As Fresca previously mentioned... Do your 737NG's have the option of biasing the FD's out of view during a normal LAND 3 ? (some 747-400's also have this pin-programmed option)
I'm hoping here that you didn't have a dual gen failure in real life and that this was just a sim exercise (Do you know for sure that this reflects real life ops? i.e. with regard to DC Bus Tie ops and FD disappearance).
I was also wondering what would happen to a 767 in this particular electrical config. As far as I can see (from my training notes/Boeing Wiring Schematics), the FCC's will send a Centre Bus isolation request to the Bus Power Control Unit, but the configuration of the L & R BTB's and GCB's will not allow Center Bus Isolation to take place (Land 3 requirement). Because of this, the control of the DC Tie is still under the control of the DC Tie Control Unit. Under single gen (APU ops), the DC Tie unit will not change the state of the DC Tie (i.e. it will remain open).
In this config, I would presume LAND2 a possibility. By the way, can you recall what A/L Status was annunciated (on the 737NG)?
I would be interested to know the reponse from Boeing on this one. I also hear that some (real) 737NG's have a disturbing habit of biasing the FD's out of view for a short period during takeoff.
Rgds.
Q.