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87th FIS Trim‐Pad J‐75 Incident by

John Dvorachek Crew Chief, 87th FIS “RED BULLS”, K.I. Sawyer AFB, MI (Jan 2014)

While on break from my FAA duties, I have a story about the durability of the J75 engine in the Six. As a young flathead assisting engine tech Don "Yogi" Baer at the trim pad at night, Bruce Hetland (a great maintainer) was at the controls for a trim run. During one particular run-up, there was a HUGE bang, followed by an impressive fire-ball o-ring of flame from the exhaust. When it happened, there was almost a suck-blow sound, like when you light off those old tennis ball cannons made from beer cans with lighter fluid... except ALOT louder. After that excitement, and throttle quickly back to idle, Yogi had Bruce run it up again... this time, showers of orange sparks blew out the exhaust. Trim run aborted, we disconnected the cables and Bruce taxied back to the Hangar... no further sparks, etc. Post-run intake inspection revealed the "Dog Pecker" lying in the bottom of the intake in front of the engine, crumpled to shit and now the size of a deflated basketball. The compressor blades had holes straight thru, and many massive gouges etc. The helicoils that once held the dog pecker bolts were sticking straight out like springs. But, not a single blade exited the case of the engine, compressor or turbine. The engine ran "normal" all the way back to the hangar. Of course, post investigation "spankings" were handed out for not shutting down on the trim pad immediately after the first compressor stall, but the spankings seemed to be minor, especially since Yogi and Bruce were some of our top notch guys. Don't know how that compressor stall blew off that dog pecker but it did, something about 300 mph air going the wrong direction I guess! Copyright © http://www.f‐  

87 FIS Trim Pad J-75 Engine Incident by John Dvorachek