What happened
On November 26, 2009, a Piper PA-38-112 was conducting flight training maneuvers, specifically takeoffs and landings, at the "Cerro Azul" airstrip near Guayaquil. The flight was operated by an instructor pilot and a student pilot.
Following the second landing of the session, the instructor pilot noted a slight impact on the underside of the aircraft. While the crew initially suspected the aircraft had brushed against a pile of old tires located at the runway threshold, they continued the training session. However, during a subsequent landing attempt, an unusual noise was heard within the cabin. The instructor decided to terminate the training and return to the José Joaquín de Olmedo International Airport in Guaya andquil.
During the approach to Guayaquil, the noise persisted. Upon communicating with Air Traffic Control, the pilot was informed that the aircraft's main landing gear was no longer attached. The crew subsequently performed a low-fuel holding pattern before executing a successful emergency landing without landing gear. The aircraft sustained damage to the lower fuselage and both wing flaps.
The investigation
The investigation focused on the structural integrity of the landing gear attachment points. Investigators examined the main landing gear bolts (part number AGNH–14A) and verified that the maintenance program, including recent service bulletins, had been properly followed. No previous mechanical failures had been reported in the aircraft logs.
Field examination revealed that the bolts securing the main landing gear to the airframe had fractured. While the crew initially believed a collision with tires at Cerro Azul caused the issue, investigators found that the tire pile remained undisturbed and that any impact significant enough to move the tires would have likely caused the aircraft to veer off the runway. The investigation determined that the noise heard during the approach was actually caused by loose metal panels on the lower fuselage that had become detached when the gear separated.
Findings
- The primary landing gear bolts suffered a failure due to overstress.
- The forces applied to the landing gear during the second landing exceeded the design limits of the attachment bolts, which are rated for up to 2.5G.
- The separation of the gear from the airframe occurred when the aircraft reached takeoff speed; once the weight of the aircraft no longer pressed the gear into its sockets, the components became free and fell away.
- There was no evidence that the pile of tires at the runway threshold contributed to the structural failure.