F-15 top speed
Alexei Gretchikhine
_____________________ _________________________________________
Alexei GRETCHIKHINE agr...@opie.bgsu.edu
Avekcen~ LPEhNXNH http://ernie.bgsu.edu/~agretch
Russian Aviation Page http://aeroweb.lucia.it/~agretch/RAP.html
"Sed quando submoventa erit ignorantia"
_____________________ _________________________________________
---------- Forwarded message ----------
Date: Wed, 13 Mar 1996 09:26:09 -0500
From: Mark Bovankovich <mbov...@orlando.loral.com>
To: Alexei Gretchikhine <agr...@OPIE.BGSU.EDU>
>
>>On Mon, 11 Mar 1996, Mary Shafer wrote:
>>> The F-15 can go Mach 2.4 or so, so you need a new guess. I worked on
>
>>Isn't its Mach number limited by the acryllic canopy? From what I have
>>heard this limits F-15 to M<2.0
>
> Not true.
I'd love to talk to Mary about this one. Here is what I know:
The F-15 achieved Mach 2.5 only on one occasion, and only in modified form.
I won't go into the details of that speed run here.
During Category II service testing, it was determined that an F-15A with
wing pylons and Sidewinders was only capable of achieving approximately
Mach 1.8 and a bit over 700 KEAS. When this deficiency was discovered, it
was decided to substitute an acrylic windscreen for the original
polycarbonate windscreen to increase birdstrike protection. The
temperature limits of the acrylic windscreen preclude flight in excess of
Mach 1.78, even though the aircraft has excess thrust at this speed in
"Vmax" mode, or when the Sidewinders are expended.
I pieced-together this information from various sources, both written and
oral, and civilian as well as military. As confirmation, I calculated the
stagnation temperature at the base of the windscreen for "standard
atmosphere" conditions at various altitudes, and compared this value with
the known maximum safe operating temperature of acrylic. It turns out that
the windshield angle of the Eagle yields a maximum Mach number of 1.78 at
36,000+ ft. I took this as confirmation of the written and oral accounts,
as I thought it too much of a coincidence that this number just _happens_
to match the accounts.
Perhaps Mary has experience with early, polycarbonate-windscreen F-15s, or
with non-service F-15s that were not retrofitted with the acrylic
windscreen. I would be very interested in hearing what Mary has to say
about this. If you speak with Mary (presumably via e-mail), please ask her
when she is due to speak at the AIAA meeting in Orlando, FL. I lost my
AIAA flyer announcing the event last year, and I would certainly like to
meet Mary in person.
Please let me know what you find out. I'm not averse to admitting I'm
wrong if I get proved so, but I'd like to hear a good explanation of the
facts.
Later,
Mark Bovankovich
Mary Shafer
<agr...@OPIE.BGSU.EDU> forwarded a message from Mark Bogdanovich that
said:
A> I pieced-together this information from various sources, both
A> written and oral, and civilian as well as military. As
A> confirmation, I calculated the stagnation temperature at the base
A> of the windscreen for "standard atmosphere" conditions at various
A> altitudes, and compared this value with the known maximum safe
A> operating temperature of acrylic. It turns out that the windshield
A> angle of the Eagle yields a maximum Mach number of 1.78 at 36,000+
A> ft. I took this as confirmation of the written and oral accounts,
A> as I thought it too much of a coincidence that this number just
A> _happens_ to match the accounts.
A> Perhaps Mary has experience with early, polycarbonate-windscreen
A> F-15s, or with non-service F-15s that were not retrofitted with the
A> acrylic windscreen. I would be very interested in hearing what
A> Mary has to say about this.
I just looked in an F-15 Dash 1 dated 31 Oct 89 and including
F-15S/B/C/D Aircraft Block 7 and above. These are obviously not early
aircraft, since the F-15 first flew in late '72 or early '73. Back in
the back, in Appendix B, where all the performance data, etc, is
shown, I found a level flight envelope which shows that the light
aircraft (38,000 lb) can get above Mach 2.4 between 40K and 50K ft on
a standard day. On a cold day (-10 deg) the envelope goes a little
over 2.5, in fact.
Now if the canopy change happened after late '89 my Dash 1 is out of
date. If that's the case, let me know and I'll go over to the Pilot's
Office and look through the current version and post an update.
I'm pretty sure that I remember 2.2 being the top speed of the
prototypes, but I'm not sure if this was before or after they clipped
the tips and snagged the tail. I think it was before, for a variety
of reasons that are too complex to explain.
A> If you speak with Mary (presumably via
A> e-mail), please ask her when she is due to speak at the AIAA
A> meeting in Orlando, FL. I lost my AIAA flyer announcing the event
A> last year, and I would certainly like to meet Mary in person.
I think Orlando is on Tuesday, the 26th, and Central Florida is on
Wednesday, the 27th. Anyone in the area is surely welcome at these
meetings, though mentioning your plans to the local AIAA people might
not be a bad idea. Please be sure to introduce yourself to me--I
really like meeting the people behind the postings.
--
Mary Shafer NASA Dryden Flight Research Center, Edwards, CA
SR-71 Flying Qualities Lead Engineer Of course I don't speak for NASA
sha...@ferhino.dfrc.nasa.gov DoD #362 KotFR
URL http://www.dfrc.nasa.gov/People/Shafer/mary.html
Mary Shafer
MS> On Wed, 13 Mar 1996 09:37:21 EST, Alexei Gretchikhine
MS> <agr...@OPIE.BGSU.EDU> forwarded a message from Mark Bogdanovich
MS> that said:
Oops, not Bogdanovich, but Bovankovich. I'm sorry. Please excuse me,
Mark and Alexei.
Petteri Pori
>
> Alexei Gretchikhine <agr...@OPIE.BGSU.EDU> wrote:
> Facts:
>
> 1. There is no such limitation in any USAF F-15C manual.
> 2. F-15's routinely exceed mach 2 on FCF flights.
> 3. It is not difficult to exceed mach 2 on an F-15 with pylons, as
> long as there are no external tanks on the pylons. I (and many
> others) have done so. It does take some fuel and some distance.
>
> What else is there to say?
How about with missiles? World Air Power Journal stated that the F-15 is
limeted to mach 1.78 when missiles are carried.
Petteri