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nrcnyc
Posts: 82
Joined: Fri Apr 15, 2005 5:50 am

RE: 747 Ditching At Sea - How Long Would It Float?

Wed Nov 09, 2005 11:22 am

There is a lot of claims with out any data to back them. Where would someone be able to find any real studies about this?

P.S. someone said a 747 could float a long time if they dumped all their fuel, yes this makes the landing easier, but lets not forget that Jet A is less dense than water.
 
jumpseatflyer
Posts: 155
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RE: 747 Ditching At Sea - How Long Would It Float?

Wed Nov 09, 2005 11:23 am

Oh and that above water ditching guess implies a wings-still-on condition.

The original post is not about whether you can survive or not in the middle of the ocean. But just for s + g, I'm going to tell you... you can't. I don't care if its 10 miles from shore. No rescue, you're screwed. As much as I'd like to think I could swim 10 ocean miles, I can't. And if I can't, the "average 170 lb" passenger can't. Don't forget that oceans have enormous waves, so if the temperature doesn't kill you in 10 minutes, you'll tire yourself out and drown.

Don't let go of that raft : ).
 
md80fanatic
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RE: 747 Ditching At Sea - How Long Would It Float?

Wed Nov 09, 2005 11:57 am

It really depends on how much water the remaining structure can displace....as to how long it will float. With the 747s large engines.....chances are you will lose one, if not both wings. That's the stinger.....the wings would normally displace as much water as the fuselage....and having them remain attached would greatly extend the float time (plus it would give a semi-dry place for pax to get their bearings before taking to the sea).

I think a huge bird has a better chance landing wheels up in the countryside than in any body of water.
 
jeb94
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RE: 747 Ditching At Sea - How Long Would It Float?

Wed Nov 09, 2005 12:41 pm

Keep in mind, an aircraft fuselage is not a completely air tight structure. There are numerous 'calibrated' leaks throughout the fuselage. These same air leaks will turn into water leaks. Air pressure will not keep it out since there will no longer be a pressure source once the aircraft is in the water.
 
SATL382G
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RE: 747 Ditching At Sea - How Long Would It Float?

Wed Nov 09, 2005 12:51 pm

Quoting Prebennorholm (Reply 41):
3. It happened close to Italian shores, a few minutes helicopter flying time away from a well prepared SAR unit.
25 out of 39 survived



Quoting Prebennorholm (Reply 41):
Fortunately there are no incidents or accidents to mention because it never happened and hopefully never will happen.

None of this supports your claim of a 99 percent fatality rate for ditching.
"There’s nothing quite as exhilarating as being shot at and missed" --Winston Churchill
 
WDBRR
Posts: 605
Joined: Tue Jan 25, 2005 11:28 am

RE: 747 Ditching At Sea - How Long Would It Float?

Wed Nov 09, 2005 1:04 pm

Quoting F27XXX (Reply 3):
About 15 minutes

My Source: "Airport 77".

(Sorry- couldn't resist)


You beat me to that....I don't remember how they got out.
Did they raise the plane?
 
georgiaame
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RE: 747 Ditching At Sea - How Long Would It Float?

Wed Nov 09, 2005 1:38 pm

Despite what the manufacturer may tell you, metal aircraft do only marginally better landing on water than they do landing in trees.

That's a fact.
"Trust, but verify!" An old Russian proverb, quoted often by a modern American hero
 
spacecadet
Posts: 3582
Joined: Thu Sep 20, 2001 3:36 am

RE: 747 Ditching At Sea - How Long Would It Float?

Wed Nov 09, 2005 2:08 pm

Quoting Jeb94 (Reply 53):
Keep in mind, an aircraft fuselage is not a completely air tight structure. There are numerous 'calibrated' leaks throughout the fuselage. These same air leaks will turn into water leaks. Air pressure will not keep it out since there will no longer be a pressure source once the aircraft is in the water.

The fact of the matter is all airliners certified for ditching have to also be certified to float long enough to evacuate 100% of the passenger capacity. That's an FAA regulation. I don't have the exact figures for every plane but I would also imagine all manufacturers build in a safety margin to allow for different configurations (i.e. I doubt a 747-400D can float any longer than a 747-400, so even a 747 configured to carry 350 passengers can float at least as long as it takes to evacuate close to 600). In addition, there is a safety margin requirement to allow for exactly the sorts of things you describe - any forseeable structural issues with the airplane must be taken into account with regard to float time.

