Why Mode A with SSR Code 7600?

[Superpilot]

I'm "studying" Air Law and have come across this. My question is wouldn't you be better off Squaking 7600 with Charlie especially if you had a comms failure!

[Gary Lager]

A) Yes.

The book probably says "squawk mode A 7600", because the 7600 is the Mode A bit. You can't see the Charlie part, that's the altitude encoding which all goes on behind the scenes (as long as it's on).

[Re-Heat]

Note that you are now allowed to (and supposed to) squawk with Alt encoding in the local circuit these days as well - I can't think of any reason therefore why it would ever be in any other mode at all under any code at all!

[BackPacker]

The option of squawking mode A only is still there in case your encoding altimeter or its connection to the transponder fails and ATC gets all sorts of wrong readings. As far as I know, they will contact you first via the radio to verify your altitude and QNH, then ask you to squawk mode A only.

Other than that, I can think of no reason not to squawk A without C.