Oops, pitot static transponder expires soon

[wombat]

@philiplane I think you are reading more into these regulations than exists.   Those are not requirements.  Appendix F to Part 43 is very clear about this.   The tests may be conducted using a bench check.

So, in order:

#1: You could break the antenna off during this morning's wash job after testing the transponder (plus aircraft systems including antenna).   Same difference.

#2: There is no requirement for confirming ADS-B Output as part of 91.413  

#3: I don't know about bench testing a GTX335/345.   Maybe those can't be bench tested in a way that conforms to 91.413 or maybe the bench test requires taking the configuration module.  I'm not a repair station.   But my GTX327 sure can.  So could my KT76, before it bit the dust. And when I installed my ADS-B out system (uAvionix wingtip) we didn't do any calibration and nobody ever has since, even when I switched from the KT76 to the GTX327.  And there is no part of 91.413 or Appendix F.  to part 43 that requires ADSB lat/long.

Re: 91.217.  Unless as installed they were tested and calibrated to be within 125' (95% probability), then yes, both the ADS-B out and transponder must be using the same source.  If you have a GTX345, or a uAvionix wing or tail beacon, or pretty much everything, that'll be the case.  Why would you have two altitude encoders? 

Re: Your shops....  That's unfortunate.  But if you are bench testing a transponder, you wouldn't know which airframe was going to receive it, so of course you couldn't make a maintenance record for an airframe at that point anyway.

Re: 91.413.b:  I think it highly unlikely that the FAA would consider sliding the transponder out and then in to its tray to be an installation or maintenance action where data correspondence error could be introduced.    If they'd consider doing that action as an installation at all....  I choose to remain silent.

 

Edited March 19, 2023 by wombat

[DCarlton]

Gotta wonder what the typical failure modes are with transponders and altitude encoders.  Do they ever slowly degrade in accuracy?  My experience has been they either work or they don’t.  Pretty obvious.  Every time I pay for one of these tests I feel like I’m paying someone to find another static leak….  in an unpressurized airplane.  :/  

[T. Peterson]

10 hours ago, M20F said:

I am just going to say the rules have been posted.  I am a fan of rules.  

That being said I don’t always drive 55, if you get what I mean. 

I like it.

 I find it amusing that so many dismiss the Bible while elevating bureaucratic legalese to Biblical proportions.

The rules are made to serve men. Men are not made to serve the rules.

[EricJ]

1 hour ago, DCarlton said:

Gotta wonder what the typical failure modes are with transponders and altitude encoders.  Do they ever slowly degrade in accuracy?  My experience has been they either work or they don’t.  Pretty obvious.  Every time I pay for one of these tests I feel like I’m paying someone to find another static leak….  in an unpressurized airplane.  :/  

The old-style grey-code encoders sometimes suffered from a stuck bit.   It's pretty easy to diagnose, and sometimes repairable, but sometimes not.  

[philiplane]

10 hours ago, wombat said:

@philiplane I think you are reading more into these regulations than exists.   Those are not requirements.  Appendix F to Part 43 is very clear about this.   The tests may be conducted using a bench check.

So, in order:

#1: You could break the antenna off during this morning's wash job after testing the transponder (plus aircraft systems including antenna).   Same difference.

#2: There is no requirement for confirming ADS-B Output as part of 91.413  

#3: I don't know about bench testing a GTX335/345.   Maybe those can't be bench tested in a way that conforms to 91.413 or maybe the bench test requires taking the configuration module.  I'm not a repair station.   But my GTX327 sure can.  So could my KT76, before it bit the dust. And when I installed my ADS-B out system (uAvionix wingtip) we didn't do any calibration and nobody ever has since, even when I switched from the KT76 to the GTX327.  And there is no part of 91.413 or Appendix F.  to part 43 that requires ADSB lat/long.

