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By Andrew Haines, chief executive of the Civil Aviation Authority - 8th July 2010
The CAA’s sole aim in this is minimise disruption without compromising passenger safety should our airspace be contaminated by ash again.
Andrew Haines
Andrew Haines, chief executive of the Civil Aviation Authority, writes for ePolitix ahead of Tuesday’s briefing for MPs on volcanic ash disruption.
Icelandic volcanic ash has been deposited in the UK at least ten times over the last 1000 years; the last occasion being in 1947. In geological terms, the gap between 1947 and 2010 is an instant, but in that time UK civil aviation grew from carrying one million people a year to over 218m. The possibility of volcanic ash reducing the numbers of flights in UK airspace to zero for six days was similarly unprecedented until earlier this year, and it took a unique combination of events to bring it about.
First, the Icelandic volcano, Eyjafjallajökull, is a glacial volcano which meant that its eruption led to enormous volumes of fine particles of ash at high levels in the atmosphere. Secondly, due to atypical weather conditions, that ash was pushed towards the UK and then did not disperse naturally but sat in some of the busiest airspace in the world for several days.
The longstanding worldwide guidance to operators is to stay well clear of ash – “regardless of concentration, AVOID, AVOID, AVOID”. This approach was developed after serious safety incidents, for example total engine failure when a BA aircraft flew through ash in Indonesia. It was the combination of this guidance, and heavy air traffic demand on UK airspace that led UK air traffic control provider NATS to withdraw its services and effectively close airspace when it became contaminated with ash.
The problems facing European aviation were real - the standard response to avoid ash by flying around it was not possible in congested European airspace. The obvious answer was to let aircraft fly through ash at agreed, safe levels, but engine manufacturers had set engine tolerance to ash at zero. In addition, there was real uncertainty around the precise volume of ash being emitted by the volcano and hence not even the best model of its type in the world could readily and accurately predict not just where ash might be found but, importantly the density of ash that might be encountered in any given area.
In the face of such uncertainty, regulators were faced with a decision on whether to set an arbitrary new standard or seek objective evidence. Our challenge at the CAA was to work, on behalf of the international aviation community, with engine manufacturers in particular, to define a safe threshold and ensure that the modelling and validation was of a sufficiently high standard to allow aircraft to operate with certainty at that new threshold. All of this took place over five days from April 15th, and flights were able to resume on the evening of April 20th, within hours of the manufacturers providing assurance of revised parameters for safe flying.
This work is on going in the knowledge that the recent ceasation of activity from Eyjafjallajökull does not mean that the threat has gone away for ever. Work continues, aimed at minimising disruption to the travelling public through the development of enhancements to modelling capability, further analysis of airworthiness conditions to refine the assessment of the safe threshold of ash tolerance, and operational and other measures to allow more flexibility around where aircraft can operate when some ash is present, and how those zones are set and monitored in a consistent fashion throughout Europe.
Many of the improvements must come from industry and the CAA will continue to facilitate progress with airlines, engine manufacturers and with our colleagues at NATS, the Met Office, and the Department for Transport. The UK cannot act unilaterally in an international environment such as this and we will continue to feed our progress back to our partners in Europe and the International Civil Aviation Organisation. The CAA’s sole aim in this is minimise disruption without compromising passenger safety should our airspace be contaminated by ash again.
The Civil Aviation Authority, British Geological Survey, the Met Office and NATS are holding a briefing for MPs and Peers on 13 July at 11.30 - 12.30 in Committee Room 19.
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