Re: 747 forced ocean landings -- survival odds

From:         Pete Mellor <pm@csr.city.ac.uk>
Date:         21 Dec 94 02:17:41 
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> There's a blazing discussion underway in rec.aviation.misc about
> forced ocean landings of 747s.  At issue are the odds of the plane
> staying in one piece, how long it would stay afloat and whether it
> would begin to leak through hull weep holes or other openings,
> whether or not passengers would be better off remaining in the cabin
> or proceeding to life rafts, etc, etc.

A few thoughts:- 

The hull is designed to withstand positive pressure *inside*. Once under 
water (assuming it would sink *before* the water filled the cabin), every 
device for keeping pressure *in* would work "the wrong way round". (The 
plug doors would be forced open by the external pressure, for example.) 
If passengers donned life-jackets, they could presumably bob up to the 
surface, *provided they could get out of the doors against a rush of 
incoming water*. (Not a cheerful survival prospect, IMHO.) 

The main question is, how long would it float? I have not flown on a 747 
recently, but I did fly on a 737-400 last week. The safety card shows the 
aircraft floating on the water after ditching, with the passengers sitting 
calmly on the wings in their life-jackets after making an exit through the 
over-wing doors. I was sufficiently surprised the first time I saw this to 
ask one of the cabin staff if the 737-400 really was designed to float, but 
I didn't get a particularly authoritative answer. 

> Would someone with knowledge of this issue please make a posting
> to rec.aviation.misc and share some insight?

Please feel free to repost this, if you think it is useful. I would be 
interested in any opinions on the 737's qualities as a flying boat! 

Regards, 

Peter Mellor, Centre for Software Reliability, 
City University, Northampton Square, London EC1V 0HB 
Tel: +44 (171) 477-8422, Fax.: +44 (171) 477-8585, 
E-mail (JANET): p.mellor@csr.city.ac.uk 
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