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Chris,

 

Excellent Analysis.

 

Since the 320 has got to be the most individually modified kit plane, could you be more specific about details of the elevator system in the 320 used for comparison:

 

1. Was the elevator bell crank arm 4" (original design) or 3" (popular mod) as this affects stick forces and movement distances?

 

2. Since the spring trim system was used, was the trim the original crucifix and spring system or was the Reichel trim wheel with stronger springs used?.  This has some effect on trim rigidity and stick forces for elevator movement away from the trimmed position.  You did mention that trim tabs could alter certain results (even the tab sizes used by builders may be quite different).

 

3. Was the bob weight installed?  Recently some builders claimed that they did not install the bob weight that was designed to increase stick forces under increased aircraft loading.

 

Considering these variables, what implications might they have with respect to observations/conclusions made in your report?

 

Thanks,

 

Scott Krueger

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Scott,

Good observations.

1. Shortened. I will add that detail along with stick travel per elevator travel.

2.  Reichel trim wheel.  I am trying to line up an abbreviated test on a small tail 360 that uses an electric trim tab to evaluate the influence of the spring.

3. Yes, bob weight installed, will add that as well.

Stick fixed stability is not affected by any of the above.  It looks at rigid elevator position regardless of how it is achieved.  Stick free response may be influenced by the spring, in particular, when getting farther off the trim point.  For example the phugoid that became somewhat violent.  Initial thoughts are that the spring could be negatively influencing the low speed end where hinge moments start dropping off rapidly.  I hope to have some data on that soon.

Chris