Location: Carlsbad, California
Status: Investigation Complete
Epilogue (EPI) (pdf 65 kb)
The occurrence took place at the end of the training day when Griffon CH146427 was flown from Camp Pendleton to Palomar Airport for refueling. After the aircrew received their clearance to land, the aircraft lost its right-hand (RH) cargo door. The aircrew heard a loud "bang" but, at the time, they were unaware that the cargo door had departed the aircraft. Both pilots immediately referred to their instruments and assessed controllability. Confident that the aircraft could be flown to the airport, an emergency was declared and the aircraft landed short of the runway.
At the time of the occurrence, the aircrew believed that the cargo door was in a fully pinned open configuration, consequently, they flew at approximately 100 knots indicated airspeed (KIAS). The evidence collected during the investigation showed that the cargo door was not secured in the open and pinned position. As a result, the aircraft was exceeding the maximum allowable airspeed for cargo doors in the in-transit configuration by 20 knots. With the aircraft in a RH turn and descent, the resultant airflow on the right hand passenger door generated sufficient lift and drag to cause the front J channel on the bottom of the cargo door to disconnect from the fuselage bottom track. Once disengaged, the additional drag on the cargo door completely tore it from the fuselage tracks.
Laboratory work was conducted to determine the condition of the latching mechanism used to secure the cargo door in the open position. It confirmed that the pit-pin used to secure the door's keeper to the latch assembly was unserviceable. The condition of the pit-pin was not detected during the pre-flight inspection and is deemed to be a contributor to the occurrence. Further, the investigation revealed that the verification of the door security done prior to the last flight relied on a "pull-test" and did not include a visual and/or tactile check of the pit-pin. The act of pulling on the cargo doors to test for security may lead to the false assumption that the door is fully secured, whereas the visual and/or tactile check would allow the FE to detect when the pit-pin is partially inserted and/or the pin locking mechanism is unserviceable/not fully engaged.
Preventive measures range from revision of the training standards to ensure all FEs are taught a procedure that requires them to confirm the pit-pin is down and locked to the requirement for a new design of the front bracket holding the bottom of the cargo door to the fuselage track.