Named the main cause of the collapse of the An-148 in the suburbs

Commission Interstate Aviation Committee (IAC) reported on the first results of deciphering the “black boxes” of the An-148 passenger plane crashed in the Moscow region.

Photo: MAC

“A preliminary analysis of the recorded information, as well as an analysis of similar cases that occurred in the past, suggest that incorrect flight speed data on pilot indicators could be a factor in the development of a particular situation in flight, which, in turn, was apparently due to icing full pressure receivers when their heating systems are off, ”the message says on the agency’s website.

According to the committee, during the entire flight, the heating of all three full-pressure receivers (devices that collect data on the air pressure acting on the aircraft during the flight) was off.

The particular situation, according to the investigation, began to develop in the plane after about 2 and a half minutes after takeoff. At that moment, the plane was at an altitude of about 1300 m and was moving at a speed of 465 – 470 km / h.

Then the liner systems recorded discrepancies in the speed readings from the air parameters module of the first total pressure receiver and a similar backup device.

At this moment, a one-time message to the crew appeared: “Dashboard - COMPARE”, it was repeated again in 50 seconds.

“After the second appearance of the specified one-time command (message), the crew turned off the autopilot. The entire further flight took place in manual mode. The speed readings from MVP1 continued to fall and 34 seconds after the autopilot was turned off they became equal to 0. At the same time, the speed readings from MVP3 were 540-560 km/h. For approximately 50 seconds after the autopilot was turned off, the flight took place at an altitude of 1700-1900 m with changes in vertical load ranging from 1,5 to 0,5 g. After this, while maintaining the speed values ​​from MVP1 at 0 km/h, the speed values ​​from MVP3 began to fall rapidly (to 200 km/h and below). Subsequently, the aircraft was transferred to an intensive descent with dive pitch angles of 30-35 degrees and a vertical overload of up to 0 g. The collision occurred around 11:27:05. Before the collision with the ground, the speed readings from MVP3 began to increase rapidly and by the time of the collision they were about 800 km/h. The speed readings from MVP1 continued to be equal to 0,” the IAC said in a statement.

“Loss of speed information” was the root cause of the emergency, the committee believes. The investigation is ongoing.

Photo: MAC

According to RBCThis is not the first An-148 disaster caused by a similar cause.

Exactly the same plane crashed in the Belgorod region in 2011 due to “loss of speed information.” But then the air pressure sensors failed not because of icing, but because of design problems, which were subsequently supposed to be eliminated on all similar boards.

Another similar crash occurred with Airbus A330 over the Atlantic Ocean in the year 2009, then the aircraft’s sensor icing also occurred.

In this case, the icing of the speed sensors is not associated with anti-icing treatment, which is carried out with the board before departure.

“It is needed not to maintain the functionality of the air pressure receivers, but to ensure that the surface of the wing is clean. The remaining ice is washed off with a special liquid, and for about thirty minutes after departure, this liquid ensures that no new ice will grow. This has nothing to do with the speed readings,” explained Honored Test Pilot Vladimir Biryukov.

According to sources, before taking off, the pilot An-148 refused this treatment.

For normal operation of the sensors, it is necessary to carry out their heating, which for some reason was turned off at An-148.

In the situation of discrepancies in the indices of the sensors, the board could still save the competent actions of the crew, said honored pilot of Russia Yuri Sytnik.

According to him, the plane has a system of air signals (CBC), which collects data from pressure receivers, makes conclusions about speed, altitude and other parameters, and then transmits the information to the computer that controls the autopilot.

“This is very important information. If the pilot does not turn on the heat and the sensors freeze, the signals may be incorrect. The autopilot can make incorrect decisions to control the aircraft,” Sytnik explained.

At the same time, he clarified that “this situation is difficult, but not an emergency.” The flight most likely would have continued normally if the pilots had been able to turn on the heating of the full pressure receiver.

“This is the very beginning of the development of an emergency situation, and if it is not followed by incorrect actions, then people can be saved,” Sytnik added.

In addition to the main system of signals, there is a backup, explained the honored pilot.

“If a discrepancy occurs, an error message is sent to the autopilot and to the instrument readings. The alarm goes off immediately - “Check your speed!” The yellow signal is on. This means the pilot must look at the backup instruments, disable the autopilot and report to the controller that he has lost readings. But it’s scary to report - you can get a scolding if you made a mistake and forgot to turn on the heating,” Sytnik said.

The sensor heating system could simply have failed, suggested pilot 1st class Andrei Litvinov: “There is a small hole there for heating, and it could have become clogged. But in this case there are clear instructions on how to pilot. We need to figure out why they weren’t implemented.”

The pilot may not have had time to understand that the data from the speed sensors did not correspond to reality, Litvinov believes: “He could have moved the steering wheel away from himself in order to increase the speed. And the speed readings were underestimated. As a result, the plane began to lose altitude at high speed.”

Recall, the plane "Saratov Airlines", performing a flight from Moscow to Orsk, disappeared from radar through 7 minutes after departure from Domodedovo 11 February. The plane crashed near the village of Argunovo in the Ramenskoye district of the Moscow region, all the people on board - 71 people - died.

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