Aircraft

Research will probably prove closer approaches possible

Airbus A380 wake turbulence in-trail separation criteria may be reduced later this year from the distances published in the safety case study late in 2006, it emerged at Eurocontrol's international WakeNet conference in Brussels, Belgium last week. Meanwhile, existing separation standards between in-service aircraft are to be reviewed.

The 180 flying-hour A380 wake vortex behaviour flight- test programme, monitored by the European Joint Aviation Authorities, the US Federal Aviation Administration and Eurocontrol, ensured that the aircraft will enter commercial service with a scientifically determined wake separation classification known as "super-heavy". FAA wake turbulence programme manager Steve Lang says it was the first time such tests had been done, but that all new aircraft will go through a similar process from now on.

At present, the separation standards are published as minimum distances between the A380 and those following it, but the JAA says these are "subject to review and possible reduction based on further study or changes in aircraft categories or operational experience".

For the A380, the agreed separation standards - set by the International Civil Aviation Organisation at a flat rate of 10nm (18.5km) before the trials - are now 6nm for a heavy aircraft following the A380, 8nm for a medium weight aircraft, and 10nm for a light aircraft. These figures are respectively 2nm, 3nm and 4nm greater than current standards for each of the categories following an in-service widebody.

According to Airbus, on approach the A380 flap-tip vortices, which merge with those from the wingtips, are the main source of turbulence. En-route in-trail wake separations for the A380 are similar to those for the A340-600 and the Boeing 747-400, says Airbus.

As for the A380 following a 747 on approach, the trials found that the A380 does not need any additional separation and its controls can deal with the most malign 747 wake encounter, "in some cases with capacity to spare".