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Darick wrote:
> I think this is the first time I've
read about the spring being
> a potential problem. My 415C
has this design with the
> crank handle on the instrument
panel. I've seen the spring
> and wondered what may be the
results of a break.
Darick,
I think we’re talking about
different springs.
Since you say you have a “crank
handle” on the instrument panel, it sounds like you have the early serial
number spring trim system that Syd described.
The later aircraft and those upgraded to
the C-85 should have (must have?) the aerodynamic trim tab on the
elevator. This trim tab is controlled by a push-pull cable.
The spring on that trim tab is to make the
tab stay firmly against the high-speed limiter in case the cable breaks or
becomes disconnected.
If that tab flops loosely, the elevator
could flop or, under the influence of the tab, perhaps flutter.
About 13 years ago, when I was editing
Coupe Capers, there was an airframe failure accident in, I think,
The investigator explained it this way:
When the tail cone broke off, there was
nothing holding the engine up so the engine’s weight dropped the nose
precipitously. The relative wind came suddenly to the upper surface of
the wings creating a VERY high negative g effect. The pilot’s seat
belt broke and he was catapulted out of the aircraft. The pilot, airframe
and empennage descended separately.
I think the investigator said the
horizontal stabilizer was still attached to the tail cone. So, what could
break a tail off a Coupe? The investigator told me he thought the trim
cable had come loose and the spring was weak allowing tab flutter causing
elevator flutter.
Or, maybe his speculation was wrong and
the guy was doing aerobatics.
After about a 25 minute Google search, I
haven’t found the NTSB report. I know it was around 1993-1994 due
to my memory of the conversation and the room I was in during the call (strange
how memory works).
At any rate, I resolved to check the
strength of that trim tab spring whenever I disconnected the cable. And,
I long ago decided to never do any aerobatics in a Coupe unless Bob Hoover was
at the controls.
For what it’s worth. . .
http://edburkhead.com
ed -at-
edburkhead???.com (change
-at- to @ and remove "???")
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