Originally Posted by
Ignition Override
The aircraft which suffered from aileron 'snatch' in some icing conditions was just one. Look up the political expression "plausible denial". When the reports are locked away in a 'Schublade' and nobody else is aware....dead bodies and fragmented aircraft parts in the frozen ground near Roselawn, Indiana. Any agency or government can have the motivation to cover something up, not just the French.
IO - I agree that the French authorities do not have a very good track record of facing up to the facts when these
might just turn out to be embarassing - call it misplaced national pride if you will.
However, you have it seriously wrong when you mention the Roselawn ATR 72 accident in the same breath. In that case, (and while the French DGAC certainly didn't shine by its cooperation with the NTSB investigation), there were a number of factors which conspired to cause that accident;
1/ The aircraft was flown in freezing drizzle (a heavy icing condition for which it had not been certificated) at the wrong IAS, with the wrong flap setting
2/ It was flown in the hold in these conditions (when the crew should have elected to leave heavy icing asap)
3/ They apparently had not Level 3 anti-icing ON throughout
As part of the accident investigation, ATR sent one of their own aircraft (before its delivery to Alitalia Express) to Edwards AFB, where it was flown by a test crew behind a KC-135 spreading water over the ATR 72's airframe in icing conditions to reproduce those experienced by the ill-fated Roselawn aircraft. While ice
did accumulate on some parts, it was mostly shed by the anti-icing when used properly, and the test aircraft did not experience any serious control difficulties or depart from controlled flight. These tests, may I add, were requested, conducted, validated and published by the FAA.
The source of the Roselawn crash was traced to a ridge of ice forming in frizzing drizzle (a known freak icing phenomenon) behind the de-icing boots, therefore disrupting the airflow over the ailerons. While not specifically requested by the FAA, ATR decided to extend the de-icing boots over a larger part of the wing chord to prevent re-occurence.
All current operators of ATRs have very strict and specific anti-icing procedures which when correctly adhered to, make the ATR no less safe in icing conditions than any other turboprop aircraft (Dash 8, Fokker 50, Saab 2000, Casa 235/295, Do-328, etc).
If it really was unsafe in icing conditions, would ATRs be routinely used by airlines in, say, Alaska, Canada, Norway, Sweden, Finland, Denmark, Germany, Switzerland, Italy or New Zealand to name but a few?
Cheers
