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ACRO E-mail Archive Thread: [IAC-L:617] IAC response to Longeron NPRM

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ACRO E-mail Archive Thread: [IAC-L:617] IAC response to Longeron NPRM


Thread: [IAC-L:617] IAC response to Longeron NPRM

Message: [IAC-L:617] IAC response to Longeron NPRM

Follow-Up To: ACRO Email list (for List Members only)

From: "Dr. Guenther Eichhorn" <gei at>

Date: Sat, 02 Aug 1997 21:29:19 UTC


Hi all,

Following is the official IAC response to the Pitts Longeron
NPRM.  This response is available on the IAC Web site at:


Guenther Eichhorn


July 22, 1997

Federal Aviation Administration
Central Region
Office of Assistant Chief Counsel
Attention: Rules Docket No. 97-CE-17-AD
Room 1558
601 East 12th Street
Kansas City,  MO 64106


On behalf of the 6,100 members of the International Aerobatic Club, I
submit the following comments regarding this proposed rules change. =

International Aerobatic Club members are the principal operators, pilots,=

and owners of the Pitts S-2 series of aerobatic aircraft and would be
heavily impacted by the proposed airworthiness directive.

The Pitts series of aerobatic aircraft are the most popular in aviation
history and the aircraft enjoys a rich history and superb service life. =

The S-2 series, available to the aviation public since the late 1960=92s,=
had an excellent record of safe flying characteristics and structural
integrity.  The S-2B, available since the late 1970=92s, was a further
development of the S-2A model and is one of the most widely used aerobati=
trainers in the world.  There has never been a fatal structural failure o=
any factory built Pitts aircraft.  The aircraft has withstood the test of=

time and the grueling arena of aerobatic competition for over twenty year=

The proposed AD would mandate repetitive longeron inspections on all S-2
series aircraft.  The International Aerobatic Club believes this to be an=

unwarranted burden on owners and operators and further contends that the
S-2A series should not be included in the AD at all.  There is no service=

history on that model which would justify the expense of these repetitive=

inspections when, in fact, no failures have occurred.

In addition, FAA has not demonstrated that the longeron failures which ha=
occurred would be eliminated by recurring inspections.  Indeed, the
solution is to prevent operation of the aircraft in violation of its
operating limitations and if such these limitations are exceeded
inadvertently, such as in a hard landing, then the inspection should be
mandatory within a reasonable time period.  This is common practice
throughout the industry -- an inspection of an airframe if a limitation i=
exceeded -- as is currently required in the event of a hard landing.  It =
our view that to require these inspections of all owners and operators is=
burden to those who carefully and conscientously operate the aircraft
within its envelope.  They should not be penalized for this.

We also believe the proposed AD does not recognize the twisting forces
imposed on th airframe by snap rolling maneuvers.  Clearly, such maneuver=
are much more likely to result in the types of failures that have occurre=
in S-2B aircraft rather than the straight, positive G=92s placed on the
aircraft in vertical maneuvers.  It is our recommendation, therefore, tha=
the FAA and the manufacturer consider a recommendation in the airplane
flight manual which would limit the G-forces in snapping maneuvers to a
lesser value than the G-limits presently prescribed in the manual (+6, -3=


Therefore, the International Aerobatic Club recommends the following

1.  Mark the G-meters which are presently required in the Pitts S-2B seri=
with the operating limitations of +6 and -3 G=92s.  We believe this will =
pilots more aware of these limitations.

2.  Remove the Pitts S-2A from the airworthiness directive entirely.

3.  Consider the implementation of G-limits for snap roll maneuvers.

4.  Delay the implementation of the AD pending further study of the effec=
of snapping maneuvers.

5.   Do not require repetitive inspections by all owners and operators of=

the aircraft.  If implemented, the AD should only require such inspection=
if the operating limitations of the aircraft are exceeded.  =

We appreciate the opportunity to comment on these matters and hope our
views are helpful.



Dr. Richard J. Rihn

------- End of Forwarded Message


© Dr. Günther Eichhorn
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