The crew began to “press” the board to the ground – this maneuver and became the cause of the disaster, experts say.
Fifteen minutes after departure from Sheremetyevo, the SU-1492, heading for Murmansk, hit a thunderstorm on board Aeroflot, Kommersant reports, citing a source close to the investigation. According to experts, the current situation was not dangerous for the passengers and crew, but the pilots made it critical. Now, the investigation should establish exactly who committed the dangerous actions before landing.
- Lightning hit the nose of the aircraft, leaving on the surface “characteristic smoky mark.” Thunderstorm protection of the SSJ 100 reacted to the lightning strike and turned off the aircraft’s generators, transferred the power supply of consumers to batteries (EEC mode), experts say;
- Due to the transition to emergency power supply, Direct Flight Control mode was activated (Direct Mode) – the on-board computer stopped correcting possible pilot errors and insuring the board against exit to extreme angles of heel, increase in instrumental speed and overloads, as well as the danger of stalling;
- An abnormal situation occurred on board. In the flight manual and methodological recommendations, the EEC mode is called emergency, but not emergency. When it is turned on, the manufacturer does not require an immediate landing, but recommends that the pilots hurry;
- According to the manufacturer, in this mode, the aircraft can be in the air “enough time” to land or go to the second round to re-enter. It also does not require a May Day distress signal – pilots only need to give a Pan Pan signal, which means that there is no danger to the life and health of people on board. The signal for the nomination of emergency services to the runway is May Day – the crew of the Superjet did not serve it, so firefighters did not meet it on the runway;
- The Direct Mode is considered to be almost regular – you can continue to fly or land in it, eliminating sharp maneuvers, accelerating to speeds above 520 kilometers per hour, and also disabling the thrust machine. In such a situation, the manufacturer recommended landing smoothly, with a vertical speed at the moment of contact, no more than 1.8 meters per second, in order to prevent damage to the landing gear;
- SSJ 100 pilots Denis Evdokimov and Maxim Kuznetsov succeeded in the second attempt to make an approach in compliance with all requirements, but they had to control the aircraft manually with the autopilot turned off and the traction machine;
- Presumably, because of this, they flew over the estimated landing point at the beginning of the runway – in the middle of the runway the plane had not yet touched it with wheels, and the crew began to “press” the board to the ground. Before landing, the pilots dramatically increased the engine’s operating mode and simultaneously lowered the nose of the aircraft. This maneuver was the cause of the disaster, experts say;
- The SSJ 100 sat down with significantly overestimated instrument and vertical speeds and landed “three points”. The collapsed front landing gear tossed it up and provided a series of even more powerful bounce off the runway. The second impact created a dynamic overload for the aircraft at about 5G, while the load of 3.75G is the limit for an aircraft of this type. The wings remained intact, but the rear landing gear pushed through the fuel tanks, which resulted in kerosene and a fire occurred. Regulatory documents on SSJ instruct pilots to stop the landing after the first rebound and begin an emergency takeoff.