Russia

Failure of the high pressure compressor disk on the engine n°2 during the takeoff procedure.

The accident with the An-2 RA-71276 aircraft occurred as a result of a collision with a mountain at an altitude of 2,780 metres above sea level perpendicular to the direction of the ridge with its minimum height of 2,960 metres conditions of limited visibility and the closure of mountain tops by clouds.
The following contributing factors were identified:
- The crew took the decision to perform a flight over a mountainous area with predicted closure of the mountains by clouds and unfavorable wind conditions,
- The crew took the decision to return to the landing site through the mountain range along an unexplored and previously unused route,
- Operational fatigue of the crew due to the significant duration of working hours on the day of the accident (more than 12 hours),
- The airplane falling under the influence of descending air currents on the leeward side of a mountain slope.

The cause of the accident with the An-2 RA-40851 aircraft was the collision of the aircraft with a reinforced concrete support and power transmission lines in a controlled flight while performing the aerial application at an extremely low altitude.
The contributing factors most likely were:
- Field processing when the sun is less than 15° above the horizon and the sun's heading angle is less than 30°,
- Insufficient prudence of the PIC when performing a VFR flight for aerial application,
- Failure of the pilot to take into account the presence of artificial obstacles in the flight area,
- Lack of marking of power lines.

The aircraft stalled during initial climb because its total weight was above the MTOW and the CofG was well beyond the aft limit. The crew failed to prepare the flight according to procedure and, failed to proceed with a mass and balance calculation and the passengers and lugages were incorrectly placed in the cabin according to the CofG.

The accident with the Boeing 737-500 VQ-BPS aircraft occurred during the landing as a result of a collision of the aircraft with a snow parapet 1.1 m high at a distance of 32 m to the runway threshold (within the paved section of the runway), which resulted in damage to the main landing gear and their subsequent "folding" in the process of moving along the runway.
The accident was caused by a combination of the following factors:
- the presence of contradictions in the Federal Aviation Rules for flights in the airspace of the Russian Federation, the airline's radio control system and the aircraft operational documentation regarding the need and procedure for introducing temperature corrections to the readings of barometric altimeters at low ambient temperatures;
- Failure by the operator of the Usinsk aerodrome to comply with the FAP-262 requirements for the maintenance of the aerodrome, which resulted in the presence of snow parapets on the paved section of the landing strip;
- the operator of the Usinsk aerodrome did not eliminate the shortcomings in the winter maintenance of the aerodrome, noted based on the results of the inspection by the Rosaviatsia commission on January 22, 2020;
- lack of risk assessment in the airline associated with the execution of approaches in the baro-VNAV mode in the presence of factors that impede such approaches (low ambient temperatures, snow-covered underlying surface, drifting snow (snowstorm), significant changes in the relief in front of the runway end, lack of PAPI-type lights), as well as appropriate recommendations to the crews on the specifics of such approaches, including after the transition to visual flight, and crew training;
- insufficient assessment by the crew during the preparation of the existing threats (hazard factors) and making an insufficiently substantiated decision to perform an RNAV (GNSS) approach (under the control of the autopilot in LNAV/VNAV mode) without introducing a correction for low outside air temperature in altitude overflying waypoints, which led to a flight below the established glide path;
- performing a flight along the "extended glide path" after turning off the autopilot and switching to manual piloting without attempting to enter the set glide path;
- the PIC may have had a visual illusion of a "high glide path" due to a snow-covered underlying surface, a snowstorm and the presence of a ravine directly in front of the runway end in the absence of PAPI type lights, which led to an incorrect assessment of the aircraft's flight altitude after switching to manual piloting, lack of reaction to timely and correct warnings of the co-pilot and exit to the runway end at a height significantly less than the established one.

The accident was caused by the fact that the PIC did not maintain a safe flight altitude in mountainous terrain, which led to the aircraft getting into strong downdrafts while flying over the leeward side of the ridge, uncontrolled descent and collision with the top of the mountain.
The contributing factors of AP, most likely, were:
- insufficient analysis of meteorological conditions and the possibility of the formation of strong ascending and descending air currents in the mountains;
- Failure of the PIC to take safety measures when flying in the mountains and to act in case of falling into downward air currents when crossing a mountain ridge;
- the use of motor gasoline with an octane rating of less than 95, which led to a decrease in engine power;
- performing a mission on the An-2 aircraft without the procedure for restoring skills and admission to flights on this type after a significant break in flights (about 15 years).

Most likely, the reason for the accident with the An-2 RA-81519 aircraft was the execution by the flight crew along the route in the mountainous terrain to the area of ​​the AHR at an altitude not ensuring its safety, which did not allow crossing the mountain pass, led to the need to perform an emergency landing and damage to the aircraft.
The contributing factors were most likely:
- Non-consideration by the crew of a significant increase of the outside air temperature during the day,
- The crew did not set the altimeter properly,
- Lack of instrument control over the flight altitude,
- Downdraft air currents on the leeward side of the mountain slope;
- Operating fatigue, leading to a weakening of attention and a decrease in level of situational awareness.