The longest glide

It's the anniversary today of the "Jakarta Incident" and I've been reading about this fascinating story of heroism, skill and luck since someone commented on it in my twitter stream this morning. Anyway if you've never heard of it then here's a quick summary.

On the 24th June 1982 BA009 a jumbo jet flying from Heathrow to Auckland NZ hit a cloud of volcanic ash as it flew near to Jakarta, Indonesia. The ash cloud wiped out all four of the planes engines but since it was nighttime the crew weren't immediately aware of the cause. As the plane started to descend the crew desperately tried to a) understand what was going on, b) calculate a contingency landing plan and c) restart the engines. 

The glide ratio of a 747 is around 15:1 meaning for every 1 km of vertical drop it will glide forward 15 km, this meant that from the altitude the plane hit the ash cloud it had roughly 170 km left before it hit the ground or ocean, being over mountainous terrain at the time the captain decided that if they couldn't get the engines going again he was going to ditch in the Indian Ocean, less than ideal. I remember when I used to fly gliders, glide ratios were always front of mind, my plane (which wasn't top of the range by any means) had a ratio of 35:1, it allowed reasonable thinking time (i.e. looking for somewhere to land!) should you run out of lift; how that crew must have felt in a 350+ ton (full) aircraft is beyond the meaning of the word stressful.

Suffice to say they exited the cloud and managed to get three of the engines going again and landed at Jakarta, interestingly the plane was so sand-blasted by the dust that the pilot couldn't taxi because he couldn't see out of the windows, his comment on this situation was "a bit like negotiating one's way up a badger's arse" which I thought wonderfully apt and perfectly understated. The plane subsequently entered the Guinness book of records at the time as the longest glide in a non-purpose built aircraft, I'm sure the crew were chuffed to bits with that one!