Thread: tso altimeter
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Old December 6th 10, 10:44 PM posted to rec.aviation.soaring
Darryl Ramm
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Posts: 2,209
Default tso altimeter

On Dec 6, 12:34*pm, Phoenixmotoman wrote:
I want to install a Winter 4FGH 40 altimeter with an EASA Form 1
certificate in my S-LSA motorglider with the Becker TSO'd
transponder. *My avionics shop says that the altimeter must be TSO'd
as well. *Can anyone cite FAA regulations about this issue? *Any
information would be welcome.

Since they are saying this did you ask them why?

Your avionics shop may be mixing up requirements in 14CFR 91.411 for
IFR aircraft that require detailed altimeter testing and either you
have to do that testing or you can use a TSO'ed altimeter to meet the
same requirement. But that 14CFR 91.411 requirement overall should not
apply to you unless you are flying IFR...

If this is an experiential aircraft then you the altimeter
requirements should be pretty simple (I'd be surprised if anything
there would ever require a TSOed altimeter - you tell me). Adding a
transponder does not change things too much. Transponder requirements
are outlined in 14CFR 91.215 (which says the transponder must meet
certain requirements as outlined in one of several possible TSOs)
nothing about altimeters there. And 14CFR 91.413 requires altimeter
systems tests outlined in paragraph (c) of Part 43 Appendix E. And
that little paragraph is just about the only altimeter related things
with transponders most of us ever need to worry about... here it is...

"(c) Automatic Pressure Altitude Reporting Equipment and ATC
Transponder System Integration Test. The test must be conducted by an
appropriately rated person under the conditions specified in paragraph
(a). Measure the automatic pressure altitude at the output of the
installed ATC transponder when interrogated on Mode C at a sufficient
number of test points to ensure that the altitude reporting equipment,
altimeters, and ATC transponders perform their intended functions as
installed in the aircraft. The difference between the automatic
reporting output and the altitude displayed at the altimeter shall not
exceed 125 feet."


Are you talking about a new Mode C transponder or existing one? If a
new one why install a Becker Mode C when the Trig TT21 Mode S is
available? Seriously, bad choice, if it is new return it and swap it
for a Trig TT21. The T21 uses less power, is more compact, easier to
install and more importantly provides a future to ADS-B 1090ES data-
out -- something nice for people adopting a PowerFLARM as it lets
other PowerFLARM receivers see you directly over long distances (much
longer then FLARM-FLARM) and will enable the PowerFLARM to provide ADS-
B capabilities like ADS-R and TIS-B (which you won't reliably receive
unless you have an ADS-B transmitter).