TSO Com?

[bob turner]

Bump. I probably need this thread. I finally decided to ask the FAA if it was possible to move one of the offending frequencies (two approach control frequencies mix and bleed through the GTR-200 receiver on our tower frequency).

This only happens on one frequency - and only with the -200. Garmin will no longer even talk to me - it is clear that this is a unique situation, and happens nowhere else in the US.

The reason I need this thread: the FAA frequency guy - a very nice guy - let the FSDO know what I was asking. The FSDO asked him for N-numbers of the aircraft experiencing interference. Being naive, I gave him a few. The FSDO then did an OKC search for installation 337s.

I am quite sure I will need all the input you guys so graciously supplied last year. My FSDO told me I was one of the "good guys" but maybe the new guys want to see if I know what I am doing.

 

[wireweinie]

Are they taking any action based on the 337 search? And I'm assuming they are looking for 337s for com installations.

Web

 

[frequent_flyer]

I finally decided to ask the FAA if it was possible to move one of the offending frequencies (two approach control frequencies mix and bleed through the GTR-200 receiver on our tower frequency).
This only happens on one frequency - and only with the -200. Garmin will no longer even talk to me - it is clear that this is a unique situation, and happens nowhere else in the US.

Intermodulation products can be hard to pin down but I doubt very much that this happens nowhere else in US. A few years ago an engineer friend was working on a similar problem reported by a customer who had taken delivery of a new business jet (not Garmin radios).

What are the approach control and local frequencies that cause the problem?

GTR 200 is standard fit in all CubCrafters airplanes that have the G3X system so should be well over a hundred of those if you are looking for GTR 200 installations. Also look for GTR 20 which is the remote mount version which likely uses the same intermediate frequency.

 

[bob turner]

Web - not yet, but I am girding myself for just such an action. Moral of the story might be "if you see a problem, keep your mouth shut."

Affected frequency is 125.7. Offending frequencies are 132.2 and 257.875. I know the difference frequency is off by .025 MHz, but either there is some frequency spreading or the receiver bandwith is too wide. Transmitting antennae are roughly four miles away. We can plainly hear the approach clearances.

Thanks for that CC info. These are truly spectacular radios - we use the open mic intercom feature in the Stearman! Works at full power! And the memory circuits are simply the best. Garmin knows how to fix them, but is not interested - their SL-40 has a much better receiver, but a lousy memory setup.

 

[frequent_flyer]

Affected frequency is 125.7. Offending frequencies are 132.2 and 257.875. I know the difference frequency is off by .025 MHz, but either there is some frequency spreading or the receiver bandwith is too wide. Transmitting antennae are roughly four miles away. We can plainly hear the approach clearances.

Sorry for the late reply. I was out of town for an amateur radio event.

Thanks for the frequencies. A simple difference intermod would produce a signal at 125.675. If you tune 125.675 do you hear the approach control signal? If so, how does the strength compare with the approach signal heard on 125.7?

The GTR 200 is designed for 25 kHz spacing but I haven't yet found a specification for adjacent channel rejection. It's too hot for me to want to take a signal generator to the hangar to test this but I may when it cools down a bit.

 

[bob turner]

Garmin has admitted that the squelch dynamic range is narrower on the 200 than on the SL-40. That was when they were considering a fix.

I was grasping at straws, getting the FAA involved. All I know is - the reason for squelch circuitry is to cut down on undesirable noise. Undesirable noise can come through the receiver filters even if it is off-frequency, if the signal is strong enough.

But I will try that! Good idea!

 

[bob turner]

As of today the FAA wants me to read the “pilots bill of rights,” now two pages long, give them a complete parts list for each installation, and a copy of the logbook entry.
I think I have the chief maintenance inspector on my side, but it sure feels like someone in middle management is gunning for me. Do you think I need yellow tags for toggle switches and mic jacks?

