What happened
On July 21, 2021, a Cessna 402C, registration HK3065, was performing a non-scheduled cargo flight from Quibdó to Bahía Solano, Colombia. The aircraft was carrying 300 kg of cargo, with 135 kg positioned in the forward cargo compartment.
During the landing roll on runway 18 at Aeródromo José Celestino Mutis, approximately 150 meters after touchdown, the nose landing gear inadvertently retracted. This sudden movement caused the ventral section of the aircraft's nose to scrape against the runway surface. The impact resulted in the immediate stoppage of both engines and propellers. The aircraft came to a halt 462 meters from the runway threshold. The two crew members on board evacuated the aircraft safely and sustained no injuries.
The investigation
The GRIAA investigation focused on why the nose gear failed to remain locked in the extended position. Investigators examined the mechanical state of the nose gear assembly and the distribution of weight within the aircraft.
Technical analysis revealed that the nose gear mechanism was not fully secured in its extended position due to a deviation in the over-center geometry of the Drag Brace Assy and Link Assy Drag components. This misalignment meant the Nose Gear Actuator lacked sufficient force to lock the mechanism. Furthermore, the investigation noted that the 135 kg of cargo placed in the nose section added additional stress to the already asymmetrical landing gear assembly. The concentration of forces eventually caused the failure of the Shelf Assy-Baggage AFT Wheel well, triggering the retraction.
Findings
- The primary cause was the inadvertent retraction of the nose gear because the system was not fully locked in the extended position.
- A deviation in the over-center position of the drag brace and link assembly prevented the actuator from securing the gear.
- The presence of heavy cargo in the forward compartment acted as a contributing factor by increasing the load on the asymmetrical gear mechanism.
- Structural failure of the baggage wheel well assembly occurred as the landing gear forces were channeled through the nose gear actuator.