service ceiling of F-22

I have seen descriptions of the F-22 having a service ceiling of 50,000 feet
which is 13,000 less than I have seen for the F-15. I thought the F-22 was
much more advanced.in every way except perhaps top speed. How can the F-22
be the air supieriority fighter of the future when its predessor can fly 2
miles higher?

What gives? Am I wrong?

On Sat, 13 Mar 2004 09:59:24 -0500, "zxcv" wrote:

I have seen descriptions of the F-22 having a service ceiling of 50,000 feet
which is 13,000 less than I have seen for the F-15. I thought the F-22 was
much more advanced.in every way except perhaps top speed. How can the F-22
be the air supieriority fighter of the future when its predessor can fly 2
miles higher?

What gives? Am I wrong?



50,000 is the most common number given for just about any modern
fighter. It's a pretty much meaningless number. The F-22 is suppose
to operate at 60k+ regularly and they've designed a pressure suit
specifically for the F-22. Unless the suit has been cancelled.
Anyway that's the last I've heard.

"zxcv" wrote in message
...
I have seen descriptions of the F-22 having a service ceiling of 50,000
feet
which is 13,000 less than I have seen for the F-15. I thought the F-22
was
much more advanced.in every way except perhaps top speed. How can the
F-22
be the air supieriority fighter of the future when its predessor can fly 2
miles higher?

What gives? Am I wrong?

F-22 is designed to operate at at least 60K ft. Besides, it will be able to
detect F-15s and other non-stealthy a/c, identify them and if necessary
shoot at them with either infrared- or radar-guided missiles without being
seen visually (paint scheme) or detected electronically (stealth shape and
construction materials) until a defender has no real chance of breaking
contact or of returning fire. FWIW, the figures for engine power and ceiling
for the F-22 appear conservative.
Thanks for the post.

Interesting in that the service ceiling number given corresponds to the
maximum permissible altitude for operations without a pressure suit. My
experience has been that ceiling figures are based on the actual performance
of the aircraft (disregarding any other factors). Maybe not in this case as
I suspect the jet is capable of greater than the 50,000 figure.

Mark


"zxcv" wrote in message
...
I have seen descriptions of the F-22 having a service ceiling of 50,000
feet
which is 13,000 less than I have seen for the F-15. I thought the F-22
was
much more advanced.in every way except perhaps top speed. How can the
F-22
be the air supieriority fighter of the future when its predessor can fly 2
miles higher?

What gives? Am I wrong?

ceiling figures are based on the actual performance
of the aircraft

In theory, "service ceiling" is the altitude at which an aircraft can
no longer climb at 100 feet per minute. "Absolute ceiling" is the
altitude at which it can no longer climb at all.

However, it is an honored tradition to hand out misleading ceiling
information. The B-36 had a service ceiling I believe in the high
30Ks, but was known to have flown at 50K and above.

I'm amazed at the notion of a 50K-plus service ceiling being thrown
around here. This modern fighters must be more like rockets than jet
planes. In the 1950s-1960s the only planes that could get up that high
were semi-gliders like the B-36 and the U-2.

What is the practical altitude limit at which a jet can no longer
ingest enough air to keep it operational?

all the best -- Dan Ford
email: (requires authentication)

see the Warbird's Forum at www.warbirdforum.com
and the Piper Cub Forum at www.pipercubforum.com

I understand that the "high power" 1950's designs (F-104, EE Lightning) were
capable of intercept climbs to 70,000+ ft (there are stories of RAF
Lighnings doing practice intercepts on transiting U-2s over UK at their
operational ceiling - without the U-2's approval!). The Vulcan could
operationally cruise at 65,000 ft (plus?) and that is (sorry, was) the
operation hight of Concorde at the end of the fuel burn on transatlantic
flights.

"Cub Driver" wrote in message
...

ceiling figures are based on the actual performance
of the aircraft

In theory, "service ceiling" is the altitude at which an aircraft can
no longer climb at 100 feet per minute. "Absolute ceiling" is the
altitude at which it can no longer climb at all.

However, it is an honored tradition to hand out misleading ceiling
information. The B-36 had a service ceiling I believe in the high
30Ks, but was known to have flown at 50K and above.

I'm amazed at the notion of a 50K-plus service ceiling being thrown
around here. This modern fighters must be more like rockets than jet
planes. In the 1950s-1960s the only planes that could get up that high
were semi-gliders like the B-36 and the U-2.

What is the practical altitude limit at which a jet can no longer
ingest enough air to keep it operational?

all the best -- Dan Ford
email: (requires authentication)

see the Warbird's Forum at www.warbirdforum.com
and the Piper Cub Forum at www.pipercubforum.com

Cub Driver wrote in message . ..
However, it is an honored tradition to hand out misleading ceiling
information. The B-36 had a service ceiling I believe in the high
30Ks, but was known to have flown at 50K and above.

