What happened
On March 29, 2013, an Embraer EMB-711 ST, registration PT-RJH, was performing a ferry flight from São José dos Campos to Taubaté, Brazil. During the landing roll on runway 08 at the Taubaté Army Aviation Base, the left main landing gear unexpectedly retracted. This malfunction caused the aircraft to yaw to the left, leading to a runway excursion approximately 600 meters beyond the threshold. The aircraft sustained damage to the left wing and the left main landing gear fairing. The two crew members on board were uninjured.
The investigation
CENIPA investigators conducted functional tests on the aircraft using hydraulic jacks. While the aircraft was energized, investigators noted that the green landing gear down-and-locked indicators were not illuminated. Upon inspection, the 5A circuit breaker for the landing gear system was found to be tripped. After resetting the breaker, the green lights illuminated; however, subsequent testing of the landing gear cycle revealed that as soon as the gear command was activated, the gear legs unlocked and the circuit breaker tripped again, interrupting the cycle.
Using the aircraft's maintenance manual and electrical circuit diagrams, investigators performed comprehensive testing of the electrical system, including wiring, gear switches, relays, microswitches, and the hydraulic pump. The investigation established that a short circuit existed within the electrical components of the hydraulic pump (P/N HYC 5005, S/N 82-5256).
Findings
- The left main landing gear retracted during the landing roll.
- A short circuit in the hydraulic pump's electrical system caused the 5A circuit breaker to trip, interrupting the landing gear actuation cycle.
- The aircraft excursion resulted in damage to the left wing and left main gear fairing.