No return on anything except Primary simply means the transponder is u/s
It seems whatever happened in MH370 at the time of the incident happened in such a way that precluded electronic information transmissions from any of the following devices:
ELT-failed/turned off
ACARS-failed/turned off/MEL unserviceable
AIRCRAFT TRANSPONDER-failed/turned off
PRIMARY & SECONDARY RADAR-failed due no primary paint or secondary transponder reception
RADIO-no comms by either crewman
For all items to fail seemingly instantaneously seems to indicate either the purposeful opening of their controlling circuits or their loss during a massive single electronic failure. The second is indicated due to the loss of secondary and primary radar contact. In the case of 9/11 the aircraft were taken over and flown by the terrorists to their conclusion within hours. There is no indication of this with immediate radar loss. Wouldn’t this indicate that cause is a catastrophic failure?