lostpilot28

lostpilot28

Well Known Member
OK, this question is for those that really know the answers! I don't mind commentary, but I am trying to get my transponder test done, and i'm running into some roadblocks.

My avionics setup is 2 EFIS systems that have altitude encoding capability. They feed that data into a Garmin GTX-327 transponder. The local (and only) mobile avionics repair guy said that he cannot certify my transponder being that my encoder is not TSO'd.

I asked him what section of the FAR he was looking at, thinking he'd say 91.413, but he said "all of them". Go figure.

My question is this - for a simple VFR transponder test and logbook signoff, do the transponder and altitude encoder have to be TSO'd? Do you have to have a pitot/static system check? Anything else you can volunteer?

Thanks!
 
Sonny, this has been rehashed here before.. the answer is -- your avionics guy is wrong and "all of them" is not the correct answer... Pretty crappy cop-out when you don't know the answer, IMHO... Find someone else to do it for you..... plus, aren't you flying? You can fly somewhere else and have it done on-field.. you shouldn't need a mobile guy :)
 
I'm not aware of any FAR that states that the encoder has to be TSO'd. My Dynon has passed the test for several years, and my "transponder guy" does this for a living on everything from experimentals to GA jets.
 
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lostpilot28 said:
I asked him what section of the FAR he was looking at, thinking he'd say 91.413, but he said "all of them". Go figure.
Click to expand...

All of them? How about 91.15 for example, that deals with dropping objects from aircraft? Me thinks that's a pretty stupid statement.
 
As an FAA certified repair station, we do lots and lots of transponder tests on both experimentals and certified airplanes.

Your guy is just plane wrong - period. The burden is not on you to prove him wrong, it's on him to prove himself right; as is always the case with the FAA. It should be about a 15 minute job if everything is working and it should take longer to do the paperwork than the actual test. Either he is ignorant of the facts, or he has been given the wrong information by his FSDO (which often happens as well).

I'd just fly somewhere and have it done by someone that knows what they are doing. It's a short/quick test and not overly expensive...if you're around here ever you can schedule it over a fuel stop!

That's my 2 cents...

Cheers,
Stein
 
Sonny,

For another data point, when we installed my 327 into my system (Dynon D100 for encoder), my avionics guy didn't bat an eye...just brought over a sticker and we slapped it in the logbook after the check.

If you have trouble finding a local (or closer) guy, 'cmon down from Boise to Reno and I'll hook you up with him. Wonder if your guy would accept a call from another avionics guy that could clear it up and give him a green light.

Cheers,
Bob
 
This FAR would...

...be more applicable - 91.215....

(a) All airspace: U.S.-registered civil aircraft. For operations not conducted under part 121 or 135 of this chapter, ATC transponder equipment installed must meet the performance and environmental requirements of any class of TSO-C74b (Mode A) or any class of TSO-C74c (Mode A with altitude reporting capability) as appropriate, or the appropriate class of TSO-C112 (Mode S).

..but luckily, the TSO approved Installation manual for the 327 only calls for a TSO on the antenna and transponder itself.

Your guy should go by 91.215 and the FAA approved Installation Manual.

The 91.413 tells you to perform the checks, and references Appendix F here on the "how to", but no mention of approvals...

http://www.ferrer-aviation.com/pdf/AppendixF.pdf

Print out the stuff and take it to him...:)

lostpilot28 said:
OK, this question is for those that really know the answers! I don't mind commentary, but I am trying to get my transponder test done, and i'm running into some roadblocks.

My avionics setup is 2 EFIS systems that have altitude encoding capability. They feed that data into a Garmin GTX-327 transponder. The local (and only) mobile avionics repair guy said that he cannot certify my transponder being that my encoder is not TSO'd.

I asked him what section of the FAR he was looking at, thinking he'd say 91.413, but he said "all of them". Go figure.

My question is this - for a simple VFR transponder test and logbook signoff, do the transponder and altitude encoder have to be TSO'd? Do you have to have a pitot/static system check? Anything else you can volunteer?

