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FlightDreamz
Posted: May 26, 2008 - 05:16 PM
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Just saw the F-22 Raptor at the Jones Beach airshow this weekend (it was excellent)! Some high angle of attack passes, some Mongo flips, can't say I saw much inverted flying though. http://www.jonesbeachairshow.com/usaf_f22.html
Obamanite
Posted: May 26, 2008 - 10:20 PM
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Newbie to posting on this forum but long-time watcher, and rather well-versed on aviation matters.
Question to all: have you noticed, like me, that the Raptor's roll rate is rather, shall we say, unexeptional? It has got oodles of energy, and can point its nose where it wants, when it wants (its pitch rate is second-to-none). Its capacity to reverse direction via one of those brain-melting J-turns is just unbelievable (never seen an aircraft do a 180 turn almost literally instantaneously). However, based on Mark-1 eyeball observation, the Viper, for instance, seems to have a much faster rate of roll. This shortcoming, if it is indeed a shortcoming, is of critical importance in close combat, the ability of a fighter to quickly change direction without broadcasting its intentions for several seconds. Now, if the Raptor does indeed have an unexceptional roll rate, why not use differential thrust vectoring (i.e. one engine pitches up, the other down) to increase roll rate? Or maybe I'm just seeing things, and the Raptor rolls as quickly as any other fighter. Any thoughts?
Keith
Posted: May 26, 2008 - 10:38 PM
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Max is not allowed to do maximum aircombat style maneuvers at airshows. The true performance is left to training and will be quite a surprise for anyone being engaged. Show one Ace, not all four.
em745
Posted: May 26, 2008 - 11:51 PM
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Obamanite wrote:
Newbie to posting on this forum but long-time watcher, and rather well-versed on aviation matters.
Question to all: have you noticed, like me, that the Raptor's roll rate is rather, shall we say, unexeptional? It has got oodles of energy, and can point its nose where it wants, when it wants (its pitch rate is second-to-none). Its capacity to reverse direction via one of those brain-melting J-turns is just unbelievable (never seen an aircraft do a 180 turn almost literally instantaneously). However, based on Mark-1 eyeball observation, the Viper, for instance, seems to have a much faster rate of roll. This shortcoming, if it is indeed a shortcoming, is of critical importance in close combat, the ability of a fighter to quickly change direction without broadcasting its intentions for several seconds. Now, if the Raptor does indeed have an unexceptional roll rate, why not use differential thrust vectoring (i.e. one engine pitches up, the other down) to increase roll rate? Or maybe I'm just seeing things, and the Raptor rolls as quickly as any other fighter. Any thoughts?
Ever notice how a figure skater will tuck his/her arms in in order to spin faster? Well, the same principle applies to airplane roll rates. It's why the A-4 had such a phenomenal roll rate (tiny, centered mass and a short wingspan). It's also why an F-14 had a sluggish roll rate with its wings extended, and a downright respectable one with its wings pinned back.
The Raptor is a "full-size" twin-engine fighter with a wingspan almost 12 ft. greater than the F-16's, so physics are a limiting factor as to how fast it can roll. As for the "differential thrust vectoring" (which the raptor does NOT have), I recall reading somewhere (probably on this forum) that it wouldn't make much of a difference.
Keith wrote:
Max is not allowed to do maximum aircombat style maneuvers at airshows.
Which is a shame . But I doubt the Raptor is capable of doing faster rolls than we've seen so far.
Obamanite
Posted: May 27, 2008 - 12:50 AM
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em745 wrote:
Ever notice how a figure skater will tuck his/her arms in in order to spin faster? Well, the same principle applies to airplane roll rates. It's why the A-4 had such a phenomenal roll rate (tiny, centered mass and a short wingspan). It's also why an F-14 had a sluggish roll rate with its wings extended, and a downright respectable one with its wings pinned back.
The Raptor is a "full-size" twin-engine fighter with a wingspan almost 12 ft. greater than the F-16's, so physics are a limiting factor as to how fast it can roll. As for the "differential thrust vectoring" (which the raptor does NOT have), I recall reading somewhere (probably on this forum) that it wouldn't make much of a difference.
