Why and How Volcanic Ash Stalls Aircraft Engines - Explained

Ash clouds from Ethiopia's Hayli Gubbi volcano are affecting air travel in India and heading towards China. Experts highlight the serious risks volcanic ash poses to aircraft safety.

The India Meteorological Department (IMD) reported that ash clouds from Ethiopia's volcanic activity are moving towards China and will depart from Indian skies by Tuesday evening. The Hayli Gubbi volcano's eruption in Ethiopia recently disrupted flight operations in India. The ash plumes affected areas like Gujarat, Delhi-NCR, Rajasthan, Punjab, and Haryana.

IMD Director General Mrutyunjay Mohapatra confirmed that the ash clouds are drifting away from India, set to clear by 7.30 pm. On Sunday, the Hayli Gubbi volcano in Ethiopia's Afar region erupted, creating a massive ash plume reaching 14 km high. This plume travelled eastward over the Red Sea, towards the Arabian Peninsula and the Indian subcontinent.

Impact on Aviation Safety

The recent eruption has led to fresh airspace advisories globally. Aviation experts are emphasising the dangers volcanic ash poses to modern jet engines. Despite appearing harmless, ash clouds are perilous for aircraft, capable of stalling engines mid-flight and damaging systems within minutes. This hazard remains a significant concern for aviation safety.

Volcanic ash is more than just a dust cloud. It comprises pulverised rock, glass particles, silica-rich minerals, metal traces, and acidic gases. These components are hard and abrasive, not easily melting, which affects their behaviour inside jet engines.

How Volcanic Ash Stalls Jet Engines

When an aircraft flies through a volcanic ash cloud, three critical events take place inside the engines:

1. Melting and Re-solidification

Jet engines operate at temperatures exceeding 1,400°C, which is enough to melt silica-rich ash.
Once ash melts, it travels deeper into the engine but re-solidifies on cooler components like turbine blades and nozzle guide vanes. This creates a glass-like coating that narrows the airflow passage.

Result: Restricted airflow → Loss of thrust → Engine stall.

2. Abrasion of Fan Blades and Sensors

Before melting, ash acts like sandpaper:

It erodes compressor blades.

It damages windscreens.

It destroys pitot tubes and sensors.

This affects the engine's ability to compress air and maintain stable combustion.

Result: Loss of engine efficiency or flameout.

3. Contamination of Fuel and Cooling Systems

Ash particles can block cooling passages and interfaces between rotating parts.

Result: Engine overheating, compressor surges, or complete shutdown.

No Warning Signs

Volcanic ash clouds often do not appear on traditional aircraft weather radar because they contain too little moisture. Pilots may enter the cloud without realising it - until they see visual cues such as:

• St. Elmo's fire-like static on windscreens
• A sulphurous smell
• Dust accumulating in the cabin
• Engine rumbling or surges

Major Past Incidents

British Airways Flight 9 (1982)

One of the most dramatic cases occurred when BA Flight 9 flew through ash from the Galunggung volcano in Indonesia.

• All four engines failed mid-air.
• The aircraft glided for several minutes before the crew could restart the engines after exiting the ash cloud.
• The aircraft landed safely in Jakarta, but with significant exterior and engine damage.

KLM Flight 867 (1989)

A Boeing 747 flying near Alaska's Mount Redoubt lost power in all four engines after hitting an ash plume.

• The engines recovered only after descending nearly 14,000 feet.
• The aircraft landed safely, but the repair bill exceeded $80 million, making it one of the costliest volcanic-ash events.

Eyjafjallajökull Eruption (2010)

Though no aircraft were lost, the ash plume from Iceland led to the largest airspace shutdown since World War II, grounding 100,000 flights over Europe.
The incident forced the aviation industry to revise ash-tolerance levels and monitoring systems.

Latest Volcanic Ash Concerns

In recent days, aviation authorities have issued advisories following new eruptions in [insert latest eruption - e.g., Mt. Ruang (Indonesia), Mt. Etna (Italy), Icelandic volcanic activity, Philippines' Bulusan/Mayon depending on current context], warning airlines to reroute flights to avoid the ash cloud drifting across regional air corridors.

Satellite imagery from global Volcanic Ash Advisory Centres (VAACs) shows the ash plume moving at high altitudes typically used by commercial jets.

• Many carriers have opted for:Flight-level adjustments
• Temporary route diversions
• Delays or cancellations depending on the ash density

What Airlines and Pilots Are Trained to Do

If a plane encounters ash, the recommended steps include:

• Immediately reducing thrust (high power can pull in more ash)
• Activating anti-ice systems
• Turning 180° to exit the cloud
• Monitoring engine parameters
• Preparing for automatic engine restart attempts

Why Ash-Related Engine Stalls Are Still a Threat

Despite improved satellite monitoring, the hazard remains because ash clouds:

• Travel thousands of kilometres with jet streams
• Spread quickly and unpredictably
• Stay invisible to cockpit radar
• Contain particles small enough to bypass filters but large enough to destroy engine components

Volcanic ash poses a unique and severe threat to aviation. Its ability to melt, re-solidify, and damage engine components makes it one of the few natural phenomena capable of shutting down multiple jet engines simultaneously. With the latest volcanic eruptions prompting new flight advisories, global aviation authorities continue to highlight the need for real-time monitoring and conservative flight-routing to keep passengers safe.