How do you test a transponder?

Are you building/buying/flying an Experimental Amateur-Built (E-AB) or Experimental Light Sport (E-LSA) aircraft? Converting an S-LSA to E-LSA? Changing or adding equipment, or otherwise modifying an S-LSA? Need help with Letters of Authorization? Or maybe designing your own aircraft? This forum is the place to discuss All Things Experimental.

Moderator: drseti

miket-nyc
Posts: 1
Joined: Mon May 26, 2014 12:34 am

How do you test a transponder?

Postby miket-nyc » Tue Jun 03, 2014 12:27 am

I'll need a Mode C transponder in my plane, and one I wanted is for sale used at a decent price from Aircraft Spruce. If I wind up getting it, I could hook it up to a battery and see that the lights go on, etc., but how would you actually test a transponder (or any used instrument, really), without having a flying airplane to put it in?

Mike Taglieri

ct4me
Posts: 332
Joined: Fri Mar 02, 2007 7:46 pm
Location: Phoenix, AZ

Re: How do you test a transponder?

Postby ct4me » Tue Jun 03, 2014 1:31 am

I think you need specific test equipment to test a transponder. They have to be checked/recert'd every two years. 'Having mine done this week. $80 or so.
Tim
-----
check out CTFlier.com

Jack Tyler
Posts: 1380
Joined: Tue Nov 30, 2010 5:49 pm
Location: Jacksonville, FL

Re: How do you test a transponder?

Postby Jack Tyler » Tue Jun 03, 2014 6:04 am

Mike, you'll want to use an avionics shop - folks who are able to certify the transponder every two years - and if it doesn't pass, Spruce does have a good return policy. You might want to ask them if that policy covers returned equipment. Last year I bought an 'opened package' product from them and the return policy was the same.
Jack
Flying in/out KBZN, Bozeman MT in a Grumman Tiger
Do you fly for recreational purposes? Please visit http://www.theraf.org

User avatar
garbageman
Posts: 55
Joined: Sun Dec 06, 2009 3:27 pm
Location: Maryland (eastern shore)

Re: How do you test a transponder?

Postby garbageman » Tue Jun 03, 2014 2:08 pm

You will also need an altitude encoder if you fly inside a "Mode C" area.

Merlinspop
Posts: 983
Joined: Mon Apr 08, 2013 2:48 pm
Location: WV Eastern Panhandle

Re: How do you test a transponder?

Postby Merlinspop » Tue Jun 03, 2014 6:17 pm

garbageman wrote:You will also need an altitude encoder if you fly inside a "Mode C" area.

(Revealing one of the many holes in my aeronautical knowledge) Do the encoder and transponder have to be tested together as a pair, or can they be tested individually/separately?
- Bruce

User avatar
MrMorden
Posts: 1897
Joined: Fri Aug 17, 2012 7:28 am
Location: Athens, GA

Re: How do you test a transponder?

Postby MrMorden » Mon Jun 09, 2014 9:41 am

If you get on flight following and tell the controller you are testing your transponder, they will tell you what altitude they are showing for you and you can compare. You can also test the ident that way. I heard somebody else do that last time I was on FF.
Andy Walker
Athens, GA
Sport Pilot ASEL, LSRI
2007 Flight Design CTSW E-LSA

User avatar
drseti
Posts: 5678
Joined: Sat Nov 28, 2009 6:42 pm
Location: Lock Haven PA
Contact:

Re: How do you test a transponder?

Postby drseti » Mon Jun 09, 2014 11:32 am

Merlinspop wrote: Do the encoder and transponder have to be tested together as a pair, or can they be tested individually/separately?


They are tested together, Bruce. The test requirement is in FAR 91.413, which references the procedure in FAR 43 Appendix E, which in turn says:

Measure the automatic pressure altitude at the output of the installed ATC transponder when interrogated on Mode C
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
Prof H Paul Shuch
PhD CFII DPE LSRM-A/GL/WS/PPC iRMT
AvSport LLC, KLHV
fly@AvSport.org
AvSport.org
facebook.com/SportFlying
SportPilotExaminer.US

Merlinspop
Posts: 983
Joined: Mon Apr 08, 2013 2:48 pm
Location: WV Eastern Panhandle

Re: How do you test a transponder?

Postby Merlinspop » Mon Jun 09, 2014 11:59 am

drseti wrote:
Merlinspop wrote: Do the encoder and transponder have to be tested together as a pair, or can they be tested individually/separately?


They are tested together, Bruce. The test requirement is in FAR 91.413, which references the procedure in FAR 43 Appendix E, which in turn says:

Measure the automatic pressure altitude at the output of the installed ATC transponder when interrogated on Mode C

Makes sense. Thanks!
- Bruce

User avatar
designrs
Posts: 1485
Joined: Wed Sep 23, 2009 9:57 pm

Re: How do you test a transponder?

Postby designrs » Mon Jun 09, 2014 3:14 pm

Hmm... reminds me of one of my first flight lessons flying an older LSA. (Not at the flight school that I finished up at). We made a little cross country hop to an avionics shop. The instructor explained that the transponder was transmitting altitude that was off by about 300 feet. I had no idea what that meant, what a transponder was for, or how any type of airspace was designated. He just said that the FAA doesn't like it. :lol:

CTLSi
Posts: 783
Joined: Thu Jun 27, 2013 7:38 pm

Re: How do you test a transponder?

Postby CTLSi » Sun Jul 06, 2014 8:54 am

......


Return to “Experimenter's Corner”

Who is online

Users browsing this forum: No registered users and 1 guest