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Volcanic ashes and flight safety On June 24th, 1982, British Airways Flight 9, a Boeing 747 enroute at 36.000 feet between Kuala Lumpur and Perth, flew into a cloud of volcanic ash thrown up by the eruption of Mount Galunggung (located some 180 km south-east of Jakarta), resulting in the flame out of all four engines.

The reason for the failure was not immediately apparent to Captain Eric Moody and his crew onboard BA 9 or air traffic control on ground. Volcanic ash clouds can be seen in daylight but they do not show on weather radar. As the chain of events started to happen at around 8.40 PM it was totally dark outside the Boeing 747 and the crew onboard only saw a bizarre, bright light on the windscreen and at the leading edges of the wings and engine nacelles.

BA 9 declared emergency, set the course towards Jakarta and as the Boeing 747 was gliding downwards the crew ran several engine-restart drills. Down at 11.800 feet they had three engines running and delivering enough power for a landing in Jakarta.

During approach and landing the crew experienced difficulties to see anything through the windscreen and had to make the approach on instruments, despite reports of good visibility in Jakarta. The windscreen had been blasted opaque by the volcanic ashes and following the landing roll out, the aircraft had to be towed to the gate.

British Airways Flight 9, sometimes referred to as the Speedbird 9 or Jakarta incident, and a few other incidents led to the creation of a global tracking system for volcano ash clouds.

Nowadays nine VAAC's - Volcanic Ash Advisory Centers around the world are responsible for advising international aviation on the location and movement of volcanic ash clouds.

- Before us, I don't think they even saw volcanic ash as a danger, said Eric Moody in a mid-April comment on the closings of European airspace due to the eruption of the Eyjafjallajökull volcano on Iceland.

Volvo Aero Corporation – headquartered in Trollhättan, Sweden, and developing and producing components for aircraft, rocket and gas turbine engines – has published an information on why aircraft and volcanic ash clouds don't go along too well.

- Ash that fills the air following a volcanic eruption has a much denser content than a normal dust or ash cloud, writes Volvo Aero. The ash comprises minerals, which are extremely small and hard rock particles. They are so hard that they can have a blasting effect on the aircraft's cockpit windowpanes but, the most serious aspect of encountering an ash cloud from a volcanic eruption is that the hard ash entails severe wear on all engine components; blades and blisks are worn down very rapidly. The ash contains sulfur, which leads to rapid chemical erosion and in turn to risks of fractures and blade damage.

- Just as serious is the fact that the ash promptly enters a number of spaces in the engine and subsequently melts in the combustion chamber. This soon causes build-ups in the turbine, which grow and inhibit the performance of the engine. In the worst case, it shuts down entirely. In addition to causing corrosion and build-up, cooling vents in the engine can also be blocked by the ash, which in turn causes the temperature in the turbine to rise sharply, thus melting the turbine blades.

- The ash could also contaminate the oil and seep into the air-conditioning system, as well as the cooling system for the technical systems in the aircraft. As if this were not enough, the ash could also contaminate the avionics systems and electrical systems, and impact the hydrological systems and smoke detectors in such areas as the cargo compartment.

- A great deal of work has gone into reducing the risk of foreign objects entering the engines, but when, as in this case, it is a matter of particles that are this small, it is impossible. Fortunately, our part of the world is not affected by volcanic eruptions so often, concludes Volvo Aero.