Re: 91.217.  Unless as installed they were tested and calibrated to be within 125' (95% probability), then yes, both the ADS-B out and transponder must be using the same source.  If you have a GTX345, or a uAvionix wing or tail beacon, or pretty much everything, that'll be the case.  Why would you have two altitude encoders? 

Re: Your shops....  That's unfortunate.  But if you are bench testing a transponder, you wouldn't know which airframe was going to receive it, so of course you couldn't make a maintenance record for an airframe at that point anyway.

Re: 91.413.b:  I think it highly unlikely that the FAA would consider sliding the transponder out and then in to its tray to be an installation or maintenance action where data correspondence error could be introduced.    If they'd consider doing that action as an installation at all....  I choose to remain silent.

 

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

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

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

(2) 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

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

(b) No person may operate any automatic pressure altitude reporting equipment associated with a radar beacon transponder or with ADS-B Out equipment unless the pressure altitude reported for ADS-B Out and Mode C/S is derived from the same source for aircraft equipped with both a transponder and ADS-B Out.

[wombat]

@philiplane  Yes, I agree, but I don't see how that's relevant here.     I'm assuming an aircraft with a TSO-C10b altimeter, and a single TSO-C88 altitude encoder.  I didn't (and don't) recommend anyone remove the altitude encoder because it's not necessary for the 91.413 test.

For my case, I've got an ACK A-30 altitude encoder, and a (Whatever model it happens to be that was produced in 1958) altimeter.     I could undo the set screw in the transponder, (GTX-327) and slide it out, hand it to the avionics shop, they could perform a test on the transponder on their bench that conforms to Part 43 appendix F, make a maintenance record of their test and results, hand it back to me, and I have it legally slid back in, and the set screw tightened, and add the avionics shop's maintenance record text (hopefully on a sticker!) to my aircraft's maintenance records.  

[philiplane]

2 hours ago, wombat said:

@philiplane  Yes, I agree, but I don't see how that's relevant here.     I'm assuming an aircraft with a TSO-C10b altimeter, and a single TSO-C88 altitude encoder.  I didn't (and don't) recommend anyone remove the altitude encoder because it's not necessary for the 91.413 test.

For my case, I've got an ACK A-30 altitude encoder, and a (Whatever model it happens to be that was produced in 1958) altimeter.     I could undo the set screw in the transponder, (GTX-327) and slide it out, hand it to the avionics shop, they could perform a test on the transponder on their bench that conforms to Part 43 appendix F, make a maintenance record of their test and results, hand it back to me, and I have it legally slid back in, and the set screw tightened, and add the avionics shop's maintenance record text (hopefully on a sticker!) to my aircraft's maintenance records.  

91.413 is not the only rule in play, once you consider how the plane will be operated. The transponder test applies to the transponder's functions only. When you fly the plane you are required to comply with altitude reporting requirements if you operate in Mode C. That means your encoder must be tested too. Hence 91.217. Operational rules are why I can sign off an annual on a plane without a valid transponder cert. You just can't fly it, if you're in airspace where a transponder is required. Maintenance rules and operational rules are separate.

And you can't install the bench-tested transponder and still say it's good. This is where the correspondence test comes in. If there's a bad coax connection or antenna, or faulty encoder connection, the transponder will not be in compliance. There's no way to ensure the correspondence is good without testing the whole system, in the plane. I'm not sure why you aren't understanding this part. 

The shop can give you a sticker for the transponder test. But they cannot give you one for the plane if they didn't work on it. That goes to part 43 maintenance records.

Just for comparison, how many Repair Station manuals have you written? Or how many FAA Avionics Inspectors have you reported to as Repairman, or Repair Station manager? Those Inspectors can point you to their FAA guidance they use to evaluate procedures and paperwork for compliance with 14CFR91.411, 413, 217, and so on. They have task cards with all these scenarios on them, and the applicable rules. You can find them yourself in the DRS, which combined the old 8300 Inspectors Handbook with everything else.

So go back and read 91.217, (A), and (2). No person may....

Edited March 19, 2023 by philiplane

[wombat]

@philiplane   I have thoroughly read 91.217(a) and 91.217(b). 

