aug 2017, 00:44

I read the same thing about the Viggie/Mig-25. Can't remember the name of the book, though-

vanshilar · by **vanshilar** » 25 Aug 2017, 00:45

phantasm wrote:Funny, I just mentioned this, and it happened to make a note in the news

https://www.rt.com/news/400687-russian- ... tor-space/

From the article:

“It will have certain elements of artificial intelligence built into the jet, because, obviously, flying at those speeds, the human brain is not capable of thinking that fast,” Poli told RT. “There are a lot of new technologies going to be put into this aircraft, for sure.”

Hahahahaha. I don't know what's supposed to be there other than just fly-by-wire. But it'll have cool new artificial intelligence, because the human brain can't think fast enough at those speeds! The Apollo spacecraft must've had amazing artificial intelligence.