Episode 36 - The 1971 Aeroflot Antonov twin crashes and the ATR-72’s achilles boot

This is episode 36 and its icy cold out there - it’s time to check out the incidents involving icing - starting with a short list and general description of the causes, then focusing on the two Aeroflot Atonovs accidents in 1971 and a design fault in the ATR-72. There’s an unfortunately long list of commercial airliners lost due to icing, more than 540 accidents and events caused by aircraft icing by the late 1980s in the United States alone and most of these were fatal. Anti-icing and de-icing research can be traced back to the early 1930s and in 1948, two scientists, AG Preston and Calvin Blackman conducted the first successful iced flight experiment in which the drag coefficient increased by 81% when the wing was covered and the pilot reported the plane was almost beyond control. I’m not sure of what aircraft they used but the results were extraordinary. Other research by NASA on the DHC-6 Twin Otter aircraft measured various conditions and ice shapes and their effect on aircraft thrust, landing flaps, and angle of attack. It’s thought that the first recorded case of a commercial airplane accident caused by icing occurred on December 15, 1920 when a de Havilland DH.4 mail plane operated by the United States Post Office Department crashed near Belleville, Pennsylvania, in the USA due to ice accumulation on the wings and control surfaces.There was a happier end to another on 19th December 1946 where a Railway Air Service Douglas Dakota 3 stalled on take-off 1 km north-east of Northolt Airport in London. This was the case of the scheduled service to Glasgow Airport from London. Four crew and one passenger were on board .. Yes, you heard correctly, one passenger.So to matters more terminal if you excuse the extremely cheesy aviation pun. That be the highly unusual twin crashes of the Antonovs in 1971 both caused by ice accretion. ot Antonov An-12s crashed on approach to Surgut International Airport, just nine days apart. The crashes occurred under near-identical circumstances due to the aircraft type’s lack of preparedness for flying in severe icing conditions. It’s the formation of an ice ridge by water droplets beyond the ice protection system and one side anti-icing system that is likely to cause rolling and overturn according to research documents. A case in point of the ridge cause was an ATR-72 crash in 1994. At that time, the airplane was at a severe level of icing condition, and the co-effect of the electric heating de-icing system at the wing leading edge and the natural conditions formed an ice ridge on the second half of the wing, resulting in a negative pressure zone on the one side's aileron.