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A recurring theme I come across is how, in an emergency, it is safer for a passenger craft (such as an Airbus) to try to land on the ground rather than at sea. My understanding is that the main reason for this is that at the high speed at which the plane would be travelling, landing in the sea would be like hitting concrete and basically break the plane up and kill most of those on board.

But if speed is the issue then why cannot a passenger craft just have a large parachute at the back that is deployed when the plane is say thirty to fifty feet or so above the sea surface so that the speed is drastically reduced (at a carefully pre-calculated rate that is safe for all on board, who would in any case be fully prepared for the landing), at which point the plane would essentially just guide gently into the sea at a speed maybe equivalent to that of a fast speedboat? To be clear I am talking about a parachute that is just intended to add drag and slow the plane down.

Would this work in practice, and if so why don't planes have such a parachute as standard?


marked as duplicate by Federico, mins, fooot, Ralph J, Danny Beckett May 24 '15 at 0:15

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    $\begingroup$ If the parachute reduces the speed quickly, everyone's injured by being thrown forwards; if it doesn't, the plane drops below its stall speed and falls out of the sky. $\endgroup$ – David Richerby May 23 '15 at 21:26
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    $\begingroup$ The comparison of water to concrete limps on both legs. Water is obviously softer than concrete and is so at any speed. However when making controlled emergency landing, the hardness is not what matters, because the vertical speed is low. What matters is roughness. The surface needs to be flat so the plane can slide on it. So rivers and lakes are usually decent option for emergency landing, but sea always has waves and the plane will slide into the valley between them and hit the next wave hard which is likely to break it. $\endgroup$ – Jan Hudec May 25 '15 at 4:56
  • $\begingroup$ On the other hand, in the short timespans of collisions, water is harder than concrete because it cannot compress as well and displacement in large object high speed collisions is negligible. $\endgroup$ – Joshua May 28 '16 at 1:20

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