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CAA “doubles the safe operating threshold of ash acceptable by engines”

Published: 17/05/2010 - Filed under: News »

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The CAA has issued new regulations enabling airlines to operate in areas with double the density of ash than before. The new “Time Limited Zone” (TLZ) is available to airlines presenting “a safety case that includes the agreement of their aircraft and engine manufacturers”, with Flybe the first carrier to qualify.

In a statement released by the CAA today (May 17) the authority said:

“The UK Civil Aviation Authority (CAA) today reports a positive outcome from discussions with airlines, regulators, and aircraft and engine manufacturers resulting in new measures to reduce airspace closures caused by volcanic ash that may be implemented from midday tomorrow.

“A new area of operations can now be introduced that creates a ‘Time Limited Zone (TLZ)’ between the black ‘No Fly Zone (NFZ)’ and the red ‘Enhanced Procedures Zone (EPZ)’. Aircraft and engine manufacturers, based on new research and analysis, have agreed that it is safe to allow operations in the new zone for a limited time at higher ash densities than is currently permitted.

“To operate in the new zone airlines need to present the CAA with a safety case that includes the agreement of their aircraft and engine manufacturers. UK airline Flybe is the first to achieve this and will therefore be able to use the new zone from midday tomorrow.

“This means that areas of our airspace that would have previously been closed can safely open, further minimising flight disruption.”

The statement adds that the new TLZ allows limited flights through ash levels of up to 4x10-3 grammes, double the the previous limit set by manufacturers of 2x10-3 grammes per cubic metre of air.

The CAA said that the introduction of the Time Limited Zone is based on measurements collected from test flights through the current ash cloud over the past month, as well as on data and evidence compiled and analysed from previous volcanic ash incidents combined with additional analysis from manufacturers.

Operations in the newly established Time Limited Zone may be subject to time limits and increased maintenance practices. The new Zone’s area will be established using Met Office forecasts, and will be approved by the CAA before operations are allowed within it.

Announcing the change Andrew Haines, Civil Aviation Authority Chief Executive, said:

“I’m pleased that the huge efforts we’re all making across aviation to keep flying safe whilst minimising the disruption from the volcano have resulted in further progress. Unprecedented situations require new measures and the challenge faced should not be underestimated. 

"Firstly because the standard default procedure for aircraft that encounter ash, to avoid it completely, doesn't work in our congested airspace. Secondly, the world’s top scientists tell us that we must not simply assume the effects of this volcano will be the same as others elsewhere. Its proximity to the UK, the length of time it is continuously erupting and the weather patterns are all exceptional features.

"The answer can only come, therefore, from aircraft and engine manufacturers establishing what level of ash their products can safely tolerate.  At an international aviation conference we held last Thursday, attended by all the leading airline operators this approach was welcomed and supported.  The manufacturers are co-operating fully and urgently in this task and the new zone is an excellent example of how the industry should be working to move the issue forward and I commend Flybe for its work.

"It's the CAA's job to ensure the public is kept safe by ensuring safety decisions are based on scientific and engineering evidence; we will not listen to those who effectively say 'let's suck it and see."

For more information visit caa.co.uk.

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