Well, the roughly 40Kft service ceiling of the B-36s was true,
pretty much, (As in it's climbing at 100'/minute at that height)
but it's still climbing, and the ceiling changes as weight decreases
as fuel is burned off. (And a climb at less than 100'/minute is
still a climb, after all.) At B-36 cruise speeds and endurance, they
had a lot of time to drift up to some amazing heights. The Engine
Operation Charts in the -1 go up to 53,000', with instructions for
the Flight Engineers on how to set things up for maximum performance
above that height. Of course, with that small an amount of reserve
power, any maneuvering will cost some height. (But it'll cost any
intercepting fighters even more. They had even less of a maneuver
margin, and a much higher stall speed, and, in order to make a gun
or rocket pass, would have to pull more G than the B-36. Eiither the
-36 turns inside them, or the interceptor (If you're talking an F-86
era jet, like a Mig-15 or 17, or a Yak-25) stalls out and has to fall
a couple of miles before it can recover.

I'm amazed at the notion of a 50K-plus service ceiling being thrown
around here. This modern fighters must be more like rockets than jet
planes. In the 1950s-1960s the only planes that could get up that high
were semi-gliders like the B-36 and the U-2.

Well, could get there, and stay there for a while. The early
supersonic fighters had supersonic combat ceilings in the low
50Kft range, for the most part. But some though, like Walt
Bjorneby's Hotrodded F-104As, with the J79-19 engine used in
the F-4E, could, when supersonic, sustain more than 65,000'.
A B-58 on its Design Mission profile, with a 500 NM supersonic
run-in to the target, was expected to be at somewhere around
63,000'. (And it had power to spare - The B-58's flight limits
were set by airframe and compressor imlet tempertures, not thrust
available)

What is the practical altitude limit at which a jet can no longer
ingest enough air to keep it operational?

Ah... That's one of those "That Depends" questions. Basically, the
answer is "The height at which the engine can no lonvger burn enough
fuel to supply more energy than the turbine take out to drive the
compressor". But that's much too simple. The big factor is the ability
of the compressor to take in enough air and compress it sufficiently
without mucking up the flow though the engine. This is a fairly
complex relationship of Mass Flow, Pressure Ratio, and Temperature,
and it's described by the Compressor Map for the engine. This can
be tricky. Westinghouse, the U.S. pioneer of Axial Flow turbojets.
(They had the J30 flying before anybody on the Allied side had ever
seen a German jet engine) had pretty much sewn up the Navy's jet
engine business woth its very successful and very reliable first
generation engines, the J30 (FH-1 Phantom, & some prototypes), the
J32 (A 9" diameter midget turbojet for guided missiles), and the J34
(Which powered the F2H Banshee, the F3D Sky Night, and was stuck,
in pods, onto a zillion P2V/P-2 Neptunes and civilianized C-82s and
C-119s as boosters). At that point, they could do no wrong.
When it came to the followon J40, however, things didn't turn out
so well. The J40 was to be a big engine, producing about 10,000# of
thrust for the next generation of Navy Jets. (A3D, F4D, F3H, F10F,
and even the original F-102.) The problem was, the engine's
compressor wasn't too good at handling off-design airflows.
(Jet engines , especially back then, were designed to operate
most efficiently at a single set of conditions.) It was so bad
that the engine would compressor stall and flame out while climbing
through 30,000', in straight, unaccelerated flight. And they
coudn't straighten it out. The somewhat smaller J46, which wasn't
o be a J34 replacement, was pretty much the same. The Navy nearly
lost all of their fighter follow-ons to the original straight-wing
jets, the Manufacturers had to scamble to find alternate engines,
(Douglas lucked out, more or less. Ed Heinemann never trusted the
J40, so he designed sufficient stretch into his airplanes that they
could take Pratt & Whitney's J57. McDonnell had to settle for the
Allison J71, which wasn't good, but not as bad as the J40. Grumman
just abandoned the F10F), and Westinghouse ended up out of the Jet
Engine Businesss.

--
Pete Stickney

Eiither the
-36 turns inside them, or the interceptor (If you're talking an F-86
era jet, like a Mig-15 or 17, or a Yak-25) stalls out and has to fall
a couple of miles before it can recover.

Yes, this is evidently just what happened. The USAF ran tests over
Florida, as I recall, and all the B-36 pilot had to do to lose an
interceptor was to start a gentle turn. The same thing was reported
(more vaguely, of course) of Chinese MiG-15s over China.

However, the USAF never agreed to play with the Navy or the RAF, both
of which begged for a trial run at the 36. (The British at that time
held the altitude record, though of course not everybody was into
setting records, since to do so was to give out information you might
want to keep to yourself.)

I heard a great story by a B-47 (RB-47?) pilot who was intercepted
over Arcangel (I don't know how to spell that). SAC was routinely
flying over European Russia with B-47s, and the RAF with B-45s, but
their immunity to interception was of course predicated on the
performance of the MiG-15. On this occasion, the MiG not only got up
there (with some difficulty, it's true) but was able to get off a shot
or two. The Finnish newspapers reported that somebody was banging away
up there, so the chase evidently went on for some little time. The
B-47 got home with a thumping big hole in the skin, which the pilot
had framed and carried about with him for show & tell lectures.

In any event, that was how SAC learned about the MiG-17....


all the best -- Dan Ford
email: (requires authentication)

see the Warbird's Forum at www.warbirdforum.com
and the Piper Cub Forum at www.pipercubforum.com