MOST US REGIONAL-airline operators of turboprop-powered aircraft will face minor operational restrictions rather than costly modifications, according to the finalised Federal Aviation Administration rules about flight in icing conditions (Flight International, 7-13 February). Major anti-icing system design changes like those demanded for the ATR 42 have not been required.
The new airworthiness directives (ADs) require pilots to leave icing conditions quickly. They are also designed to help crew recognise hazardous icing conditions.
The 18 ADs affect 29 different aircraft models with unpowered controls and pneumatic deicing boots. They require aircraft operating manuals to provide pilots with instructions for operating in freezing rain and drizzle; give them cues to identify such conditions; and, offer instructions on how to leave.
The ADs result from the probe of the American Eagle ATR 72 crash at Roselawn, Indiana, on 31 October 1994 which took 68 lives. US operators of ATR 42s and 72s were required to install larger de-icing boots to counter unusually large water droplets not covered by any certification requirement.