What happened
On August 16, 2012, a Beechcraft B 58, registration PR-ODM, departed from Atibaia Aerodrome (SDTB) in São Paulo, Brazil, to perform a flight test for an initial technical inspection. During the takeoff climb, while the pilot was retracting the landing gear, the aircraft suffered a total electrical system failure. This failure caused the landing gear to stop in an intermediate position.
The pilot entered the traffic pattern to manage the emergency. After attempting to extend the gear using the standard landing gear lever, the pilot decided to land. To assist with the emergency, the pilot requested that the passenger perform the manual emergency extension procedure. Before landing, the pilot performed low passes over the runway to visually confirm the gear position with ground personnel, who signaled that the gear appeared to be down. Despite the electrical failure, the cockpit indicator lights showed green, suggesting the gear was down and locked.
Upon touchdown, the landing gear inadvertently retracted, causing the aircraft to decelerate on its fuselage, resulting in substantial damage to the aircraft. Both the pilot and the passenger were uninjured.
The investigation
CENIPA investigators examined the aircraft's electrical system and maintenance history. The investigation revealed that the aircraft had recently undergone a 100-hour inspection. During the pre-flight preparations, maintenance personnel had incorrectly installed battery cables with reversed polarity, and a new battery had been installed shortly before the flight, though its specific charge condition could not be verified.
Investigators found blown alternator fuses, suggesting that voltage variations following the engine start may have caused the alternator to disconnect from the bus, subsequently impacting the electric motor responsible for the landing gear actuation. The investigation also noted that the flight was being conducted under an ANAC experimental flight authorization that specifically prohibited the carriage of passengers, a regulation that was violated during this operation.
Findings
- The primary cause of the gear failure was the improper execution of the emergency extension procedure by a passenger who lacked the required technical training.
- The pilot's decision to delegate a critical emergency procedure to a non-crew member contributed to the failure to properly lock the gear.
- An electrical failure, likely linked to blown alternator fuses and potential battery issues, prevented the gear from functioning normally.
- The operation violated the flight authorization restrictions by carrying a passenger on a flight intended to be single-occupant.