THE US FEDERAL Aviation Administration's imposition on 16 August of new wake-vortex approach-separations will create delays claim busy airports. Los Angeles International Airport, California, potentially the worst affected, claims that delays could go up by 72%.

The official Wake Turbulence Government/Industry Team, set up to take part in forming the policy, has complained that it was excluded from the late stages of decision making, and has called for implementation of the rules to be rescinded. Increased separation is required for aircraft following the Boeing 757 - notorious among narrow-bodies for its wake-vortex power - and the FAA has reclassified some 57 types into the "small-aircraft" category.

The reclassification affects some 900 regional airliners in the USA, says Regional Airlines Association president Walter Coleman. The three categories - small, large, and heavy - have been adjusted so that "small" means a maximum take-off weight of less than 18,614kg, raised from 5,675kg The new "small" classification now includes the Embraer 120 Brasilia, Beech 1900 and Aero International (Regional) Jetstream 31 and 41.

The "large" range now starts at 18,615kg, and the minimum weight for the "heavy" classification has been reduced by about 20,000kg to 115,770kg, elevating two aircraft - the Boeing 707 and McDonnell Douglas DC-8 - into to the heavyweight category.

The minimum approach separation for small aircraft travelling behind a 757 has now been increased from 7.4km (4nm) to just over 9km; and behind a "heavy" aircraft, separation must be 11km.

Even a "large" type may not follow a 757 closer than 7.4km. "Large" types may not get closer than 9.3km behind "heavies", and heavies have to trail, one of their own category by 7.4km.

In 1994, the FAA set a temporary minimum separation of 7.4km for aircraft trailing the 757, pending results of research on 757 wake vortices. There had been five incidents since late 1992 in which landing aircraft hit 757 wake vortices, of which three were fatal.

Source: Flight International