Forum: General F-22A Raptor forum

cywolf32 wrote:

Well sferrin, please elaborate on "don't mean squat"???

ASLAM went Mach 5.4 with a fixed inlet. BOMARC Mach 3+ with fixed inlets. The XF8U-3 Crusader III Mach 2.4 with a fixed inlet. (And they figured it was good for Mach 2.6+ with a different windscreen.) There is more than one way to skin a cat.

cywolf32 wrote:

As for T-50, it's already a given it's stealth is nowhere near US capabilities, so it makes speed up for this fault. Or have you not read what the Russians already know??

Whether it's as stealthy or not is completely irrelevant as we're talking about materials.

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VG inlets are nice for minimizing airflow spillage by having the ramps reconfigure to match the oblique shock angle but the YF-23 with the YF-120 engine supposedly had a top speed in the high Mach 2 range with fixed inlets so along with the other examples it is possible for an aircraft to achieve tremendous speeds if the engines are strong enough.

tacf-x wrote:

VG inlets are nice for minimizing airflow spillage by having the ramps reconfigure to match the oblique shock angle but the YF-23 with the YF-120 engine supposedly had a top speed in the high Mach 2 range with fixed inlets so along with the other examples it is possible for an aircraft to achieve tremendous speeds if the engines are strong enough.

It has to do with where in the flight envelope your propulsion system (intake to afterburner) is designed to operate and also how airflow is manipulated. Some look at externally visible VG intakes, like the F-15, or F-4, and think that's the only way to do it. It isn't.

Look at the Viper as a prime example.

The inlet/engine can exceed MACH 2... The Viper's inlet is fixed and can still give the engine enough air to power the aircraft to it's own demise.

TEG

The thing is the F-16 uses a pitot intake which generates a powerful normal shock to slow the flow to subsonic speeds. This leads to a MASSIVE loss in stagnation pressure (especially in the mach 2 regime) and the resulting pressure recoveries are rather poor as a result. In fact shouldn't that limit the F-16's top speed to below mach 2.5 or something?

haavarla wrote:

Well then, pls explain to me how he manage to insult IAF pilots by claiming they were rookies, but at the same time adding "their(MKI) jets will beat our F-15 and F-16 on a regular basic"?
You know, he contradicted him self several times, so its is not wise to even use him as an source..

"oh and thrust me, i wont mention anything other than Jane's material here" a few sec later he stated the 28 deg/sec High alpha on the F-22.. great work man!
That man was a a joke.

your right, a nellis weapons school instructor is a "joke". (plug sarcasm here)

Guys, (especially haavarla) get back on topic.

Sferrin. Ramjets are not turbofans. Also, said Crusader needed huge ventral fins and a liquid fueled rocket to assure it would reach those speeds. And we are talking usable thrust I hope. Missiles are a one shot deal, not a 30 year in the loop multirole fighter.

cywolf32 wrote:

Sferrin. Ramjets are not turbofans. Also, said Crusader needed huge ventral fins and a liquid fueled rocket to assure it would reach those speeds. And we are talking usable thrust I hope. Missiles are a one shot deal, not a 30 year in the loop multirole fighter.

Go back and reread your sources again. If you still can't figure it out, let me know, and I'll educate you.

Isn't the question here not: can you achieve Mach 2.5 with fixed inlets. but instead: can you achieve Mach 2.5 more efficiently with mobile inlets and or other less stealthy aerodynamic shapes?

If that is the case, it is easy to imagine that the PAK-FA can have speeds rivaling the F-22, with less powerful engines, because the plane accepted lower stealth for higher speed.

Think about it this way, the F-35 can reach the same top speed as smaller aircraft, even those the smaller aircraft have much less raw engine power.

Its an interesting fact, but the USAF apparently doesn't think that top speed matters, so according to them the point is largely moot.

arkadyrenko wrote:

Its an interesting fact, but the USAF apparently doesn't think that top speed matters, so according to them the point is largely moot.

Well said

There are two primary reasons why fixed inlets are favored over variable inlets:

1) Stealth. With S-ducts blocking the engine's fan blades, fixed inlets make the most sense.
2) Simplicity. Fixed inlets are both cheaper and come with a lower weight penalty, both are desirable in a fighter design.

They knowingly excluded variable inlets in the F-16 for the reason that they wanted a simpler and lighter fighter than the F-15. Knowing that it probably wouldn't hit speeds above mach two, they found that the F-16's performance at subsonic and transonic speeds was quite reasonable with just fixed inlets.

If PAK-FA is indeed faster than the F-22, more power to them. The F-4 far outpaced the MiG-17, yet that didn't prevent scores of Phantom kills by Fresco driver during the Vietnam War. I'm sure the guys and gals at Sukhoi know that pursuit of superiority in a metric such as max speed can definitely hobble your performance elsewhere, I remember reading that the MiG-25s/31s (fairly sure it was 31s, but I'll try and find the source) that tried to intercept SR-71 flights used up almost the entirety of East German airspace making turns to intercept while at their maximum airspeeds. I'm sure the Raptor will fair just fine. Any speed advantage possessed by the PAK-FA will probably be equalized at the merge anyhow, that is if they plan on maneuvering whatsoever.

Has there been any news on the development of the suitable powerplant for this aircraft? Or do they plan to share the Su-35BM's engine for production standard birds?

HV

One might also remember (on a dedicated F-16 web site) that the first USAF Viper kill (belonging to a D model block 42) was made against an Iraqi MiG-25 which is considerably faster than an F-16 of any block. (not to mention having as much power in each of it's twin R-15BD-300 than a block 42's single F100-PW-220!)

http://www.f-16.net/aircraft-database/F ... ofile/3150

http://www.youtube.com/watch?v=UrYcxXIg5fI

Once again history proves that training/tactics almost completely nullify maximum speed in combat situations. (Esp if your a MiG-25 within 10 miles of an F-16)

Hence the fact that speed is no longer the holy grail of aircraft performance as it was up into the 1970s when it was found most combat was done far below Mach 2.

Keep 'em flyin' Thumb

TEG

Everyone here seems to forget that the F-22's top speed was once given as only 1.8 Mach. No one was worried about speed then, and there's no reason to worry about it now. The Russians will always go the extra mile to have something a little faster, bigger, or more maneuverable in order to impress 3rd world $hithole dictators at airshows, and when these guys finally decide to cross the US with their shiny new Russian hardware flown by their favorite nephews, they will find that there is no substitute for training, maintenance, and stuff that actually works.

Forum: General F-22A Raptor forum

Moscow Times: PAK-FA Faster than F-22