Forum: General F-22A Raptor forum

Hey all, quick question and that is is the F-22's top speed limited to M1.8? Its just that some kiddie on another forum keeps repeatedly claiming it is due to heat build up.

Of course he offers up no proof whatsoever (I suspect petty jealousy spurs this nasty rumour as he is a European) and so I thought perhaps its time to look into this and put this story to bed once and for all. I can find no evidence of it being limited, can anyone else Question

Ok, I did a bit of hunting and found a GAO report from 2003 that states:

"F/A-22 estimated performance in the areas of supercruise, acceleration,
maneuverability, radar observability, combat radius, and range in
searching targets have so far been met or exceeded. However, problems
have surfaced related to overheating during high-speed flight-testing,
reliability, avionics that perform radar, communication, navigation,
identification and electronic warfare functions as well as excess
movement of the vertical tails. Modifications are being made to some
test aircraft to address some of these problems. For now, however,
testing in some areas is restricted."

and also:

"Overheating in the rear portions of the aircraft has
significantly restricted the duration of high-speed flight-testing. As the F/A-
22 flies, heat builds up inside several areas in the rear of the aircraft.
Continued exposure to high temperatures would weaken these areas. For
example, a portion of the airframe that sits between the engines’ exhausts
experiences the highest temperatures. This intense heat could weaken or
damage the airframe. To prevent this heat buildup during flight-testing, the
aircraft is restricted to flying just over 500 miles per hour, about the same"

It also says:

"The Air Force may incorporate a modification that adds copper sheets to the rear of the aircraft to alleviate the problem.
The Air Force began these modifications in January 2003 and plans to
complete them by July 2003."

Now i'm pretty sure this is fixed now isn't it as Raptors routinely move about at speeds above 500 miles per hour, and we are 7 years on from that Report, infact I don't think the F-22 had even reached IOC had it when that report came out? Anyway any input from you guys would be appreciated.

The full GAO report for those that are interested: http://www.gao.gov/new.items/d03603t.pdf

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I have read about this as well, though it was said that M 1.8 is just a kind of safety limit and to preserve airframe life. But was some time ago and I haven't found it again.

You may want to point out that the F-22 reached IOC in 2005, and the early issues have been addressed, not to mention trying to use old documents like that, is a bit disengenuous on his part.

The F-22 haters will pick on anything to try and attack it. Their attitude is "it's not perfect so it's not worth it." Why not cite the fact that many planes are g limited in training to preserve airframe life? Does that mean they can't get it done when it counts?

@ww,
I have read that around 2006-2007 timeframe. Dunno whether it's still valid or not, but as Shingen said it doesn't matter that much as the aircraft can do it when it is necessary. M 1.8 is sufficient anyway and won't do the F-22 any harms in terms of combat effectiveness. The aircraft can do so with full warload and even approaches that speed in supercruise. The acceleration is more important anyway and once again it is expected that the F-22 is unmatched here.

Dude realize you're reading articles from 7-10 years ago. EVERY new aircraft has problems, they are extraordinarily complicated machines. The F-22 is the best air-to-air fighter in the world, that's all I will say.

flyboy22 wrote:

Dude realize you're reading articles from 7-10 years ago.

Err, yeah I do realise that, hence me writing:
" I did a bit of hunting and found a GAO report from 2003 that states"

I think you're barking up the wrong tree/got the wrong end of the stick here because i'm the one who's trying to prove that it is not still limited to M1.8 and that the initial problem was before IOC was achieved.
All the evidence so far would point toward the problem being fixed anyway so I very much doubt any M1.8 limit is still in place.

EF Typhoon has engines that have pecae and war settings. No one criticizes that because the operators get long life in peace and high performance in war. Not that that particular platform probably even needs the war setting to beat its opposition.

@shep, why do you even bother arguing with morons like that in the first place?

@Shingen,
why should anybody criticise it at all? That example doesn't really fit here, because the EJ200 is designed for a 60 kN/90 kN thrust which was the requirement. The war setting further increases the thrust above that requirement as the EJ200 has been designed with a 15 % performance margin in mind, of course by trading engine life time. It's not like with German MiG-29s where the thrust was actually reduced over the original requirement to preserve engine life time.

To make it clear to the US observer, it would be as if the F-135's demonstrated higher than required engine thrust would be implemented as war setting. Wink

shingen wrote:

EF Typhoon has engines that have pecae and war settings. No one criticizes that because the operators get long life in peace and high performance in war. Not that that particular platform probably even needs the war setting to beat its opposition.

@shep, why do you even bother arguing with morons like that in the first place?

WTFO? You are ignorant, buddy.

EF's opposition is MiG-29/35 and Sukhoi T-10 series. I see nothing but absolute EF dominance. Let me know why I'm ignorant. I don't see the F-35, F-15, or F-22 as opposing Euros.

ANY engine with a modern FADEC in the control system can be 'made' to give higher/lower thrust based on the needs/wants of the customer.

IF the USAF wanted the F100-PW-229 to make more power, it is a simple software upgrade that could be done via computer without even removing the engine. Same holds true for the F119. Simple software changes would allow a higher turbine temperature and thus increase thrust.

Downside to this: decreased TBO.

The EJ200 does this with a switch, I believe, like the old F100-PW-100/200 and -220. It was called "vMAX". The feature was 'disabled' in the software of the PW-229 but could always be 'programed' back into it at the whim of the USAF. This is why the PW-232 was capable of 29K, 32K, or 34K based on customer needs. The engine was also tested to 37K. (but wouldn't have lasted very long in operational use)

Computer controlled engines allows the OEM to walk the very narrow line between maximum performance and maximum durability. If you slide one in a positive direction, the other typically moves in the negative.

Keep 'em flyin' Thumb

TEG

PS- Don't we have a topic covering what the Raptor can/can't do for top end? Shrug

EDIT: Misspelling of FADEC - darn spell check!?!

@TEG,
do you programme it directly on the aircraft? I suppose your FADEC box has a subsequent connector to allow it?

In the Eurofighter that switch is labelled DATUM ADJUST/TRIM. Don't know whether that war setting is programmed in all the time or not.

Scorpion82 wrote:

do you programme it directly on the aircraft? I suppose your FADEC box has a subsequent connector to allow it?

Yes it would be programmed with a computer used to download engine performance and statistical data.

The computer is also used to 'upload' new software "logic" into the engine as/when needed through regular updates and modifications. It is typically used when changes are needed to increase reliability, durability, or diagnostic capabilities. This upload/reprogramming could also be used to change performance characteristics.

TEG

We were used to remove the FADEC box from the aircraft and programme it in the shop, usually in conjunction with error flags, though it was possible to programme it on aircraft as well.

Forum: General F-22A Raptor forum

F-22 top speed limited?