Sir - The dispute between the US and French investigation authorities over the background to the Roselawn ATR 72 accident (Flight International, 17-23 July, P6) centres on the transfer of safety information between authorities, manufacturers, airlines and aircrew.
If the US National Transportation Safety Board's view is justified, it will not be the first icing accident in which this has been a major factor.
Following a crash in the late 1950s, I believe, it was discovered that, in some circumstances, the Vickers Viscount's tail de-icing was not fully effective and that ice remaining on the tailplane leading edge could cause it to stall in the high downwash generated by the flaps in the landing position.
Procedures were changed and, if there was any likelihood of residual ice, a lower flap angle was used for landing. At least, one crew was subsequently caught out, by unsuspected icing, but, recognising this "well-known" problem, was able to reduce flap rapidly and recover from the sudden nose-down pitch.
As aircraft were sold on to second- and third-level operators, however, it seems that this knowledge did not always travel with them and, in January 1977, a Viscount approaching Stockholm-Bromma in Sweden crashed because of tailplane stall which had been caused by icing.
In reviewing procedures for the dissemination of safety information across the world, we must not forget that it has to spread through time as well.
PATRICK HASSELL
Bristol, UK
Source: Flight International
