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
