Originally Posted by
ATC Watcher
Yes and no . No: There was no reset in the Legacy in Brasil , they just pushed a button on the side of the screen ( presumably by the shoe or by opening the laptop screen of the F/O during cruise) which turn the SSR to SBY, and they did not notice as there is no real warning of this ( just small letters at the bottom of the screen)
Without rereading through all the stuff back of 2006 and following years I seem to recall, that the cause of why the transponder went into the standby was never fully established, an inadvertent contact by the crew was suspected but not proven (whether inadvertent or not was the major reason of conflict between Brasilian and US investigators).
What strikes me in the new report of Bulgaria now is, that the NIM (Network Interface Module) restart takes 5 seconds while the last transponder operating mode is stored only for 3 seconds, in other words, any NIM restart would drop the transponder into Standby. This result was stated in a SB of Dec 13th 2007 - obviously in response to the accident of GOL-1907 and the Embraer Legacy.
Hence, is it possible, that this service bulletin of 2007, so far unknown here as far as I recall, actually identified why the Legacy's transponder dropped into standby, even without any pilot inadvertent action?
The indications to the crew are another matter of concern indeed, again proven by the near collision over Bulgaria in 2015