From: "Marvin Kaye" <marv@lancaironline.net>
Subject: Re: Gross Weight & Balance of IV-P, Other considerations for
 Lancairs
To: lml
Date: Sun, 14 Sep 2003 14:07:40 -0400
Message-ID: <web-2579146@logan.com>
In-Reply-To: <002301c37abe$350f35b0$0100000a@tednoel>
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Posted for "Ted Noel" <tednoel@cfl.rr.com>:

Scott,

Let us consider your numbers in a different light. Essentially you are arguing 
for maintaining the 8.8G implied max limit for the L-IV P based on Lancair's 
overbuilding. They use 2* rather than 1.5* design load as required by the FAA. 
But if we accept that the FAA number has been shown over the years to be safe, 
and that the Lancair test was accurate, the results of your math come out 
differently.

Basically, if you divide that max test number by 6.6G, we get 31240/6.6=4733# 
max gross. This is a 4.4G design and 6.6G max load limit. This leads to the 
higher Va I presented (157kts vs. 132 kts.). Only if you insist on Lancair's 
overconservative 8.8G ultimate limit do you get the lower Va. (BTW, your math 
below was wrong. 31240/4550=6.87G not 3.4G. You left out the factor of 2.)

You are correct that the breaking load doesn't care what the airspeed is. That 
is a non-aerodynamic issue. The aerodynamics are concerned with how one 
applies that load.

The essential question is this. Do we play conservative by keeping the higher 
margins, or are we comfortable with the margins that the FAA has used for 
eons? Are we confident that our wing is as strong as the Lancair test wing?

BTW, heavy airplanes are less responsive to control inputs. Could that explain 
the autopilot symptoms you report?

Ted Noel