Posts about: "TRU" [Posts: 2 Pages: 1]

Originally Posted by Sailvi767

I suspect both recorders will contain the same data. Given the radio transmission after the loss of thrust the aircraft still had at least the emergency electrical bus powered. This should have kept both recorders online. It is however possible given the 10 minute battery backup that Boeing chose to put the the recorders on another bus but that\x92s not the norm.

Originally Posted by Someone Somewhere

I am not certain on that. Remember the 737 didn't have them on the standby bus (Jeju). The NTSB doc states they're powered from the L/R 28VDC buses on the 787.

This shows the centre TRUs can only power the instrument buses not the L/R DC buses, the RAT can't really power the right TRU without powering both R1/R2 buses, and powering the left TRU would require powering the left 235/115 ATU which would probably be a lot of magnetising current even if not much actual load. The contactor naming supports that.

My money is on the L/R DC buses being unpowered in RAT operation; only the CA/FO instrument buses and the 235VAC backup bus.