JDG1@Lehigh (10/30/90)
From: JDG1@Lehigh
I have a question about the proposed powerplants for the YF-23.
Will they be afterburning? If so, are they equipped with some sort
of nozzle which can expand when the burner lights? And what are the
differences/problems stemming from the use of a rectangular nozzle
opposed to a round one? And how good are the IR suppression techniques
when the afterburner is being used?
Jonathan Goldstein
Lehigh Universitymorse@mprgate.mpr.ca (Daryl Morse) (11/01/90)
From: morse@mprgate.mpr.ca (Daryl Morse)
In article <1990Oct30.053122.7829@cbnews.att.com> JDG1@Lehigh writes:
I have a question about the proposed powerplants for the YF-23.
Will they be afterburning? If so, are they equipped with some sort
of nozzle which can expand when the burner lights? And what are the
differences/problems stemming from the use of a rectangular nozzle
opposed to a round one? And how good are the IR suppression techniques
when the afterburner is being used?
Jonathan Goldstein
Lehigh University
Yes, the engines for both the YF22 and YF23 are afterburning. Two
engines are being evaluated for use in whichever aircraft wins the ATF
contract, one by GE, and one by P&W. Two of each of the planes will be
built to serve as testbeds for the engines.
I believe the rumours about these engines being non-afterburning
stems from the fact that both planes will be capable of what is known
as "supercruise". That is, they will be able to *easily* cruise at
supersonic speeds *without* afterburners. The information that I have
read (AW&ST) indicates that both planes will be capable of ~Mach 1.5,
fully wet, without afterburners. (The YF23 achieved supercruise for
several minutes on its fifth flight.) Supercruise has been
demonstrated using current technology (the SuperTomcat variation of
the F14, for example), but only under ideal conditions, and then, only
slightly over Mach 1, and I think, in a clean configuration.
As for nozzles, that is an interesting matter. I recently saw photos
of both planes in AW&ST. First, the YF23... Northrup and McDonnell
Douglas appear to have emphasized the stealthiness of the YF23 to a
greater degree than was done for the YF22. (Not surprisingly, the YF23
looks very much like a sibling of the B2.) The nozzles of the YF23 are
hidden in a very B2-like trough, that will most certainly reduce its
infrared signature. (I couldn't tell what shape they were from the
photos.) However, at the same time, the trough significantly limits the
degree of thrust vectoring which is possible. Some side-to-side
vectoring appears possible, in addition to up vectoring, but down
vectoring does not appear possible.
The YF22, on the other hand, has completely visible, round nozzles.
Lockheed, et al, appear to have made no efforts to reduce the infrared
signature of that aircraft. The nozzles did not appear to have any
thrust vectoring capabilities, either.
Correct me if I am wrong, but I believe that thrust vectoring was
not intended to be part of the initial ATF contract, due to cost and
weight considerations. Also, in the article in AW&ST, it was implied
that the "loss" of thrust vectoring on the YF23 was not considered a
problem, because it is generally ineffective at high speeds, and
pilots don't like to go slow, just so they can use thrust vectoring.
Daryl
--
Daryl Morse | Voice : (604) 293-5476
MPR Teltech Ltd. | Fax : (604) 293-5787
8999 Nelson Way, Burnaby, BC | E-Mail: morse@quark.mpr.ca
Canada, V5A 4B5 | quark.mpr.ca!morse@uunet.uu.netsysmgr@KING.ENG.UMD.EDU (Doug Mohney) (11/03/90)
From: sysmgr@KING.ENG.UMD.EDU (Doug Mohney) In article <1990Nov1.025414.12746@cbnews.att.com>, morse@mprgate.mpr.ca (Daryl Morse) writes: >greater degree than was done for the YF22. (Not surprisingly, the YF23 >looks very much like a sibling of the B2.) Any similarities between the B-2 and the YF-23 are concidential; the B-2 was "black" and compartmentalized such that the YF-23 team had to "relearn" many techniques which were being used (figuratively speaking) 2 doors down in the B-2 program. The '23 team didn't even get a close-up look at the F-117 until last year...(so saith an Aero prof here who has talked with another prof who was previously on the YF-23 team at Northrop).
military@cbnews.att.com (William B. Thacker) (11/07/90)
From: p0.f7.n391.z1.fidonet.org!Scott.Johnson (Scott Johnson)
DM> reduce the infrared signature of that aircraft. The nozzles
DM> did not appear to have any thrust vectoring capabilities,
DM> either.
I think that the -22 has 2 dimensional nozzels with limited
thrust-v capability. I'll go back and check.
DM> ineffective at high speeds, and pilots don't like to go slow,
DM> just so they can use thrust vectoring.
That's not the point of T-V in that application. It is mainly
meant to give a shorter takeoff run/higher gross payload. Today's
airforce hardware are ground HOGS. If war broke out the runways would be
the first target, and almost none of the AF iron can operate without
long runways. Their use in combat would be, as you stated, of small use.