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1. 12:41 PM - encoder approval ()
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| Subject: | encoder approval |
--> Avionics-List message posted by: <bakerocb@cox.net>
8/12/2006
Responding to an AeroElectric-List message previously posted by Kevin
Horton.
Hello Kevin,
1) You wrote: "So, once an encoder had a significant period of satisfactory
in-
service use, it would be legal to use that encoder in service. This
might work for currently existing encoders, if we accept that there
is a reasonable probability that an in-service problem would be
detected. But how would this approach help for a new encoder?"
A) Altitude encoder fundamentals are well understood and the technology is
not that exotic.
B) All encoders, including the newly designed non TSO'd encoder, must
receive the appropriate tests called for in the appropriate provisions of
FAR 91.411, 91.413, and appropriate Appendices to FAR Part 43 before being
used in flight and then every 24 calendar months during use.
C) If the newly designed non TSO'd encoder passed the above listed tests and
was installed in an amateur built experimental aircraft it would be
considered in compliance with FAR 91.217 (b) and legal for in flight use.
D) If the newly designed non TSO'd encoder proved to be deficient in service
after passing the above listed tests pilots, ATC, and the market place would
very quickly have it out of service.
E) Please read FAR 91.217 (b) carefully -- note the use of the words "as
installed". We are not talking shake, bake, rattle, and roll tests in this
paragraph. Then read FAR Part 43 Appendicies E and F carefully. Now tell me
that the testing intent of 91.217 (b) is not met by the tests described in
Appendicies E and F.
2) You wrote: "Surely the manufacturer must do a reasonable amount of
testing before
they determine that the encoder actually works correctly."
Agreed. No rational person who expects to remain in business produces a
functioning product and puts it out in the market place for customers to do
all the testing.
3) You wrote: "I wonder why they can't document that testing and use it as
part of a TSO
submission. Maybe the answer is to improve the TSO process. Review
the TSO, pull out any unneeded tests, reduce the bureaucratic
paperwork, and streamline the review process. As it is, my
recollection is that the FAA has 30 days from the time a TSO package
is submitted to accept it. That isn't bad (if my memory hasn't
failed me)."
I can't answer your question from first hand experience, but I'd like to
make two comments:
A) There have been two companies in our arena that I am aware of that have
been through the TSO process for their products in recent years: Vision
Microsystems (Lance Turk) and JP Instruments (Joe P..). Maybe they can shed
some light on the rationallity of the process.
B) There are some very smart and very experienced people in our arena (I
have in mind the Tru Trak people right now) who have produced some very
successful products for the amateur built experimental aircraft community.
Don't you think that they would like to have their products in every type
certificated Cirrus, Diamond, and Columbia airplane that is produced? But so
far the TruTrak people have not created any TSO'd products. Do you suppose
it is because they don't want to get wrapped around the axle of some no
value added TSO approval process?
OC -- The best investment we will ever make is in gathering knowledge.
<<AeroElectric-List message posted by: Kevin Horton <khorton01@rogers.com>
> AeroElectric-List message posted by: <bakerocb@cox.net>
>
> Responding to an AeroElectric-List message previously posted by
> Kevin Horton
>
> 2) You wrote: " How can you be assured that a non-TSO'd encoder
> will operate correctly at
> temperature extremes, or when subjected to vibration, humidity,
> voltage variations, electromagnetic interference, etc?
>
> I would base my confidence in a proven non TSO'd altitude encoder
> on two things:
>
> A) The superior newer technology used in manufacturing the encoder.
>
> B) The actual past performance of that encoder over years of use in
> the field.
>
> 3) You wrote: "If the manufacturer hasn't tested his encoder under
> the full range of
> conditions, then he has no idea how well it will work there."
>
> I worked for years in the airborne weapons testing field and I
> assure you that there is no such thing as ground or laboratory
> testing "under the full range of conditions". Actual satisfactory
> performance in the field after a significant period time in use is
> the best indication of the suitability of a piece of equipment for
> its intended use.
So, once an encoder had a significant period of satisfactory in-
service use, it would be legal to use that encoder in service. This
might work for currently existing encoders, if we accept that there
is a reasonable probability that an in-service problem would be
detected. But how would this approach help for a new encoder?
>
> 4) You wrote: "If he has done the testing, and it does operate
> properly over the full
> range of conditions, why would the manufacturer not want to get a
> TSO for it?
>
> Two words -- time and money. When a small business sets out to
> create, manufacture, and sell a better mouse trap that it has
> developed it can only operate for so long on the capital available
> before some income has to arrive in order to sustain the business.
> If that capital is totally dissipated in un needed tests and
> bureaucratic paper generation before sufficient income arrives the
> company dies and the better mouse trap with it.
Surely the manufacturer must do a reasonable amount of testing before
they determine that the encoder actually works correctly. I wonder
why they can't document that testing and use it as part of a TSO
submission. Maybe the answer is to improve the TSO process. Review
the TSO, pull out any unneeded tests, reduce the bureaucratic
paperwork, and streamline the review process. As it is, my
recollection is that the FAA has 30 days from the time a TSO package
is submitted to accept it. That isn't bad (if my memory hasn't
failed me). Kevin Horton >>
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