Thanks!
Click to expand...
 
Thanks for all the help, fellas. I'm going to call this guy on Monday and just "inform" him, although I know how it will go. He's kind of a know-it-all, so I doubt he'll change his mind. :rolleyes:
 
Update!

OK, Round 2. I spoke with the local FSDO office this morning and he pointed out FAR 91.217. Note paragraph c, below.

91.217 Data correspondence between automatically reported pressure altitude data and the pilot's altitude reference.

No person may operate any automatic pressure altitude reporting equipment associated with a radar beacon transponder—

(a) When deactivation of that equipment is directed by ATC;

(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

(c) Unless the altimeters and digitizers in that equipment meet the standards of TSO-C10b and TSO-C88, respectively.

By what the FSDO guy told me, it would seem that anyone and everyone using altitude reporting equipment (transponder, altimeter, encoder) are in violation of this rule if their equipment isn't TSO'd. Wouldn't that to just about every experimental EFIS company out there (Dynon, MGL, Blue Mountain, etc)? I think there are also a lot of experimental aircraft out there with non-TSO'd altimeters.

:confused:
 
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lostpilot28 said:
(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

(c) Unless the altimeters and digitizers in that equipment meet the standards of TSO-C10b and TSO-C88, respectively.[/I]
Click to expand...

Sonny, look more closely, there is an "OR" after part (b) which is to say you need to meet (b) or (c) not both. At least that's how I'm reading it.
 
Tobin and Paul, I hope you guys are right! I'm almost embarrassed to admit I didn't see the "or" when I read it. Normally I think I would pick up on that.

I did call the FSDO guy back and left a voicemail this morning...but I never heard back. I'm wondering if he's doing more research before calling me back. :rolleyes:
 
They are right....there are hundreds upon hundreds of RV's and other experimentals flying this way. We do a LOT of these checks each year, and our FSDO guys are now "educated" as to experimentals. Luckily Minnesota is a hotbed for aviation (lots of homebuilders, airlines, manufacturers, BRS, etc..), so if our guys don't know what's going on, they quickly learn.

Cheers,
Stein
 
Sometimes I just want to gouge my own eyes out. Talking with the FAA this morning gave me cause to believe that they are not really there to help.

Basically, the guy said that he did point out the "or" in the statement (he didn't, which is what led us both to discuss during our first conversation the thousands of illegal experimentals flying in the U.S. airspace system). He then went on to say that yes, section "b" would be fine for my non-TSO'd system, but the repair station would HAVE to prove the part in perinthesis (on a 95 percent probability basis) to sign off my system as being compliant.

OK, says I, how does a repair station do that? He didn't know! He said he didn't want to get into the "legalities" of it. I asked what legalities...I just want to know HOW they will prove the 95% probability (of what, exactly, anyway?). What test would they use? He said "I don't know, they could use Fault Tree Analysis or something". :eek:

I don't think the guy has a clue what Fault Tree Analysis is. I'm amazed that tax money goes to paying salaries for idiots like this. I was so frustrated, I basically (politely) told him that guys like me go to guys like him for guidance to be safe and compliant with the regs. He just sat there and had nothing to say.

Needless to say, I need to find someone else to perform my transponder check. :rolleyes:
 
lostpilot28 said:
He said "I don't know, they could use Fault Tree Analysis or something".
Click to expand...

jayzus. How about at least getting the right field of study. (probability and statistics 101).
Don't you just want to blast them with a load of BS as a demonstation of compliance? "I performed a TQM analysis using Ishikawa diagrams and leveraged ISO9000 methods indicating a 98th percentile least-squares fit. I abandoned an alternative matrix inversion method because...YOU'RE AN IDIOT!"

yeah, find another place to do your check.
 
As a point of interest. Some of the efis's output the encoding info therefore one would wire and efis into the transponder. If you add an encoder, make sure you turn off the efis encoder output so they don't fight each other. When you get an alt cert. they will not be able to calibrate with both of them.
 
Nah.... that would be dumb logic...

