engine & exhaust
 

There were 2 different engines used by the YF-23 as part of the Dem/Val phase. PAV-1 used Pratt & Whitney YF119's and PAV-2 used GE YF120's. For the first time time ever we present clear colour pictures of the GE YF120 as fitted out for the YF-23. We are the first aviation-oriented publication to do this. The nozzle system employed on the YF-23 was unique, with a single paddle system providing adjustment to latent air pressure from above. There was no similarly shaped paddle at the bottom, just a fixed straight surface which met the start of the efflux trough. The nozzle for the GE YF120 was slightly wider than the version built for the P&W YF119. New pics of the GE YF120 can be found at Scott Lowther's Unwanted Blog. He has won another award for this effort.

 

September 2011: the clearest shot yet published of the GE YF120 as fitted to YF-23 PAV-2. This engine was briefly put on display in the R&D Hangar at the USAF National Museum in Ohio, next to the AFTI F-16 and P&W powered PAV-1. You saw it first on YF-23.net.
 

This is a Youtube video uploaded by Kenrushia taken at an airshow held at Pease AFB in 2010. Even though the exhibit signs state the engine is a production variant for the F-22, it is in fact a complete Pratt & Whitney YF119 engine as configured for YF-23 PAV-1. Kenrushia shows every aspect of the engine in closeup detail. It is not clear whether this engine was actually pulled from PAV-1 or was an extra test engine. Thanks to Flateric for posting this video at the Secret Projects forum.

 
 
 

The engine bay longerons were spaced to be able to accomodate either engine with only slight changes to the positioning of mounting lugs and couplings. The bays were lined with heat reflective material. The troughs used for the GE YF120 on PAV-2 were slightly wider than those for the P&W YF119 on PAV-1. The nozzle shroud assembly was different as well. PAV-1 had a shroud that hinged downward with the paddle whereas PAV-2 had a fixed shroud covering the paddle. The Lamiloy tiles used in the exhaust trough had exactly the same matrix pattern on both PAV's except that the outer row on PAV-2 was slightly wider. The angle of the trough sidewalls was 90; there was no attempt incorporate stealthy angles. The tiles lining the troughs were not shaped for stealth: they had 90 corners. Some of the tiles on the trough walls were angled but this was merely to accomodate the slope of the nacelle. Air was bled from the engines and passed through the structure of the troughs to cool them. This air exited through a series of tiny perforations just underneath the trailing edge of the troughs. PolymerStew has won an award for the photograph he took included in this section.

 

PolymerStew's rendition of the exhaust trough on PAV-1 at the National Air Force Museum after its return to pristine condition.

Last updated May 2012.

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