Sorry, there is a recent FAA decision that replacement of equivalent
parts may be made at the A&P's discretion. An A&P can, in fact, accept a
Radio Shack 2N3055 transistor even though it has no other "paperwork"
than it's generic part number. I refer you to this weeks Avweb.

Rip


JohnN3TWN wrote:

From: 8300.10 chg 17 - The Inspectors Handbook

"(2) Airworthiness:
(3) Since “airworthiness” is not
defined in the FA Act of 1958, as amended, or in the regulations,
a clear understanding of its meaning is essential in
conducting a violation investigation. A review of case law
relating to airworthiness reveals two conditions that must be
met for an aircraft to be considered “airworthy.” These
conditions a
(a) The aircraft must conform to its type design
(certificate). Conformity to type design is considered
attained when the required and proper components are
installed and they are consistent with the drawings,
specifications, and other data that are part of the type
certificate. Conformity would include applicable
supplemental type certificates and field approved alterations.

(b) The aircraft must be in condition for safe
operation. This refers to the condition of the aircraft with
relation to wear and deterioration. Such conditions could be
skin corrosion, window delamination/crazing, fluid leaks,
tire wear, etc."

part (b) is pretty straight forward although this is the part that open to the
most "opinion".....what is ok to one won't be ok to another. Admittedly, most
mechanics err on the side of safety here.

part (a) states that the aircraft must conform to its type
design.....basically, what this means is that the airplane must be in a
condition that matches the day it came from the factory -or- be in conformance
with applicable STC's or field approvals. The form 337 is the official vehicle
that indicates a change from the original type design, that is its purpose.
(that’s why its important that the IA doing your annual have all these
337’s available for review). Interpreting further, repairs or alterations
that can be construed as minor must be documented in the aircraft records
–the catch- here is that these repairs, alterations and the parts associated
with them must be shown to be “consistent with the drawings, specifications,
and other data that are part of the type certificate”. The big problem here
is that most manufacturers will not release the type of information required to
make this determination in the field, and even if they did, it would probably
require the services of a DER to verify conformity. No mechanics, at least
that I’m familiar with are capable of doing an engineering analysis that
would satisfy the FAA. So, the next best way to assure conformity is to buy
parts from the original manufacturer. They want you to buy parts from them to
maintain their products for reasons of liability anyway. Additionally, parts
with PMA or TSO approval could (not absolutely would) also be acceptable.

Getting back to what got ME involved with this thread from the beginning was a
non-standard panel lighting dimmer system. From the definition above it should
be very obvious that unless the aircraft is equipped with the system it came
from the factory with, it is not considered airworthy unless there is a 337
associated with an STC or field approval for the system installed......because
the aircraft no longer conforms to its type design, or quite literally, it
doesn’t match the blueprints the manufacturer supplied to the FAA when the
aircraft was certificated. This is an issue most owners just don’t
understand. I’m not saying that modern PWM dimming systems are bad or good,
I’m not saying the original lighting system is bad or good, and I’m not
saying that the approval/certification system is fair and just.....I’m just
saying that is the way it is. And as an A&P/IA/chief inspector dats wot I
godda do! Another issue that I will mention (but I WILL NOT discuss) is the
issue of parts for this dimmer system. The regs would imply that the $20
2N3055 transistor from Piper is a suitable replacement part but the $1.50
2N3055 transistor from Radio Shack is not a suitable part. The implication is
that the batch of transistors Piper gets, each and every unit is tested and
verified to “some standard” whereas the batch that Radio Shack gets has
only one in every 10,000 units tested to “some other standard” thus driving
up the price for the part the manufacturer sells. The saving grace here is IF
the manufacturer lists the part by its generic number in the parts
catalog....then the Radio Shack part would probably be OK.

This also touches on the issue of owner manufactured parts. FAR 21.303 gives
the owner authority to manufacturer parts, however, what makes this impractical
in most cases is AC 20-62 which states:

"4. DEFINITIONS. The following definitions apply to this AC:
b. Acceptable Parts. The following parts may be found to be acceptable for
installation on a type certificated product:
(1) Standard parts (such as nuts and bolts) conforming to an established
industry or U.S. specification.
(2) Parts produced by an owner or operator for maintaining or altering their
own product and
which are shown to conform with FAA-approved data.
(3) Parts for which inspections and tests have been accomplished by
appropriately certificated persons
authorized to determine conformity to FAA-approved design data."

The dreaded words “FAA approved data” appear in (2) and (3).....when an
owner supplies a mechanic with a part he has produced, he must also supply the
mechanic with data to prove compliance with the necessary specifications. How
do you get these specifications and how do you show compliance with them?
Remember, the installing mechanic has the responsibility to assure the parts he
installs meet certain specs.....FAR 43.13 states:

"(b) Each person maintaining or altering, or performing preventive maintenance,
shall do that work in
such a manner and use materials of such a quality, that the condition of the
aircraft, airframe, aircraft
engine, propeller, or appliance worked on will be at least equal to its
original or properly altered
condition (with regard to aerodynamic function, structural strength, resistance
to vibration and
deterioration, and other qualities affecting airworthiness)."

I might make note here that the above excerpt also puts the burden of
acceptable parts on an owner performing preventive maintenance. The primary
point is that this is why mechanics with a good working knowledge of the FARs
will balk when you bring a part to them of questionable origin for installation
onto a type certificated product.

This brings to mind something that was discussed at great length in this
forum....the infamous Yellow Tag. To clarify that point, this document is
nothing more than a log book entry when the log books aren’t available.
Yellow is the accepted color, but it can be any color you desire as long as it
contains the required information and signatures. It doesn’t even have to be
a tag. It can actually be a log book entry, it can be an 8 ½ X 11 sheet of
paper, it can even be the back of a McDonalds napkin as long as it contains the
required information and signatures and becomes a part of the permanent
aircraft records.

Yes Mr. Weir, I realize that everyone has an opinion and this is mine, as
“smelly” as it may be. I welcome you or your General Counsel buddy to cite
specific regulatory references that refute my opinion. I may even learn
something new.