Yes, I'm aware the Raptor's sheer size and wingspan is a limiting factor, and although it is an immensely powerful dogfighter (like the Flanker), means it is not as nimble as, say, a Viper. A smaller oponent would of course seek to exploit this in close combat (although I doubt any sane Raptor pilot would ever get into the phone booth unless s/he absolutely had to). Which, by the way, may be why the only airplane that has thus far bested the Raptor WVR is, drum roll please, the Viper. In fact, I would say the MATV Viper would wax the Raptor's tail in close combat nine times out of ten. Of course, as someone else in this forum said, modern air-to-air combat is more about long-distance assassination than dogfighting!
em745
Posted: May 27, 2008 - 01:09 AM
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Obamanite wrote:
Yes, I'm aware the Raptor's sheer size and wingspan is a limiting factor, and although it is an immensely powerful dogfighter (like the Flanker), means it is not as nimble as, say, a Viper. A smaller oponent would of course seek to exploit this in close combat
Yes, but we were just talking about roll rates. There's also pitch and turn rates to consider. And in those areas, the Raptor is pretty much unmatched. Not even a Viper can keep up.
Lest we also forget how F-4 pilots managed to rack up high kill ratios in 'nam once they began playing up their jet's power advantage over the smaller, more nimble MiGs.
I agree, and that's what I had referred to earlier. That's one maneuver where the roll rate seems more respectable, while the turn rate, well, I've NEVER seen a combat-coded aircraft do that (that's what, 180 degrees in 2 or 3 seconds, followed by a complete reversal in even LESS time... wow). And it also looks like an actual combat maneuver where someone's on your tail, you fake right, roll 180 degrees and reverse to a left turn and do a quick 180 turn and quickly reverse into another 180 degree turn and you wind up right behind the other guy's tail, with plenty of energy left over instead of trying one of those dumb Pugachev Cobra stunts that leave you a sitting duck. For my money, that is the single most impressive maneuver I have seen the Raptor do to date. It's eyewatering...
I have to say, the roll rate doesn't appear to be lacking in the videos I've watched (including that one). Looks at least on par with the F-15.
You're right, it's not lacking compared to the F-15. I was comparing it to, say, the F-16 or the Typhoon. The latter's roll rate is freaking insane, much as I think it is an otherwise execrable, 4+ Gen relic (having just achieved IOC, I mean - would have been impressive in the late 1980s, where it belongs).
sprstdlyscottsmn
Posted: May 28, 2008 - 12:58 AM
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the small fighters will always have the best roll rates. I bet an old F-104 could out roll a Viper. I know that the Mirage 2000 has a disgustingly fast roll rate. Roll is one performance measuer that CANNOT be compared between disimilar aircraft. Even the Hornet has a slower max roll rate than a Viper.
The only big fighter I have seen roll at Viper speed is an F-14 at 55 degree sweep, still gets to use both spoilers and stabilators to roll 360/sec. It seems a little slower at 68 deg sweep, probably because the spoilers dont work at that sweep.
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Scorpion1alpha
Posted: Jun 06, 2008 - 09:09 AM
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That's funny. I've seen the Flanker and Typhoon and I'm not particularly impressed watching their roll rates.
Some of the best roll rates I've seen are from clean F-16s, Mirage 2000/Kfir, and the F-22 (and no, not the airshow demo).
Tinito_16
Posted: Jun 06, 2008 - 02:18 PM
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If the engine nozzles of the F-22 aren't mechanically linked to each other, there is no reason other than software to prevent the nozzles from operating asymmetrically. However, there might be some problems: you'd have to redo alot of the code that controls the nozzles, and the aircraft might not be structurally strong enough to take the strains. What I mean by that is, when the Raptor pitches up or down, the entire a/c wants to go up or down. But if you have asymmetrical thrust vectoring and you roll, now half the a/c wants to go up and the other half wants to go down. If the aircraft was not designed to take the extra strain, it'll wear down prematurely or worse, have a faliure midflight. These are probably the reasons why the Raptor doesnt have asymmetrical thrust vectoring.
As for it's effectiveness in helping roll the aircraft, it should work. Think of a double head sprinkler; when you turn it on, it turns like crazy while the water comes out. Should be a noticeable difference, because even though the max nozzle position is only +-20 deg, the engine is putting out 20-35,000 lbs thrust, and that's plenty to affect the roll rate positively. Using what I learned in physics this year, I came up with this: At 25,000 lbs of thrust (possibly mil power), and full nozzle deflection, each side of the aircraft is subject to 8,550 lbs of force either up or down, depending on which way the nozzles are deflected. Which means when a Raptor pitches up at that throttle setting the back end (behind the pitch axis) is subject to 17,100 lbs of force pointing down, which in turn points the nose of the a/c up. If someone knows the separation between the engine center axis and the centerline, I can tell you how much torque that would generate.
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. But I doubt the Raptor is capable of doing faster rolls than we've seen so far.
