Message-ID: <3C7915A7.3000603@regandesigns.com>
Date: Sun, 24 Feb 2002 08:32:39 -0800
From: Brent Regan <Brent@regandesigns.com>
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To: Lancair List <lancair.list@olsusa.com>
Subject: RE: Lancair 4P Vne & Mach Limit (Mmo)...True or False?
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Good news and bad news for Jeff.

The bad news is that he forgot that Mmo is TAS and Vne is IAS.

The good news is that 0.52 Mmo is likely very conservative. The reason 
makes an interesting story.

Without getting into a detailed explanation, suffice it to say that the 
calculated Mmo limit is partially dependent on the stiffness of the 
airframe. The design stiffness of the was determined by Martin Hollmann 
who, being the good engineer he is, performed tests on sample layups to 
determine their stiffness. (see "Composite Aircraft Design" M. 
Hollmann). Sounds great ..... except that the procedure Martin  used did 
not adequately allow for nonlinearities in the test fixture. According 
to a former PAC engineer, these tests were repeated for the certified 
aircraft program and it was determined that the original values were too 
low by about 25%. Based on the newer values, Mmo should be 0.58 or 342 
KTAS at FL300.

This is the limit I tested my airplane to and used during the cross 
country race.

Having said that, I must restate that the published limit is 0.52 and 
under NO circumstances should you ever exceed the published limit.

Especially if you are racing against me.

Opps....did I say that out loud ?? :0

Regards.
Brent Regan

PS. Check the archives for Fred Moreno's explanation on accurately 
converting between TAS and IAS given the significant effects of 
compressibility at these speeds.
BR

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