What happened
On April 20, 2011, a Beechcraft 58, registration PT-LRS, was preparing for a ferry flight from Aeródromo da Pousada Thaimaçu (SNFJ) to Alta Floresta (SBAT). During the takeoff roll on runway 25, the pilot noticed a significant tendency for the aircraft to yaw to the right. Believing the aircraft might have a punctured tire, the pilot decided to abort the takeoff.
During the aborted takeoff roll, the right main landing gear retracted without command, causing the aircraft to veer off the runway to the right. Following the excursion, the left main landing gear also retracted, and the nose gear collapsed. The aircraft eventually came to a stop after striking a small rise in the terrain at an angle of approximately 135 degrees from the original takeoff heading. The aircraft sustained substantial damage, including damage to the nose gear, both wingtips, the right engine propellers, and the lower fuselage. The pilot was uninjured.
The investigation
CENIPA investigators examined the landing gear assembly and the maintenance history of the aircraft. While the wheel hub was in good condition and the tire showed no punctures or tears, the tire was found to be completely deflated. During the disassembly of the right main gear, the inflation valve detached from the inner tube, revealing a transverse cut likely caused by the wheel itself after the tire had lost pressure.
Investigators also noted that the tire lacked the required red radial alignment marks that should match the rim. These marks are a recommended safety practice to help pilots and mechanics identify if a tire has slipped inside the rim, which often occurs due to low inflation pressure. The aircraft had undergone maintenance just thirteen days prior, during which the main tires were replaced, but the inner tube from the right tire was reused.
Findings
- The investigation suggests the right main tire was likely operating at an inadequate pressure during the pre-flight inspection, which may have gone unnoticed by the pilot.
- The lack of alignment markings prevented the identification of tire slippage within the rim.
- It is probable that the tire slipped within the hub during ground operations or the takeoff roll, damaging the inflation valve and leading to the rapid loss of pressure.
- The reuse of the existing inner tube during recent maintenance may have introduced an unidentified deficiency that contributed to the pressure loss.
- Inadequate technical supervision during maintenance or inspection processes may have allowed these discrepancies to persist.