What happened
On July 3, 2009, a private Beechcraft 95-B55, registration N-999LT, departed from San Luis Aerodrome in Menorca for a recreational flight to Mallorca. During the initial climb, after the pilot raised the landing gear lever, an amber unsafe gear light remained illuminated. Subsequent attempts to extend the gear resulted in a partial lock, where only the nose and right main gear showed green lights, indicating the left main gear remained unseated.
The crew diverted to Mahón Airport to consult with tower control, which confirmed the left gear was not extended. The pilot then returned to San Luis Aerende to attempt manual gear extension with assistance from local mechanics. Despite using the emergency manual extension procedure, the gear remained stuck. To manage the situation, the pilot continued flying for over an hour to consume sufficient fuel before declaring an emergency at 15:05 local time.
During the emergency landing on runway 19R at 15:25, the aircraft initially maintained the centerline. However, as speed decreased, the left wing dropped, making contact with the pavement. The aircraft then veered left, completing a 180-degree turn before coming to a stop 55 meters from the runway centerline. The aircraft sustained significant damage to the left wingtip, flap, aileron, propeller, and landing gear.
The investigation
The investigation focused on the mechanical failure of the left landing gear. Investigators found the left gear was stuck in a position near the retracted state. The mechanism was obstructed by a deformed part within the locking rocker, which interfered with the retraction mechanism. Additionally, the push-pull tube had buckled due to compressive overload during the failed extension attempts.
Examination of the landing gear components revealed widespread degradation, including corrosion, dirt, and solidified grease in the joints. While the owner had used specialized molybdenum disulfide grease to combat wear, the investigation found that the right main gear also exhibited malfunctioning locking rocker springs, suggesting a systemic issue rather than an isolated component failure.
Findings
- The primary cause of the incident was the obstruction of the left landing gear caused by interference between the locking rocker and the retraction mechanism.
- The failure of the gear to extend was further compounded by the buckling of the push-pull tube due to mechanical overload.
- Inadequate maintenance was a critical factor; the aircraft had missed its required annual inspection by three months.
- The aircraft's infrequent use (only 49 flight hours in the 15 months prior to the accident) contributed to the degradation of moving parts.
- The aircraft was stored in a humid, saline environment without adequate protection, leading to corrosion and the buildup of solidified grease in the mechanisms.