 

[wireweinie]

Bob. You could have saved a lot of time and energy if you just got a better radio.8)

Web

 

[bob turner]

True, but you have to see how great the memory circuits and display are on this thing, and experience the intercom in a Stearman to truly appreciate these radios.

 

[frequent_flyer]

If you tune 125.675 do you hear the approach control signal? If so, how does the strength compare with the approach signal heard on 125.7?

 

[bob turner]

I will try it next week. Off to Trinity today.

 

[wireweinie]

I've worked with more com systems than you can shake a stick at. The best I can say about a GTR-200 is that it's 'ok'. Much better quality options out there, even from Garmin itself. Do a google search on the -200: Garmin doesn't specifically claim the -200. They bill it as designed by 'Team X'.

Learn from the collective knowledge here. If you are in more remote areas, the -200 may work well for you. If you are in areas that have high communications traffic (not just aircraft commo) then get a better quality radio.

Web

 

[frequent_flyer]

I've worked with more com systems than you can shake a stick at. The best I can say about a GTR-200 is that it's 'ok'. Much better quality options out there, even from Garmin itself. Do a google search on the -200: Garmin doesn't specifically claim the -200. They bill it as designed by 'Team X'.

Learn from the collective knowledge here. If you are in more remote areas, the -200 may work well for you. If you are in areas that have high communications traffic (not just aircraft commo) then get a better quality radio.

Web

In what areas does the GTR 200 fail to comply with the requirements of RTCA DO-186B section 2.2 for a class C receiver?

I use a GTR 200 near KPHX which I would not consider a remote area in terms of communication traffic. I have experienced no problems with transmission or reception with this radio.

 

[frequent_flyer]

Garmin doesn't specifically claim the -200. They bill it as designed by 'Team X'.

Team X is Garmin's experimental development group:

"We understand the decisions you face when choosing the right avionics installation for your aircraft. That’s because our team of experimental engineers are homebuilders and light sport pilots themselves. We call them Team X and they have a knack for doing things their own way. They’re not afraid to get their hands dirty to create the kind of smart and capable avionics they’d be proud to install in their own cockpits."

 

[bob turner]

Got a call today - FAA wants me to remove all the GTR-200s, because unapproved parts are not allowed in standard certificated airplanes. They cite 14 CFR 21.8 and 21.9.
Only way they will allow these radios is if I go experimental airshow exhibition or Garmin certifies them. Garmin has certified the 200B, but only if it is installed in combination with the G-750.

 

[bob turner]

In response to the "what areas" query above, the interference is local to KMYF. I just flew the length of California and back using the 200. Flawless performance.

 

[wireweinie]

Got a call today - FAA wants me to remove all the GTR-200s, because unapproved parts are not allowed in standard certificated airplanes. They cite 14 CFR 21.8 and 21.9.
Only way they will allow these radios is if I go experimental airshow exhibition or Garmin certifies them. Garmin has certified the 200B, but only if it is installed in combination with the G-750.

B.S. They are installed in a CAR3 aircraft. CAR3 has no requirements for these to be 'certified'. And ask them what they consider a certification of a radio.

Web

 

[bob turner]

They say TSO only. And the little Cubs are CAR 4a.
If they force the issue, is there a way to appeal it? While we use handhelds?

 

[wireweinie]

Tell them to put everything in writing, including each and every regulation backing up their mandate. That will give you ammo to fight back.

Web

 

[bob turner]

Wilco!

 

[wireweinie]

These are from CAR4a for 'non air carrier' aircraft. No radios required for day VFR. 4a.534 requires a RECEIVER for night VFR. 4a.535 requires the receiver plus a transmitter. None of these require any certification. Compare that to the radio requirements for 'air carrier' aircraft in CAR4a 4a.548 which requires 'type certificated' radio equipment.

Web

 

[wireweinie]

Also part 91 doesn't require a radio unless operating IFR.

