---------------------------------------------------------- Avionics-List Digest Archive --- Total Messages Posted Sun 04/20/08: 2 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 05:55 AM - Questions on avionics () 2. 10:49 AM - Avionics cooling (N81JG) ________________________________ Message 1 _____________________________________ Time: 05:55:37 AM PST US From: Subject: Avionics-List: 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" 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 _____________________________________ Time: 10:49:25 AM PST US From: N81JG Subject: Avionics-List: 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 ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message avionics-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Avionics-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/avionics-list Browse Digests http://www.matronics.com/digest/avionics-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.