Part (a) is talking about the difference in reported pressure altitude between the altimeter and altitude encoder.    I have not mentioned anything about removing either of those.   There is no change to either of them.   So 91.217(a)(2) remains 'true'.  As does 91.217(a)(3) (Both of the "unless" statements)

In the case of my aircraft, I've got an ACK A-30 altitude encoder that meets TSO-C88 requirements. I have a GTX-327 that does not.  No GTX-327 meets TSO-C88, because it's not applicable to a transponder.

In the case of a GTX 3X5, the GAE module meets TSO-C88, but the transponder itself does not.    See http://www.aero-hesbaye.be/dossiers/GTX335/GTX 345 335 installation.pdf, page 1-13 table 1-11, row 1, columns 1 and 2, footnote #2.  If you slide the transponder out of the sled, the GAE module remains undisturbed and no re-test under 91.217 is required.

 

And 91.413 is the only test I'm saying can be complied with by sending the transponder in for a bench test.  There is no periodic re-test of an altitude encoder required as part of 91.217.   The encoder is installed, tested, then remains good.  For the transponder, The record for compliance is for the transponder itself, not the aircraft.

To re-emphasize my point, the correspondence test is between the altitude encoder and the altimeter, and has nothing to do with the transponder. For VFR there is no periodic testing requirement for altitude encoders and I have thoroughly read 91.412 and 91.217 and part 43 appendix F. 

I'm familiar with transponder to altitude encoders using gray code and RS-232, both of which are digital and not subject to signal drift.  They are either correct or incorrect.   There is no coax on the signal from the altitude encoder to the transponder.  The only coax is between the transponder and antenna which the FAA says you don't need to test because they clearly state that a bench test is sufficient.

 

 I'm still not finding your argument convincing.   And while you have an impressive background, that's not enough to convince me and I'm sorry because I think you've been steering your customers wrong for a long time.  Fortunately this probably isn't a situation that comes up often.     While an appeal to authority may convince me to dig deeper into the regulations, this seems pretty clear and the deeper I read the more the evidence indicates that a bench tested transponder satisfies the requirements of 91.413.

 

[philiplane]

1 hour ago, wombat said:

@philiplane   I have thoroughly read 91.217(a) and 91.217(b). 

Part (a) is talking about the difference in reported pressure altitude between the altimeter and altitude encoder.    I have not mentioned anything about removing either of those.   There is no change to either of them.   So 91.217(a)(2) remains 'true'.  As does 91.217(a)(3) (Both of the "unless" statements)

In the case of my aircraft, I've got an ACK A-30 altitude encoder that meets TSO-C88 requirements. I have a GTX-327 that does not.  No GTX-327 meets TSO-C88, because it's not applicable to a transponder.

In the case of a GTX 3X5, the GAE module meets TSO-C88, but the transponder itself does not.    See http://www.aero-hesbaye.be/dossiers/GTX335/GTX 345 335 installation.pdf, page 1-13 table 1-11, row 1, columns 1 and 2, footnote #2.  If you slide the transponder out of the sled, the GAE module remains undisturbed and no re-test under 91.217 is required.

 

And 91.413 is the only test I'm saying can be complied with by sending the transponder in for a bench test.  There is no periodic re-test of an altitude encoder required as part of 91.217.   The encoder is installed, tested, then remains good.  For the transponder, The record for compliance is for the transponder itself, not the aircraft.

To re-emphasize my point, the correspondence test is between the altitude encoder and the altimeter, and has nothing to do with the transponder. For VFR there is no periodic testing requirement for altitude encoders and I have thoroughly read 91.412 and 91.217 and part 43 appendix F. 

I'm familiar with transponder to altitude encoders using gray code and RS-232, both of which are digital and not subject to signal drift.  They are either correct or incorrect.   There is no coax on the signal from the altitude encoder to the transponder.  The only coax is between the transponder and antenna which the FAA says you don't need to test because they clearly state that a bench test is sufficient.

