Randy, et al.

Many airplanes have a force discrepancy between pitch and roll forces. When pitch force is lighter than roll it can lead to unacceptable handling qualities because if you transition from a roll input to a pitch input rather rapidly the pitch rate generated can be unacceptable. This is especially true in aerobatic aircraft where someone is doing a roll and tries to ‘ease the stick forward’ while inverted and ends up accidentally pushing negative 4-6 g resulting in very much uncomfortableness for the occupants, (plz don’t try - trust me on this). 14 CFR Part 23.155 gives good guidance for pitch force gradients. Ideally, something in the 4-7 lbs. per ‘g’ is considered acceptable. The LNC2 is notorious for generating some pretty significant pitch rates (and ‘g’ onset) when the stick is accidentally bumped, (both positive and negative).

There are several cures for this phenomenon as shown in the book Aerodynamics for Naval Aviators.  Springs, bob-weights, anti-servo tabs, etc. can be used to tame excessive pitch rates and low stick force gradients (what you term as “sensitive”). LNC2s constructed in Australia are required to have a bob weight installed that provides for a greater stick force/g gradient. (See attached)

Before you take a drill or saber saw to your control linkages, consider consulting with a properly qualified test pilot or flight test engineer to explore the options available for harmonizing the control forces of your airplane more to your liking.

Brgs,

Randall Harris

LI-V, N524BA

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To: All LNC2 drivers and anyone else that wants to weigh in on the subject,

Subject: Stick force harmony (or stick movement vs. control surface movement) between pitch and roll

My Lancair 360 (N360DE), which I have flown now for 450 hours, has an characteristic that I would like some input on from all you well-informed and intelligent LML readers and contributors.

The characteristic is: Very sensitive pitch axis that is not harmonized with the roll axis.

I have gotten used to the difference and frankly don't plan on changing anything about it unless someone out there has a good suggestion.

I have some questions:

1. Is this typical of the LNC2?

2. What kinds of things should I be concerned about in considering any changes to the linkage of the system?

3. Has anyone made any changes and what were the results?

4. Does anyone out there have any experience with using full pitch deflection - in any portion of flight? I imagine it might be needed in landing, full flaps, lower speeds - but I have not seen it.

It seems to me the way to make an increase in aileron sensitivity is to change the mechanical linkage geometry to effectively make the control surface move more degrees of rotation per degree of stick movement. This would (and could) be done but the resultant would be the stick not getting full deflection (as compared to now) in the cockpit when the aileron was at full deflection. This might not be a bad thing because right now the stick has to be jammed up against one or the other of your thighs in order to get the aileron to full deflection.

Ideally I would like to have less sensitivity in pitch, resulting in more stick deflection for the same pitch results as now - and less total stick deflection in roll, which should result in more roll sensitivity.

For clarification purposes - my horizontal stab and elevator are a one-off design of Chuck Brenner. Chuck was involved with part of the construction of this project prior to my involvement with it.

Randy Hartman

Cell (319) 360-9775

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