Originally Posted by Roo
The Alt gear ext DC motor and actuator have a limit of two duty cycles followed by a 10 min cool down. Normally this would be no problem as the actuator takes just over 5 sec to run at which point a limit switch shuts it off. The QRH directs the crew to leave the switch in DN for the remainder of the flight. So if something precluded the actuator from moving, it cannot reach the limit switch and it will attempt to run continuously. Because it has a duty cycle, you would eventually expect a circuit breaker to trip. It could have tripped well after the crew attempted the unsuccessful ALT extension for all we know.
In this case the CB C4248 (LANDING GEAR - ALT EXT MOTOR) should trip and
not the CB C829 (BAT BUS DISTR).