Some interesting claims about the F-22 on Wikipedia

Anything goes, as long as it is about the Lockheed Martin F-22 Raptor
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sferrin

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Unread post25 May 2006, 03:13

Meathook wrote:I have a nice video if I can get it to post here...never mind, say the file is too big - sorry guys


How big is it? (Like they say "where there's a will there's a way" :) )
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Brad

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Unread post25 May 2006, 19:41

I attempted to edit the F-22 file to reflect more recent information, such as the empty weight of ~43,000lbs (was going to use USAF official “40,000lb class”), correct the ferry range, T:W, wing loading etc. Either I’m not doing it right or somebody is coming along after me and changing it back. Maybe someone else gets bored as I was and can change it.

There has been some questions regarding the F-22’s range so I did some crude number crunching for the F-22’s range based on the Stevenson’s PPT slides. Now the obvious caveat is the source of information (Riccioni’s ilk) but we’ll go with his numbers for lack of any other references. He gives Specific Range numbers based on a nominal 60,000lb weight at various altitude and mach points. He cites a nominal SR of ~0.04 nm/lb at M1.5, 45,000 feet. He does not show numbers for higher altitudes and his envelope that he has for dry thrust says that the F-22 can’t go above 50K with dry thrust (M1.7+ is reached at ~36K) and to reach FL500 the F-22 has to be at ~M1.5-- I don’t know if this is true or not.

The USAF has said that the F-22 will go 1,724 miles ferry—but doesn’t specify if this is nautical or statute or if this is with internal gas or not:

http://www.f22-raptor.com/technology/data.html

If this is in statute like I suspect, then Stevenson’s SR of 0.76 at M0.9/40,000’ means that is must have at least 19,740lbs -- and that is with absolutely no fuel reserves. He does give a SR of 0.07 at M0.8/30K which is about ~0.005 mi/lb better than at M0.9/30K. I do not think that the USAF’s figure is for internal + external gas as even at 0.76 that’s over 2,600nm so its probably on internal gas only. With that being said it does not look like the ~ 18,400lbs is correct for internal unless the SR is better that what Stevenson’s slides suggest.

Now I know many aren’t too high on Kopp but for the most part his numbers on specs are correct and he’s reporting 20,650lbs internal. This seems to me more realistic as that’s about 2,200lbs more than the F-35A, which would also have similar internal space limitations with deeper bays and a more narrow fuselage profile with smaller overall size. This suggests that a nominal SR on internal gas of about 1,805sm or about 1,570nm. Still not enough for taxi/TO/reserve + 1724 mi but closer and if this profile is at M0.8 at 40K there’s a possibility that the SR is somewhat better making it more realistic. Either way the range is probably better -- either by internal gas or TSFC -- than what Stevenson’s slides suggest.

Interestingly if we consider that AFA article that stated the Raptor’s range with sub + SS of 405 +100nm radius and use Stevenson’s SR numbers that gives us a total fuel burn of about 15,100lbs. At 18,348 that gives a margin of only 3,000lbs, but if it has a 20,650 internal that’s about 5,000lbs for TO/climb/combat or loiter.

I don’t think the AFA scenario is very realistic so I crunched some numbers for a nominal strike/OCA sortie but instead of a specific range I looked at how far could the thing go if it had two tankings and cruised at M1.5 with a SR of 0.04 and 0.045 (A SR of 0.045 is extrapolated for 50,000’). I did this with 18,500 and 20,650lbs. Here is some of the criterion common to both (crudely estimated):

1st Leg (ingress)

Taxi/TO Burn- 1,100lbs
Climb (FL450)- 2,500lbs (100nm)
Reserve- 2,000lbs
Cruise: ?

Penetration Radius (Tank in - fight - Tank out)

Combat- 4,100lbs
Reserve- 2,000lbs
Radius: ?

3rd Leg (egress)

Descent- 1,500lbs (135nm, 3° descent)
Reserve- 3,300lbs
Cruise: ?

In this first two the 2,000lbs give about 18 min for tanking. This may be too tight or not accurate but this is what I went with. The 3,300 lbs of reserve on the last one is about 30 minutes or so of reserve fuel at home plate.


18,400lbs

Ingress leg gives a total distance of 610nm with 510nm at M1.5 and a total time (including 15 minutes for tanking) of 66 minutes with a SR of 0.040. If the SR is 0.045 then the distance goes up to 679 and time to 70 minutes. The penetration leg gives a radius of 245nm and 55 minutes, which again includes 15 minutes of tanking on the way back and 10 minutes of combat or about 35 minutes of loiter (M0.8 at 30K). If we assume SR of 0.045 then the radius goes up to 278 and time to 59 minutes with the other numbers staying the same. Finally on the way back we can go 677nm total in about 58 minutes at 0.04 or to about 751nm and 62 minutes at SR of 0.045. This last leg theoretically shouldn’t be any longer than the first unless there’s a head wind but it at least gives an idea. Admittedly these numbers are pretty bare assed and maybe too tight but are there for illustrative purposes.

