View Full Version : Transponders and Mode C

7th Aug 2002, 07:30
I'm told that the Transponders in the light aircraft I hire do not have Mode C, yet they have a setting labelled "Alt".

This may be a silly question, but how do you know if a Transponder in a particular aircraft has Mode C or not?

Captain Stable
7th Aug 2002, 09:29
The aircraft probably does not have an encoding altimeter, so the transponder does not receive the altitude information to send.

Apart from being told, you'd only find out by checking the aircraft documentation.

Check 6
7th Aug 2002, 11:31
If your altimeter provides the altitude information for your transponder, it might say "encoder" or "encoding" on the face, but not in all cases.

If the aircraft has a "blind" encoder, i.e. a remoted unit, then Capt. Stable is correct, you might have to check the "equipment list" for the aircraft to see if one is installed.

:D :D :D

Capt Pit Bull
7th Aug 2002, 21:11

Make sure you understand the difference between 'Mode C' and 'Altitude Reporting'. Many people think that they are the same, and consequently say one when they mean the other.

Search this forum for Mode C versus my user name if you don't follow.


Mark 1
8th Aug 2002, 13:26
It was my understanding that if you did not have an encoder then the transponder should be placarded with "NO ALTITUDE INFORMATION" or words to that effect.

Kalium Chloride
9th Aug 2002, 21:44
Perform a few rollercoaster climbs and descents in a row. If ATC asks you what the f*ck you're doing, you're transmitting ALT information.