Sticky1 said:
As a point of interest. Some of the efis's output the encoding info therefore one would wire and efis into the transponder. If you add an encoder, make sure you turn off the efis encoder output so they don't fight each other. When you get an alt cert. they will not be able to calibrate with both of them.
Click to expand...

So I checked the GTX-327 Installation Manual, and it describes a logical system of priority for getting altitude data.

1 - RS-232 - if set up for altitude data
2 - The Parallel Gray code that would come from an old encoder.
3 + 4 - specific Shadin and Icarus data format inputs.

They do not "fight" each other, but if you want the encoder only as a master, then you must set the RS-232 Altitude OFF in the configuration.

However, the slick solution would be to set up and wire the "non-certified" EFIS output as a Shadin or Icarus format. This makes the parallel encoder would as the master.

Then, if your certified parallel encoder failed, the 327 would automatically switch to the EFIS data for altitude.
Built-in redundancy for free...:)
 
Update again...still not done!

OK, this is getting really old. I still don't have my transponder tested, and I'm out of Phase I. :mad:

After calling the regional FAA office in Seattle and complaining about the local FSDO, the local guys suddenly decided to play nice and start being helpful. To a point. They had already called every avionics shop in Idaho and Eastern Oregon and told them they weren't allowed to test any transponder without all TSO'd parts (alt encoder, included) or they'd fine them or pull their repair license. Well, now they said they'd work with me to get this done.

So I found one local shop who was willing to work with the FSDO and me, and figure out the FAR's so they could do this test. After weeks of waiting they just told me that they don't know how to test a transponder within the "95% probability basis" that 91.217(b) calls out. Heck, I don't even know how to prove that an encoder is going to be right 95% of the time!

Anyone out there have any ideas? :confused:
 
One suggestion...

lostpilot28 said:
OK, this is getting really old. I still don't have my transponder tested, and I'm out of Phase I. :mad:

After calling the regional FAA office in Seattle and complaining about the local FSDO, the local guys suddenly decided to play nice and start being helpful. To a point. They had already called every avionics shop in Idaho and Eastern Oregon and told them they weren't allowed to test any transponder without all TSO'd parts (alt encoder, included) or they'd fine them or pull their repair license. Well, now they said they'd work with me to get this done.

So I found one local shop who was willing to work with the FSDO and me, and figure out the FAR's so they could do this test. After weeks of waiting they just told me that they don't know how to test a transponder within the "95% probability basis" that 91.217(b) calls out. Heck, I don't even know how to prove that an encoder is going to be right 95% of the time!

Anyone out there have any ideas? :confused:
Click to expand...

The FAR says...

(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 requires an error rate of less than one in twenty.

So, using their IFR certification equipment, have them run 40 different altitude tests, and if 2 or less readings are out of tolerance, you should be good to go. As the FAR states, the reference is your flight altimeter set to 29.92.

This should be easily doable with their existing equipment, just a few more calibration points than a usual IFR certification. They can get the reported altitude from the RF transponder pulses, no need to get into your encoder to transponder wiring. Make sure your altimeter (if it's not the EFIS one) is accurate first.

No comment on this bit....:rolleyes:

"To a point. They had already called every avionics shop in Idaho and Eastern Oregon and told them they weren't allowed to test any transponder without all TSO'd parts (alt encoder, included) or they'd fine them or pull their repair license."
 
Sonny,

You're out of Phase 1. Take a weekend, or a day - it is an RV! Go somewhere friendly for the test. Look up resources on line (sorry, I've no recommendations).

John Siebold
 
See Gil's post.

Time to get EAA and AOPA involved. Stuff like this is why I am members in both organizations.
 
Finally!

I finally got my transponder test done! After my frustrated post a few days ago, I called the local FSDO and left a voicemail (they never returned the call) but the local avionics shop called them as well and got the thumbs-up to perform the test. Maybe they were getting tired of me calling, but I am thankful that this local shop wasn't afraid to ask the right questions and get the FAA to do their job.

If anyone needs a transponder check in this area, I would definitely recommend Skyline Aviation in Nampa, ID.
 
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