Avionics News September 2016 - 13

FREQUENTLY ASKED QUESTIONS
United States
Repair verses alteration
The following information is from the Civil Aeronautics
Manual 18 and Federal Aviation Administration
regulations, guidance and policy.

QUESTION:

I recently received an email from a student that
stated:
We recently listened to a lecture you did on
337s. Here at the school, we have a Cessna 337
that had something done, which brings me to
the heart of this email. The school replaced the
tach gauge and the issue of 337 came up. I was
not part of this directly, but it has become a fun
debate whether we need a 337 or this is a minor
repair. The repair only replaced the gauge from
its original to a digital gauge. There is an STC
for this repair, but all the FARs indicate this to
be a minor repair. Can you offer any input?

ANSWER:

This question raised three different but related issues.
Certainly, the obvious question is about major and
minor repairs. But also, was this a repair or alteration?
And finally, is there a requirement for all supplemental
type certificates to be recorded on the FAA Form 337.
First, is there a regulatory requirement that all modifications being done via an STC must be recorded on
the FAA Form 337? I cannot find one. § 43.9 (d) states,
"In addition to the entry required by paragraph (a) of
this section, major repairs and major alterations shall
be entered on a form, and the form disposed of, in the
manner prescribed in appendix B, by the person performing the work."
If you assume that the provisions of § 21.113 (b)
limited STCs to only major changes in type design,
then it would be a fair argument that § 43.9 (d) would
require the FAA Form 337. However, § 21.113 (b)
states, "If a person does not hold the TC for a product
and alters that product by introducing a major change
in type design that does not require an application for
a new TC under § 21.19, that person must apply to the
appropriate aircraft certification office for an STC."

It does not state that all STCs must be major changes
in type design.
I would suggest, however, that the confusion made
by not recording STCs on an FAA Form 337 would
be so confusing and time consuming to defend your
actions that it would not be worthwhile not to utilize
the form.
The first part of the question is regarding a determination of major or minor. As much as I protest asking
the FAA to make a determination, that is the responsibility of the installer. I will not make that call, certainly not through the limited information in an email.
However, the AEA does have three checklists on its
website that are derived from the regulations in Part
43, which will assist in the determination of a major
alteration/repair. Remember, the regulation is explicit
that if you cannot determine and defend the alteration/
repair is major, the alteration/repair is classified as
minor.
The third question asks if the corrective action is
a repair or alteration? Civil Aeronautics Manual 18
(dating back to the 1940s) as well as the more current FAA Order 8110.37E, Designated Engineering
Representative Handbook, generally describes a
repair as a restoration, while an alteration is a modification to its design.
A discrepancy exists when the aircraft (or a part to
the aircraft) is no longer in a condition for safe operation, i.e something is broken, worn, out of limits, etc.
So to correct this discrepancy, one could choose to
restore the aircraft (or part) to its current design, or one
could take advantage of the discrepancy to upgrade or
modify the aircraft. Either way, the discrepancy would
be resolved: One method would be a repair, while the
other method would involve an alteration.
How can you tell? It's all in the design. If your
corrective action retains the current design, that is
the original type design plus all of the proper alterations, then it is a repair. On the other hand, if your
chosen corrective action modifies the current design,
it is an alteration.
So back to the original email: "The repair only
replaced the gauge from its original to a digital gauge."
Because the corrective action modified the aircraft's
design, the corrective action would have been accomplished via an alteration to the aircraft.
Continued on following page

avionics news

september

2016

Table of Contents for the Digital Edition of Avionics News September 2016