What happened
On November 30, 2020, a Cessna T210N Centurion, registration OB-1557, operated by Aero Palcazu S.A.C., was performing a scheduled cargo and passenger flight from Yurimaguas to San Lorenzo. The aircraft was carrying the pilot and five passengers.
After landing normally on the runway at San Lorenzo Aerodrome, the aircraft proceeded to taxi toward the parking area. Approximately 80 meters before reaching the parking zone, the nose landing gear suddenly retracted. This collapse caused the propeller blades to strike the ground, resulting in a propeller strike. The pilot immediately executed emergency procedures, including shutting down fuel and battery systems to prevent fire, and assisted passengers in evacuating the aircraft. There were no injuries to the six occupants, and no fire occurred.
The investigation
The investigation conducted by the CIAA examined the aircraft's maintenance history and the mechanical state of the landing gear assembly. While recent 50, 100, and 200-hour inspections had been completed satisfactorily, investigators focused on the nose gear locking mechanism.
Upon inspection of the nose gear components, investigators found that the spring guide protective cone (part number 1280207) was cracked. This component is responsible for keeping the spring compressed and aligned to ensure the gear remains in the down-and-locked position. The investigation also noted that the aircraft had been operating on irregular runways, which can generate vibrations capable of affecting landing gear components.
Findings
- The primary cause of the incident was the uncommanded retraction of the nose gear due to a cracked spring guide protective cone, which failed to keep the locking spring properly compressed and aligned.
- The crack in the guide cone allowed the gear locks to move from their secured position during the landing and taxi sequence.
- The propeller strike caused significant damage to the propeller blades, nose gear doors, and potential internal engine damage.
- Operations on irregular runways acted as a contributing factor, as such surfaces can induce vibrations that impact the extension and retraction systems.