What happened
On January 17, 2013, a Piper PA-31T1, registration PT-OVE, was prepared for a ferry flight from Maringá Airport (SBMG) to Bacacheri Airport (SBBI). The aircraft was operated by Executive Air Taxi-Aéreo LTDA. with a pilot and two passengers on board.
During the engine start sequence, specifically while starting the left engine, the pilot attempted to check the hydraulic pump functionality. Following the procedure, the pilot moved the landing gear lever to the "DOWN" position. However, due to a lack of attention, the pilot inadvertently moved the lever to the "UP" position. This action triggered the retraction of the nose gear (bequilha). As the nose gear retracted, the aircraft shifted, causing the propellers to strike the ground. The left propeller blades sustained damage from ground contact, and the right propeller experienced both bending and scraping against the surface. The aircraft sustained substantial damage, though all three occupants remained uninjured.
The investigation
CENIPA investigators examined the landing gear control mechanism to understand why the nose gear was able to retract while the aircraft was still on the ground. According to the aircraft's operating manual, a "locking solenoid" is positioned above the landing gear lever to prevent accidental retraction while the aircraft is weight-on-wheels. This solenoid is designed to remain engaged, mechanically blocking the lever from moving to the "UP" position unless the aircraft is airborne.
Technical analysis, supported by maintenance specialists, revealed a failure in this locking solenoid. The mechanical pin, which should have prevented the lever from being moved upward, failed to deploy. This malfunction allowed the pilot's erroneous lever movement to result in the actual retraction of the nose gear. The investigation could not determine if the failure was caused by component wear or improper maintenance.
Findings
- Pilot error: The pilot moved the landing gear lever to the "UP" position instead of the required "DOWN" position during the hydraulic pump check.
- Mechanical failure: The locking solenoid failed to function, which should have prevented the gear lever from being moved to the "UP" position while the aircraft was on the ground.
- Maintenance uncertainty: It was undetermined whether the solenoid failure resulted from material wear or inadequate maintenance.
- Aircraft status: The aircraft was within weight and balance limits, and all required certifications and maintenance logs were up to date.