 

 I'm still not finding your argument convincing.   And while you have an impressive background, that's not enough to convince me and I'm sorry because I think you've been steering your customers wrong for a long time.  Fortunately this probably isn't a situation that comes up often.     While an appeal to authority may convince me to dig deeper into the regulations, this seems pretty clear and the deeper I read the more the evidence indicates that a bench tested transponder satisfies the requirements of 91.413.

 

You're still missing the key point. The encoder reports altitude via the transponder's transmission, not magically through the air all by itself. This is where the correspondence test applies. If you remove the transponder, and re-install it, that is where you introduce the chance of correspondence errors. This drives the need to test the entire system in the plane, and it's the only way that a shop can give you a log entry saying that the aircraft is compliant. A bench check won't do that. Bent pins and broken wires are the leading cause of correspondence errors. These happen during installation. Especially with the newer high density D-sub pins. They are fragile.

Owners have been tripped up by things like this during enforcement actions, while the FAA was digging into a plane as a result of a pilot deviation. This is where the FAA investigates a pilot for an error, and a result, they hand the plane and the logs to a Maintenance Inspector, and an Avionics Inspector. Those guys go right for the easy things. AD's, IFR or VFR certs, compass correction cards, flight manuals & supplements, and panel placards. Nine out of ten times they come up with more than one violation, most of which are inadvertent but that doesn't matter much.  

If you remove and re-install the transponder for any reason, you are obligated to do a data correspondence check per 91.217. Call any FAA FSDO Avionics Inspector if the regulation cited doesn't convince you. They'll ask you how you can guarantee that your bench checked unit is performing in the plane, transmitting correct data at the right wattage and frequency.

Avionics Repair Stations don't steer customers, they follow the rules, and get reviewed annually by multiple FAA Inspectors. Imagine the fun when you are running an Avionics Repair Station, an Airframe Repair Station, and a Part 135 Charter company, working on your own company planes. You answer to a dozen Inspectors of all disciplines. You have to know ALL the rules and be able to defend your work. The FAA doesn't tell you what to do, they expect you to know what to do, and be able to defend yourself. 

If you installed an ADSB transmitter, you would generate and retain a PAPR report to document that it is compliant: https://adsbperformance.faa.gov/PAPRRequest.aspx

ADSB has its' own rule, 91.227. If you are equipped, you must test it at each 24 month interval to ensure it meets the standards.

Edited March 19, 2023 by philiplane

[wombat]

No, you are reading something that doesn't exist.    The correspondence test applies between the altitude encoder (The TSO-C88 device) and the altimeter.   NOT the transponder.  Removing and then reinstalling the transponder does not introduce the chance of correspondence errors any more than washing the plane does.

Why do you think Part 43 appendix F says "The ATC Transponder tests required by 91.413 of this chapter may be conducted using a bench check..." ?    Are you saying that line is completely useless and means nothing?

[MikeOH]

3 hours ago, philiplane said:

ADSB has its' own rule, 91.227. If you are equipped, you must test it at each 24 month interval to ensure it meets the standards.

@philiplane

Where is this requirement for ADSB 24 month testing?  I did NOT see it in 91.227

[PT20J]

[philiplane]

3 hours ago, wombat said:

No, you are reading something that doesn't exist.    The correspondence test applies between the altitude encoder (The TSO-C88 device) and the altimeter.   NOT the transponder.  Removing and then reinstalling the transponder does not introduce the chance of correspondence errors any more than washing the plane does.

Why do you think Part 43 appendix F says "The ATC Transponder tests required by 91.413 of this chapter may be conducted using a bench check..." ?    Are you saying that line is completely useless and means nothing?

Please show me where the altimeter and encoder talk to each other. List part or model numbers to be clear, since I've never seen one in the last few thousand jobs from small planes to corporate jets. How do they correspond? Grey Code, RS232, A429, CANBUS? Or maybe Latin? Sign language perhaps? 

