Dash 8-200
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Less Severe; Ground Event / Encounter Other / Unknown
General Flight Cancelled / Delayed; General Maintenance Action
Aircraft; Weather
During push back; first flight of the day; the tug driver asked us to set brakes. As they were disconnecting; the #2 engine torque uncontrollably surged in a very quick manner. By the time I recognized what was going on and immediately moved my hand to the condition lever to shut off the engine; I believe that the #2 torque reached a value of approximately 120% as it was shut down. The #2 T-handle was also pulled. We got onto the ops frequency to request a tow-in back to the gate. As the ground crew was hooking up the tow bar to us again; the #1 engine began to surge upward rapidly. Since it just happened to #2; I was watching the engine gauges very closely as it happened and was able to catch this one early. I shut down the #1 engine as quickly as I could and I believe that the torque may have reached about 60% or so; although it happened so fast; I'm not sure how valid the values that I thought I saw were. The #1 T-handle was pulled and we were towed back into the gate running on battery power. The aircraft was deplaned and the discrepancy recorded in the maintenance logbook. It was still night; IMC at the time; with light snow falling; temps around 10F and we had approximately 20' of snow the day/night prior. No snow was observed in the intakes during preflight.
The Captain states that the DHC8 engines are normally started in feather and stay that way until cleared to taxi. The Captain believes that the high torque is the result of a fuel control malfunction that is dumping fuel into the engine with the propeller in feather. Forty percent is the normal torque limit with the propeller feathered.
DHC8-200 Captain reports starting both engines in the gate on a very cold morning then being pushed back. As the ground crew disconnects; the number two engine torque surges uncontrollably above 120% and the engine is shut down. The number one engine then begins surging and is shut down before the torque reaches 60%.