The cause of the crash in May that killed all four people aboard the P-3CK maritime patrol aircraft was not clearly identified. Investigators could not pinpoint the cause because the aircraft did not have a cockpit voice recorder (CVR) or a flight data recorder (FDR). The Navy said it believes a combination of various factors—mechanical, human, and environmental—likely contributed and plans to prepare measures to prevent a recurrence.
The accident response headquarters and the civil-military joint accident investigation committee said on the 13th, while announcing the results of the investigation, that they could not identify the exact cause that led the P-3CK to lose lift. On May 29, the P-3CK crashed into an open field near the Navy base in Pohang, North Gyeongsang, six minutes after takeoff. The crash killed four Navy officers, noncommissioned officer pilots, and crew members. The Navy immediately set up an accident response headquarters and has been investigating.
The aircraft type did not have an FDR. The CVR was also damaged by impact and could not be recovered. Based on this, the committee analyzed footage captured by the base perimeter closed-circuit (CC) TV to determine the aircraft's position from takeoff to the time of the crash, altitude, nose direction, attitude angle, and bank angle. It also used a P-3 aircraft training simulator to recreate the situation at the time of the accident.
According to the committee, the aircraft's speed, altitude, and attitude were all normal during the takeoff phase at the Navy airfield. However, during the turning phase to gain altitude, its speed decreased compared with normal flight and its climb became minimal. The angle of attack (the angle between the direction the wing extends and the direction of the airflow) was large, and the propeller pitch was also small.
In this state, the Navy determined, the aircraft's speed decreased from 160 knots (296 kph) to 67 knots (124 kph), causing a loss of lift and a loss of control, leading to the crash. If the altitude had been sufficient, it could have recovered lift with the speed increasing due to gravity, but the stall point altitude at the time was 950 feet (290 meters), so lift was not restored.
The committee also looked into mechanical factors such as power loss and the engine, propeller, fuel, control, and hydraulic systems. However, it confirmed that all were operating until ground impact. In particular, damage from foreign object ingestion was found on stage 1 of the power turbine of engine No. 1 among the four engines. The committee said the damage may have had some effect on the pilots, but it did not see it as the direct cause of the accident.
The committee further cited mechanical factors as one of the causes, given that the aircraft itself was an older model. A Navy official said, "It was an older type without an FDR, and the gauge to check the angle of attack was also in a difficult position, so there is a possibility that the crew failed to recognize stall cues in time."
The committee also suggested the pilots likely failed to respond properly to the stall because they had not received stall and loss-of-control recovery training. On this day, Joint Accident Investigation Committee Chair Cho Jung-gwon said, "We cannot discuss this without considering the pilots' actions," adding, "We judged there is a likelihood that recognition of approaching stall cues and the development of the ability to perform recovery procedures were insufficient, and a high likelihood that energy management and attitude management during flight performance were inadequate."
To prevent a recurrence, the Navy will strengthen flight training for flight crew and conduct periodic stall and loss-of-control recovery training for pilots. It is also considering installing stall warning devices on the aircraft type involved and relocating the gauge that indicates the angle of attack to a position where pilots can easily check it at a glance.
Separately, the Navy said it will decide later when to resume flights of the P-3CK involved in the crash.