Altitude reporting spotty

Huckster79

Huckster79

Pattern Altitude
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Huckster79
I’m getting close to needing a re-cert on the transponder and such, well my alt reporting works sometimes and not other. Got booted of flight following because of that. Seemed accurate when it was working.

mis that likely the encoder bad, or the transponder? It’s an old one 76a I think...

I don’t want to do the re-cert if it’s likely ****ing in the wind...and I just need a whole new unit. if it’s likely the encoder that is cheap... but I’m not going to put cash into the transponder itself as I’m assuming it’s not worth fixing...

I’m contemplating a tailbeacon but no point if the transponder is shot.
 
Huckster79 said:
my alt reporting works sometimes and not other.
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As in ATC sees you but no ALT or inaccurate ALT? If it still works on occasion it may just be a loose connector. Make sure the xpndr is fully seated in the tray and the encoder connector is tight. But the best way to really T/S it is to hook up the same type equipment used to certify it.
 
Bell206 said:
As in ATC sees you but no ALT or inaccurate ALT? If it still works on occasion it may just be a loose connector. Make sure the xpndr is fully seated in the tray and the encoder connector is tight. But the best way to really T/S it is to hook up the same type equipment used to certify it.
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when ATC sees it- it’s pretty accurate but they lose it now n again or don’t get it at all at times. Rarely an issue where I fly but if I’m going to get a tailbeacon it’s gotta be working... I did clean xpinder contacts - no change...

so the certify process could help just in the troubleshoot? I’ve never had one before... so this is a new one for me..
 
Bell206 said:
As in ATC sees you but no ALT or inaccurate ALT? If it still works on occasion it may just be a loose connector. Make sure the xpndr is fully seated in the tray and the encoder connector is tight. But the best way to really T/S it is to hook up the same type equipment used to certify it.
Click to expand...

I will check encoder contacts - idk why I didn’t check there too
 
Not that probabilities mean anything, but I've been through 4 encoders and only one transponder over time.
 
Huckster79 said:
so the certify process could help just in the troubleshoot?
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Yes, in most cases. When t-shooting a intermittent problem I would suck down the system and monitor the xspnder code while performing a wiggle test on all the connections. Doesn't work all the time but has fixed the easy problems. Since ATC still sees your discrete code and your altimeter doesn't fluctuate when ATC loses the ALT my money would be on the encoder. Unfortunately some encoders aren't worth having bench checked vs replacing. There are a few more items to check but perhaps ask the people who will perform your 411/413 checks for their input considering any repair/replacement of the xspndr/encoder will require new 411/413 check.
 
Bell206 said:
Yes, in most cases. When t-shooting a intermittent problem I would suck down the system and monitor the xspnder code while performing a wiggle test on all the connections. Doesn't work all the time but has fixed the easy problems. Since ATC still sees your discrete code and your altimeter doesn't fluctuate when ATC loses the ALT my money would be on the encoder. Unfortunately some encoders aren't worth having bench checked vs replacing. There are a few more items to check but perhaps ask the people who will perform your 411/413 checks for their input considering any repair/replacement of the xspndr/encoder will require new 411/413 check.
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thats good to know...
 
GeorgeC said:
Mine's been flaky for the first few minutes of my last couple of flights as well, then resolves on its own. Wonder if something got damp. Wish I'd put in a GAE12 when I put in my 335...
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I think if I have to do a new transponder I’ll get a appaero stratus esg...

I’d be tempted to just S can it as I’m not really a controlled space guy when on my 140 missions but I’m even finding missions I’d like to fly that ADSB is limiting me from... so I think I need to get it working and do the tailbeacon or the new transponder with ADSB...
 
Rgbeard said:
I vote for the transponder with ADSB built-in.

Fewer interconnecting items = better in my book. (yeah, I know the tailbacon doesn't interconnect hardwire)
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i know this probably sounds silly but I hate the idea of a new looking unit in her panel... but it’s probably more economical... being once I get a tail beacon if the old king pukes I’ll still be on the hook for a new transponder... instead of just all at once...
 
GTX-327's are going pretty cheap these days if you have to change transponders. It's a good digital transponder, not ads-b which is why they are cheap as folks are removing them to install ads-b stuff.
Sure does sound like a bad encoder or wire from encoder though.
 
I’ve flown an old club plane with an encoder that worked only in summer, and in the winter after the cabin warmed up. If the intermittent OP’s intermittent problems developed only in winter, that might suggest that kind of temperature-related problem with an encoder.
 
NoHeat said:
I’ve flown an old club plane with an encoder that worked only in summer, and in the winter after the cabin warmed up. If the intermittent OP’s intermittent problems developed only in winter, that might suggest that kind of temperature-related problem with an encoder.
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no it was before winter.
 
FORANE said:
GTX-327's are going pretty cheap these days if you have to change transponders. It's a good digital transponder, not ads-b which is why they are cheap as folks are removing them to install ads-b stuff.
Sure does sound like a bad encoder or wire from encoder though.
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yea I’m going to clean everything first... I did the tray contacts but not the ones on the encoder. Makes sense it’s connection...
 
I have a 330es with adsb out that I need to sell if you end up going that route.
 
I can’t remember specifically what was spotty in my intermittent transponder reception by ATC years ago, but changing the coax and insuring a good ground plane connection worked wonders for my KT76a. Hate the intermittent stuff since you want it to be evident when you take it to your avionics shop to troubleshoot/certify.
 
MajorTurbulence said:
I can’t remember specifically what was spotty in my intermittent transponder reception by ATC years ago, but changing the coax and insuring a good ground plane connection worked wonders for my KT76a. Hate the intermittent stuff since you want it to be evident when you take it to your avionics shop to troubleshoot/certify.
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Great point. Many forget the coax and antenna bonding to ground connection.

I had a similar issue with my radio. Was flying to get fuel when i was advised to switch to com 2. Didn't have one of those so when I got on the ground was told that while I was readable it wasn't very clear. I tried another headset but no difference. A new antenna (not sure that was needed) and a replacement coax and shazam! It worked perfectly and I could get a 5X5 radio report 35 miles away in the pattern.
 
From the description, it could easily be a bad connection. A competent avionics shop can evaluate it. That’s where you’ll have to go regardless. This is not one of those things you can make a guess and throw a part at it. That’s never the best approach anyway. Find a good shop and let them sort out the problem.
 
Economics As long as the car is up on the lift.......

I think you are are in need of ADSB out as this time as well, and I think you have an ancient transponder from what I can tell.

A tail beacon is $2000. For $3000 you can get a GTX 335 that will give you a new transponder and ADSB Out.

Add in a new encoder, and you have a nice tight solution.
 
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