Incident Overview
On January 19, 2018, about 1630 central standard time, a Swearingen SA227-TT airplane, registration N6UP, experienced an electrical malfunction during climb. The flight crew executed a forced landing to Ellington Airport (EFD), Houston, Texas. The two pilots and two passengers were not injured, and the airplane sustained substantial damage to both engines during the landing. The airplane was registered to and operated by AIRCO JN LLC, Freedom, Oklahoma, as a Title 14 Code of Federal Regulations Part 91 corporate flight.
Flight Details
Visual meteorological conditions prevailed at the time of the accident, and an instrument flight rules flight plan had been filed. The flight departed Beaumont, Texas, at 1515, and was destined for Uvalde, Texas.
Sequence of Events
According to the pilots, during climb about 18,000 ft, both generators failed and would not reset. The pilots attempted to troubleshoot the problem and could not regain electrical power. The battery power was rapidly deteriorating, so the pilots declared an emergency and diverted to EFD as the nearest airport. Due to the loss of electrical power, the pilots lost communications and had to manually extend the landing gear. They could not verify if all the landing gear were extended and locked with the control tower personnel.
During the forced landing, the nose landing gear was retracted, and the airplane skidded on the forward fuselage after touchdown. Due to the nose gear being retracted during the landing, both propeller assemblies and engines sustained substantial damage.
Post-Accident Examination
Examination of the airplane by Federal Aviation Administration inspectors and a mechanic revealed the right generator current limiter was failed (blown). The mechanic connected a battery to the airplane and the left propeller immediately began to rotate. After troubleshooting, the mechanic determined there was uncommanded voltage to the left starter, which was caused by the left starter relay that failed at the engine start prior to the flight. During the flight, the right generator was managing all the airplane's electrical load, and the cumulative electrical load exceeded the capacity of the right generator current limiter, leading to its failure. At that point, the airplane electrical load was only being supplied by battery power.
According to the mechanic, on January 2, 2018, the emergency landing gear extension was successfully tested during the airplane's most recent inspection. During the postaccident examination, a mechanical reason for the nose landing gear not extending during the pilots' emergency landing gear extension procedure could not be determined.