What happened
On September 25, 2002, a Cessna 402-B, registration EC-EMH, was performing a non-scheduled cargo flight from Melilla to Málaga Airport. During the initial approach and touchdown, the pilot noticed the green indicator light for the right main landing gear had extinguished, signaling that the gear was no longer down and locked. The pilot immediately aborted the landing, climbed, and proceeded to the Torremolinos area to attempt gear deployment cycles.
After several unsuccessful attempts to lock the gear, the crew initiated the emergency extension procedure. Despite the gear appearing visually deployed to air traffic control during a subsequent low pass, the crew decided to proceed with a second landing attempt. Upon touchdown during this second attempt, the right main gear began to collapse, causing the right engine propeller to strike the pavement and the aircraft to veer to the right. The crew subsequently shut down the engines as the left main gear also collapsed. The aircraft slid on its fuselage and came to rest approximately 30 meters from the runway edge. The two crew members escaped the aircraft without injury.
The investigation
Investigators examined the wreckage of the Cessna 402-B and focused on the mechanical state of the retractable tricycle landing gear. The inspection of the right main gear revealed several structural failures, including a broken bellcrank pivot bolt, a fractured bellcrank, a broken trunnion ear, and a broken push-pull tube. Fractographic analysis of the bellcrank pivot bolt confirmed a static failure caused by shear loads.
Regarding the left main gear, investigators found a broken adjusting screw. Examination of the landing gear actuator showed it was positioned midway between the up and down positions, indicating the gear was not fully extended.
Findings
- The primary cause of the right gear failure was an incorrect adjustment of the extension, retraction, and locking mechanism.
- It is believed the mechanism was adjusted slightly outside of the "over-center" position, which prevented the lateral arm from properly absorbing landing loads. This misalignment caused the bellcrank and associated components to bear stresses they were not designed to handle, leading to the structural breakage.
- The collapse of the left main gear was caused by the crew's failure to complete the full manual emergency extension procedure, leaving the gear in an unlocked, intermediate position.
- The aircraft sustained significant damage to both main landing gear legs, both propellers, the fuselage, and the right flap.