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Comment by pj_mukh | Hacker News Reader

" If the plane had come down in any other part of the bay, such as the 30-foot deep waters to its east or the dry flats to the west, Flight 2 would have either sunk, or likely set ablaze"

Wait wait wait, plane fuselages don't naturally float? I always assumed they did?

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I mean, depends how hard you hit, and people need to get out... Water is not soft at ~150 knots; even Flight 1549 in the Hudson's perfect ditching resulted in the plane sinking when they opened the doors.

https://commons.wikimedia.org/wiki/File:US_Air_Flight_1549_r...

In this case, the ditching wasn't really intentional (the Hudson flight knew they were going down; this one just... flew into the sea due to fog), so it could have looked more like this if they were less lucky:

https://en.wikipedia.org/wiki/File:Ditching_of_Ethiopian_Air...

Per Wiki:

> Asoh later stated that he realized the plane was too low once he spotted the water after the plane broke through the fog with an air speed of 177 mi/h (285 km/h). He grabbed the control stick to gain altitude and advanced the throttles in anticipation of having to abort the landing and perform a go-around, but the plane's main landing gear had already struck the water...

The Hudson flight was very challenging flying, but they did have four minutes of "we're going down", and enough time before "we're going down in the water" to do things like raise the gear.

>even Flight 1549 in the Hudson's perfect ditching resulted in the plane sinking when they opened the doors

Because a passenger freaked out and opened one of the aft doors before an FA could stop them.

IIRC for 1549 there also wasn’t enough time to run the checklist and so they didn’t press the “ditch switch” which closes off a bunch of vents, although given the damage to the aircraft skin it’s not clear whether it would have made a difference

flight 1549 took on a fair amount of water, but did not sink completely

https://www.reddit.com/r/submechanophobia/comments/7qse0g/us...

maybe it would have had it not been tied up, but it never did.

DC-8 a 1950's jet in 1968 so modern buoyancy may not have applied. Everyone made it to shore without getting wet and the airplane was back in the air within a year. Remarkable.

They do for a bit...

I doubt they are water tight, so eventually they'd fill with water. It's not like they're designed for space and need to be perfectly sealed

They're certainly not airtight. There's intentional leaks in a pressure cabin. This is used to regulate the pressure, there is constant engine bleed air flowing in. If you allow more air than it leaks out the pressure will rise, if you lower the airflow it will drop. This mechanism also takes care of refreshing the cabin air. There's also some catalytic conversion going on to remove the high ozone content that's present at high altitudes.

But I think it's pretty hard to ditch a plane without damaging the fuselage to some extent.

You have about 20 minutes depending on the plane and it being upright. The Hudson plane stayed up for 24 minutes.

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