DC, this problem of aircraft cycling through 2 (or more) callsigns during a flight is a know problem with the systems in the aircraft itself. There's long discussions about this over on Kinetic's forum at:
http://www.kinetic-avionics.co.uk/forums/viewtopic.php?t=4242http://www.kinetic-avionics.co.uk/forums/viewtopic.php?t=3120I've observed similar changes on:
- VIR19 switching to VIR19 1, and VIR1IR1
- VIR43 switching to VIR IR4, VIR 3 4, VIR43 4, and VIR4IR4
- KLM601 switching to KLM LM6, and KLM6LM6
- KLM685 switching to BM6LM6, GM LM6, KLM LM6 and RM LM6
Found this official statement about B747 problems:
Changing Flight Identification – B747: The call-sign or flight identification on some Boeing 747s has been observed to change randomly during flight. The problem has been isolated to the ACSS transponder. A service bulletin is expected by the end of March 2007 to address the problem. The flight identification is the primary means of coupling the ADS-B track to the ATC flight plan within the air traffic management system. A change in flight identification would cause a decoupling, resulting in problems for the controller. This problem also has implications for the European Mode S radar program and will need to be resolved for airlines to gain compliance.