What happened
On April 18, 2022, a Beechcraft 58, registration PT-WSA, was performing a police operation flight from Guarapuava to Curitiba, Brazil. During the approach to Bacacheri Aerodrome (SBBI), the crew executed the landing gear extension checklist. Although the crew heard an unusual noise from the lower fuselage, the cockpit indicator displayed a green light, signaling that the landing gear was down and locked. The crew also verified the extension of the nose gear via internal mirrors.
Upon landing, the aircraft experienced a sudden sink on the right side. Approximately 300 meters after crossing runway 18, the right wing and the right engine propeller struck the ground, causing the aircraft to veer off the right side of the runway. The aircraft sustained light damage, and all three occupants (two pilots and one passenger) were uninjured.
The investigation
CENIPA investigators examined the aircraft' and found that while the landing gear actuator had functioned correctly, the right main landing gear remained stuck in the 'up' position. The investigation revealed that the aircraft's indication system was designed such that a single green light indicated the position of the actuator arm rather than the individual status of each landing gear leg. Because the actuator arm had moved, the microcontactor closed, triggering the green light even though the right gear leg had not extended.
Physical inspection of the right main gear revealed a damaged retraction rod, which was consistent with the mechanical stress caused by the actuator attempting to move the gear while it was stuck. Investigators also examined the uplock cables, blocks, and bearings, finding no evidence of corrosion, fatigue, or overload. While the possibility of a foreign object being present during recent maintenance was considered, no evidence of debris was found in the gear bay or actuator compartment.
Findings
- The landing gear indication system, by design, provided a false positive by indicating a 'down and locked' status based on the actuator arm position rather than the actual position of each gear leg.
- The right main landing gear remained mechanically locked in the 'up' position.
- The crew followed all standard landing procedures and checklists.
- The crew had no visual means to verify the position of the main landing gear legs other than the single green indicator light.
- The damage to the retraction rod was caused by the actuator's operation while the gear was stuck.
Safety action
It is recommended that the National Civil Aviation Agency (ANAC) evaluate the investigation findings and coordinate with the aircraft manufacturer to review the landing gear position indication system, ensuring that cockpit indicators accurately reflect the real-world position of each landing gear leg.