What happened
On August 23, 2012, at approximately 11:50 local time, a Cessna 421C, registration HK-4683, was performing a taxi flight for medical transport purposes when it departed the runway at Santiago Perez Airport in Arauca, Colombia. The aircraft was operating a multi-leg route between Bogotá, Yopal, Arauca, and Bucaramanga, carrying two crew members and three passengers.
During the landing phase on runway 11, the pilot encountered a strong right crosswind. To maintain the aircraft on the centerline, the pilot applied power, which resulted in a heavy touchdown on the runway. Following the initial contact, the aircraft traveled approximately 3/00 meters before a severe lateral vibration occurred, leading to the separation of the left main landing gear. The aircraft subsequently drifted to the left, exiting the runway and coming to rest 16 meters beyond the left safety margin. There were no fatalities or injuries among the five occupants.
The investigation
The GRIAA investigation examined the aircraft's maintenance records, the physical wreckage, and the mechanical integrity of the landing gear assembly. Technical analysis of the landing gear components, supported by failure analysis from the Universidad Pontificia Bolivariana, focused on the trunnion, the upper barrel, and the link assembly.
Investigators reviewed the maintenance history, noting that the aircraft had complied with all applicable Airworthiness Directives and Service Bulletins, including recent inspections of the landing gear trunnion. The investigation also analyzed the impact marks on the runway, which showed heavy tire scrubbing and propeller blade strikes caused by the left engine making contact with the pavement during the excursion.
Findings
- The primary cause of the accident was the separation of the left main landing gear due to the failure of the bushing connecting the Link Assy Main Gear Strut.
- The heavy touchdown caused by the crosswind wind-correction maneuver led to the loss of the bushing, which triggered a sequence of mechanical failures.
- The loss of the bushing caused the gear to become unstable, leading to the breakage of the actuator's attachment ear and the catastrophic failure of the trunnion.
- The aircraft's left engine and wing sustained significant damage due to contact with the runway surface during the uncontrolled drift.
- The aircraft was found to be in an airworthy condition with all maintenance and inspections up to date prior to the event.