Request Advice for Potentially bad interaction with ATC

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hifly

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hifly
Looking for some advice. Recently I contacted an ATC tower for a radio check. I have a mode S transponder and ADS-B out. I was climbing to 5500 feet and the controller said my indicated altitude was 700 feet, so I hit altitude hold on my autopilot. He asked me my altitude and I told him 4900 feet. He told me to reset my transponder and descend to 4500'. I complied but the problem did not go away.

I later determined that the static line to my altitude encoder was kinked 180 degrees during maintenance and was not sending the correct pressure altitude to my transponder. My altimeter was correct (separate static line). Obviously I should have checked the pressure altitude on my transponder, but it has never been wrong before.

I have corrected the problem, verified that the pressure altitude is correct, done a PAPR, and I check PA on the transponder during every runup.

So my question is: do I wait for FAA to send me a letter, or should I contact FAA proactively? I understand there is a reporting system that perhaps prevents/reduces penalties. What would you do?
 
I've had variations along this issue before. It was no issue either time for me. One occasion I never heard from anyone. The other time I received a call, explained that we found and fixed the problem, and that was the end of it. Personally, I would forget about it and carry on.
 
hifly said:
Looking for some advice. Recently I contacted an ATC tower for a radio check. I have a mode S transponder and ADS-B out. I was climbing to 5500 feet and the controller said my indicated altitude was 700 feet, so I hit altitude hold on my autopilot. He asked me my altitude and I told him 4900 feet. He told me to reset my transponder and descend to 4500'. I complied but the problem did not go away.

I later determined that the static line to my altitude encoder was kinked 180 degrees during maintenance and was not sending the correct pressure altitude to my transponder. My altimeter was correct (separate static line). Obviously I should have checked the pressure altitude on my transponder, but it has never been wrong before.

I have corrected the problem, verified that the pressure altitude is correct, done a PAPR, and I check PA on the transponder during every runup.

So my question is: do I wait for FAA to send me a letter, or should I contact FAA proactively? I understand there is a reporting system that perhaps prevents/reduces penalties. What would you do?
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This is the thing you are thinking of. https://asrs.arc.nasa.gov/ I see no need for you to use it for this though.
 
All the controller was doing is something we do in ALL cases which was to verify your altitude. Anything less than 300' difference in what you say and what we see, we send you on your merry way. If more than 300' we tell you that you have an issue. Nothing to worry about. You fixed the problem so go on your merry way. Next time you talk to the controller, thank them for letting you know you had an issue. They were only doing their job.
 
Thanks everyone. If it is unlikely that the controller will report the issue, then I won't do anything. My assumption is that, as PIC, I should have noticed the incorrect PA on my transponder before I took off. The other troubling part is that he told me to descend to 4500 (said I was flying near an IFR altitude, when I was actually planning to pass through that altitude). I was flying VFR.
 
hifly said:
Thanks everyone. If it is unlikely that the controller will report the issue, then I won't do anything. My assumption is that, as PIC, I should have noticed the incorrect PA on my transponder before I took off. The other troubling part is that he told me to descend to 4500 (said I was flying near an IFR altitude, when I was actually planning to pass through that altitude). I was flying VFR.
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FWIW, most transponders don't even display the pressure altitude. Regarding altitude, just let ATC know what you were planning on doing. Assuming you were not in C or B airspace, an altitude assignment would have included a reason (i.e. traffic). If you were just passing through that altitude, let the controller know (i.e. 5,000 climbing 6,500).
 
Flying to Sun-N-Fun last year with a friend we had the transponder drop out on us ... twice. The first time I didn't notice it until the controller alerted us to the transponder signal being lost. Told them we would recycle (when in fact it was a poor connection from some recent work). Got it to come back up and they said "have a nice flight."

One of the controllers on here made a statement one time I thought was excellent when he said, "we ain't the sky police" or words to that effect.
 
I had something similar happen. At first it was "Cherokee xyz, say altitude", then a request to reset the transponder a couple of times. I was VFR going out of Albany class C. Pretty clear that the transponder and altimeter were off by more than 1000'. They just asked if I was OK maintaining terrain separation and I was on my way. Turned out to be some problem with the transponder. No issue with ATC, during or after.
 
FAA Order 7110.65 states:

2. If the altitude readout continues to be invalid:
(a) Instruct the pilot to turn off the altitude-
reporting part of his/her transponder and include the
reason; and
(b) Notify the operations supervisor-in-
charge of the aircraft call sign

The OSIC will log the invalid Mode C. Once per month the facility will gather all the invalid Mode C entries and forward them to FSDO. What happens after that is just a guess.
 
My transponder doesn't show the altitude it's reporting. On the way to oshkosh I got the "say altitude" question, and found out it was reading 400' off my altimeter. When I got home my shop found that it was taking its altitude from the g5 hsi (instead of the encoder)...which wasn't plumbed to the static system. It had been reporting cabin altitude for months and I had no idea until a slightly bored controller decided to ask. Never heard anything else about it. It costs nothing to file a nasa report if it helps you sleep better, but I didn't bother.
 
Jim K said:
My transponder doesn't show the altitude it's reporting. On the way to oshkosh I got the "say altitude" question, and found out it was reading 400' off my altimeter. When I got home my shop found that it was taking its altitude from the g5 hsi (instead of the encoder)...which wasn't plumbed to the static system. It had been reporting cabin altitude for months and I had no idea until a slightly bored controller decided to ask. Never heard anything else about it. It costs nothing to file a nasa report if it helps you sleep better, but I didn't bother.
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What did they about it? Can the g5 get hooked up to the static system? Was it just a boo boo that they didn't do that? Or was the boo boo wiring the transponder to the g5 instead of the encoder?
 
luvflyin said:
What did they about it? Can the g5 get hooked up to the static system? Was it just a boo boo that they didn't do that? Or was the boo boo wiring the transponder to the g5 instead of the encoder?
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It was simply a software setting. They obviously didn't go through the set up process per the manual. When the garmin transponder saw the pres alt message on the canbus, it defaulted to that instead of using the old hardwired encoder. A better shop probably would've hooked the g5 up to pitot & static, but it's not required for the hsi.
 
Clip4 said:
Seriously, who bends a static line during maintenance?
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I'm about to. I have to run a new wire for the upgrade nav/strobe lights to the cabin. Right side was easy, just shrink wrap the new wire to the old and pull it through. Left side not so much because of the pitot static heater wire in the same hole. The pitot static hard lines are in the way to get my arm up into the lightening holes to feed the new wire through the grommets.

I'll be gentle.
 
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Clip4 said:
Seriously, who bends a static line during maintenance?
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You'd be amazed at what I've found on aircraft that just came from "maintenance," it would-- I mean it has-- filled a metal box. What gets used as a handhold, or what the back end of a flex bar gets bounced off of.

It was always fun explaining the situation when you couldn't fly because a plane that just had a write up resolved had a brand new write up that didn't exist before it "got fixed."
 
I’m way late to this but about the same time as the OP’s issue, I was cleared and flying east through the ORD bravo at 3800’ just a few miles north of ORD. My transponder went TU and Approach called me up asking my altitude. I responded and gave the ORD altimeter reading too to support it. My transponder was reading 400’ high and it stopped transmitting ADSB. They had me drop to 3500 to be sure, and that allowed separation for the jet inbound for PWK too. I advised I would get it addressed when I landed. I reached the lake, did my skyline tour and they cleared me back through again heading west but at 2800 and when I returned home I put it on the squawk list. Nothing else. If you weren’t given a number to call, I wouldn’t sweat it. Malfunctions happen, they helped you identify it, and you both worked through it.
 
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