Originally Posted by
PPRuNe Radar
From ICAO Annex 2:
b) in airspace where radar is used in the provision of air traffic control, maintain the last assigned speed and level, or minimum flight altitude if higher, for a period of 7 minutes following:
1) the time the last assigned level or minimum flight altitude is reached; or
2) the time the transponder is set to Code 7600; or
3) the aircraft’s failure to report its position over a compulsory reporting point;
whichever is later, and thereafter adjust level and speed in accordance with the filed flight plan;
I don't understand how this works. How would ATC and the airplane crew start their 7 minute clocks simultaneously? Especially if the transponder doesn't work.
Hypothetically, if the crew realized they had radio communications failure, squawked 7600 and then, 7 minutes later, changed to their flight planned altitude, wouldn't that be extremely dangerous if ATC didn't receive the transponder and didn't realize there was a radio problem?
Its ambiguous the other way as well. What altitude is ATC to think the plane is flying if they realize that there is communications failure but they don't know whether the crew knows this or not?