Transponder codes

[tylanna]

To signal a communication failure, do you squawk 7700 for 1 minute, then switch to 7600? or has there been a change to simply squawking 7600 and leaving it there?

[BOHIXON]

It has always just been 7600 for Com failure.

[SeaAir]

I can't find my old books, but I remember something about squaking 7700 first then switching to 7600 to wake up the controllers. It probably went away just as did of doing equilateral triangles on lost comm.

7600 will wake the controllers up as well.

7700, 7600 and 7500 are all treated the same as far as alarms and such. The proper way is to use 7600 immediately for comm failure. However, check to see if your mic is stuck first. This often results in some of the many comm failures.

I believe that 77xx and 76xx where xx is any octal number will also be treated as an emergency. 7500 is the only hijack code. So be careful when you are dialing in those codes, you may actually hit an emergency code along the way.

[tylanna]

Thanks everyone for your input, I was finally able to get an instrument instructor to explain. Apparently, the method used to be squawk 7700 for a minute, then squawk 7600 for fifteen minutes. He showed me the reference in the Aeronautical Information Manual (6-1-2) that now 7600 also triggers an alarm now, so squawking 7700 first is no longer necessary.