New relaxation on ash flight safety allows underflying

New relaxation on ash flight safety allows underflying

Volcanic eruptions and ash clouds should cause proportionally fewer flight cancellations in future following a further change in safety policy by the Civil Aviation Authority (CAA).

A CAA safety notice issued yesterday notified carriers, air traffic services and airports that aircraft may now fly below identified zones of volcanic ash, or Temporary Danger Areas (TDAs).

The relaxation applies with immediate effect.

The CAA also issued a verbal slap to airlines, such as Ryanair, which have suggested this week that airspace has been closed. It said: “A Volcanic Ash TDA does not imply airspace is closed and such terminology should not be used.”

Changes to the rules after last year’s ash crisis mean airlines may now fly through low concentrations of ash, and may be allowed to fly through medium and high densities if the CAA accepts a safety case, submitted jointly with engine and airframe manufacturers.

Airlines were already able to fly over the top of an ash cloud and the CAA confirmed this week that all UK carriers had been cleared to fly through medium densities of ash, but none at high level densities.

The CAA’s notice yesterday acknowledged: “Volcanic Ash TDAs have previously extended from surface level to the upper limit of the modelled areas of high ash concentration . . . as a result of insufficient assurance for the accuracy of the vertical modelling . . . there has not previously been the ability for operations beneath areas of high ash concentration.”

From now on, safety notices on ash TDAs will include the upper and lower vertical extent of high concentrations, possible “due to improvements made by the Met Office to the dispersion model that predicts the movement of volcanic ash in the atmosphere”.

However, the change is likely to cause delays as air space becomes congested in areas open for flying.

The CAA warns of aircraft being required to take holding patterns en-route, of re-routing and potential restrictions on speed. It also points out aircraft will use more fuel and be more subject to the weather.

Aircraft will not be allowed to operate between layers of volcanic ash.

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