UK revises wake spacing for heavy departures

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UK authorities are to impose a wake-separation requirement between departing 'heavy' aircraft, but intend to remove a similar separation requirement which currently applies to pairs of arriving Airbus A380s.

While ICAO standardises a 4nm (7.4km) wake separation between two departing aircraft in the 'heavy' category, the UK's air traffic control procedures do not specify any figure.

The Civil Aviation Authority says there has been no "supporting analysis" to back up the use of the ICAO criteria.

But an assessment of incident data, it says, shows a "disproportionate" number of wake-turbulence encounters during heavy-heavy take-off sequencing, and it has chosen to adopt the 4nm departure standard from 20 February next year.

Higher numbers of 'heavy' category aircraft combined with greater take-off weights have prompted the CAA to take the new measures.

"The current absence of any UK wake turbulence criteria between heavy-heavy departures results in an unmitigated potential for wake turbulence encounters at low altitudes and critical stages of flight," it states.

This should be "corrected", it adds, and is encouraging early introduction of the new procedures.

But the CAA is also remaining flexible by allowing an alternative means of compliance, if supported by sufficient safety assurance, allowing an "appropriate blend of prescriptive and risk-based safety regulation".

Its own specific minimum separation of 4nm for in-trail A380s, however, will be rescinded in favour of the ICAO standard which states that no wake spacing needs to be applied between pairs of A380s on approach.

This approach minimum was established by the CAA in 2006, a year before the A380 entered service, despite analysis from a wake-vortex steering group which concluded that it was unnecessary.