Volcanic ash and aviation safety

Volcanic ash is hard and abrasive, and can quickly cause significant wear to propellers and turbocompressor blades, and scratch cockpit windows, impairing visibility.

[4] The costs of air travel disruption in Europe after a volcanic eruption in 2010 forced aircraft manufacturers to specify limits on how much ash they considered acceptable for a jet engine to ingest without damage.

In April, the UK CAA, in conjunction with engine manufacturers, set the safe upper limit of ash density at 2 mg per cubic metre of air space.

[6] To minimise further disruption that this and other volcanic eruptions could cause, the CAA created a new category of restricted airspace called a Time Limited Zone.

[citation needed] Experts recognised that there was an issue following British Airways Flight 9 in 1982, and therefore the ICAO established the Volcanic Ash Warning Study Group.

Due to the difficulty in forecasting accurate information out to 12 hours and beyond, the ICAO later set up Volcanic Ash Advisory Centers (VAACs).

[10] The ash enters the atmosphere from the force of the eruption and convection currents from the heated air, and is then carried away from the volcano by winds.

The most sensitive surface is the high-pressure turbine nozzle guide vanes (NGVs), situated immediately downstream of the combustor.

If this area is reduced due to an accretion of ash, a smaller mass flow rate of gas passes through the engine core.

Restarting an engine at altitude can be difficult, due to the lower temperatures and pressures of the ambient gas, but is not normally a problem.

Fine ash that enters electronic components within the engine or airframe can cause electrical failure—which poses an immediate hazard to the aircraft.

Additionally, the detection methods have limitations, as both species have the potential to be masked by other types of aerosol, such as water or ice; this contributes to great variability in the data.

Volcanic ash from the eruption of Eyjafjallajökull disrupted air travel in Europe in 2010.
Ash cloud from the 2008 eruption of Chaitén volcano stretching across Patagonia from the Pacific to the Atlantic Ocean
Volcanic ash deposits on a parked McDonnell-Douglas DC-10-30 during the 1991 eruption of Mount Pinatubo , causing the aircraft to rest on its tail. While falling ash behaves in a similar manner to snow , the sheer weight of deposits can cause serious damage to buildings and vehicles, as seen here, where the deposits were able to cause the 120 ton airliner's centre of gravity to shift.