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1. 05:55 AM - Questions on avionics ()
2. 10:49 AM - Avionics cooling (N81JG)
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Subject: | Questions on avionics |
4/20/2008
Hello Ira, You wrote:
1) "This is just the performance test."
I assume that you mean the testing required every two years by FAR Sec's
91.411 and 91.413 as appropriate.
I apologize for not having made the situation clearer to you. I also wanted
the testing required by 91.411 / 91.413 to sufficiently meet the
requirements of 91.217 (b) so that one could operate with an EFIS that
contained the only atitude encoder in the airplane and that altitude encoder
would be non TSO'd. So I wrote to FAA HQ asking that question. Here is an
exact quote of their response:
"Your letter posed the following questions:
1. If an amateur built experimental aircraft has an installed TSO'd ATC
transponder as required by Title 14 Code of Federal Regulations (14 CFR)
section 91.215, but a non-TSO'd altitude encoder and the installation has
passed the test and inspection requirements of 14 CFR sections 91.411 and
91.413 within the preceding 24 calendar months, does the installation meet
the requirements of 14 CFR section 91.217(b), and therefore make that
installation acceptable for IFR operations?
2. If the answer to question one is No, can you please tell me
why?
The answer to question one is "No." The testing required to show the
transmitted altitude data corresponds within 125 feet (on a 95 percent
probability basis) is more rigorous than the requirements referenced in 14
CFR sections 91.411, 91.413, and 14 CFR, part 43 appendices E and F. The
tests required by 14 CFR part 43 appendix E(c) measure the automatic
pressure altitude at a sufficient number of test points to ensure the
altitude reporting equipment performs its intended function.
Title 14 CFR section 91.217 paragraphs (b) and (c), state that pressure
altitude reporting equipment must be tested and calibrated to transmit
altitude data correspondence within stated specifications; or, the
altimeters and digitizers must meet the standards in TSO-C10B and TSO-C88,
respectively.
Should the owner/operator elect to exhibit compliance with tests and
calibration provided in 14 CFR section 91.217(b), a test method would need
to be developed that ensures the transmitted data corresponds within 125
feet of the indicated altitudes from sea level to the maximum operating
altitude of the aircraft
on a 95 percent probability basis. This testing also needs to ensure the
performance characteristics of the equipment are not impacted when
subjected to environmental conditions (voltage fluctuations temperature,
vibration, etc.) which may be encountered in airborne operations.
Completed tests and calibration results should be maintained in the
aircraft records.
Thank you for your interest in aviation safety."
So you can see that FAA HQ does not agree with our wishes. Further you can
see that an amateur builder attempting to comply with the FAA HQ version of
the testing requirements of 91.217 (b) in order to avoid having a TSO'd
altitude encoder installed in his airplane would have a very difficult /
impossible time doing so.
2) "It says nothing about TSO."
That is correct. The TSO part is found in 91.217 (c). So the person
mentioned in the beginning of 91.217 is given two choices -- he can comply
with either 91.217 (b) or (c).
3) "Part 21 and 23 do not apply to owner built aircraft with special
airworthiness certificates."
Basically true, but not specifically relevant to this discussion unless the
builder would try to use a non TSO'd altitude encoder by requesting approval
to deviate from TSO C-88b and its references in accordance with the
procedures of FAR Sec 21.609 -- not a trivial task.
Please let me know if I have not adequately described the situation.
'OC' Says: "The best investment we can make is the effort to gather and
understand knowledge."
-----------------------------------------------
Time: 07:01:52 AM PST US
Subject: AeroElectric-List: Re: Questions on avionics
From: "rampil" <ira.rampil@gmail.com>
Again, back to 91.217 (b):
(b) Unless, as installed, that equipment was tested and calibrated to
transmit altitude data corresponding within 125 feet (on a 95 percent
probability basis) of the indicated or calibrated datum of the altimeter
normally used to maintain flight altitude, with that altimeter referenced to
29.92 inches of mercury for altitudes from sea level to the maximum
operating altitude of the aircraft; or
This is just the performance test. It says nothing about TSO.
Part 21 and 23 do not apply to owner built aircraft with special
airworthiness certificates
--------
Ira N224XS
Message 2
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Subject: | Avionics cooling |
Does anyone know how one can cool the older avionics stacks that have solid aluminum
box trays stacked on one another without any cooling ports to connect a
fan manifold to? Could you cut side or rear openings and direct cooling air from
a ducted fan? Would those modifications require a 337 form or just an A&P sign-off?
Is there an STC for this modification? Is it necessary to cool these
solid state instruments when the front panels get quite hot to the touch or are
they designed to handle these temps? A thermocouple test is underway to determine
the case temps under actual flight conditions.
John Greaves
Redding, CA
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