So how do we "prove" this to the FAA. I wonder if we need to hire a
DER which I understand the FAA listens to?
I don't propose doing this until we are in the comment period of an
actual AD; but maybe we need to be ready
for it. I see very little emphasis placed on the overloading of the
wings by "manuevers". If you stress any plane
beyond it's limits it is going to fail someplace (most likely the
wings or aileron).
Dan Caliendo
Ercoupe Mach 0.14
3658H
On Sep 27, 2009, at 9:19 AM, [email protected] wrote:
Ed,
You presume that the FAA requires a higher burden-of-proof than
suspicion that the holes contributed to an inflight breakup. They
will probably take the most conservative course in the name of
"acting in the public interest". They don't have to show anything.
WE do. Without current data to show the FAA that our main spars are
not subject to increased structural fatigue due to additional holes
is the main spar cap, I'm afraid all these arguments are moot. They
can brush off any 337's they approved, the certification of the
Forney and Alon main spar, and even the Fred Weick letter simply by
stating that "new information has come to light concerning
cumulative fatigue in modified main spars as a result of the
Sebring mishap". It's done all the time-- part of the reason UPS
parked our re-engined and modernized 727-100 QF's rather than
comply with the AD's the FAA required under the Aging Aircraft
Program.
We need data, not arguments. Unfortunately, I'm afraid the burden
of proof is going to fall on us to prove to the FAA that our
aircraft are safe. It may not be fair, but it is what it is
Dave
--- In [email protected], "Ed Burkhead" <e...@...> wrote:
>
>
>
>
>
> Hartmut suggests these possibilities for holes found in the
center section
> spar:
>
> > We should give reasonable advice on how this
>
> > amendment will look like.
> >
> > 1. First , no extra holes , no further action
> > 2. Extra holes, documented - verify that it follows
>
> > an approved pattern
> > 3. Extra holes, not documented - certify if it follows
>
> > the approved number and pattern
> > 4. Extra holes not following an approved pattern
>
> > or number. Replace spar cap or add stiffener
>
> > provided by Univair ( has to be developed)
>
>
>
> At the least, I would suggest a second remedy to option 4:
Provide an
> engineering analysis by a DER or other qualified individual
showing the
> extra holes do not degrade the spar strength beyond required limits.
>
>
>
> For example, the designer's letter:
>
> http://edburkhead.com/Ercoupe/fred_weick_reply_on_holes.htm
>
>
>
> And, indeed, before an AD is issued or amended, the FAA should
show that
> spar holes degrade the strength beyond acceptable limits. So far,
we have
> only a single instance in which a spar failed, very possibly due
to extreme
> loads due to aileron flutter and/or a sudden high-g pull-up,
possibly at
> higher than normal airspeed. I question that this instance justifies
> grounding aircraft due to the spar holes.
>
>
>
> As always, aircraft which have controls that don't meet the
specifications
> in ERCO Service Department Memorandums 56 and 57 are unairworthy.
>
>
>
> Ed
>
