What happened
On September 19, 2022, at approximately 18:55 local time, a Beechcraft 1900C, registration TN-AIQ, was performing a commercial passenger flight from Brazzaville to Pointe-Noire. The aircraft, operated by Equaflight Service, was carrying two crew members, one cabin crew member, and 16 passengers.
During the final approach to Agostinho Neto Airport, the crew noted that the right main landing gear failed to show a down-and-locked indication after standard deployment attempts. The crew performed an emergency extension procedure, which successfully triggered all three cockpit indicators, leading the crew to believe the gear was secure.
Upon landing on runway 17, as the aircraft decelerated and weight transferred to the landing gear, the right main gear began to collapse. This caused the right propeller, trailing edge flap, and wingtip to strike the runway surface. The crew declared a MAYDAY, and airport emergency services responded to the scene. The impact punctured the right wing fuel tank, causing fuel to spill onto the runway. All occupants evacuated the aircraft safely, and fire crews applied water and foam to mitigate fire risks.
The investigation
The BEA conducted an examination of the wreckage and performed ground tests on the landing gear system, which successfully replicated the failure. Laboratory analysis of the right main gear actuator revealed that a locking spring was significantly compressed, providing only 69 lb of force instead of the required 125 lb. Additionally, investigators found that a position switch (lock/unlock) had been improperly installed, leading to unreliable operation.
Technical examinations also noted that while the Cockpit Voice Recorder (CVR) provided clear audio of the event, the Flight Data Recorder (FDR) was limited by insufficient parameters and a lack of UTC time-stamping, which hindered a full reconstruction of the gear collapse sequence. Furthermore, the maintenance history for the specific actuator could not be fully traced due to incomplete records.
Findings
- The mechanical failure of the right main landing gear to lock in the extended position was caused by a non-compliant locking spring with insufficient length and force.
- An improperly installed position switch provided erroneous cockpit indications, masking the fact that the gear was not securely locked.
- Deficiencies in quality control during the receipt and installation of the actuator prevented the detection of these non-conformities.
- Inadequate maintenance documentation and traceability for critical components hindered the ability to identify the origin of the faulty part.