mode c

[much2much]

transponder malfunctioning on mode c , reading 15000ft at 2000 . 11000 at 1100.. its not connected to a encoding alt ie is blind , any ideas??

[riverrock83]

Don't know what you mean by "it's blind". Presumably you mean that it has a built in encoder? Otherwise it couldn't report its height / Mode C...

It would have helped if you said what sort of transponder it is (and used capital letters and punctuation ;)).

If its a built in encoder, it will have a static port / connection (which should be the same static source that your altimeter is using). Check that is OK. Otherwise, its a trip to the avionics shop for diagnosis / repair.

[much2much]

sorry about the capitals,i thought it still readable,(unlike the altitude) and thought the.. and .. were punctuation, blind i believe is the expression used to mean connected to it,s own encoder which has it,s own static outlet.
that is to say not receiving information from a encoding altimeter.
not my machine , so the make may well of helped;once again i will work on my English.
20 years in Glasgow helped but alas now i am down south all has gone to pot,still 20 years stealing you women and jobs was great.
that in mind we may well have met:O
seriously thanks anyway , a shot in the dark

[Lone_Ranger]

Gi it malky, son

[riverrock83]

sorry about the capitals,i thought it still readable,(unlike the altitude) and thought the.. and .. were punctuation, blind i believe is the expression used to mean connected to it,s own encoder which has it,s own static outlet.
that is to say not receiving information from a encoding altimeter.
not my machine , so the make may well of helped;once again i will work on my English.
20 years in Glasgow helped but alas now i am down south all has gone to pot,still 20 years stealing you women and jobs was great.
that in mind we may well have met:O
seriously thanks anyway , a shot in the dark
Lol - being originally from N. Ireland I can't talk about stealing Glasgow women...:ouch:

If the static inlet is clear, I doubt there are any user serviceable parts. Does it report its altitude onto a screen? I presume that's wrong too?

It could be an internal connection to its internal encoder has broken, or maybe the internal barometer, or maybe the encoder itself is broken. Or it could be in one chip, doing all of that, which just needs replaced.

Sorry I'm not much help.

[Big Pistons Forever]

transponder malfunctioning on mode c , reading 15000ft at 2000 . 11000 at 1100.. its not connected to a encoding alt ie is blind , any ideas??

In every instance where I have seen similar symptoms the remote encoder itself had failed. They don't seem very reliable but they are easy to function check and unless mounted in a silly place, usually easily replaced and not that expensive (By airplane standards I mean).

[phiggsbroadband]

Hi M2M, I think this sort of problem was discussed some time earlier, and the reply was that it is likely to be an encoding problem. The code used is Grey Code, which changes only one bit at a time, which is different to Binary Code. It could be just one wire connection loose... So try rattling each connector, to get a better joint.

Does the fault only occur at those two heights +- 50ft ?
Or is it continuously wrong ?

and I take it you mean Flight Levels.