The encoder doesn't even know there is an altimeter in the system. It reports pressure from the static system, to which both devices are attached. The encoder is useless without the transponder. ATC doesn't see your altimeter reading, it sees your encoder output via the transponder broadcast. If you have an encoding altimeter, then the two are one, but again, ATC only sees the encoder output which is referenced to 29.92 inches of mercury.

Let me simplify it further. If you operate a Mode A transponder, there is no correspondence test, because there is no encoder reporting altitude. Only 91.413 applies.

If you operate a Mode C or Mode S transponder, you have an encoder that reports altitude to ATC, via the transponder broadcast. This is where correspondence checks come into play. And 91.217, which says if you have altitude reporting, it must be tested. 

If you have ADSB out, that equipment must also be tested to ensure ATC is receiving correct information. There is no way that a bench test can verify that. 

If you like, you can send me the list of all the installed equipment, the tests you had done, where you operated the plane, and I can tell you exactly what applies, and what you have overlooked. It's what Repair Stations have to do on an annual basis. 

This is where you are prohibited from installing a transponder, and where it is required to be tested once in the plane, per part 43, Appendix A:

Owner maintenance privileges: Removing and replacing self-contained, front instrument panel-mounted navigation and communication devices that employ tray-mounted connectors that connect the unit when the unit is installed into the instrument panel, (excluding automatic flight control systems, transponders, and microwave frequency distance measuring equipment (DME)). The approved unit must be designed to be readily and repeatedly removed and replaced, and pertinent instructions must be provided. Prior to the unit's intended use, an operational check must be performed in accordance with the applicable sections of part 91 of this chapter.

Those applicable sections include 91.227

Edited March 20, 2023 by philiplane

[philiplane]

40 minutes ago, MikeOH said:

@philiplane

Where is this requirement for ADSB 24 month testing?  I did NOT see it in 91.227

there is not a specific requirement called out, it becomes part of the 24 month test via the 91.225 operational rule that says you must have it to fly in Rule airspace, and to fly in Rule airspace, you must be compliant with 91.411 & 91.413. That directs you to 91.227, which says Typical FAA rule making where you have to assemble and interpret multiple regs based on your operations, not just on your equipment. You will also find continuing inspections for ADSB equipment required under each manufacturers Instructions for Continued Airworthiness. Those are often more explicit than FAA rules. So your ADSB equipment is tested during your IFR cert, and the shop adds the line "found ADSB compliant" to the log entry. They have to check the performance listed in 91.227 b, c, and d. 

It's also recommended to request an annual PAPR report so you can ensure your ADSB is working correctly. They are already sending out letters to planes whose equipment is out of spec. If your plane is registered to a Delaware LLC for example, and that mail gets forwarded to your home address, and you don't receive the non-compliance letter for weeks or months after it was sent, you can still be violated for each non-compliant flight. I've had to help defend two pilots on this so far. 

Edited March 20, 2023 by philiplane

[MikeOH]

@philiplane

Hmm, so your position, unsupported as far as I can tell, is that the FAA can go after pilots for violating a non-existent requirement?! Sorry, color me skeptical.  Ignoring a letter that your ADSB is non-compliant is another matter, entirely.  Additionally, I'd argue the fact that the FAA is monitoring ADSB outputs for proper performance and subsequently notifying owners of said non-compliance is strong evidence that there is not even any need for a 24 month check!

Your 'logic' of somehow using 91.411 and 91.413, which make NO mention of ADSB, nor any "direction to 91.227" (explicit or implicit) to require ADSB to be checked is equally unconvincing.

Based on your contention that logbooks need to be notated with "found ADSB compliant", and my pragmatic nature, I'm curious how many other owners have that notation in their logs for static/altimeter/encoder/transponder certification entry.  Mine does not.

