Mildly interesting story

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Senior Airman
Oct 25, 2005
Found this story which I found mildly amusing.

TRMOAS: While writing the engine maintenance manuals, one of our customers
was the Republic of Singapore Air Force. They'd taken brand-new F404 engines
and dropped them into rather old A-4 Skyhawk airframes. The result was actully
very good, they wound up with a very hot little airplane that could outfly
most other things in their class. Our folks knew the engines very well, of
course, but were far less knowledgable about the airframes.

The RSAF suddenly started to register complaints about the engine, saying
that they were experiencing compressor stalls. (That's a condition that
arises when the engine can't handle turbulance or airflow distortions in
the air flowing into the engine.) The normal symptom is a loud "bang" from
the engine area (not an explosion, more like a slamming noise). There is
also a momentary loss of performance, only a nusiance in peacetime but
dangerous in combat. RSAF was very unhappy.

The tech pubs folks heard rumors that the engine was experiencing these
occasional compressor stall, but we had no data. Engineers started to look
into the problem, but were stumped. I was at the bottom of the information
chain, nobody told me details.

About six months into the study, no answers in sight, I was sitting in a
meeting when the subject came up. For the first time, I heard details on
the problem. One or two pilots were experiencing the problem, and only when
they made certain aerobatic maneuvers in their airplanes.

"Oh." I said. "Of course. That explains it. He's flying an A-4. It's not
a compressor stall, and that's why you can't duplicate it." Amazed looks
from around the table. I continued "The McDonnell-Douglas A-4 Skyhawk was
designed with an automatic movable wing leading edge extension. To allow
proper lift and control, at specific times the leading edge is supposed to
move forward, and provide a little more lift. The pilot has no control over
this. But it never worked quite right, and those leading edges were well
known for actuating on their own when the pilots make certain aerobatic
maneuvers. It got to be so annoying that when the U.S. Navy's Blue Angels
flew Skyhawks, they had to rivet the doggone things shut." The motion of the
leading edge would also account for the slight change in flight pattern
the pilots had reported.

Apparently, that was the problem. And, as none of the engineers had the
right airframe/engine integration background, it had never crossed their
mind. Within a week, the issue was resolved.

And I almost hate to confess where -I- found the information on the leading
edge problem. It was in the instruction sheet for a plastic model kit
of the Blue Angels A-4 Skyhawk.

Funny how inspiration comes from the strangest places sometimes.

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