Accident Overview
On August 4, 2013, at approximately 1210 eastern daylight time, a Mooney M20R, registration N1034S, experienced a precautionary landing at Tallahassee Regional Airport (TLH) in Tallahassee, Florida, resulting in substantial damage to the fuselage. The private pilot and passenger were uninjured. Visual meteorological conditions prevailed, and the flight was operating under an instrument flight rules (IFR) flight plan.
Flight History
The flight originated from TLH around 1200, bound for Bartow Municipal Airport (BOW) in Bartow, Florida, as a personal flight under Title 14 Code of Federal Regulations Part 91. After receiving his IFR clearance, the pilot departed from runway 36 and contacted the departure air traffic controller. He was cleared to climb to 5,000 feet. As the airplane climbed through 2,500 feet, it entered cloud cover. Near 5,000 feet, the pilot reported hearing an "indescribable noise" in his headset. Immediately afterward, the primary flight display and the multi-function display lost power. The pilot attributed the total loss of electrical power to a short circuit, given the abrupt nature of the failure.
The pilot descended the airplane below the clouds and, once in visual conditions, used a portable electronic device to navigate back to TLH. Concerned about a possible electrical fire and smoke in the cockpit, he wanted to land as soon as possible. Consequently, he did not perform the emergency procedure for manual extension of the airplane's electrically actuated landing gear. Upon reaching the airport, the pilot observed a green light gun signal from the air traffic control tower and landed on runway 36 with the landing gear retracted. The fuselage structure was substantially damaged during the landing.
Post-Accident Examination
A Federal Aviation Administration inspector examined the airplane after the accident. When the inspector powered up the electrical system using the number 1 battery, the primary flight display operated normally. The number 2 battery was found to be inoperative. The landing gear actuator circuit breaker was engaged (not tripped or pulled). A detailed examination of the entire electrical system by a maintenance facility revealed no discrepancies except for an internal electrical short in the number 2 battery.
System Description and Emergency Procedures
According to the airplane's pilot operating handbook, the electrical system consists of two 24-volt 10-ampere-hour storage batteries located in the tailcone and one 100-ampere self-rectifying alternator (producing 99 amps). The number 1 battery, on the left side of the tailcone, is the primary source for sustaining the electrical system and starting the aircraft. The number 2 battery, on the right side, is a backup kept fully charged by trickle charge through a diode system. If the number 1 battery is depleted, it can be de-selected and the number 2 battery selected using a rocker switch. The master switch controls battery power from either position.
The emergency procedure for a suspected fire in flight instructs: Master Switch OFF, Alternator Field Switch OFF, Cabin Ventilation OPEN, Heating Controls CLOSED, and LAND AS SOON AS POSSIBLE. If electrical power is essential, the procedure advises turning the Master Switch and Alternator Field Switch ON and selecting essential switches one at a time to identify the faulty circuit.
The emergency procedure for failure of the landing gear to extend electrically includes: airspeed 140 KIAS or less, pull the Landing Gear Actuator Circuit Breaker, select the Landing Gear Switch DOWN, engage the Gear Manual Emergency Extension Mechanism, pull the T-Handle 12 to 20 times and return until the gear is down and locked, then verify the GEAR DOWN light and visual gear indicator.