In addition, airliners must be designed such that if properly landed on water, there will be no immediate injury caused to the passengers. (This would obviously include injuries caused by structural breakup... in other words, airplanes must be designed such that they will not break up in the event of a water landing.) Windows and doors must also be strong enough to withstand greater than the maximum pressures a water landing would create upon them.

These requirements are contained in FAR Part 25, section 801 if you'd like to look them up.

Doesn't put an end to this topic because it still doesn't answer the question of exactly how long the 747 can float, but it will hopefully at least put to rest some of the silly and uninformed comments about water landings being unsurvivable. Water crashes are sometimes (though not always) unsurvivable. Water landings (e.g. ditching) are perfectly survivable and in fact can result in few or no injuries and a repairable airplane.
I'm tired of being a wanna-be league bowler. I wanna be a league bowler!
 
jeb94
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RE: 747 Ditching At Sea - How Long Would It Float?

Wed Nov 09, 2005 2:19 pm

So give the aircraft 10 minutes or less on average. It really doesn't take very long to evacuate an aircraft, even on water.
 
RAMPRAT980
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RE: 747 Ditching At Sea - How Long Would It Float?

Wed Nov 09, 2005 2:30 pm

It will stay afloat for as long as God allows it to do so.
With gun control there can be no democracy.. With gun control there can be no Freedom
 
Lp0815
Posts: 206
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RE: 747 Ditching At Sea - How Long Would It Float?

Wed Nov 09, 2005 3:09 pm

I was duty travelling on one of my company's M1F recently and was chatting with the cockpit crew about ditching into the water and the chances of getting out of the a/c.

The comment of the FO:
"This plane is designed to float in the same way as a boat is designed to fly!"


That pretty much said it all.

Cheers,
Lp0815
Time waits for nobody
 
jasond
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RE: 747 Ditching At Sea - How Long Would It Float?

Wed Nov 09, 2005 3:50 pm

Quoting F27XXX (Reply 11):
Quoting Fokker70NG (Reply 9):
If I recall correctly, I once heard in a documentary on plane crashes that there has never been a modern jetliner that managed to ditch in the water without breaking up in a lot of pieces. Even if it's a somewhat controlled ditch, it's almost impossible.
Tony

Correction ALM DC-9-33 as mentioned. Don't recall the 'float' time though. Might have been 15-30 minutes but no more and was intact on impact. Only a small number of fatalities thankfully. Cause of accident was stated to be inadequate fuel management by crew compounded by prevailing weather conditions. Apparently the original destination was unavailable due to poor weather so crew decided to go to the alternate. That decision was reversed either due to the alternate getting worse or the original destination improving, can't recall which. Most of the reserve fuel was used by high engine power at low altitudes while crew 'struggled' to make decisions.
 
sllevin
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Joined: Wed Jan 30, 2002 1:57 pm

RE: 747 Ditching At Sea - How Long Would It Float?

Wed Nov 09, 2005 4:15 pm

I think it depends on the actual dynamics of the landing. Not long ago (maybe 10 years?) a Nimrod ditched due to fire and floated for quite a long time.

Light planes are also known to float a long time. However, when I had to ditch my plane, it was a pretty smooth impact, but it didn't stay afloat but maybe 6 or 7 minutes.

Steve
 
airforum
Posts: 170
Joined: Fri Jun 23, 2000 10:48 pm

RE: 747 Ditching At Sea - How Long Would It Float?

Wed Nov 09, 2005 6:21 pm

Quoting Ftrguy (Reply 23):
There is a video of that 767 ditching. (I have no idea how to find it so don't ask) It touched the water in about a 30 to 40 degree angle of bank turn. The wingtip dragged in the water for a second before the plane started tumbling and breaking up.

http://www.cnn.com/WORLD/9611/26/comoros.crash/index1.html
What goes up, must come down. Let's hope the sky never went up.
 
hawker
Posts: 103
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RE: 747 Ditching At Sea - How Long Would It Float?

