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Originally Posted by hw711
(Post 10441511)
Has anyone ever done a water landing? I've only seem it in movies.
http://en.wikipedia.org/wiki/Nationa...nes_Flight_193 |
Originally Posted by BearX220
(Post 10442179)
Yeah, that was the end of a hijack drama involving a 767 off the African coast. The aircraft ran out of fuel and ditched. This was the incident that pretty much put the lie to the idea of the pillow-soft, no-worries water landing as depicted on the emergency card. Calm sea, no wind, full daylight, fully controllable aircraft, and still everything went to hell:
http://www.youtube.com/watch?v=nV7yE4hK2hI Now try it at night in a rolling North Atlantic sea. :eek: |
2002: Boeing 307 Stratoliner ditches in Elliott Bay
The Stratoliner would present a rather clean profile -- nothing hanging down down to induce drag as it touches the water. Two Boeing Stratocruisers (much larger B-29 based airliner) ditched in 1956. In one case they ditched near a picket ship. It sank 3 minutes after all occupants were rescued. In the other case the plane ditched in Puget sound & remained afloat for 15 minutes, but there were several casualties. The 767 would have a couple large engines hanging down. Unless they separated cleanly & quickly, it might not be a very flat & stable impact. When a Lockheed EP-3E collided with a Chinese fighter, one of their concerns in choosing between a water vs. land landing was that they didn't know how the electronics comparments attached to the underside of the plane would affect the stability & structural integrity once they hit the water. The crew opted for an emergency landing on a Chinese airfield. It sounds like the best alternative when you don't have a runway, but it's hardly a sure thing. |
Haven't any of you watched "Cast Away" ? :):)
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The story is wrong. None of the NW 747-400's hold 425 pax.
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Originally Posted by jjvan
(Post 10444303)
The story is wrong. None of the NW 747-400's hold 425 pax.
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Have confidence in redtail airmanship. I do.
Do you remember the recovery of NW85 on October 9, 2002? http://findarticles.com/p/articles/m...7/ai_106872569 If you read this carefully, you will see that this was truly a desperate situation. A sudden and uncommanded 35 degree roll during cruise, followed by a struggle to maintain safe flying attitude requiring multiple - and unsimulated - control modes, then a descent into the challenging environment of Turnagain and a landing at ANC using differential thrust on two engines to maintain lateral control - all resulting in a safe recovery of the a/c with no injuries. You'll appreciate that this was a spectacular effort by Captain Hanson and his crew. They thoroughly deserved their ALPA Superior Airmanship award. Well done you guys, we the redtail riders don't forget. This ought to give you confidence in the guys up front and the redtail ethos. |
Most impressive.
It's good to know that the guys up front are that good... but I can't say I want a demo. ;) |
Originally Posted by DanTravels
(Post 10444326)
Full would be what, 403? And 22 crew to make up the difference seems a little bit high... ;)
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Originally Posted by BearX220
(Post 10442179)
This was the incident that pretty much put the lie to the idea of the pillow-soft, no-worries water landing as depicted on the emergency card. Calm sea, no wind, full daylight, fully controllable aircraft, and still everything went to hell
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Originally Posted by NWstu
(Post 10449070)
I'm not saying that ditching is not fraught with all sorts of perils, but complicating the ditching was that the hijackers grabbed the controls and fought with the pilots with the new objective of turning the hijacking into a suicide mission. The ditching might have gone better without the, ahem, distraction facing the pilot.
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Originally Posted by avidflyer
(Post 10449142)
Boeing 307 engines are mounted in the wing not under it. The issue is you have 2 giant cups grabbing the water (engines) and stopping while the rest of the AC continues forward end over end.
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Originally Posted by NWstu
(Post 10449217)
Assuming the pilot makes a 3-point impact, wouldn't the engines snap off and take with them part of the wing while the plane continues to bounce and careen forward? When you say end-over-end, do you mean tail over nose, spinning around or cartwheeling? If it's not a 3-point impact with one engine hitting the water first, the plane would likely spin around the y-axis.
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Water is virtually - for engineering purposes - incompressible. The physics of ditching on a flat calm sea are initially not much different than a wheels-up landing on a concrete runway. The vertical and longitudinal loading on the pylons is rearward and upward, rapidly increasing as the aircraft slows and the wing is relieved of aerodynamic loading.
Engine pylons are designed to separate under certain load regimes to protect the wing spar. At some point during slideout, the pylon fails under the bending moment and the engine separates. But it's more complex here. During flight, engine separation almost certainly means the dead mass drops away from the airframe. During ditching, what happens to this mass? It is rammed into the wing spar, as the a/c rides over the top of the engine, or it rotates back and over the wing, possibly gyroscopically impacting into the fuselage further aft. 15,000lbs of JT9 smashing into the cabin. But that's not even the most likely scenario. The key question is whether the dynamic load regime would cause pylon failure along the design failure paths. Pylons are relatively strong in longitudinal and vertical axis loadings, much less so for azimuthal loadings. Flight dynamic loads are designed to damp such stresses, so the static structure is relatively weak. If you experience moderate or severe turb from the top deck of the 744, look out and watch the multi-axis motion of the pylons and you'll see how this structural system damping works. The problem comes when roll or yaw are introduced during this landing. If the sea is anything less than mirror smooth, parts of the a/c not designed to take such stress will contact the water. Unlike runway slideout, when contact of the wingtips and other a/c parts can have a stabilizing influence, the uneven contact with the sea will induce further roll or yaw that will increase local stress and cause catastrophic structural failure. Once this happens, still at moderately high velocity, hull motion will become unpredictable and most likely one local structural failure will lead to others. Disintegration of the fuselage is almost inevitable. As in the Comoro Islands 767 crash. Run it in slow-mo and you can see chains of structural failure. Ditching a large airliner with engines mounted below the wing is an extremely hazardous operation that will likely result in many casualties under the best of circumstances. The only scenario I could see where pylon failure may possibly map the design mode and allow non-catastrophic separation would be a low-speed ditching...like, for instance, a westerly low-energy runway overrun at LAX, followed by slideout across the beach and into the Pacific. So, keep us out of the water! |
I think I'll bring a parachutte. :p
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