F-22 RAM Coatings/Limits on speed?

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f119doctor

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Unread post29 Sep 2022, 23:34

The F-22 has a basic Mn / KCAS max speed envelope in the Dash-1, with a time limited allowable exceedance beyond that basic envelope. That time limited portion of the envelope is a heat related limit. No, I can’t tell you those limits for OpSec.
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Unread post30 Sep 2022, 11:02

f119doctor wrote: No, I can’t tell you those limits for OpSec.

Naturally.
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Unread post30 Sep 2022, 15:59

There was an image (at least one I found) online of an F-22, where it *seemed* as though the tip of its nose, the coatings on it, had been subjected to prolonged and/ or high air-friction heating; like carbon scoring almost...
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Unread post30 Sep 2022, 16:29

jetblast16 wrote:There was an image (at least one I found) online of an F-22, where it *seemed* as though the tip of its nose, the coatings on it, had been subjected to prolonged and/ or high air-friction heating; like carbon scoring almost...

Page 2 of this thread?
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Unread post29 Nov 2022, 07:30



F-117 and F-22 test pilot Jim Brown on the F-22, with some numbers and an envelope chart. At Mach 2, 40,000 ft, the F-22 isn’t even close to using max power, only using 118% throttle while full afterburner is 150%. Also the envelope chart shows limit of 60,000 and Mach 2 but those look like artificial lines for operational limits rather than true aerodynamic limit. He said they tested out to Mach 2.1 as buffer space but I think it went well beyond that. He also says there’s a total temperature limit of 467 F or 242 C, which for heating is closer to Mach 2.4 or 2.5. Also the altitude limit seems to be more for pilot safety in case of depressurization than limit of the aircraft.

Also, it accelerates almost twice as fast from Mach 1.6 to Mach 1.9 than from Mach 0.9 to Mach 1.2. So this aircraft really does live and excel supersonic. Honestly, an F-22 with an air-launched ESSM would, being both fast and stealthy, quite outclass the MiG-31 and R-37M. The weapon would fit but it would probably take the place of 2 AMRAAMs, but new missiles weren’t a priority until a few years ago.
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Unread post29 Nov 2022, 12:36

disconnectedradical wrote:

F-117 and F-22 test pilot Jim Brown on the F-22, with some numbers and an envelope chart. At Mach 2, 40,000 ft, the F-22 isn’t even close to using max power, only using 118% throttle while full afterburner is 150%. Also the envelope chart shows limit of 60,000 and Mach 2 but those look like artificial lines for operational limits rather than true aerodynamic limit. He said they tested out to Mach 2.1 as buffer space but I think it went well beyond that. He also says there’s a total temperature limit of 467 F or 242 C, which for heating is closer to Mach 2.4 or 2.5. Also the altitude limit seems to be more for pilot safety in case of depressurization than limit of the aircraft.

Also, it accelerates almost twice as fast from Mach 1.6 to Mach 1.9 than from Mach 0.9 to Mach 1.2. So this aircraft really does live and excel supersonic. Honestly, an F-22 with an air-launched ESSM would, being both fast and stealthy, quite outclass the MiG-31 and R-37M. The weapon would fit but it would probably take the place of 2 AMRAAMs, but new missiles weren’t a priority until a few years ago.


Nice, those will make excellent data points for me
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Unread post29 Nov 2022, 16:40

disconnectedradical wrote:




Also, it accelerates almost twice as fast from Mach 1.6 to Mach 1.9 than from Mach 0.9 to Mach 1.2. So this aircraft really does live and excel supersonic. Honestly, an F-22 with an air-launched ESSM would, being both fast and stealthy, quite outclass the MiG-31 and R-37M. The weapon would fit but it would probably take the place of 2 AMRAAMs, but new missiles weren’t a priority until a few years ago.

AIM-260 will give more range than ESSM, without sacrificing magazine depth.
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Unread post29 Nov 2022, 16:45

sprstdlyscottsmn wrote:
Nice, those will make excellent data points for me


How do these numbers line up with your modeling? I’m surprised that the F-22 accelerated that much faster in supersonic rather than transonic. Just from thrust and drag perspective it’s surprising there’s that much difference. Also, I don’t know if throttle percent can be correlated to thrust directly, especially dynamic thrust.
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Unread post29 Nov 2022, 19:06

disconnectedradical wrote:How do these numbers line up with your modeling? I’m surprised that the F-22 accelerated that much faster in supersonic rather than transonic. Just from thrust and drag perspective it’s surprising there’s that much difference. Also, I don’t know if throttle percent can be correlated to thrust directly, especially dynamic thrust.

I have not gotten to check them against my model, but I am pretty sure M2 at 40k needs way more than ~36% of the afterburner in my model. With how modern afterburner rings work it can be a linear progression in terms of what is being added to the military thrust, but that would take some engine modeling at a level that I am working on but am not there yet.
What I would have to do for my current model is look at the Mil and AB thrust and make sure the drag line is just over a third of the way between them. I am NOT surprised by the faster supersonic acceleration as pilots have mentioned that their best climb speed is 1.4M+. A lot of that has to do with inlet design. The F-22 has a fixed inlet for reduced weight and RCS, that fixed inlet is optimized for supersonic flight at high altitude. As such at subsonic/transsonic and lower altitude conditions the inlet is not operating at peak performance.

