Calibration

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 crew lost control of the aircraft which resulted in significant loss of altitude; as they attempted to recover, they collided with the mountain. According to the SAWS report, there was significant cloud coverage below 1,500 feet above ground level at the time of the accident as observed in the METARs. Mountain tops were obscured as seen on the webcam. The aircraft route which is 17 NM arc passes over the obscured mountains. From the limited FDR reading the aircraft attitude drastically changed into an unusual attitude when approaching the mountain area. This indicates that most probably, the pilot has entered an unusual attitude during transition from VFR to IFR flight without preparation. The accident flight plan was VFR.
The following contributing factor were identified:
- The presence of low clouds at about 1,500 feet above ground and obscured mountains with clouds,
- The incapability of the crew to recover from unusual attitude,
- Lack of supervision and disregard of the Civil Aviation Regulations requirements by the FIU (operator),
- Overbanked and steep dive maneuver, unable to gain the required altitude before impact,
- Lack of upset prevention and recovery technique (UPRT).

Controlled flight into terrain after the crew continued the approach in poor visibility without visual contact with the environment. Misidentification of the environment on part of the crew was a contributing factor, as well as the fact that the crew deactivated the GPWS alarm and failed to initiate corrective maneuver.

Regarding aforementioned analyses it seems that the fatigues of pilots have caused incapability to adopt themselves with flight conditions and their interactions are due to spatial disorientation
(illusion). This type of error prevented pilots to avoid from crash in to the sea.
Contributing Factors:
- Malfunction of aircraft radio altimeter.
- Flight crew fatigue.
- Lack of enough supervision on flight calibration operations.

The investigation identified the following primary causal factor:
The two aircraft collided because their respective pilots either did not see the other aircraft, or did not see it in time to take effective avoiding action.
The investigation identified the following contributory factors:
1. The likelihood that the crew of G-EYES would see G-BOLZ in time to carry out effective avoiding action was reduced by the small size of G-BOLZ, its position relative to G-EYES and the high rate of closure between the aircraft.
2. Insufficient or inaccurate information was provided to the pilots, which did not assist them in fulfilling their duty to take all possible measures to avoid collisions with other aircraft.
3. The Aerodrome Controller’s sequencing plan, which was based on an incomplete understanding of the nature of G-EYES’ flight, was unlikely to have been successful. By the time the risk of a collision was identified, it was too late to devise an effective method of resolving the situation.
4. There were no effective measures in place to give G-EYES priority over traffic in the visual circuit

Controlled flight into terrain.

Controlled flight into terrain after the crew descended too low under VFR mode in IMC conditions. The following contributing factors were identified:
- The crew canceled the IFR flight plan for an approach under VFR mode despite weather conditions were marginal and the visibility was insufficient,
- The crew failed to follow the approach checklist,
- The crew failed to complete an approach briefing,
- The crew did not proceed to any callouts on approach,
- The second pilot was procedurally not involved in cockpit work processes and decision-making,
- On approach, the crew referred to the Flight Management System (FMS type III series) which was initially dedicated to flight inspection purposes only,
- Measurement was performed by the flight engineer.

The landing speed, the touchdown point, the runway length and runway condition were considered as good. The problem was the consequence of an expired adjustment screw of the speed controller ('prop governor') on the right engine, so that it did not come into 'reverse pitch' but continued to provide forward thrust, causing an asymmetric aerodynamic braking effect. It was also determined that the Beta light indicator burned and could not light on, preventing the pilot from a possible issue on the reverse thrust system.

It was determined that the accident was the consequence of an incorrect execution of the turn to the magnetic heading of 276°.