Ditching is always a high risk option, but this US Airways A320 crew made the right decision under the prevailing circumstances.
They then showed the world how ditching should really be done.
They reminded us that this exercise can be completely survivable, given piloting skill and the right weather and visibility conditions.
Pilots are informed how ditching should be done, but practically nobody actually trains for it, even in a simulator.
The reason why training is not offered is rather obscure, but it's probably a combination of two facts: it hardly ever happens nowadays - especially to jets - and the probability of passenger and crew survival is - subliminally - considered low, so it's not reckoned to be worth it.
Propeller-driven aeroplanes normally have a better chance of ditching successfully simply because they can touch down more slowly on the water.
But there has been one almost completely successful jet airliner ditching in the last ten years:
That was a Garuda Boeing 737-300 that suffered engine flame-out in a rainstorm in November 2002 and ditched on a river near Jogjakarta, Indonesia. Only one person died in that event.
There have also been two successful business-jet ditchings in the last decade, both in North America.
In April 2003 a Dassault Falcon 20 ran out of fuel and ditched in the Mississippi near St Louis. Everyone survived that.
And in July the same year a Canada-based Cessna Citationjet ditched with very limited pitch control because of a trim failure, but set down in Oak Harbour, Victoria, near the shore.
The two pilots - the only people on board the Citationjet - swam ashore.
In 2005 a turboprop aircraft - a Tuninter ATR72 - ran out of fuel and ditched in the Mediterranean north of Sicily. There were 16 fatalities out of the 39 people on board. A high-wing aircraft like the ATR series gives less time for evacuation, because the wings don't provide flotation until the fuselage has disappeared beneath the surface.
And ditching in the sea, as opposed to on a river, is usually more risky because large waves and swell are more likely.
But what of this US Airways A320 accident?
What did the pilots face?
From the time the birds hit the aircraft's engines the crew could see that they had insufficient power to remain airborne.
And they quickly became pretty sure they couldn't glide back to LaGuardia - the captain's first instinct - or divert to Teterboro airport, because they knew that if they attempted that and got it wrong, they would crash-land in a built-up area, risking all those on the aircraft and also lives on the ground.
So almost instantly the crew turned left toward the Hudson river, looking out for any opportunity to put down on a large, flat unobstructed piece of land.
No such land space existed within the distance the pilots knew they could stretch their glide, so they committed to ditching as the best option, and briefed the cabin crew to prepare for it.
When the birdstrike happened, the aircraft was at a height of about 3,000ft, approximately 900m.
From that height, they settled into a rate of descent of about 1,000ft per minute, leaving flaps and gear up initially, and deploying them shortly before touchdown on the water. The crew had about three minutes to prepare for ditching having made that decision, and touchdown took place about 3.5min from the birdstrike.
The considerations for ditching are basically these:
- Aim to touch down with the aircraft speed sufficiently high to retain full control, because stalling and letting a wing drop would be disastrous.
- If one wingtip or engine touches the water before the other does, the aircraft swings violently and breaks up.
- On final approach to touchdown, selecting some flap (about 20deg) allows a slower impact and ensures the aircraft attitude is not too nose-high.
If the nose is too high, the tail strikes the water first and can break off, letting water into the hull.
Here is a pictorial guide to some of the considerations when forced to ditch:
And they are rightly receiving praise for having very cool heads.