Aircraft flying within the vicinity of volcanic ash clouds can suffer extreme damage to a number of functions critical to the safe operation of the aircraft.
One example of these effects, and possibly the most important incident in aviation history that has lead to a better understanding of the effects of volcanic ash on aviation, was in 1982 involving British Airways flight 9.
Enroute from Jakarta, Indonesia to Perth, Australia, the flight encountered ash from the eruption column of the Mount Galunggung volcano.
The crew first experienced a weather phenomenon known as St. Elmo's Fire, a luminous plasma created by statically charged air coming into contact with a moving object. This is now known to occur in thunderstorms and volcanic clouds. Because volcanic ash is typically dry, weather radar is not able to detect the cloud and this lead to the confusion of flight 9's crew, as they assumed they had clear skies ahead.
After a noticeable odor of sulphur in the cabin and passengers witnessing flames extending from the rear of the engines, the Boeing 747 experienced a 4-engine surge and flameout while cruising at an altitude of 37,000ft.
After multiple attempts to restart the engines as the plane was slowly gliding towards the ocean, the crew managed to reignite the engines at a lower altitude. They then ascended to a higher altitude as they made an emergency return to Jakarta where the St. Elmo's Fire returned and had one engine flamed out.
They then maintained an altitude high enough to clear a mountain range on return to Jakarta, but low enough to avoid any further engine surges and flameouts.
Despite a severely damaged windscreen from the volcanic ash and extensive damage to the aircraft and engines, the plane landed safely in Jakarta.
The crew were initially oblivious to the cause of the incident.
The abrasive ash had caused damage to the leading edges of the aircraft, as well as making the windscreen impossible to see out of. But the critical damage came as all four engines ingested molten ash and adhered to the inner components causing disruption to the airflow. As the molten ash cooled from the inactivity of the engines, it simply fell off allowing airflow through the engine and enabling restart.
All aircraft encountering volcanic ash, can experience a number of effects that can have potentially catastrophic consequences;
- abrasive damage to windscreens, leading edges, propeller and turbocompressor blades
- contaminates fuel systems and clog fuel nozzles
- contaminates water systems
- jams gears and moving parts of engines and control surfaces
- clogs combustion chambers of engines
- can damage pitot tubes and avionics
Nowadays, a lot more is known about the effects volcanic activity can have on aviation. The industry has established worldwide centres known as "Volcanic Ash Advisory Centres". They work to monitor and advise the aviation industry of potential threats to aircraft operation, and ICAO have 9 endorsed centres globally.
In 2010, an Icelandic volcano caused major disruptions to air travel to and from Europe and costs were estimated to be hundreds of millions of dollars every day, but through the advent of the VAACs, the industry was aware of the threat and avoided any repeat of Flight 9.
Written by: Luke Hague, GlobalPilotLife.com Media Correspondent.