'Engine flame out': Why is volcanic ash so dangerous to aircraft?

Volcanic ash poses hazard due to hard, abrasive particles

- BY JAY HILOTIN Senior Assistant Editor

In 1989, a Boeing 747 (KLM Flight 867) Amsterdam-Tokyo flight flew into a volcanic ash cloud from Redoubt Volcano (Alaska). All four engines “flamed out”. This recorded incident is an example of the hazards posed by volcanic ash to aircraft in flight.

What an aircraft “engine flameout” means: When an aircraft engine “flames out,” it means combustion stops, and the engine loses its ability to produce thrust, likely causing it to spin in a “windmilling” state.

While pilots are trained to handle this by following emergency procedures, like restarting the engine if possible, and preparing for an emergency landing if a restart fails. Here's a Q&A about the aviation hazards posed by volcanic ash.

What exactly is volcanic ash, and why is it a threat to aircraft?

Volcanic ash consists of very small, hard, sharp-edged particles of rock and volcanic glass (silicates) that form during explosive eruptions, according to the US Geological Survey.