On 01/18/2009 12:53 PM, Jon S. Berndt wrote: >> Newer aircraft are better at it than older aircraft. And that's >> not a fluke or any kind of "miracle". It's something they design >> for. > > You are simply asserting what aircraft manufacturers are *supposed* > to do.
You think I am just making this up? Gimme a break. 1) When I say "newer planes are better at it" I mostly repeating what I've heard from FAA and NTSB guys, although I have also seen some of the data first-hand. 2) When I say "it is something they design for" I am repeating what I heard from guys who worked at Boeing and Embraer. 3) You are right that they are "*supposed*" to do it. In fact it is required by the FARs. Do you take that as evidence that they don't do it, just because they are supposed to? > The ditching instructions are so clear in the short information card > that passengers are told to read, but those instructions are for a > wildly optimistic outcome. Even in pristine water conditions, I would > think that the landing must be precise. Agreed. It has to be precise. That's why the pilot gets the big bucks. And BTW, concerning the case you mentioned of the 767 that ditched just offshore in the Comoros.... That would have turned out a lot better if one hijacker had not lunged for the controls at the last moment. That caused a wing to dip into the water, which in turn caused a horrific cartwheel. And no, I'm not making that up either. I'm quoting Captain Abate, who survived and went on tour talking about his experiences. Did you think the pilot *intended* to touch down wingtip-first? That doesn't work even on land. Did you think he just didn't notice that one wing was low? Gimme a break. http://i2.cdn.turner.com/cnn/2009/US/01/16/air.crash.ditching/art.ethiopia.crash.wtn.jpg > I'd like to know how manufacturers test an aircraft for water > ditching performance, in all sorts of conditions. How can the > manufacturer prove they meet the FAR requirements? They do it the same way they design for performance in air, starting with ... if you can believe it ... a lot of computer models. It turns out that CFD (computer fluid dynamics) can handle fluids other than air. They also build and test physical scale models. They also reason by analogy to full-scale tests that have been done. They also read big fat books on naval architecture. > FAR requirements? What are those, specifically? Some requirements are sprinkled throughout part 25. For starters, there is 25.801(b) which says >> Each practicable design measure, compatible with the general >> characteristics of the airplane, must be taken to minimize the >> probability that in an emergency landing on water, the behavior of >> the airplane would cause immediate injury to the occupants or would >> make it impossible for them to escape. FAR 25.801(d) requires the aircraft to stay afloat for a while. FAR 25.807 requires that there be enough usable exits to get everybody out after ditching. (Typically exits in the rear are not usable after ditching.) The above applies to everybody. There are additional requirements if you want to be certified for extended overwater flight. And no, I'm not making that up, either. You you can read for yourself at e.g. http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgFar.nsf/FARSBySectLookup/25.801 If you want really detailed "specifics" you will find that the FARs are not overly specific on this topic. But the FAA guys in their usual way have backfilled with memos explaining their "interpretation" of the FARs. You can find some of these by googling. ------------------------------------------------------------------------------ This SF.net email is sponsored by: SourcForge Community SourceForge wants to tell your story. http://p.sf.net/sfu/sf-spreadtheword _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
