Emergency Use of Transponder Codes
In the event of an emergency, pilots should transmit the following codes appropriate to their status:
EMERGENCY - Mode 3A Code 7700 (except that aircraft already receiving an air traffic service and transmitting a code normally retain the code in use)
COMMS FAILURE - Mode 3A Code 7600
UNLAWFUL INTERFERENCE - Mode 3A Code 7500
I suspect the helo pilot got confused and dialled the 7500 code - that would provoke a supersonic "charge" straight out of CGY!
LJ