Mailing List lml@lancaironline.net Message #43214
From: <rwolf99@aol.com>
Sender: <marv@lancaironline.net>
Subject: Re: Elevator Controls
Date: Tue, 24 Jul 2007 17:11:11 -0400
To: <lml@lancaironline.net>
Bryan -

The purpose of the bobweight is to increase the steady-state stick-force-per-G (already woefully low in 320/360's unless the CG is rather far forward).  The bobweight does this in the 320/360 by being located aft of the pivot point.  When you pull G's, the bobweight is pulled down.  If you imagine the geometry, this is pushing back on the control stick.  The pilot is trying to lift the bobweight by pulling the control stick aft, and the g forces are pulling the bobweight down, resisting the pilot's efforts.  This increases the force that the pilot must apply to deflect the elevator.

All of this happens by torques imposed on the idler.  As a result, the important thing is to have the bobweight aft of the pivot point by the proper amount.  If your system was rigged so as to have the bobweight directly above the idler pivot point, it would not do its job at all.  Putting the bobweight on the lower part of the arm, rather than the upper part, is a step in the right direction.  However, if it's still 45 degrees in the air rather than mostly hrizontal, it will be less effective.  I'd have to see a sketch before I could say it was good enough, but you have it in front of you and now you understand what the objective is.

Myself, I consider the flight control system to be the most important system in the airplane --  I'd want it perfect.  I'd redo the aft pushrod to make it the right length.  We have almost $100,000 in our airplanes, what's another $100 in the grand scheme of things?

- Rob Wolf
Lancair 360 85% complete

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