Wed Nov 09, 2005 8:24 pm

If you are considering the case of a big twin, then no matter how carefully you flare, the very large engine cowlings are going to hit the water first. With the relatively high landing/stalling speed, the forward momentum will mean the engines will dig in to the water immediately and this will almost certainly break the fuselage open.

Remember the recent thread on the MD80 heavy landing when the whole tail fell off.
 
airforum
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RE: 747 Ditching At Sea - How Long Would It Float?

Wed Nov 09, 2005 8:33 pm

Quoting Prebennorholm (Reply 41):
2. It happened in the warm Mediterranean in the middle of summer - 6th August. You could swim for ever in that water. Like the nicest, heated swimming pool. And no sharks!

No sharks? Great whites are being spotted there regulary. Actually the area is considered to be a breeding place for great whites! It's not likely they'll show up to take a nip of you, but that's another story Big grin
What goes up, must come down. Let's hope the sky never went up.
 
skywatch
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RE: 747 Ditching At Sea - How Long Would It Float?

Wed Nov 09, 2005 10:51 pm

Here is a video of the 767 ditching:
http://www.alexisparkinn.com/aviation_videos.htm The wing was clearly catching the water before the fuselage made contact with the water, and then it cart-wheeled. A very sad video indeed. Definitely not a controlled ditching.

----Skywatch
------Forever Watchin' The Sky------
 
Hantsflyer27
Posts: 55
Joined: Mon Oct 03, 2005 2:07 am

RE: 747 Ditching At Sea - How Long Would It Float?

Wed Nov 09, 2005 10:54 pm

I wonder if the question refered to the floating time of a 744 if were gently place on calm water by crane etc if were possible. This would perhaps elimanate all externalities and variations in the events of all known ditchings of airliners so far.

Has this ever been tested?? Quoting Jeb94 - a good point, the fusalage is not airtight, so although the shape of the fusalage, combined with wings as stabilisers could make an efficient floating device, voids within the structure would evenually fill with water, causing the density of the mass to gradually become greater than that of the water supporting it. Thus sinkage....although not for many hours i would susupect.

Quoting all accidents we know about, there are too many externalities such as engine and wing structure disentigration (Hijacked 767) on impact or deployed landing gear (Kai-tak/Air China incident). Because we have so few of these incidents to study (few of which might be considered a perfect controlled ditching), speculating floating time from this scenario is just too difficult....just too many externalities. Interesting topic and ideas though. Regards HF
 
skywatch
Posts: 851
Joined: Mon Mar 07, 2005 11:36 am

RE: 747 Ditching At Sea - How Long Would It Float?

Wed Nov 09, 2005 11:25 pm

Quoting Skywatch (Reply 66):
Here is a video of the 767 ditching:

I forgot to tell y'all to scroll down to the one entitled "Ditching at Sea". Sorry 'bout that.

---Skywatch
------Forever Watchin' The Sky------
 
YYZYYT
Posts: 1090
Joined: Tue Apr 05, 2005 12:41 am

RE: 747 Ditching At Sea - How Long Would It Float?

Wed Nov 09, 2005 11:42 pm

Quoting Jumpseatflyer (Reply 49):
I'm guessing [aka don't bother quoting me] that a fully laden 474 would be deplanable for 5-8 minutes.

Indeed, it should take no more than 90 seconds, according to the certification tests carried out.

(At lease that is the case for a 747, and all other commercial aircraft I have heard of. I don't know about this Boeing 474.  Wink )
 
stuckinMAF
Posts: 1022
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RE: 747 Ditching At Sea - How Long Would It Float?

Thu Nov 10, 2005 1:01 am

Of course, this is a much smaller plane, but here's an NTSB report on a PC-12/45 that had to ditch and apparently stayed afloat for at least several HOURS.

http://www.ntsb.gov/ntsb/brief2.asp?...710X01344&ntsbno=SEA01WA125&akey=1
"A fear of weapons is a sign of retarded sexual and emotional maturity" -Sigmund Freud
 
F27XXX
Posts: 617
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RE: 747 Ditching At Sea - How Long Would It Float?

Thu Nov 10, 2005 6:04 am

Quoting RAMPRAT980 (Reply 59):
It will stay afloat for as long as God allows it to do so.