20,650lbs

I’ll just simplify:

Ingress:

0.040- 702nm/71 minutes
0.045- 784nm/76 minutes

Penetration:

0.040- 291nm/60 minutes
0.045- 331nm/65 minutes

Egress:

0.040- 769nm/63 minutes
0.045- 855nm/69 minutes

Totals:

18,400lbs

Radius: 1,532nm (0.04)
Time: 3hours, 9 minutes

Radius: 1,709nm (0.045)
Time: 3hours, 11 minutes

Fuel Burn: 47,774lbs

20,650lbs

Radius: 1,762nm (0.04)
Time: 3hours, 15minutes

Radius: 1,970nm (0.045)
Time: 3hours, 30 minutes

Fuel Burn: 54,650lbs

By comparison for the F-15C w/3 bags and a nominal 1,500nm radius (1 tanking assumed)

17,542lbs

Radius: 1,532
Time: 3 hours, 54 minutes.

Fuel Burn: 27,241lbs

Sortie per day (ignoring pilot availability and assuming 1hour in between launches)

F-22A- 5.8
F-15C- 4.9

Thus if one assumes a standard availability of 80% then one squadron of each aircraft should produce in a day:

F-22A- 120
F-15C- 102

If the jet still had the reported 25,000lbs internal then it should be able to go about 2,200nm ~ 2,460nm with the above scenario.

Brad
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Angels225

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Unread post27 May 2006, 20:53

About the max Altitude of the raptor, I read some dude took an early block viper above 80,000 ft, In fact the link was posted here, but darn it i forgot where it was, Comsidering the greater T/W ratio of the raptor, I reckon it should be able to go a bit further than that.
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Unread post27 May 2006, 21:22

Has anyone been informed what it does going vertical? :shock: :notworthy:
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Unread post27 May 2006, 22:03

Angels225 wrote:About the max Altitude of the raptor, I read some dude took an early block viper above 80,000 ft, In fact the link was posted here, but darn it i forgot where it was, Comsidering the greater T/W ratio of the raptor, I reckon it should be able to go a bit further than that.


Hmm, although it may be fun/impressive, is there any real tactical advantage in flying at mega- altitude? Flying at 50,000ft above enemy fighters is`nt going to help you shoot him down....

I think only recon` aircraft would benefit from flying at mega high alt` to get photo coverage. There are PLENTY of SAM systems that can reach higher than most fighters max` altitude... I would also think that flaming out is not a popular circumstance to flirt with as well as popping canopy seals....

I don`t actually doubt the F-22 could fly VERY high. If you can`t see it though, wouldn`t 60,000 ft be quite adequate?
"I may not agree with what you say....but I will defend to the death your right to say it".
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sferrin

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Unread post27 May 2006, 23:53

The higher you are the further your missiles will go. 1. they've got more altitude to trade for range, 2. thinner air for less drag, and 3. less backpressure so you get better ISP out of your motor. As far as the fuel load the YF-22's was given as 23,000lbs internal. Granted they slimmed down the F-22A's fuselage somewhat but I'd be surprised if they lost so much volume that they gave up 5000lbs of fuel if they didn't have to.
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snypa777

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Unread post28 May 2006, 18:09

sferrin wrote:The higher you are the further your missiles will go. 1. they've got more altitude to trade for range, 2. thinner air for less drag, and 3. less backpressure so you get better ISP out of your motor. As far as the fuel load the YF-22's was given as 23,000lbs internal. Granted they slimmed down the F-22A's fuselage somewhat but I'd be surprised if they lost so much volume that they gave up 5000lbs of fuel if they didn't have to.


Cool, I understand the range advantage with higher altitude cruise and weapons. I wonder why ALL fighters don`t cruise at 80,000+ ft though? It isn`t technologically that difficult, except when you include "high speed". In fact, aircraft speed drops at altitude (Standard fighters at their ceiling limits) where there isn`t enough air for engine efficiency. I can see the advantage in getting range for dropping bombs, but launching missiles will only give you range, not speed if the aircrafts speed is relatively low.

A fighter pilot will tell you that it is not impossible to out-manouver a missile that has expended all of it`s fuel and is coasting...

I have read dozens of pilot interviews which stated that there is little tactical advantage of swanning about at 80,000+ft, so they rarely do it. Unless you have "speed". Now, if the F-22 can cruise at Mach 2 at 80,000+ft I would be impressed! That would impart great velocity and range to your AMRAAMS! The F-22 can already do that at 65,000+ft.