*EDIT* The F119 is the modern J79. The faster it goes the faster it wants to go. Would have loved a B-1R to be real.
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Unread post29 Nov 2022, 19:11

Another data point from Jim Brown, that sea level to 60,000 ft in 3:30 number, that’s when the F-22 levels out at altitude at Mach 1.7. For comparison, even the Eurofighter Typhoon, which is quite optimized for supersonic, takes 1:30 to go from brake release to 36,089 ft at Mach 1.6.

About the J79, one thing I remember reading is a pilot saying that the F-4 compares favorably to even an F-15 at high speed high altitude.
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Unread post29 Nov 2022, 19:39

This is the first time that I have heard a knowledgeable program participant spell out the envelope boundaries for the F-22 in public, including the total temperature limit.

One thing JB noted was the effect that outside air temp has on supercruise performance. While most textbooks show ambient air temps of -69F at 36K and higher, there can easily be +/- 10F variations depending on the day’s weather. This can have a dramatic impact on performance in the parts of the envelope where excess thrust is limited. Losing 5% thrust due to high temps can stop acceleration, while adding 5% thrust on a cold day might double excess thrust and acceleration. The SR-71 could maintain M3.2 cruise at minimum AB on a cold day, while requiring Max AB on a warm day.
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Unread post29 Nov 2022, 20:08

With F-22 total temperature limit being 467 F, now Paul Metz’s statement about max speed being 1,600 mph (Mach 2.4+ at altitude) makes sense. Also, the Aronstein, Hirschberg, and Piccirillo book on F-22, skin heating at Mach 2 is about 230 F and at Mach 2.5 is about 500 F. So interpolating the temperature limit for approximation gives a number somewhere between Mach 2.4 and 2.5.

I think Edwards being in a desert tends to have hotter air that decrease engine performance, while pilots in Alaska might see increased performance.

Also, 800 knots limit at sea level give Mach 1.21. I think there were some sources that says Mach 1.4, but I think that’s because they mistakenly divided 800 knots by the speed of sound at altitude. Although I have no doubt F-22 aerodynamically can do more than Mach 1.2 at sea level, the structure is the limit here.
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Unread post29 Nov 2022, 20:35

disconnectedradical wrote:Another data point from Jim Brown, that sea level to 60,000 ft in 3:30 number, that’s when the F-22 levels out at altitude at Mach 1.7. For comparison, even the Eurofighter Typhoon, which is quite optimized for supersonic, takes 1:30 to go from brake release to 36,089 ft at Mach 1.6.

About the J79, one thing I remember reading is a pilot saying that the F-4 compares favorably to even an F-15 at high speed high altitude.


That climb to 60K he stated he was restricted to subsonic below 30k so it sounds to me like he could've shaved some time off that climb had he had no restrictions. Your anecdote about the Typhoon shows what a beast that airplane is too.
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Unread post29 Nov 2022, 21:31

disconnectedradical wrote:I think Edwards being in a desert tends to have hotter air that decrease engine performance, while pilots in Alaska might see increased performance.


This true in the summer at low altitudes. Once you reach the tropopause (approx 36k ft), the temperature tend to run in that +/- 10F band around standard day -69F. Surprisingly, it is often on the warmer side in winter, and some of the coldest temperatures are over the South Pacific.
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Unread post30 Nov 2022, 07:57

disconnectedradical wrote:

F-117 and F-22 test pilot Jim Brown on the F-22, with some numbers and an envelope chart. At Mach 2, 40,000 ft, the F-22 isn’t even close to using max power, only using 118% throttle while full afterburner is 150%. Also the envelope chart shows limit of 60,000 and Mach 2 but those look like artificial lines for operational limits rather than true aerodynamic limit. He said they tested out to Mach 2.1 as buffer space but I think it went well beyond that. He also says there’s a total temperature limit of 467 F or 242 C, which for heating is closer to Mach 2.4 or 2.5. Also the altitude limit seems to be more for pilot safety in case of depressurization than limit of the aircraft.

Also, it accelerates almost twice as fast from Mach 1.6 to Mach 1.9 than from Mach 0.9 to Mach 1.2. So this aircraft really does live and excel supersonic. Honestly, an F-22 with an air-launched ESSM would, being both fast and stealthy, quite outclass the MiG-31 and R-37M. The weapon would fit but it would probably take the place of 2 AMRAAMs, but new missiles weren’t a priority until a few years ago.


:shock: :shock:
Wow... the F-22 is a real powerhouse and loves to fly high and fast. People who say speed isn't necessity doesn't know the F-22.
The F-22 is truly the king of air-to-air in the west. :drool: :notworthy:

It was really cool to hear more about the F-117.

I enjoy that Youtube Channel. They have plenty of individuals that give incredible insight.
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