[philiplane]

44 minutes ago, MikeOH said:

@philiplane

Hmm, so your position, unsupported as far as I can tell, is that the FAA can go after pilots for violating a non-existent requirement?! Sorry, color me skeptical.  Ignoring a letter that your ADSB is non-compliant is another matter, entirely.  Additionally, I'd argue the fact that the FAA is monitoring ADSB outputs for proper performance and subsequently notifying owners of said non-compliance is strong evidence that there is not even any need for a 24 month check!

Your 'logic' of somehow using 91.411 and 91.413, which make NO mention of ADSB, nor any "direction to 91.227" (explicit or implicit) to require ADSB to be checked is equally unconvincing.

Based on your contention that logbooks need to be notated with "found ADSB compliant", and my pragmatic nature, I'm curious how many other owners have that notation in their logs for static/altimeter/encoder/transponder certification entry.  Mine does not.

what requirement is non-existent?

FAA rules are never written concisely and clearly. You have to read each one, and follow the next step into the rabbit hole. You also have to consider the operations of the aircraft to know what additional rules apply. Someone operating a mode A Cessna 150 on the plains of Kansas will have different compliance than someone operating the same plane with Mode C or S under a Class C veil. The rules allow flexibility, and with that comes complexity.

Read 91.225, 91.227. You will see that if your plane is equipped, it has to be tested. It doesn't make sense to install critical traffic separation equipment and then allow it to be non-conforming, does it?

Yes, the FAA does send ADSB non-compliance letters out. They come from Oklahoma City, specifying a flight where the performance requirements were not met. I see a few per year. They monitor the airspace here more than other places due to international flights. It's not a violation letter, it states that the plane is non-compliant, and if you continue without corrections, then you will be violated. You have to make corrections and then send in a fresh PAPR report to show it's been fixed. 

Current FAA policy is that the ADSB found compliant must be included on the certification statement by a repair station during a transponder check of an ADSB equipped plane. Call and ask if you doubt that. The Ops inspectors here have been directed by HQ to check for this. After the initial installation log entry as follows, it has to be tested when the related systems are tested to insure conformity: "From the FAA ADSB policy dated March, 2016; 1. The ADS-B OUT alteration must be documented in the aircraft maintenance record per section 43.9(a) and include the statement, ?'The installed ADS-BOUT system was shown to meet the equipment performance requirements of 14 CFR section 91.227."

You will also find that many repair stations are not good at what they do. They eventually get caught during an audit, and then they catch up to current practices. But that does not relieve the pilot, who is ultimately responsible for compliance with all these myriad rules that are clear as mud.

Edited March 20, 2023 by philiplane

[MikeOH]

@philiplane

You are the one that stated, "There is not a specific requirement called out". Yet you insist a violation occurs if ADSB is not tested and documented every 24 months...that sure sounds like a "non-existent requirement" to me!

I've read both 91.225 and 91.227 and see absolutely NO requirement for testing; it is a performance standard, NOT a test spec/requirement.  Please point me to the paragraph(s) that require the testing you claim.

I do not see anywhere owners are required to know or follow (or even know where to look for) "current FAA policy"; can you cite that regulation, please?

I can't speak to what 'shops' are required to conform to (e.g. 'op' specs) but I do not believe aircraft owners have any responsibility to know or comply with them.  Again, if you can cite a regulation where we owners are responsible, please let me know.

[DCarlton]

1 hour ago, MikeOH said:

 Additionally, I'd argue the fact that the FAA is monitoring ADSB outputs for proper performance and subsequently notifying owners of said non-compliance is strong evidence that there is not even any need for a 24 month check!

Yep.  It could very well be that technology has made this requirement obsolete.  I would add that a failure is just as likely to occur one month after a recertification test than it is 23 months after recertification.  I’d like to see data to prove this wrong or to at least support the 24 month requirement.  Again, what are the failure modes?  Is there ever a case of slow degradation in performance that falls below spec ?  ATC has told me every time I’ve ever had a transponder or altitude reporting problem.  Now if work is done on the system it needs to be retested.  

