Hi Hartmut,
Comments interspersed below.
Regards,
WRB
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On Sep 27, 2009, at 10:59, Hartmut Beil wrote:
[Attachment(s) from Hartmut Beil included below]
Guys.
Look at the attached image. It shows the factory drawing on how to
drill in the spar cap.
What "factory drawing" (Title, date, revision level) is this section
taken from? What model Ercoupe does it pertain to? What is the size
of the holes?
The radii in the extrusion profile is not to be touched.
That's what I mean with a standard pattern.
If you have holes closer to the edge of the spar cap, going through
the radius of the outer or inner sides, you are weakening the spar
cap.
Maybe not enough that it creates an instant problem, but it will be
then the weak spot in your spar, where it will break first. It will
flex more there and maybe crack easier.
Agree completely.
The tragedy of the Sebring breakup is that whatever the cause was for
the breakup, be it the pull-up with two people or the aileron flutter,
it can happen to you too.
I experienced aileron flutter myself and I also was stupid enough to
pull up from a dive doing 144 indicated ones. I survived. (My spar is
like from the factory.)
I respectfully, but strongly disagree. Aileron flutter will NOT occur
if the owner/pilot and/or his/her mechanic comply with ESM 56 or 57, as
appropriate. In most cases I believe (but am not willing to
demonstrate) if power is chopped and the aircraft put in a turn to the
right or left so as to "load" the ailerons, moment flutter is
perceived, the flutter will cease immediately without damage. I
further believe either course of action taken alone would have the same
likely outome.
My thinking is: would any of you let your children fly with a known
wrongly drilled spar that got signed off with a 337?
Of course not. But let's look at this "logic another way. You presume
that a pilot has knowledge that the spar in his/her plane is "wrongly
drilled"? What pilot would take such a ship aloft thus risking his/her
own worthless butt? People trust their mechanics... ;<) That's, for
most, the "real world".
What if they experience aileron flutter?
See the above.
Or just pull up for the fun of it?
Such decisions of the pilot in command have consequences. Sometimes
those consequences are defined in a court of competent jurisdiction and
damages are awarded.
If the award is against a dead pilot, the lesson(s) still need not be
lost on the rest of us. i think that's why many subscribe to Tech...to
be aware of stuff like this even if they NEVER make their presence
known by actual participation here.
I surely would not let them fly. And the logical conclusion then is
that I should not too.
Absolutely agree.
We have to make the FAA an offer.
That has been done, perhaps several offers. Some may be ill advised.
If we claim that the center spars are structural ok, holes or not, Mr.
Caldwell can ground the whole fleet.
I emphatically disagree. The FAA can ground the whole fleet, but Mr.
Caldwell is but one tiny link in the chain of events that must be
forged in order for the FAA to do this.
It is my presumption that the position Mr. Caldwell holds is the
weakest link in that chain I would break.
Because when we claim that the holes drilled did not affect the spars
strength, then ALL Ercoupe spars are in danger of breaking up in case
of aileron flutter or a sudden pullup that you do when avoiding other
traffic for example.
Hartmut, you paint with far too wide a brush here. Most Ercoupe pilots
have never personally experienced aileron flutter. If they see that
their mechanics maintain their aircraft properly, they never will.
There is not and can not be evidence that a "sudden pullup" will
initiate structural disintegration of an airworthy Ercoupe, et. al.
The accounts I submitted with my comments clearly show that the Ercoupe
has been dived to speeds well over the maximum permissible speed of 144
mph and recovery initiated successfully in the great majority of cases
even then. Proper recovery at 144 mph is not a sudden jerk of the yoke
to aft maximum position. Yes, that might initiate structural
disintegration; but only because the pilot has imposed stresses well in
excess of design on his airframe and such failure is therefore not
because the airframe design is deficient, but that the skill level or
judgment of the pilot is. ADs are not issued on pilots (fortunately).
I might add to my list of actions required a dye check of the spars
upper caps , maybe not recurring.
Hartmut
Again I would respectfully disagree. If you or your mechanic have any
reason to believe the spar in your individual aircraft is unairworthy,
you should definitely proceed with such a check. That said, I don't
think most of us want you to propose to the FAA that such checks are
justified and should be mandated for the entire fleet in the absence of
any proof whatsoever as to a fleetwide airworthiness concern. You
don't need authorization or direction from the FAA to have such a check
done. I say this in response also to the similar comments on Tech by
Bill Biggs several days ago.
Respectfully,
WRB
