Air accident involving the Antonov An-24 LZ-ANA of the Balkan Bulgarian Airlines

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Air accident involving the Antonov An-24 LZ-ANA of the Balkan Bulgarian Airlines
Burgas Antonov An-24 LZ-ANF.jpg

Cockpit section of an identical aircraft of Balkan Bulgarian Airlines
Accident summary
Accident type Stall at takeoff, fall into river (icing)
place River Iskar at Sofia airport , BulgariaBulgaria 1971Bulgaria 
date November 22, 1975
Fatalities 3
Survivors 42
Aircraft
Aircraft type Soviet UnionSoviet Union Antonov An-24B
operator Bulgaria 1971Bulgaria Balkan Bulgarian Airlines
Mark Bulgaria 1971Bulgaria LZ-ANA
Departure airport Sofia Airport , BulgariaBulgaria 1971Bulgaria 
Destination airport Varna Airport , Bulgaria
Bulgaria 1971Bulgaria 
Passengers 42
crew 3
Lists of aviation accidents

The flight accident of the Antonov An-24 LZ-ANA of Balkan Bulgarian Airlines occurred on November 2, 1975 on a domestic scheduled flight of Balkan Bulgarian Airlines from Sofia to Varna . A set with 42 passengers and three crew members Antonov An-24B fell on that day when you start in winter conditions in a stall and plunged into the river Iskar . 42 inmates survived in the accident, but the first officer and two passengers were killed.

plane

The aircraft was an Antonov An-24B built in 1966 with the factory number 67302708 . The twin-engined short-range - passenger aircraft was equipped with two turbo-prop of the type Iwtschenko AI-24 equipped with a power of 1,877 kW (2,552 hp).

Passengers and crew

42 passengers started the flight from Sofia to Varna. There was a crew of three on board the machine.

the accident

There was heavy snowfall at Sofia Airport in Bulgaria as the Antonov An-24 was being prepared for the evening flight to Varna. The machine was de-iced and rolled to the starting point of runway 10. The runway was still closed for some time, however, as snow clearing vehicles had been deployed along the runway for winter service .

After the runway had been cleared, the crew was given take-off clearance. The An-24 failed to gain altitude after takeoff and fell into a ditch in the Iskar River about two minutes after takeoff, 990 meters southeast of the runway . No fire broke out. The first officer was killed and two passengers drowned in the water. 18 passengers were injured, four of them seriously. Rescuing the passengers took 40 minutes.

causes

During the investigation, the Commission found a number of infringements. After its last landing at Sofia Airport, no protective plugs were attached to the designated places. They protect the engines from the ingress of water. The aircraft was treated with a mixture of water and de-icing fluid. However, this happened with the Bulgarian mixture "Ledogon" instead of the English "Kilfrost" or the Soviet "Arctic". In addition, the product was incorrectly diluted that day by the service personnel. As a result, the aircraft was sprayed with 75% water and only 25% Ledogon. The hold-up time for de-icing had expired during the snow clearing work; a new de-icing of the wings, which had meanwhile become again contaminated by snow and ice, was not carried out. The crash occurred because the contamination by ice crystals affected the aerodynamic properties, which resulted in stalling at takeoff.

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