While the recent Icelandic volcanic eruption did not impact air travel, Gavin Dixon, from our Prestwick Centre, discusses why some do…

When the call came through on 20 March to inform us that there had been a volcanic eruption near Iceland’s capital city, we were well prepared. Volcanic eruptions happen far more often than you may think, and by now you could say we are quite used to dealing with them; …. especially thanks to the well-developed ATC policies, procedures and checklists we have at our disposal.

Despite what some people think, volcanic activity doesn’t always mean that there will be widespread impact on aviation. In fact, it’s the accompanying ash cloud, the location/density of that cloud, and the wind that determine the impact, rather than the actual eruption itself.

So, what does happen in the aviation industry when a volcano erupts and just how much disruption can its subsequent ash cloud cause?


How do we find out about a volcanic eruption?

The first indication we get in the ops room of potential volcanic activity is usually a phone call from an air traffic control supervisor in Reykjavik (dependent on the activity being in Iceland of course!). Often, this phone call is shortly followed by a NOTAM.

A NOTAM (or ‘Notice to Airmen’) is a notice filed with an aviation authority to alert pilots to potential hazards along a flight route, or at a location that could affect the safety of that flight. Soon after a NOTAM is filed, we receive further regular information in the form of contamination charts, volcanic ash advisories, and weather reports.


Why is ash bad for aircraft?

At this point, you’re probably wondering why volcanic ash causes such trouble within the aviation industry? It’s because in the past, when volcanic ash has been ejected into the atmosphere, it has been known to cause damaging effects on aircraft.

Quite simply, ash particles can be abrasive and can damage forward facing parts of an aircraft such as the windscreen, fuselage surfaces and compressor fan blades. Ash contamination can also lead to the failure of critical navigational and operational instruments and when it is sucked into the engine, it can melt and re-solidify, which can lead to a loss of thrust power.


How do we plan during a volcanic eruption?

When an eruption occurs, we are sent regular volcanic ash graphs and advisories by the London Volcanic Ash Advisory Centre which contain helpful forecast information which takes into account the impact that the jet stream may have on transferring ash around the globe. The jet stream is a core of strong winds around 5 to 7 miles above the Earth’s surface, which blows from West to East. Sometimes, like in a fast-moving river, the jet stream’s movement is very straight and smooth, however its movement can also buckle and loop, like a river’s meander.

These winds can have a huge impact on how far even a small ash cloud could spread and the disruption it may cause – so you can understand why it is so important to know how the jet stream is behaving when an incident like this occurs.

Each volcanic ash graph and volcanic ash advisory contains six-hourly level banded forecasts for different flight levels over the following 18 hours so we can assess what the impact may be for the different levels of our airspace throughout the day.

These volcanic reports are received in the Civil Aviation Communications Centre and are automatically forwarded to airports as well as to our various Ops rooms between Swanwick and Prestwick, including the military and our Airspace Capacity Management (ACM) team. On top of these reports, the MET Office also issues a corresponding significant weather report (SIGMET) which, in addition to advising pilots where the latest Ash Concentrations exist, can be converted pictorially and provide ATC with a better understanding of the impact.

Being able to foresee where an ash cloud may reach is really important for the ACM team as it helps them to plan ahead and ensure there is as minimal disruption to traffic in our sectors as possible.

During any volcanic ash event, pilot-observed volcanic ash encounters outside the forecast areas are also reported to air traffic control for onward declaration to ensure the most up to date information is made available to the wider aviation community and operation.


What happens when it is a significant volcanic eruption?

In the rare event of a large volcanic eruption with a subsequent ash cloud (like Iceland’s Eyjafjallajökull in 2010), the National Airspace Crisis Management Executive (NACME), which is chaired by the CAA, may be activated. This body is called together whenever a major air traffic management incident is anticipated or declared, and it is the responsibility of the CAA’s Safety and Airspace Regulation Group to notify all NACME members. This includes representatives from NATS, the Ministry of Defence, the Military Aviation Authority and the Department of Transport. The group was initially formed to manage crises in airspace, for instance the airspace implications of a major interruption to Air Traffic Control, and was put to the test with the eruption of Eyjafjallajökull.

The ash cloud from Eyjafjallajökull in 2010

If the volcanic event is indeed significant, ISAVIA may establish a temporary danger area (TDA) around the centre of the activity, up to 120 nautical miles in area. For safety reasons, this means that, from the time the TDA is established, aircraft will be unable fly within this area and may require diversion/reroute to avoid it.


What part does ATC play during an eruption?

While ISAVIA can employ a temporary danger area, and ATC will co-ordinate aircraft around it, it remains the responsibility of jet engine manufacturers, the aircraft operator, and their country of registry, to determine the tolerable level of ash concentration that an aircraft can fly through.

Outside of any temporary danger area, it is down to the airline and pilot to make a decision as to whether they need to make changes to their planned route. This means that, from an air traffic control perspective, we can’t tell an aircraft whether it should or shouldn’t fly its planned route. Instead, controllers have a responsibility to inform pilots of the presence of a high volcanic ash concentration before a flight enters or operates in such an area. Controllers also need to make pilots aware that unusual, non-standard manoeuvres may occur (such as 180 degree turns, descents) for flights operating within or in proximity to such areas.

From an Operations Supervisor perspective, we have several checklists providing guidance to follow when a volcanic situation arises. This guidance is broken down into phases of eruption – pre-eruption, start of eruption and ongoing eruption. Once notified of volcanic activity, the Prestwick supervisor will initially ensure all duty ops staff are made aware, and co-ordinate with ACM and supervisors at Swanwick to work out a traffic plan to best suit the event. The plan and associated measures put in place may change regularly depending on the location and predicted forecast of the ash cloud(s).

Thankfully, we were quite lucky with the recent volcanic eruption in Krísuvík in that it had very little operational impact. The eruption was minor and the accompanying ash cloud was minimal, therefore the jet stream impact didn’t take effect.

So, to answer my previous question of just how much disruption can a volcanic eruption and subsequent ash cloud cause? Well, the answer, my friend, is quite literally blowing in the wind.


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