Message-Id: <9809219064.AA906417346@inet001.cardell.com>
Date: Mon, 21 Sep 98 18:29:11 -0500
From: <dechaze@cardell.com>
To: <lancair.list@olsusa.com>
Subject: Re:Landing Gear Loads
Mime-Version: 1.0

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About landing gear loads Ed Armstrong writes:

> You can do this for the wings. Just figure out how much the 
> wings can support from the old ratings. The wings can support 1685 x 9 G's 
> = 15,165 lbs. 15,165lbs / 2000 lbs =7.5G's. However, this is wrong 
> because it doesn't cover everything. They are overlooking the real limiting 
> factor, the landing gear. 

You are quite right Ed, but it's more wrong than at first it appears.  1,685 is
not the right number to multiply by the 9gs.  This is because the wings support
themselves and the fuel they carry when in flight.  The load that breaks the
structure is from the fuselage (engine, people, tail, stuff).  This is what you
multiply by 9.  After baselining this for the factory load limit, run up the
scenario weight as you describe.  The bad news is that this is more severe than
what you laid out above (unless your extra weight is in the wings).  Going to
2,000 lbs gross is a BIG jump if it's to be people and cargo.  

Obviously, Lancair is telling us they think the gear (could also be wing
structure between the gear)is the limiting factor.  For us, F=ma is probably
good enough.  F is what causes the plane to break so hold it constant and vary
'a' (how softly you land) with change in weight (m).  Maybe assume worst case -
weight in question is fuselage weight just like above - in case the problem
isn't the gear structure itself.  Problem is we don't know exactly what breaks
and how hard we can hit, so we don't really know what we are giving up (do you
have to grease it in?).  

The safe play absent detailed factory information is leave landing weight at
1,685lbs.

Ed de Chazal