“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 under control. I trust you are not in too much distress.”

Picture the scene. It is a dark night on June 24, 1982. The City of Edinburgh, a British Airways Boeing 747, is travelling at its cruising altitude of 36 000 feet (11 000m) above the Indian Ocean south of Java when one by one, all four engines surge and quit.

In one stroke, the giant airliner is converted into a large and not very efficient glider with glide ratio of 15 to 1, meaning that without power, the best you can hope for is 15 metres of forward travel for every metre you lose in altitude.

Oh, and there are 263 passengers and more than a dozen crew on board.

So, now what?

The crew reckoned that from its current altitude, the 747 would be able to cover about 170km before it ran out of sky. Senior First Officer Roger Greaves declared an emergency and Moody turned his obese glider onto a heading back to Jakarta, the nearest airport. They could reach Jakarta alright but there was just one little snag: the mountain range between the 747 and the airport which they would need at least 3 500m of altitude to clear safely.

If he couldn’t lift City of Edinburgh over the mountains, Moody would have no option but to try and ditch the 747 in the ocean. At night.

Without its engines, the aircraft’s cabin pressure could not be maintained and the oxygen masks deployed from the ceiling, as they are meant to. However, some masks were apparently not working. To prevent those luckless passengers from asphyxiating to death, Moody had to get the aircraft down and fast. He put the aircraft into a shallow dive, dropping at 1 800m per minute, giving up precious altitude in exchange for air to breathe.

At this point, none of the crew had a clue why all four engines had quit.

The rapid descent was the thing that saved them. The rush of air flushed out whatever crud it was that had fouled the engines and at 4 100m, the crew managed to get first engine number four started and then number three, allowing Moody to put the 747 into a gentle climb. Shortly afterwards, Senior Engineer Officer Barry Townley-Freeman managed to start the other two engines.

City of Edinburgh had been gliding for 13 minutes.

As it turned out, their troubles were not over. The windshield had been sandblasted by volcanic grit and the pilots had almost zero forward visibility. So Moody flew an improvised instrument approach and he put the 747 down perfectly on Jakarta’s runway. In the trade they call it airmanship.

The subsequent investigation showed that the aircraft had flown into a cloud of volcanic ash – dry, engine clogging grit, actually – from the eruption of Mount Galunggung in Indonesia.

Volcanic grit does horrible things to aircraft engines: the engines suck in the debris, turning it into glass in the hot engine intakes. The glass builds up rapidly and the engine quickly starves.

And that, travellers, is why flights across England and Europe, are grounded today, all because of a pesky little volcano in faraway Iceland.

PHOTO: A composite illustration of the City of Edinburgh with its leading edges and engine nacelles lit up by an electrical charge from the volcanic ash. SOURCE: Wikimedia Commons