[philiplane]

10 hours ago, MikeOH said:

@philiplane

You are the one that stated, "There is not a specific requirement called out". Yet you insist a violation occurs if ADSB is not tested and documented every 24 months...that sure sounds like a "non-existent requirement" to me!

I've read both 91.225 and 91.227 and see absolutely NO requirement for testing; it is a performance standard, NOT a test spec/requirement.  Please point me to the paragraph(s) that require the testing you claim.

I do not see anywhere owners are required to know or follow (or even know where to look for) "current FAA policy"; can you cite that regulation, please?

I can't speak to what 'shops' are required to conform to (e.g. 'op' specs) but I do not believe aircraft owners have any responsibility to know or comply with them.  Again, if you can cite a regulation where we owners are responsible, please let me know.

Like many other regs, this one is additive. 91.413 says you must test the transponder every 24 months. 91.225 says you must have ADSB to operate in Rule airspace, and the equipment must meet specs in 91.227. When the tech does the transponder test, he will verify that the output contains the data and meets the standards required in 91.227. (those are embedded in Garmin GTX series line maintenance manuals) Upon successful completion, he will issue a log entry for the 413 test and a statement that the equipment is ADSB compliant. If the ADSB portion fails, he can issue the 413 test certificate with a non-compliant entry for the ADSB. Then the pilot has to deal with the applicable ops rules if he wants to fly it as-is. Once it's non-compliant, the system has to be deactivated and placarded like any other inoperative equipment. If it's a UAT, that's easy. If it's a GTX transponder, you have to turn off the GPS portion so it will behave as a regular Mode S transponder without ADSB out.

When the tech does a 413 test on a Mode S transponder, he has to verify the data transmission in the correct uplink format. This is different from Mode A and Mode C testing, it is additional for the extra data coming through for ADSB. Any way you look at it, your ADSB is being tested every 24 months by default, not by a specific written rule. When asked about this as the implementation date approached, the FAA's response was that the above noted rules and the new equipment's maintenance manuals were sufficient to ensure regular testing would occur. They did not plan to amend 91.413. They probably should, to eliminate confusion, but that's not how government works.

Repair Stations start with an incoming inspection of the item or airplane that generates a work order. In the example of the guy dropping off a transponder for test, the receiving document will list make model and serial of the transponder. It will not have a tail number, since the shop is not working on a plane, they'e working on a component that could go into any plane after it leaves, or be sold on eBay. This is why the shop can't give you an airframe log entry for a bench test. They give you an 8130 for an equipment test. When they open a work order for an aircraft, it will list the components installed, and the type of testing required, the maintenance manuals or ICA's, and the applicable regulations. At the end all the boxes will be checked and a log entry generated. 

Flying with inoperative ADSB in Rule airspace is not a maintenance issue, it's an operational issue of non-compliance with 91.225. That is a pilot violation, same as flying out of annual, out of medical, etc.  

You're always encouraged to ask the top authority for clarification: 

https://www.faa.gov/about/office_org/headquarters_offices/agc/practice_areas/regulations/interpretations/

And Garmin has their specs which a Repair Station must use:

8.6 Regulatory Test

With the transponder operating in normal mode and in an airborne state (refer to Section 8.5), the following regulatory tests are required to be performed every 24 calendar months.

1. Altitude reporting equipment tests in accordance with 14 CFR Part 91.411 and Part 43 appendix E.

2. ATC transponder tests and inspections in accordance with 14 CFR Part 91.413 and Part 43 appendix F.

If the transponder is removed, replaced, or modified, sufficient testing in accordance with Part 43 Appendix E paragraph C must be completed.

For software updates, only a basic system functional test is required to verify normal transponder operation and ADS-B system performance is functional.

Edited March 20, 2023 by philiplane

[T. Peterson]

Wow! What a thread. When even the heavy hitters can’t agree after quoting myriad regulations and legalize, what is an average smuck like me supposed to think? I have only learned that my cynicism and contempt for bureaucrats and their minions is justified. It is utterly absurd that our regulations are written so poorly and incomprehensibly. It seems like a purposeful attempt to entrap citizens rather than enhance safety.

