Antonov AN-26

The cause of the accident was that the airplane was flying over the radio beacons of runway 05R of Khabarovsk-Novy) Airport in instrumental meteorological conditions (IMC) at an altitude of 600 metres QFE, which was significantly lower than the established minimum safe altitude of 1,200 metres QFE in the sector where the accident occurred, which led to a collision with the mountain slope and resulted in a controlled flight into terrain (CFIT).

The following contributing factors were identified:
- Lack of current regulatory documents governing the conduct of flight inspections of ground-based flight support equipment, avionics, and civil aviation lighting equipment systems, including for airfields whose topographical features do not allow inspections to be conducted according to standard procedure;
- Unreasonable establishment of a continuous exclusion zone from 0 m to 6000 m by altitude within a radius of 99900 m from KTA for the function of signaling aircraft descent below the minimum safe altitude (MSAW), which excluded issuing a corresponding warning to a DPC dispatcher;
- Absence of the ATC Dispatcher's Work Procedure at the ATC and other documents of the ATC of EU ATS (Khabarovsk):
- procedure for ATC specialists when flying over the aerodrome's RMS;
- procedure for practical training of ATC specialist performing direct ATC under the control of ATC instructor, including their interaction and responsibility for ensuring flight safety.
- Making a decision to combine two sections of trainee navigator training without the necessary risk analysis and risk mitigation measures;
- Insufficient preliminary preparation of the crew for the overflight, including failure to take into account the terrain features (presence of zones with considerable elevation) and geographical features (proximity to the state border) of the airfield, as well as the presence in the crew of a trainee navigator not admitted to independent flights and to this particular type of work;
- Insufficient cooperation between the crew and ATC specialists when preparing and performing the overflight, including coordination by the crew and ATC specialists during the flight of the maneuver with violation of the established minimum safe altitude when performing a flight under instrumental weather conditions;
- Interference of the instructor navigator in the flight procedure (route change) without assessing the relevant risks in the absence of the pilot's control;
- Failure of the trainee navigator to comply with the operating procedures in terms of comprehensive use of aircraft equipment for precise piloting, maintenance of safe altitudes and timely informing the crew about turns, as well as lack of proper control over his actions on the part of the instructor navigator;
- Lack of control over the aircraft flight by the trainee controller and instructor controller at their minimum workload (controlling only the aircraft which had suffered a crash).
- The Operator's Flight Operations Manual lacked standard operating procedures for crew operation regarding the EGPWS Mark VIII system installed on board the aircraft. There were no warnings of this system during the flight. Probably, the system was not activated by the crew prior to the flight, maybe to avoid frequent activation during the flight. Due to the complete destruction of the system as a result of the crash, it was impossible to determine the cause of its failure. A proper use of this system may have prevent the accident.

The cause of the An-26B-100 RA-26085 aircraft crash was the crew's violation of the established instrument approach procedure to Palana aerodrome, which was manifested in flying with significant deviation from the set route and descent well below the established minimum descent height (MDH) under weather conditions that excluded stable visual contact with ground landmarks, leading to the collision of the aircraft with a coastal cliff in controlled flight, its destruction, and the death of the crew and passengers.
The following contributing factors were identified:
- The crew's failure to execute a missed approach with the acquisition of the established minimum safety altitude (MSA) when information about the bearing indicated a significant deviation of the aircraft from the established approach procedure;
- The absence in the Palana aerodrome dispatcher's work technology of actions in the presence of information about the bearing indicating a significant deviation of the aircraft from the established approach scheme, as well as the dispatcher's passivity when such information was available;
- The lack of warning signals from the early ground proximity warning system under conditions that should have triggered it. It is not possible to determine the reason for the absence of the warning signals;
- The overestimation of the barometric altimeter readings in the final phase of the flight due to the specific airflow around the steep coastline creating a low-pressure zone and the overestimation of the variometer readings, the cause of which cannot be determined.

The Commission of Inquiry into the accident with AN-26B aircraft operated by South-West Aviation Co. Ltd, registration number EX-126, concluded that the cause of the accident near Juba, Central Equatorial State, Republic of South Sudan, has not been established. However, the flight was operated by an aircraft without a valid Certificate of Airworthiness and by the crew of South-West Aviation Co. Ltd, which did not hold a valid Operator's Certificate.