TIL: encoder warm up time

That is true. 10 minutes seems too long, but they often need to warm up a bit before sending accurate data.
 
Mine takes about 7 minutes. This caused some real panic after my ESG install. Hasn't been an issue for me.
 
The backstory: It was cold when I flew last week. While I was waiting for the engine to warm up, I spent a few minutes pairing my headset and gdl39 to my new phone, so I turned on my avionics later than usual. I got airborne and ATC briefly couldn't see my mode c. I'll have to see if the transponder's pressure altitude displays anything while the encoder is still warming up...
 
I usually put a space heater in the cabin in the winter and warm it up before flight till one day i just had to go and wasn't prepared, ATC reported no mode C till about 15 minutes after departure, it clicked in my head what had happened so I made sure a brand new encoder accompanied my brand new ADS-B out solution at install. While I was at it, a brand new antenna and coax seemed cheap insurance after spending over $4k for the ADS-B transponder.

No more mode C issues.
 
Must be true as I recently had my transponder certification done and when it first came on it was not reading correctly and I was concerned. A couple of minutes later it was spot on. I looked the the avionics guy and he just grinned and told me that was quite common.
 
GeorgeC said:
My avionics guy told me yesterday that some older encoders can take up to 10 minutes before they begin sending mode c data
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FYI: there were a number of older equipment that either had a heating circuit built in or had a temp sensor that controlled start up. There were times we removed certain items overnight to keep warm if they had an early launch, but the encoder was not one of them. The ironic thing is today that the same type equipment shutdowns when it gets too hot and you have to cool them down for it to work. There is a particular instrument in a particular helicopter that once it shutdown due to heat we would remove it and put it in the freezer for 10 minutes then reinstall it and it would work perfectly.
 
GeorgeC said:
I'll have to see if the transponder's pressure altitude displays anything while the encoder is still warming up...
Click to expand...
Sure enough, when I turned the avionics on this morning, the 335 displayed "-----" for pressure altitude. At T+5 minutes, the 335 displayed a "PRESSURE ALTITUDE FAILED" message. At T+7 minutes, the encoder had warmed up, and the 335 finally displayed the pressure altitude correctly.
 
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