F8U Engines


First some clarification on F-8 engines: from a modeling standpoint there are two types - we'll call them early and late - distinguishable by their afterburner sections.  The early engines—the P4, P12, P16 and P22—all had an afterburner tube that was like a corrugated pipe. Their flame holder was a five-spoke design and the AB petals had a pattern that I call the "waffle iron" pattern. 

This engine configuration applies to the F8U-1/F-8A, F8U-1E/F-8B/F-8L, F8U-1P/RF-8A/RF-8G*, and F8U-2/F-8C/F-8K.



 
The later engines—P20, P20A, and P420—are characterized by an AB petal that I refer to as the "wave pattern", a four-spoke flame holder, and an AB tube comprised of overlapping rings.

This engine configuration applies to the F8U-2N/F-8D/F-8H, F8U-2NE/F-8E/F-8J, F-8E(FN)/F-8P ......AND the RF-8G after 1978.





A note about the P420 engine.  It came about because the F-8J, which weighed 1500 pounds more than the E and therefore incorporated Boundary Layer Control (BLC) over the trailing-edge flaps for more lift, was seriously under powered, particularly in the landing pattern where bleed air from the engine compressor was diverted for the BLC, thus reducing thrust.  On a hot day, the APC (Approach Power Compensator = auto-throttle) could not cope with the power demands because it could not give 100% power.  A number of interim solutions were tried, including reducing the wing incidence to 5 degrees, but in the long run the solution was more thrust.  Pratt and Whitney responded with the P420, which had considerably more: just under 1,000 lbs in basic and 1,500 lbs in burner.  These were not new-build engines: the existing P20A's were overhauled to P420 standard and supplied initially to the fleet J's and eventually to the H's still serving in the Reserves, giving the H a near 1:1 thrust to weight ratio at low fuel weights.  It was a hot rod!

*In 1977, the last F-8 fighters were retired, leaving just the RF-8G.  The P420 engines were removed from the H's and J's, along with their improved A-7 style MLG struts, and installed in the remaining RF-8G's.  I refer to these airplanes as the RF-8G+ but that is my terminology and not official. However, it is useful for differentiating between the two.  The G+ is easily identified by the fact that it has the AB-cooling scoops on the tailpipe and a single outlet for the ACM exhaust on the right forward fuselage.  RF-8s with the early engines had a longer bifurcated ACM exhaust and on the G+, the forward section was simply blanked off.




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