Jet fighter top speed at military power

The F-15C has better engines than the
F-15A. Maybe that is the cause for
the discrepancy.

I think its like this:

A- 25,000 lbs each
C,E- 29,000 lbs each

Nope. Only some of the E's have the IPE (PW-229). The remainder as well as
all the A's through D's have PW-220s or PW-220Es (except for the C/D's at
Langley, Eglin, and Tyndall, and several A/B ANG units that still use the old
PW-100s).

During flight test the clean E with PW-229s easily cruised above M 1.0 at mil,
whether accelerating up to it or decelerating down to it. It is not likely the
fully loaded E can do this.

During flight test the clean E with PW-229s easily cruised above M 1.0 at
mil,
whether accelerating up to it or decelerating down to it. It is not
likely the
fully loaded E can do this.

By clean, do you mean w/o conformal tanks? By easily cruised, do you mean
accelerated through mach w/o resorting to A/B? Is this based on personal
experience?

I have little doubt the clean F-15E can sustain 1.2 give-or-take in mil ...
but the acceleration through transonic might be a problem. By the same
token, the F-14B/D's can also supercruise, but they need A/B to get there
first.

The difficulty is handling the transonic drag rise, largely a function of
the design drag characteristics of the jet. Low aspect ratio, area-ruled,
thin-winged aircraft tend to do best (think F-104, Mig-23). Drag rises
sharply starting around .92 or so and peaks around 1.1-1.2. Most aircraft
run into a wall here (particularly at military thrust) and the difference in
speeds attained is remarkably little (I found the F-8 to be a wee bit faster
in military than the F-4, but I never flew the older and cleaner Phantoms
.... the F-4H1 was reputedly good for 1.04 or so, similar to F-104). And
recent designs have generally abandoned minimum-drag configurations to
attain other, more useful, characteristics.

A/C top speeds are illusory ... sometimes I think they're based more on what
comes from marketing than engineering. The F-14 was attributed with 2.34
(it attained 2.41 ONCE in flight test and was artificially limited to 1.88
in the fleet ... though it got there easily enough). The F-18 has a 1.8
claim ... I know NO ONE who's seen close to that (so maybe once in flight
test?). The F-15 is always attributed with 2.5/1650mph ... again maybe once
in flight test? (The PsubS curves I've seen would suggest otherwise, and
perhaps nobody told them about what happens to plexiglas at those speeds.)
Of course when you hang some ordnance, drag goes up and speed goes down ...
sometimes dramatically.

If one restricts the argument to military thrust only, top speed ranges from
..92 or so (low thrust or high drag limited) to maybe 1.04. Not much of a
difference if you're trying to outrun an AIM-120.

R / John

Thanks for the responses!

A/C top speeds are illusory ... sometimes I think they're based more on what
comes from marketing than engineering. The F-14 was attributed with 2.34
(it attained 2.41 ONCE in flight test and was artificially limited to 1.88
in the fleet ... though it got there easily enough). The F-18 has a 1.8
claim ... I know NO ONE who's seen close to that (so maybe once in flight
test?).


Sometimes I wonder if the marketing guys just go something like "well
it's got a thrust to weight of X, it's got them there fixed intakes so
it's automatically less than two, and it's not quite as streamlined as
an F-16, let's slap '1.8' on it and call it good".

Any 4th generation aircraft with fixed intakes is automatically
assigned 2 or less and if it's got variable intakes they'll give it a
2.2 or a 2.35. Those seem to be the magic criteria but I doubt
they're based on anything but numbers pulled out of somebody's
backside.

On Sun, 30 Nov 2003 03:13:36 GMT, Scott Ferrin
wrote:


I think it has more to do with the government/military original
specifications, I would think it goes something like this..

Military "We'd like a M2.5 aircraft..."

Manufacturer "Ah but they would require a variable inlet more
development work and thats more expensive!!"

Military "so how fast can you go without all the extra expence?"

Manufacturer " about M2.0"

Military " Ok close enough"

These figures are then carried through the life of the program, even
when those figures are exceeded by a large margin..


cheers



A/C top speeds are illusory ... sometimes I think they're based more on what
comes from marketing than engineering. The F-14 was attributed with 2.34
(it attained 2.41 ONCE in flight test and was artificially limited to 1.88
in the fleet ... though it got there easily enough). The F-18 has a 1.8
claim ... I know NO ONE who's seen close to that (so maybe once in flight
test?).


Sometimes I wonder if the marketing guys just go something like "well
it's got a thrust to weight of X, it's got them there fixed intakes so
it's automatically less than two, and it's not quite as streamlined as
an F-16, let's slap '1.8' on it and call it good".

