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Date: Mon, 29 Mar 2010 16:54:37 -0400
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From: Paul Miller <paul@tbm700.com>
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Subject: Re: [LML] Re: Fox Article
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J Johnson you appear to be correct.  This documents lists the number as 
an old CAR requirement (quote below)

http://www.easa.eu.int/ws_prod/r/doc/CRD%202008-08.pdf

This document is part of the petition for EASA to adopt a higher stall 
speed for Pilatus and other SE turboprops as the FAA has permitted.   In 
it, the Pilatus asserts that survivability is not related to stall speed 
but on the energy absorption capability of the aircraft (also noted by 
Farnsworth on LML).

In my experience, Socata sought and won a 64 knot stall for the newer 
TBM on the basis of improved structure, Hi-G seats with demonstrated 
survivability and a number of other additions to the airframe. They 
argued that aircraft was safer than the 61 knot version and I think they 
are correct.   Pilatus and others want the same rules in Europe.   It is 
interesting reading on this topic and perhaps it would cause  the AP 
author to pen a slightly different story.   Personally, I don't think 
the recent IV-P accident is any different than the Hudson River ditching 
not long ago and I wonder why that comparison isn't made as both 
aircraft landed successfully in low-population areas but one had a 
horrible and, probably, unavoidable outcome.   Perhaps the Lancair pilot 
was simply making a wise choice of picking a long beach, contrasted 
water/sand making it easier to see that line through a contaminated 
windshield.  Perhaps choosing that route was deemed safer to all versus 
proceeding inland where trees, town, roads or other possible landing 
spots could involve people or the ocean where survivability was an 
avoidable additional risk.

Quotation:

"The origin of the 61 kts stall speed limitation for single engined 
aircraft dates
back to the US CAR3 regulations, which specified this limit as 70 mph. 
It was
just a "common sense" qualitative limit, defining an arbitrary number to 
reduce
the effects of a crash landing, not based on any rational motivation. This
number has since become gospel and has remained unchanged in the
subsequent FAR23, JAR23 and nos CS23, but its arbitrary nature is still
evident.
This limitation has the unfortunate effect to limit the wing loading in the
neighborhood of 100 kg/m2, and therefore to influence the design of the
aircraft tying it to a wing dimension which might be excessive. It is 
our belief
that a high speed touring aircraft should go to a wing loading of 130140
kg/m2 to obtain a better speed and a reduced turbulence/gust response, but
this would entail a stalling speed above the regulatory limit. Even 
worse is the
situation for the forthcoming single personal jets, which should go to 
an even
higher wing loading to have acceptable performance and gust response
characteristics."

Paul Miller
N357V Legacy

H & J Johnson wrote:
>
> For the record I believe the 'odd' 61knt number comes from 70mph. You 
> have to draw the line someplace, I guess that was the best statistical 
> number, I wouldn't know however.
>
> Fwiw
>
> J Johnson
>

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