Why is volcanic ash a problem?

shutterstock_53309389 - image credit Shutterstock.com

From 15th -20th April 2010, most aircraft scheduled to fly in western or northern European airspace were grounded, leaving passengers and crews stranded and causing large economic losses to the airline and airport industry. There were further significant airspace restrictions in European airspace during the following weeks.

Why was this?

The Icelandic volcano Eyjafjallajökull (Eyja) erupted, ejecting ash 9 kilometres up into the atmosphere. Flying through volcanic ash can damage aircraft components. Abrasion on aircraft surfaces including cockpit windows can result in reduced visibility for pilots.  Ash ingestion and accumulation can cause engine damage, surge and/or failure and cause sensitive aircraft monitoring systems to misread.

A combination of factors resulted in the significant level of impact caused by the Eyja eruption. Whilst not being a particularly large eruption, at 39-days the ash-rich phase was relatively long lived and the ash went high enough to be spread far and wide by jet stream winds. Secondly, a persistent area of high pressure over the north-eastern Atlantic maintained a predominantly north-westerly airflow down from Iceland and into Europe and consequently into some of the busiest and most congested airspace in the world. This was important as the globally agreed practice at that time was to avoid all airspace with any level of volcanic ash contamination given the challenges associated with fully understanding the vulnerability of various aircraft components to volcanic ash exposure.

What has changed now?

The impacts on the aviation industry associated with the eruption of Eyja in April and May 2010 resulted in the development a new volcanic ash contingency plan for European and the North Atlantic airspace. The European aviation regulators’ approved plan is based on the use of supplementary volcanic ash contamination thresholds (how much ash) to inform an airline safety risk assessment approach to volcanic ash avoidance.

The Met Office hosts the London Volcanic Ash Advisory Centre (VAAC), which is one of 9 centres worldwide. The London VAAC is responsible for issuing advice to aviation for volcanic eruptions originating in Iceland and the northeast Atlantic based on the expert interpretation of eruption information sourced from the Iceland Meteorological Office, a range of observational capabilities, world-leading numerical weather prediction and atmospheric dispersion model output.

Further details can be found at http://www.metoffice.gov.uk/aviation/vaac/.

Debi Turp- Senior Applied Scientist and Claire Witham- Scientific Manager

Image credit: Shutterstock.com

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