REFLECTOR: avionics shop on the field

[davedent at comcast.net]

Let me clear a few things up related to Transponder checks and pitot/static 
testing. In accordance with FAR 91.413(c) the transponder test can be 
accomplished by a certified repair station or the manufacture of the 
aircraft to in which was installed, that is provided that the transponder 
was installed by the aircraft manufacture.  Otherwise if you built the 
aircraft and you installed the transponder, you could test the transponder. 
But of course you must have the proper equipment.  Flying past a tower and 
having them reading your transponder does not constitute a test of the unit 
or the encoder.  This requires a sign off by the manufacture of the aircraft 
and or a certified repair station having the proper test equipment. The 
airport tower is not the proper equipment.

Another issue comes up, if and when the pitot/static system is opened for 
any reason a test should be performed on the system.  Just like you did when 
you first installed the equipment.  Before a FAA/DAR sign off, a sign off in 
the log should be made that this test has been completed.  If you or an A&P 
removes and replaces a component within the pitot/static system a test must 
be done to assure it reliability.  You the manufacture of the aircraft or an 
A&P can do this.  It does not require a repair shop to do this.  If the A&P 
or manufacture of the aircraft has the proper equipment to do it, there is 
no problem. There should also be a sign off of the test done.

Now another issue that must be covered.  If the aircraft is to be flown 
under IFR conditions in a controlled airspace a static pressure system, each 
altimeter instrument, and each automatic pressure altitude  or encoder 
system needs testing in accordance with part 43 appendix E, every 24 
calendar months. And or if the system had been opened.  This can be done by 
the manufacture of the aircraft, A&P or a certified repair station. An 
airframe certified mechanic holding the certificate to do the test and all 
testers require the proper equipment.  The encoder test equipment is not 
cheap and must show calibration up dates.

Another test that must be performed every 12 months is the ELT impact or 
functional test.  As per FAR 91.207.  This one is missed during most 
condition and annual inspections. Also if the transmit meter has been use 
for one hour of or 1/2 half its battery charge the batteries must be replace 
and a functional test be done on it.  On the hour to 15 minutes after the 
hour. ( normal ELT testing time at most airports). This requires a sign off 
in the airframe log.

I hope this a has put some more light on the subject of transponder testing 
and hasn't muddied the waters.
Dave
A&P/IA