British Airways 9, 24 June 1982

On 24 June 1982, British Airways Flight 9 flew into a cloud of volcanic ash over Java and lost all four engines. Everybody aboard survived.

The aircraft was G-BDXH, a Boeing 747-236B named City of Edinburgh, flying London to Auckland via Bombay, Kuala Lumpur, Perth and Melbourne. There were 263 people aboard — 248 passengers and 15 crew.

Why nobody saw it coming

The ash came from an eruption of Mount Galunggung. The crucial point is that dry volcanic ash does not show on weather radar, which is designed to detect water droplets. The crew had no indication they were flying into anything at all.

What they saw instead was St Elmo’s fire on the windscreen and a glow from the engines. What the ash was doing was sandblasting the windscreen opaque, and melting inside the hot section of each engine, where it fused into a glassy coating and choked the airflow.

All four Rolls-Royce RB211s failed within about a minute, at 37,000 ft.

Twenty-three minutes

A 747 without thrust is a glider with roughly a 15:1 glide ratio. The crew calculated they could stay airborne about 23 minutes and cover 91 nautical miles — which was not enough to reach anywhere with a runway if they could not restart, and meant a ditching in the Indian Ocean.

Captain Eric Moody then made the announcement that made the flight famous:

Ladies and gentlemen, this is your captain speaking. We have a small problem. All four engines have stopped. We are doing our damnedest to get them going again. I trust you are not in too much distress.

The restart

The engines came back because of physics rather than procedure. As the aircraft descended out of the ash and into cooler, denser air, the fused ash cooled, solidified and cracked off the engine internals.

At about 13,500 ft, after repeated attempts, the engines relit. Number two had to be shut down again for heavy vibration, so the aircraft continued on three.

They landed at Halim Perdanakusuma airport, Jakarta — with the windscreen so badly abraded by ash that the crew had to look through a small clear strip at the side to land.

No injuries.

What changed

The accident, and a similar Singapore Airlines encounter weeks later in the same area, established volcanic ash as a serious aviation hazard rather than a curiosity.

The result was the international network of Volcanic Ash Advisory Centres, which track eruption plumes and issue warnings to aircraft, plus procedures for crews who find themselves in ash: reduce thrust, leave the cloud by the shortest route, and expect the engines to fail.

Those procedures are why the 2010 Eyjafjallajökull eruption closed European airspace rather than being flown through. That caution traces directly to this flight.

Related

• All 747 accidents
• Engines through the generations
• The 747-200