Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!zaphod.mps.ohio-state.edu!pacific.mps.ohio-state.edu!linac!att!cbnews!cbnews!military From: morse@mprgate.mpr.ca (Daryl Morse) Newsgroups: sci.military Subject: Re: RE:YF-23 ENGINES Message-ID: <1990Nov1.025414.12746@cbnews.att.com> Date: 1 Nov 90 02:54:14 GMT References: <1990Oct30.053122.7829@cbnews.att.com> Sender: military@cbnews.att.com (William B. Thacker) Organization: MPR Teltech Ltd., Burnaby, BC, Canada. Lines: 64 Approved: military@att.att.com 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.net