Altitude Encoders

[ptrotter]

I'm putting in GRT's Horizon I EFIS that has an altitude encoder output. Is there any reason to install a seperate altitude encoder? Has anyone had any issues with their transponder check if they don't have a TSO's encoder? Do the regs say anything about a TSO's encoder for IFR operation? An encoder is fairly cheap but it takes up space and just adds one more thing. If I do put one in, what is the opnion on the best choice? There is an obvious advantage to using the output from the GRT as your transponder would agree with your instruments.

[brian]

I went through a huge saga on this. I have both BMA and GRT EFIS systems. Both produce encoder output. My local avionics guy, who has a stellar reputation, but little experimental experience, said he would not wire up the avionics for me unless I bought a TSO encoder. Going ot another shop was not really an option for me.

We went around and around on it for months, also getting opinions on it from EAA and local FSDO. EAA said OK, FSDO said no. I also started what was quite a long thread about it on the BMA discussion group. In the end, I gave up arguing about it and bought a Sandia encoder, although it irked me to do so.

I understand there are lots of people out there flying IFR using the encoder from their experimental GRT or BMA EFIS. So, it really comes down to what you are comfortable with, and what your avionics installer/tester is comfortable with.

Details starting at http://brian76.mystarband.net/avionicsAug04.htm#aug31

good luck with it - it's a very confusing and ambiguous situation
brian

[Ironflight]

I feel for you Brian - I have myself experienced the frustration that comes from the differing opinions between FSDO's around the country (back when I owned certified airplanes). It kind of puts a lie to the whole "Federal Agency" thing when you get directly opposite opinions from two different offices, and BOTH of them are allowed to take enforcement action against you....

That said - I had no problem whatsoever getting my system IFR checked by a local avionics tech using the GRT encoder. I know.....it's not fair!

Paul

[Martin Sutter]

Just had my GRT system IFR certified and encountered absolutely no problems. The encoder output was dead on and the altimeter only 20' off, easily adjusted in the set-up pages.

Martin Sutter
RV6 868CM, RV7A 678CM

[AZtailwind]

Some of this answer will depend on your transponder- I know the Dynon system I am planning on will require a serial to gray code converter. My older King transponder is gray codec for Mode-C reporting.... Another box. So I was thinking of just buying an encoder for my Mode-C and using the serial output of the Dynon for the GPS IFR required encoding. This would make half of a TSO'd system "legal". Kind of like a FAA/government setup- One half wouldn't know what the other is doing

Brad
RV6A
panel-Finishing