Wake vortex modelling and early airborne trials of the Airbus A380 show that it has a significantly heavier wake signature than any other airliner, says the International Civil Aviation Organisation. This will have repercussions for its operations at airports, in terminal areas and during en-route flying, ICAO’s initial guidance reveals.
Since 2003 Airbus has been working with wake turbulence experts at the US Federal Aviation Administration, the European Joint Aviation Authorities and Eurocontrol on predicted results for the A380. They had been using well-tried computer modelling, but now early airborne tests appear to validate forecasts of significantly more turbulence than is produced by the Boeing 747, says ICAO.
Since the A380, still undergoing its certification test programme, is beginning to be dispatched to airports from which it will operate, ICAO has produced the initial guidance to advise air traffic controllers on how much spacing they must apply for aircraft taking off, landing, or flying en route behind the new giant.
Final trial results “will be ready in early 2006”, predicts ICAO, and it expects to issue formal guidance in mid-2006. But at this stage the trials being carried out at Toulouse and Istres airports in France have led ICAO to advise considerably greater separation than for existing types. ICAO says spacing should be 10nm (18.5km) on approach and 15nm for all other phases of flight including en-route. It rules that 1min additional delay should elapse before smaller aircraft take off behind an A380.
A characteristic of A380 wake vortices, reveals ICAO, is that “they may descend 2,000ft [600m] and possibly pose a passenger comfort issue rather than a hazard” for following aircraft two flight levels (2,000ft/300m) below it.
“There are indications from the initial analysis of data that wake vortices from an A380 may be encountered by aircraft flying 1,000ft below at greater strengths than from current aircraft of the heavy wake turbulence category,” the organisation says.
“Because it has not yet been possible to establish the level of hazard associated with these wake vortices, offset tracks or additional vertical spacing is advised until the final vertical spacing guidance has been established,” it adds.
Airbus has confirmed the ICAO details, but emphasises more is known about wake vortex characteristics for the A380 than for any other new type before its service entry.
Airbus adds: “Once [the wake vortex characteristics] are fully understood by the authorities, it will become clear what the appropriate separation should be...remember that in the beginning the separation for the 747 was higher than it is today.”
DAVID LEARMOUNT/LONDON
Source: Flight International
