Dangers To Aircraft From Volcanic Eruption Clouds
More than 80 commercial aircraft have unexpectedly encountered volcanic ash in flight and at airports in the past 15 years. Seven of these encounters caused in-flight loss of jet engine power, which nearly resulted in the crash of the airplane. A range of damage may occur to airplanes that fly through an eruption cloud depending on the concentration of volcanic ash and gas aerosols in the cloud, the length of time the aircraft actually spends in the cloud, and the actions taken by the pilots to exit the cloud.
Ash ingested by jet planes may lead to the immediate deterioration in engine performance and engine failure. The principal cause of engine failure is the deposition of ash in the hot sections of the engine. Glass from melting volcanic ash will coat fuel nozzles, the combustor, and turbine, which reduces the efficiency of fuel mixing and restricts air passing through the engine. This causes surging, flame out, and immediate loss of engine thrust. Ash may also seriously erode moving engine parts, including the compressor and turbine blades, which reduces the efficiency of the engine.
Volcanic ash is highly abrasive because it consists of hard, sharp rock fragments that easily scratch and erode plastic, glass, and metals. Any forward-facing surface of an airplane is likely to be damaged, including the cockpit and forward cabin windows, landing light covers, leading edges of wings and tail rudder, engine cowlings, and the radar nose cone. Cockpit windows may become so abraded and scratched that pilots have extreme difficulty seeing the runway on which to land the plane.
Air that enters an airplane’s interior first passes through the engines. Some ash particles ingested through the engines will travel through the plane’s ventilation ductwork throughout the plane. The ash may clog air-filter systems and spread throughout the cabin, contaminating cabin fixtures, carpeting, seat covers, and cushions. The ash can also damage the plane’s electronic system, including power generators and navigation instruments.
