B737 Loss of Both Engine Driven Generators
This non-normal is covered during type rating and recurrent training. Scenarios differ depending on the simulator instructor, but usually involves a failure of one engine driven generator while airborne followed soon after by the second engine driven generator. A lengthy non-normal checklist follows. Once that is completed, an instrument approach (with limited flight instruments in some aircraft) and landing completes the exercise.
There have been documented cases where a lightning strike affected the electrical systems including failure of an engine driven generator. On one occasion when the crew attempted to restore the faulty generator, that action caused the second generator to fail, leaving for a short while loss of both engine driven generators. All this takes place while airborne.
In the case of the 737 Classic for example, a double generator failure during the take off roll presents an entirely different situation than an airborne double generator failure. At night, the flight deck goes to total darkness including all instruments. Partial lighting can be restored by actuation of the Standby Power switch to ON but the PM has to be quick and know instinctively the position of that switch in a darkened environment. The flight/ground logic is disturbed which can result in false aural signals such as the takeoff warning sounding while the aircraft is still rolling and erroneous stick shaker operation at rotation. Once airborne, the flap indicator is inoperative as well as the electrically operated stabiliser trim switch.
Last, but by no means least, rotating on and subsequent flying on the standby ADI and using the RMI as a compass brings its own challenges. Loss of the inboard Anti Skid system means a high speed abort would likely cause the inboard tyres to fail and thus partial loss of braking capability. It is generally safer to continue the take off and sort out the problem at leisure when airborne rather than risk an over-run if on a runway limiting take off with loss of partial anti-skid.
The above scenario paints quite a dramatic picture and coping successfully takes considerable flying skill and good airmanship. Despite this, one rarely sees this non-normal practiced during type rating or recurrent simulator training. The danger is not the airborne part; but where the proliferation of false warning signals and the surprise factor leads the pilot to unnecessarily abort the take off