As Iceland’s Eyjafjallajökull volcano continues to erupt and cause havoc with air travel across Europe, it’s time to reminded of the danger it poses to aircraft operation. In short, volcanic ash is composed of very abrasive silica materials which can shut down engines among other things.
As Iceland’s Eyjafjallajökull volcano continues to erupt and cause havoc with air travel across Europe, it’s time to reminded of the danger it poses to aircraft operation.
In short, volcanic ash is composed of very abrasive silica materials, which can damage the airframe and flight surfaces, clog different systems, abrade cockpit windows and flame-out jet engines constituting a serious safety hazard.
Volcanic ash spewn into the atmosphere at high altitudes affects aircraft operation in four main ways:
Sandblasting effect
Ash can sandblast the windscreen, “blinding” pilots; damage the fuselage; and coat the plane significantly altering the weight and balance. In addition, the sandblasting effect can damage the landing lights, making their beams diffuse and unable to be projected in the forward direction.
Clogging of the aircraft’s sensors
Accumulation of ash can block the aircraft’s pitot tubes, leading to the failure of the aircraft’s air speed indicators.
Electromagnetic wave insulation
Volcanic ash particles are charged and can disturb air-ground radio communication.
Combustion power failure
As jet engines suck in large amounts of air for combustion, volcanic ash particles (particularly glass-rich if from an eruption under ice) sucked in melt at about 1,100 °C, fusing onto the blades and other parts of the turbine (which operates at about 2000 °C). They can erode and destroy parts, drive it out-of-balance, and cause jams in rotating machinery. The effect on the operation of a jet engine is often to cause it to shut down—failure of all an aircraft’s engines is common.
The best known example of an aircraft’s engines shutting down is British Airways Flight 9, a Boeing 747, which [unknowingly] flew through the Mount Galunggung (Indonesia) volcanic ash cloud in June 1982. All four engines shut down, the aircraft descended from 36,000 to 12,000 feet where the engines got restarted, and an emergency landing was made. [Watch the re-enacted videos - Pt.1, Pt.2, Pt.3, Pt.4, Pt.5].
By descending, the infusion of cold, clean air was enough to cool, solidify, and shatter the glass, unclogging the engines.
Advisories
Frequent aircraft incidents from atmospheric ash prompted the International Civil Aviation Organization to distribute information about ash events through the Volcanic Ash Advisory Centers (VAAC). There is one VAAC for each of the nine ICAO regions of the world. VAACs issue advisories and serve as liaisons between meteorologists, volcanologists, and the aviation industry.
