Hi Jim,
Your thinking is "right on" logic.
The first requirement of solving any problem is to understand that
there is, in fact, a problem.
Here we are as the Rabbi on the corner pleading "I have answers...who
has questions?"
IF there is a genuine "Ercoupe fleet" problem here, and neither we nor
the FAA knows that to be the case from a single accident when even the
investigating NTSB report is "Preliminary, subject to change". Some
one has authored a "airworthiness concern". We don't know if that
person is with the NTSB or the FAA. We don't know their name, title,
training, or experience. We do know that this person has urged
amendment of an existing AD on an entirely different part of the Eroupe
wing with an entirely different declared "problem", that of corrosion.
We know that this person suspects "unauthorized holes" in the failed
spar to be responsible for its failure. We do not know if the center
section was analyzed in such detail as to determine if it failed under
negative G forces, positive G forces, or both (sequentially). We do
not know if the outer wing panels were analyzed so as to determine if
wing tip rib failure under aerodynamic load occurred. We do not know
how much play existed in the aileron system at the time of the
accident.
We do know that excessive aileron play will cause flutter at some speed
in an Ercoupe, and that such flutter can, if not stopped quickly, can
initiate a sequent of events which will end in identical catastrophic
structural failure WITHOUT REGARD TO THE PRESENCE OR ABSENCE OF "EXTRA"
SPAR HOLES.
We do know that an AD mandating annual compliance with ESM 56 and 57,
as appropriate, could prevent ALL accidents caused by the most likely
scenario in the future; and that this is NOT in keeping with the
thinking behind the present ACS. If that thinking is clearly wrong,
then we do every party involved a favor in getting them on the right
track. In the process, someone must explain to the Emperor he has been
"had"...he is wearing no clothes.
I would suggest that if, and ONLY when, the FAA actually publishes
something in the Federal Register suggesting a problem in spars of
Ercoupes that we then, and only then, propose a simple static load
testing with sandbags to the strength required by CAR 04. That is how
ERCO did it, and that is how I understand Marv did it. The EOC could
coordinate group "inspection" (witnessing by a FAA DER, etc.) of such
testing.
My response to you suggestion is also that of a layperson and is
offered in the belief that we all, each and every one, want our
aircraft to remain both safe and affordable to fly. This is only
possible to such extent as we and the AOPA collectively discourage a
frequent and unfounded game of "what if" with the FAA.
Respectfully,
WRB
--
On Sep 27, 2009, at 17:32, [email protected] wrote:
This may be completely "off the wall" but I wonder if it would be
reasonable to suggest that load testing be done to investigate the
effect of these holes to confirm Fred Weick's opinion and possibly
show that the failure forces were way beyond any normal conditions.
I believe Marv Dunlap did some failure analysis on his four
passenger project. Perhaps he has some relevant info. If such a
test could be done at a reasonable cost perhaps Univair would be
willing to do it or maybe the EOC could raise the money or some
combination of resources might accomplish it. I can see that it would
require some fairly expensive parts that might be sacrificed and a
competent person to design , execute and document the test but I
expect the test itself might be fairly simple. I imagine there are
others on the forum who would be qualified to comment on this
layperson's suggestion.
Jim Graham
N2418H
1946 415 C
