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A Tiger Bites Its Tail


On Sep 21, 1956 Grumman test pilot Tom Attridge shot himself down in a graphic demonstration of two objects occupying the wrong place at the same time—one being a Grumman F11F-1 Tiger [138260], the other a gaggle of its own bullets..

It happened on the second run of test-firing four 20mm cannon at Mach 1.0 speeds. At 20,000' Attridge entered a shallow dive of 20°, accelerating in afterburner, and at 13,000' pulled the trigger for a four-second burst, then another to empty the belts. During the firing run the F11F continued its descent, and upon arriving at 7,000', the armor-glass windshield was struck, but not penetrated, by an object..

Attridge throttled back to slow down and prevent cave-in of the windshield, flying back to Grumman's Long Island field at 230 mph. He radioed that a gash in the outboard side of the right engine's intake lip was the only apparent sign of damage other than for the glass, but that 78 percent was maximum available power without engine roughness occurring..

Two miles from base, at 1,200' with flaps and wheels down, it became evident from the sink rate that the runway could not be gained on 78 percent power. Attridge applied power and said "the engine sounded like it was tearing up." It then lost power completely. He pulled up the gear and settled into trees less than a mile short of the runway, traveling 300 feet and losing a right wing and stabilizer in the process. Fire broke out, but, despite injuries, Attridge managed to exit the plane and get away safely, to be picked up by Grumman's rescue helicopter.

Examination of the F11F established there were three hits—in the windshield, the right engine intake, and the nose cone. The engine's inlet guide vanes were struck, and a battered 20mm projectile was found in the first compressor stage..

How did this happen? The combination of conditions reponsible for the event was (1) the decay in projectile velocity and trajectory drop; (2) the approximate 0.5-G descent of the F11F, due in part to its nose pitching down from firing low-mounted guns; (3) alignment of the boresight line of 0° to the line of flight. With that 0.5-G dive, Attridge had flown below the trajectory of his bullets and, 11 seconds later, flew through them as their flight paths met..

that wasn't to hard now was it?????

1956

Sounds like they were trying to see if they could actually create a situation to damage the jet with guns. Progressing the arguement to go all missiles on the jets which turned into a disaster (okay a problem) with F4's in early vietnam.

Now they just have both and make sure they don't shoot themselves down.

Actually the pilot was a guest on the TV show "I've Got a Secret". He stumped the panel!

And yes, I saw it when it originally aired!

quote:

Originally posted by xgrunt:

Two miles from base, at 1,200' with flaps and wheels down, it became evident from the sink rate that the runway could not be gained on 78 percent power.

I'm not so sure that was the proper procedure. 78 % power should have been adequate to maintain flight. His mistake was hanging out all of the "barn doors". He created so much drag with the flaps and gear he dragged himself down. Not exactly what you want to do to extend glide with a compromised powerplant.

Years ago, when I was flying to a nearby airport to meet a FAA examiner for my private ticket ride, my Cessna 152's newly overhauled engine carbon fouled at 400 ft AGL on climb out. It had about 60% power. I trimmed it into slow flight and waddled around the pattern to land it. If I had used the flaps I would not have made the runway. After grabbing a POS C150 that had a VOR dial that only turned in one direction, I proceeded on my journey. The examiner asked me to make a couple of turns then said "land it". I thought I had F'd up royally. When I shut the engine down he signed off on my ticket. He said he had listened to my radio traffic on the emergency landing and knew I could fly.

It's probably interesting and amusing to be one of the very few men to have shot himself down with guns anyway...


With a turbine engine dammaged by an errant 20mm projectile (presumeably an inert (non explosive) projectile) 78% INDICATED power probably isn't the same thing as 78% power.

I don't know about you, and though I'll note that I am NOT a pilot, I will say I've worked building your toys and I know enough to say that you cannot believe guages that are attached to a damaged engine.

And as increasing the throttle caused vibration and precipitated the ultimate failure of the engine.... I'd say that the engine was probably damaged worse than the guages and/or thrust setting position indicated.



Frankly he's not the first pilot to fail to make the field with unexpected and unnatural holes in the airframe... however those holes came to be there.


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