The only aircraft that can do 80,000+ft right now at high speed is the Mig-31 and POSSIBLY the F-22.. I may have answered my own question there!!!!
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Angels225

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Unread post28 May 2006, 20:19

Of the raptor could pull off that sort of peformance,(hell its done stuff only dreams are made of) It make one hell of an interceptor
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Unread post28 May 2006, 20:54

No F-16 can maintain level flight at 80,000 ft. If an F-16 reaches 80,000 ft, it does so in a zoom climb. An F-16's service ceiling or even absolute ceiling is around 60,000 ft. It's about the same for an F-15 too. Despite the F-15's wing area being over twice that of an F-16's, its higher empty weight negates any service ceiling advantage. I highly doubt an F-22 will be maintaining level flight at 80,000 ft. Perhaps 70,000 ft at very high mach.
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Unread post29 May 2006, 21:02

The ability to pull a lot of g's isn't what makes a high performance fighter. Above the mach you can pull 9g's and have a turn radius the size of Texas. More important is how to have a small turn radius with a high turn rate. Rate being how fast you track around that circle. With thrust vectoring you can accomplish positive rates and radius without pulling a lot of G. Same is true in the Viper. It's best turn speed is actually a range. At the top end you pull more g to max perform while at the low end you only pull about 4-5 g's. Off topic a bit, sorry.
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Brad

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Unread post30 May 2006, 06:26

sferrin wrote:The higher you are the further your missiles will go. 1. they've got more altitude to trade for range, 2. thinner air for less drag, and 3. less backpressure so you get better ISP out of your motor. As far as the fuel load the YF-22's was given as 23,000lbs internal. Granted they slimmed down the F-22A's fuselage somewhat but I'd be surprised if they lost so much volume that they gave up 5000lbs of fuel if they didn't have to.



Yes I would have been to but luckily I found official unclassified info:

http://www.0x4d.net/files/AF1/R11%20Segment%2012.pdf

This is USAF TO (Technical Order 00-105E-9) and discusses danger areas along with fire/rescue information etc. On pp. 15 you can see the fuel loads of each tank and the total.

Total is 5,450 gallons or 36,515lbs of JP-8. When you remove the 4 external 592 gallon tanks that leaves you with 3,082 gallons or 20,649.4lbs. So Kopp was correct and POGO/Riccioni/Stevenson and his ilk are wrong. That puts the FF at just under 0.31 or about .0308, not the .2775 they suggested.

Brad
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Unread post01 Sep 2006, 01:43

Angels225 wrote:About the max Altitude of the raptor, I read some dude took an early block viper above 80,000 ft, In fact the link was posted here, but darn it i forgot where it was, Comsidering the greater T/W ratio of the raptor, I reckon it should be able to go a bit further than that.


I think I read that too. In the Semper Viper edition of Code One with all the Joe Bill Dryden articles. Problem is (and he addressed this) is that its hard to run a jet engine at that altitude unless its specifically trimmed. The SR-71 was one of the few (probably the only) aircraft to be able to trim its engines from the cockpit. But for the moment say that the F-22 has a superb fadec that does it automatically. Now the next problem is sufficient airflow to support combustion. What forward speed would it take to feed the compressor face of an engine like the F110-129 at the air density you'd find at 80,000 feet. If its below the Raptor's public top speed of around Mach 2.x then theoretically it would be possible.

Oh and don't forget needing to plumb the pressure suit into the environmental system.


As always, if I missed/messed up anything, may the experts chime in.
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Unread post01 Sep 2006, 16:13

80,000 ft is not a sustained altitude. It's reached in a zoom climb. Neither the F-16 or the F-22 can cruise at that sort of altitude. Both can surely reach this altitude (and even higher) in a zoom climb though. The F-16 can theoretically perform a zoom climb to an altitude of nearly 100,000 ft. The F-22 will likely go a lot higher. However, sometimes a fighter loses stability at these altitudes before they can actually reach their theoretical maximum.
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Unread post01 Sep 2006, 18:43

80,000 ft is not a sustained altitude. It's reached in a zoom climb. Neither the F-16 or the F-22 can cruise at that sort of altitude. Both can surely reach this altitude (and even higher) in a zoom climb though. The F-16 can theoretically perform a zoom climb to an altitude of nearly 100,000 ft. The F-22 will likely go a lot higher. However, sometimes a fighter loses stability at these altitudes before they can actually reach their theoretical maximum.


More likely to flameout at 100,000 ASL.
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Unread post01 Sep 2006, 19:34

I don't know how much airflow is necessary to keep the combustion process going at those altitudes, but you'd likely have to be going pretty fast. Then again, you have to be going pretty fast at those altitudes just to keep from stalling. Not only that, but you have to have enough airflow over the control surfaces to maintain stability. I have no idea whether you'd starve the engine of oxygen before stalling or losing stability. It's likely aircraft dependent.
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