Um ... i hope you're not serious .... if you are, that's the most stupid thing ever said on A.net

 laughing 
I'M BAAAAAAAACK!
 
57AZ
Posts: 2371
Joined: Tue Nov 02, 2004 2:55 pm

RE: 747 Ditching At Sea - How Long Would It Float?

Thu Nov 10, 2005 5:23 pm

Even many of the old propliners usually broke up on impact with the water. The Pan Am 377 that ditched on the HNL-West Coast run due to a runaway prop broke up and sank in less than 30 min. Fortunately the captain reseated the passengers who were at the very rear, fearing that the fuselage would fail and they were able to ditch near the position of the USCG Cutter Ponchartrain.
"When a man runs on railroads over half of his lifetime he is fit for nothing else-and at times he don't know that."
 
na
Posts: 9823
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RE: 747 Ditching At Sea - How Long Would It Float?

Thu Nov 10, 2005 8:03 pm

Hawker got it right, I also would think that on a calm sea a 777 or in general any mainly twinjet-configurated airliner with its monster-engines hanging down underneath wing/fuselage level would have the least chance because of the massive engines stopping it abruptly.
 
RAMPRAT980
Posts: 584
Joined: Sun Mar 13, 2005 1:06 am

RE: 747 Ditching At Sea - How Long Would It Float?

Thu Nov 10, 2005 9:47 pm

Quoting F27XXX (Reply 71):
Um ... i hope you're not serious .... if you are, that's the most stupid thing ever said on A.net

Ok Patrick Starfish drool  calm down. If what I said, according to you, is stupid then its the 2nd most stupid thing ever said on A-net. Being that you don't see sarcasm and wit, I would say that your reply has to be the most(what word should I use since stupidest isn't in the english dictionary)lets use the word dumb or idiotic because there is no word to describe your ignorant response. With that I want to congratulate you leather boy.

Lets all hear it for leather boy for winning the buthead butthead  trophy  of the year award  praise   praise   praise   praise 
With gun control there can be no democracy.. With gun control there can be no Freedom
 
md80fanatic
Posts: 2365
Joined: Tue Apr 13, 2004 11:29 pm

RE: 747 Ditching At Sea - How Long Would It Float?

Thu Nov 10, 2005 10:18 pm

Quoting F27XXX (Reply 71):
Quoting RAMPRAT980 (Reply 59):
It will stay afloat for as long as God allows it to do so.

Um ... i hope you're not serious .... if you are, that's the most stupid thing ever said on A.net

laughing

I thought RAMPRAT980's response was the most intuitive, and absolutely the only irrefutable comment on this thread. In fact I wish I had said it first....sometimes I forget about the Big Guy, and that's not good.

It sure takes guts to tell the truth around here, bravo RR.  veryhappy 
 
RAMPRAT980
Posts: 584
Joined: Sun Mar 13, 2005 1:06 am

RE: 747 Ditching At Sea - How Long Would It Float?

Thu Nov 10, 2005 10:37 pm

Thanks MD80. I appreciate your comment.
With gun control there can be no democracy.. With gun control there can be no Freedom
 
ARCJET
Posts: 277
Joined: Sat Aug 23, 2003 4:12 am

RE: 747 Ditching At Sea - How Long Would It Float?

Thu Nov 10, 2005 11:03 pm

Until the Lead Actor and Actress are rescued and removed from the aircraft.
Charleston, SC
 
RAMPRAT980
Posts: 584
Joined: Sun Mar 13, 2005 1:06 am

RE: 747 Ditching At Sea - How Long Would It Float?

Fri Nov 11, 2005 2:57 am

Quoting ARCJET (Reply 77):
Until the Lead Actor and Actress are rescued and removed from the aircraft.

hey Leather Boy what do you have to say about that quote.
With gun control there can be no democracy.. With gun control there can be no Freedom
 
glacote
Posts: 357
Joined: Thu Jun 02, 2005 1:44 am

RE: 747 Ditching At Sea - How Long Would It Float?

Fri Nov 11, 2005 12:33 pm

Quoting Zvezda (Reply 10):
A B787 would have a much, much better chance of remaining intact in a ditching.

Source? Explanation?

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