From: [email protected]
To: [email protected]
Subject: RE: [ercoupe-tech] Improper holes in spar cap
Date: Mon, 21 Sep 2009 05:54:58 -0500
Die penetrant inspection can be done by anyone who can read instructions and a
kit is inexpensive. If I had any holes in my upper spar cap I would certainly
die check the area around the holes. Who knows what loads were placed on the
airframe at an earlier date.
Who knows what engineering Forney did when they added the holes.
I suspect if this investigation does get "teeth" this will be the procedure.
Similar problems (cracking at holes, these being factory) have happened with
Cessna 150 tails and Beech spars and that was the FAA mandated test.
My life is worth more than that.
Bill
To: [email protected]
From: [email protected]
Date: Mon, 21 Sep 2009 02:39:05 -0500
Subject: Re: [ercoupe-tech] Improper holes in spar cap
Hi Ed,
This "Airworthiness Concern Sheet", at present, merely indicates that someone
unnamed unilaterally initiated "safety recommendation" 09.087 proposing
revision of AD 2003-21-01 so as to require repetitive inspection of the
complete wing spar for "corrosion, damage and any unauthorized maintenance
actions performed on the wings of all Univair Aircraft Models. It does not
purport to duplicate the actual wording or contents of "safety recommendation"
09.087, nor does that document appear to be available on the FAA site by any
link to AD 2003-21-01. Searches using the words "safety reccomendation" do not
lead to listing of such purportedly pending documents. This, and the
conspicuous lack of specific information on the number, size location and
proximity to each other of the "unauthorized holes" seems consistent with an
intent to consciously discourage credible technical responses before the stated
deadline and thusly "run out the clock" on the required comment period.
It seems to suggest that if one or more "unauthorized holes" may, in the
abstract, reduce the original structural load carrying capability of an Ercoupe
wing in the slightest, that any and each such reduction constitutes a genuine
threat to the present and continuing airworthiness of subject fleet. That is
simply not true. It is also preposterous to suggest that one or more
"unauthorized holes" of a given size and proximity adversely affect the load
carrying capability of an operational Ercoupe wing more than one or more
"authorized" (approved) holes of the same or larger size (except as specific
engineering analysis can show this to be the case).
The FAA has only the obligation to assure that such "unauthorized holes" do not
reduce the load carrying capability of an Ercoupe wing to something below
required design requirements light aircraft in the CAR 03 Normal category.
They do not have the obligation, nor should they be given the authority, to
arbitrarily declare a spar with "unauthorized holes" unairworthy. Such would
do absolutely nothing in terms of genuinely improving operational safety of the
Ercoupe fleet. It would impose such draconian financial burdens on affected
owners as would likely result in numerous perfectly safe and currently
operational aircraft being scrapped. It would make a mockery of any illusion
of meaningful cost-benefit analysis in the Airworthiness Directive process.
If the FAA is truly concerned about holes in the spar that may actually reduce
the aerodynamic load carrying capacity of a given operational wing structure
below applicable design requirements, then let it actually state such concern
and propose an empirical engineering evaluation method consistent with such
concern for our review and comments prior to final consideration or adoption.
It is interesting that this "Airworthiness Concern" is an "end run" around the
normal regulatory process, purporting to merely amend an existing AD. Not so.
The "unsafe condition" presented in AD 2003-21-01 is "...to prevent wing
damage caused by a corroded wing outer panel structural component, which, if
not detected and corrected, could progress to the point of failure." Such
"unsafe condition" of suspected corrosion in the wing outer panels is of
entirely different origin, location and purpose than this new "Airworthiness
Concern".
It would authorize an open-ended repetitive "witch hunt" for "damage and any
unauthorized maintenance actions performed...". It would address an entirely
different "unsafe condition" located in an entirely different section of the
aircraft. This would be "...to prevent such in-flight wing failure(s) in the
fuselage center section of the wing spar as might originate from one or more
"unauthorized holes" therein." I plan to specifically accuse the FAA of
attempting to circumvent its own process for the initiation of new ADs, and
demand that said process be complied with in full in this instance for the
simple reason that a single crash does not establish the existence of a
fleetwide problem requiring FAA action or "correction" in the field.
But we also must encourage responses to this "Airworthiness Concern Sheet". I
have been working on a very comprehensive one for several days. I will send it
both by email and U.S.P.S. Certified Mail, Return Receipt requested; and then
post it to Tech. That makes it harder for the FAA to "lose" or ignore comments
(claim they did not get them). Everyone is welcome reproduce any portion of it
or incorporate any of my thoughts expressed herein in their comments with the
single exception of the following:
Should any of us wish to engage in engineering evaluation, i will share a
letter dated 10/12/49 from ERCO's Thomas M. Mountjoy, Assistant Chief Engineer,
addressed to the British Joint Services Mission in Washington, D.C. At that
time a 415-CD was being officially evaluated in England.
Airplane limit load factors
CAR 04 1260 lb. +4.58 (- not available)
CAR 03 1400 lb. +3.50 -1.40
Limit wing load factors
CAR 04 1260 lb. +4.64 -1.75
CAR 03 1400 lb. +3.59 -1.32
Ultimate load factor = 1.5 x limit load factor
And no, I'm not an engineer of any kind either ;<)
Regards,
William R. Bayne
.____|-(o)-|____.
(Copyright 2009)
--
On Sep 20, 2009, at 08:43, Ed Burkhead wrote:
One thought: It seems to me that holes in the upper spar cap would most likely
be a problem when pulling negative g’s, wouldn’t they? Or, during extreme
vibration (i.e. flutter)? I wouldn’t think normal flying loads within the
normal positive g limits would strain the upper spar cap.
But, then, I’m not an engineer of any kind.
Are there appropriate non-destructive diagnostic means to inspect for cracks in
the spar cap? Dye penetrant? Portable x-ray?
Do we have any aeronautical engineers here?
Ed
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