[EricJ]

20 minutes ago, T. Peterson said:

Wow! What a thread. When even the heavy hitters can’t agree after quoting myriad regulations and legalize, what is an average smuck like me supposed to think? I have only learned that my cynicism and contempt for bureaucrats and their minions is justified. It is utterly absurd that our regulations are written so poorly and incomprehensibly. It seems like a purposeful attempt to entrap citizens rather than enhance safety.

I think it's just that the FAA is populated with people who also have different experiences and interpretations of things.   Even the folks from the Scottsdale FSDO that have talked at the IA Seminars have said different things about the same topics.   When you talk to them they're well aware of the phenomenon.  My fave quote from one of them when asked a fairly pointy question:   "If it's not a problem, it's not a problem.   If it's a problem, then it's a problem."   I knew exactly what he meant, and it's probably one of the more practical ways to think of some of the regs, especially for GA.

[PT20J]

1 hour ago, T. Peterson said:

Wow! What a thread. When even the heavy hitters can’t agree after quoting myriad regulations and legalize, what is an average smuck like me supposed to think? I have only learned that my cynicism and contempt for bureaucrats and their minions is justified. It is utterly absurd that our regulations are written so poorly and incomprehensibly. It seems like a purposeful attempt to entrap citizens rather than enhance safety.

It's actually really simple.

1. Get the transponder and static/altimeter/encoder certs done every 2 years.

2. If something doesn't pass, get it fixed.

3. If the certs have expired, don't file IFR and stay out of airspace where a transponder or ADS-B is required or get advance permission from ATC.

The details of how to perform the certifications are the responsibility of the maintainer. 

 

Skip

[T. Peterson]

17 minutes ago, PT20J said:

It's actually really simple.

1. Get the transponder and static/altimeter/encoder certs done every 2 years.

2. If something doesn't pass, get it fixed.

3. If the certs have expired, don't file IFR and stay out of airspace where a transponder or ADS-B is required or get advance permission from ATC.

The details of how to perform the certifications are the responsibility of the maintainer. 

 

Skip

Good. The OP should just fly his airplane to the closest place to get it certified and don’t sweat the small stuff.

[T. Peterson]

1 hour ago, EricJ said:

I think it's just that the FAA is populated with people who also have different experiences and interpretations of things.   Even the folks from the Scottsdale FSDO that have talked at the IA Seminars have said different things about the same topics.   When you talk to them they're well aware of the phenomenon.  My fave quote from one of them when asked a fairly pointy question:   "If it's not a problem, it's not a problem.   If it's a problem, then it's a problem."   I knew exactly what he meant, and it's probably one of the more practical ways to think of some of the regs, especially for GA.

You are exactly right and your quote goes right to the heart of the issue. The regs are subjective, which leaves the citizen at the mercy of the bureaucrat. Who gets to decide if it’s “a problem” or “not a problem”? If an inspector doesn’t like you for whatever reason, or just happens to be in a bad mood he has broad interpretive powers. Does anyone remember Bob Hoover?

[MikeOH]

33 minutes ago, PT20J said:

It's actually really simple.

1. Get the transponder and static/altimeter/encoder certs done every 2 years.

2. If something doesn't pass, get it fixed.

3. If the certs have expired, don't file IFR and stay out of airspace where a transponder or ADS-B is required or get advance permission from ATC.

The details of how to perform the certifications are the responsibility of the maintainer. 

 

Skip

While that sounds swell and all, what should the log entry say?

Mine makes NO mention of ADSB compliance. Does yours? And to my question, should it? If so, show me the reg that required it!

Despite @philiplane explaining in excruciating detail all the steps in the process I still didn’t see where we owners could be shown a requirement! His claim that 91.411 and 91.413 somehow tie to the 91.225 and 91.227 regs doesn’t even rise to tenuous!