From: Sky2high@aol.com
Message-ID: <4d.20ecad.26db7c7f@aol.com>
Date: Mon, 28 Aug 2000 04:27:43 EDT
Subject: Runaway trim
To: lancair.list@olsusa.com
Reply-To: lancair.list@olsusa.com
Mime-Version: 1.0

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Interesting topic.

In my 320, all the trim systems utilize springs with the aileron and rudder 
being MAC servo operated.  The elevator is controlled thru the Reichel geared 
wheel.  Any of the systems can easily be overidden against the force of the 
springs if the servo goes to the max.

The Legacy 2000 kit comes with all three trim tabs installed and all are 
driven by MAC servos.  So:

1) How much force  would be required to overcome the airstream force from the 
servos being driven to their max extension or retraction?  

2) Should the servos be slowed down with the option available from MAC?

3) At approach and landing airspeeds, is the max out-of-trim condition more 
manageable?

4) Can and should the max trim displacements be physically limited (stops) to 
the max trim needed for the flight envelope?  

I especially liked the "dead-man" switch approach so that a stick mounted 
finger switch must first be depressed before electricty is applied to any 
trim circuit.  This would limit the extent of the runaway since you would 
feel it starting during application of trim and could simply stop it by 
lifting a finger (You know which finger to raise?).

Scott Krueger
N92EX
Legacy #2
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