What happened
On September 1, 2010, a Cessna U 206F, registration PT-LMZ, departed from Boa Vista Aerodrome (SBBV) bound for Surucucu, Roraima, for a cargo flight. Approximately ten minutes into the flight, the pilot notified Air Traffic Control that the aircraft was returning to the departure airport due to technical issues.
During the approach, the pilot performed a landing without reaching the runway threshold. The aircraft struck the ground forcefully on a grassy area before the runway, causing the main landing gear to collapse. The aircraft then slid approximately 15 meters, striking a concrete box and hitting light poles. The aircraft came to a stop 108 meters from the initial impact point. The pilot was uninjured, but the aircraft sustained severe damage, including damage to the landing gear, fuselage wrinkling, propeller blade deformation, and engine damage.
The investigation
CENIPA investigators examined the aircraft's power control mechanism and discovered that the throttle control lever had broken. Technical analysis conducted by DCTA revealed that an incorrect, longer screw (PN AN3-11 instead of the specified PN AN3-7) had been used to secure the power control cable terminal.
This improper screw created excessive play, allowing washers to move and cause abrasive wear on the lateral surface of the lever. This abrasion reduced the cross-section of the lever, eventually leading to failure under load. The investigation also noted that the aircraft had departed 120kg above its maximum takeoff weight. Furthermore, the pilot's approach did not follow standard emergency procedures for power loss, such as maintaining a high approach profile or delaying flap deployment until the landing was assured.
Findings
- Improper maintenance: The use of an incorrect, longer screw in the power control assembly led to abrasive wear and the eventual breakage of the throttle control lever.
- Pilot judgment: The pilot failed to execute an appropriate high-profile approach for an engine power loss scenario and deployed flaps before the landing was secured.
- Operational non-compliance: The aircraft was operated significantly above its maximum allowable weight.
- Inadequate oversight: There was a lack of sufficient supervision regarding the quality of maintenance services performed by the contracted workshop.