Web

 

[dgapilot]

Got a call today - FAA wants me to remove all the GTR-200s, because unapproved parts are not allowed in standard certificated airplanes. They cite 14 CFR 21.8 and 21.9.
Only way they will allow these radios is if I go experimental airshow exhibition or Garmin certifies them. Garmin has certified the 200B, but only if it is installed in combination with the G-750.

21.9 applies to the person that “produced” the part, not an installer or user. So it doesn’t apply for to a radio already installed. 21.8 simply says if an item needs to be approved, it has to be PMA, TSO, or part of a PC or STC, or “any other manner approved by FAA”.

Did you classify the installation as a minor alteration or major alteration? Only major alterations require “Approved data”. If you called it a minor alteration, document your decision logic using the definition in Part 1, Part 43 appendix A, and the flow chart in AD 43-210A. Use FAA guidance to support your position.

I’m assuming the radios have the appropriate FCC acceptance.

You might also point out that all those ARC 328s, Narco MK12s, and King KX-170 series radios out there installed in thousands of airplanes are not TSO or PMA approved either!


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[hotrod180]

..... Moral of the story might be "if you see a problem, keep your mouth shut.".....

Sounds like you were right.

 

[wireweinie]

21.9 applies to the person that “produced” the part, not an installer or user. So it doesn’t apply for to a radio already installed. 21.8 simply says if an item needs to be approved, it has to be PMA, TSO, or part of a PC or STC, or “any other manner approved by FAA”.

Did you classify the installation as a minor alteration or major alteration? Only major alterations require “Approved data”. If you called it a minor alteration, document your decision logic using the definition in Part 1, Part 43 appendix A, and the flow chart in AD 43-210A. Use FAA guidance to support your position.

I’m assuming the radios have the appropriate FCC acceptance.

You might also point out that all those ARC 328s, Narco MK12s, and King KX-170 series radios out there installed in thousands of airplanes are not TSO or PMA approved either!


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Add KMA-24s and most stand alone intercoms to the list.

I like using the rules to fight them; they'll never see THAT coming, lol.

Web

 

[frequent_flyer]

I’m assuming the radios have the appropriate FCC acceptance.

Yes they do. They couldn't be legally used to transmit in experimental aircraft if they didn't.

The GTR 200 is also claimed to be complaint with the relevant transmitter and receiver specifications of RTCA DO-168B. However, Garmin makes no claim that the GTR 200 "meets the requirements of" TSO-C169A. ("Meeting the requirements of" a TSO is less demanding than having TSO approval).

Garmin advertises the GTR 200 for use in experimental and LSA aircraft. Retailers usually seem to say the GTR 200 is sold for experimental only. I'll be interested to hear how this is resolved.

 

[bob turner]

Yes - I will report back. I did point out the KX 170. Inspector shrugged it off. I will point out the above.
Web's CAR 4a post is quite helpful.

The 21.8 "any other manner approved by the FAA" along with the definition of "approved" in 1.1 seems to allow them to make all this go away with a field approval.

Under the category of "uses of a 337" only now do I see that a minor alteration might possibly warrant a 337. So, I have prepared two of them. If they decide not to approve, I will ask for the required written reasons. I have done a lot of field approvals, and lately they have been no problem at all.

As always, thanks for the great help and insights.

 

[wireweinie]

As DGA pointed out part 21 is geared toward manufacterers.

And 337s are NOT required for minor alterations.

Web

 

[dgapilot]

Only if you are calling it a Major Alteration. minor alterations need no approval. Again go to the regulations, ACs and Orders. I think you will find there is no justification to call it a Major Alteration. The only gotcha here is that your "complaint" may have triggered the "or other qualities affecting airworthiness" part of the Major Alteration definition.

 

[bob turner]

Did I mention that the GTR-200B is TSO if used in conjunction with a G-750 or something? Only difference - 200B has Bluetooth.

Dave - I agree that this is a minor alteration - but perhaps the 337 is a tool to approve an otherwise unapproved part? I am going to try it both ways. I thought I had high level backing for all this - now not so sure.