THE US FEDERAL Aviation Administration (FAA) has approved the use of larger de-icing-boots on the ATR 42 and 72 regional turboprops. The modification, developed and tested by the Aerospatiale/Alenia consortium, is aimed at preventing the formation of an ice ridge on the wing by nearly doubling the effective coverage of the boots.

The FAA says that installation of the modified de-icing boots on ATR types operating in the USA must be completed by 1 June. About 174 aircraft are effected.

The modification results from the fatal crash of an ATR 72 near Chicago in October 1994. Accident investigators concluded that an abnormal icing condition not covered by any certification requirement could have occurred.

Following the accident, the FAA banned flights in known icing conditions. It later lifted the prohibition, but set strict rules about the use of flaps. The restrictions remain in place until the aircraft modification is completed. ATR successfully tested the enhanced wing de-icing-boot at Edwards AFB, California, on 6-7 March.

A new airworthiness directive will soon be issued covering new operational and flight crew procedures, which are to be used in conjunction with the larger de-icing-boot.

The FAA, meanwhile, is to broaden its de-icing inquiry to other aircraft. The FAA says that it wants to know whether they also could suffer from aileron-induced roll conditions under severe icing conditions. The investigation could extend beyond turboprops. "We are still discussing whether to limit it to turboprops or define other criteria to define the population that will be reviewed," says the FAA.

Source: Flight International