The Russian An-148 airliner, carrying out a domestic flight, crashed in the Moscow Region on February 11, 2018, killing all 71 people onboard. Investigators maintain that wrong data of flight speed, apparently due to icing, could have led to the crash. The yet unanswered crucial question is whether the pilots failed to switch on the heating unit or was it a technical issue that led to speed sensors’ malfunction.

The Saratov Airlines An-148-100B passenger plane was flying from Moscow to the city of Orsk in the Ural Mountains, Russia’s Orenburg Region, when it crashed minutes after takeoff. Radio and radar contact with the Flight 703 was lost several minutes after it took off from Domodedovo airport (DME) outside Moscow at 14:21 (local time), the Interstate Aviation Committee (IAC) performing the investigation of the crash reported.

The An-148 had apparently plummeted into a snowy field about 40 miles (64 km) southeast of the capital, near the village of Stepanovskoye in the Moscow Region’s Ramensky district. All 65 passengers and six crew members on board died in the crash. Russia’s Emergency Situations Ministry said the plane’s fuel tanks exploded on impact with ground, scattering wreckage across a wide area.

Nearly 1,500 body parts have been recovered from the crash site by February 13, 2018, and almost 5,000 pieces of debris were found since search operations started. As of February 18, 2018, the operations at the site, spanning across 50 hectares, were completed, a spokesperson for the emergency response headquarters told Sputnik. Pieces of the wreckage were transported to the Gromov Flight Reasearch Institute for examination.

Opening the Pandora’s box

On February 12, 2018, the Moscow-based IAC released an official statement saying that it had recovered onboard recorders (both FDR and CVR) from the An-148-100B RA-61704 aircraft.

After deciphering the data of the flight recorder and the preliminary analysis of the information, the Committee said a “special situation” with the An-148 plane began some 2 minutes 30 seconds after takeoff at an altitude of about 4,265 feet (1,300 meters) and speed of around 292 mph (470 km/h).

According to investigators, the flight recorders showed divergences in the data from the plane’s two airspeed sensors. These divergences reached about 18.6 mph (30 km/h), after which the one-off command for the crew appeared: “The Instrument Panel – Compare!” This command was repeated at an altitude of about 6,561 feet (2,000 meters) as the difference between the readings grew even bigger. After the second command, the crew turned off the autopilot and took manual controls.

The speed indications of the plane’s air parameter modules differed significantly from each other. One indicator showed the speed at 0 mph and the other was showing about 342 mph (550 km/h). Before the plane hit the ground, one of the sensors continued to show a speed of 0 mph while the data on the other started to fall intensively to 124 mph and lower (to 200 km/h and lower).