What happened
On August 15, 2011, a Piper PA-39, registration PT-IUN, was performing a flight instruction mission from Salgado Filho Aerodrome to Belém Novo Aerodrome, Rio Grande do Sul. The aircraft was being operated by Aeroclube do Rio Grande do Sul with two pilots on board, including a student and an instructor.
While entering the visual traffic pattern for runway 26, the aircraft touched down without the landing gear being fully extended and locked. Following the touchdown, the instructor shut down the engines. The aircraft continued along the runway for approximately 150 meters before veering off to the left side of the pavement. The impact caused substantial damage to the propellers, engines, antennas, and landing gear. Both occupants were unharmed.
The investigation
CENIPA investigators determined that the landing gear was in an intermediate position rather than the required "down and locked" position. The investigation revealed that the student pilot had failed to extend the gear, a mistake that the instructor attempted to correct only late in the approach, during the base leg.
Technical analysis of the aircraft's electromechanical landing gear system showed that the left alternator had a loose and damaged pulley, which led to a failure in the left alternator's operation. This failure likely compromised the electrical system, contributing to a delayed gear extension cycle. Additionally, investigators found that the aircraft battery charge was below the required level for the operation. The crew did not utilize a checklist during the flight, and communication with the club's coordination team was lost during the downwind leg of the pattern.
Findings
- Failure to use a checklist during the flight operations.
- Pilot error regarding the omission of the landing gear extension.
- Reliance on memory rather than procedural verification.
- Electrical system malfunction due to a faulty left alternator.