Any 4th generation aircraft with fixed intakes is automatically
assigned 2 or less and if it's got variable intakes they'll give it a
2.2 or a 2.35. Those seem to be the magic criteria but I doubt
they're based on anything but numbers pulled out of somebody's
backside.

John Cook

Any spelling mistakes/grammatic errors are there purely to annoy. All
opinions are mine, not TAFE's however much they beg me for them.

Email Address :-
Spam trap - please remove (trousers) to email me
Eurofighter Website :- http://www.eurofighter-typhoon.co.uk

I think it has more to do with the government/military original
specifications, I would think it goes something like this..

Military "We'd like a M2.5 aircraft..."

Manufacturer "Ah but they would require a variable inlet more
development work and thats more expensive!!"

Military "so how fast can you go without all the extra expence?"

Manufacturer " about M2.0"

Military " Ok close enough"

These figures are then carried through the life of the program, even
when those figures are exceeded by a large margin..


cheers


I've seen it go both ways. I've seen many say a clean F-4 could no
way in hell break 2.2 clean despite the fact it reached 2.62 when it
was going for the speed record (yes I'm aware of the water injection
etc. etc.) On the other hand there was someone a while back that said
they were familiar with an individual who reached 2.83 in an F-111F
briefly even though it's generally listed as 2.5. I know I remember
reading that it was limited to five minutes at a shot over 2.2 or so
because of heating. I guess the only way to know for sure would be to
get a clean aircraft up to it's optimum altitude, top of the tanks,
and put the pedal to the metal until you either stopped accelerating,
were about to exceed heating limits, or were out of gas. LOL I wish
they'd do that for aircraft about to be retired anyway. I'd have
loved it if the Blackbird would have went out with new high marks for
speed and altitude. Oh well.

I've seen it go both ways. I've seen many say a clean F-4 could no
way in hell break 2.2 clean despite the fact it reached 2.62 when it
was going for the speed record (yes I'm aware of the water injection
etc. etc.)

Early F-4B's were good for an easy 2.2 (skinny wing and lack of add-on
antennas) and I suspect with the right conditions and trimmed engines,
somewhat more. Best I saw was 2.05 out of a late J (S-config without the
slats) and it had the wing pylons attached. The Skyburner F-4 was the early
one with small nose and canopy ... certainly not representative of
production A/C.

On the other hand there was someone a while back that said
they were familiar with an individual who reached 2.83 in an F-111F
briefly even though it's generally listed as 2.5.

I've heard a number of claims for the F as well. It had higher thrust
engines and w/o pylons etc was VERY clean.

I know I remember
reading that it was limited to five minutes at a shot over 2.2 or so
because of heating. I guess the only way to know for sure would be to
get a clean aircraft up to it's optimum altitude, top of the tanks,
and put the pedal to the metal until you either stopped accelerating,
were about to exceed heating limits, or were out of gas.

It's usually gas and (these days) airspace. The F-8U3 never exceeded 2.39
because of canopy problems. Inlet heating is also a biggie.

LOL I wish
they'd do that for aircraft about to be retired anyway. I'd have
loved it if the Blackbird would have went out with new high marks for
speed and altitude.

I think they came pretty close with the last records. I asked Darryl
Greenameyer why the SR couldn't just do a nice smooth pull up from 80K for
the absolute altitude record and he said it wouldn't work.

R / John

I think they came pretty close with the last records. I asked Darryl
Greenameyer why the SR couldn't just do a nice smooth pull up from 80K for
the absolute altitude record and he said it wouldn't work.

R / John

It still boggles my mind that that Mig-25 made it all the way to
123,000ft.

On one of the last flights (for the Air Force anyway) when they set a
few new records the Blackbird flew one stretch of the flight at 2242
mph or Mach 3.4.

John Carrier wrote:

Early F-4B's were good for an easy 2.2 (skinny wing and lack of add-on
antennas) and I suspect with the right conditions and trimmed engines,
somewhat more. Best I saw was 2.05 out of a late J (S-config without the
slats) and it had the wing pylons attached. The Skyburner F-4 was the early
one with small nose and canopy ... certainly not representative of
production A/C.

Most of the F-4 (E-model) mach logs I saw topped out
about 1.8-1.9, with only a few FCFs pushing it to 2.2
or so.

However, in those (1970) days of slick wings (no slats)
and the short gun fairing, I did see one F-4E come out
of phase and pull a mach 2.4 FCF before returning to
the flightline at Korat. Nobody believed it - so they
checked the TAS system. It was accurate. A dirty old
warbird from the Korat flightline could still pull 2.4
without any preparation (other than pylon/stores removal).