Saturday, April 6, 2013

Adjusting


As I get more comfortable in the plane, I'm finding that I want to range a little further and in a different direction than my trips down south to Portsmouth. One trip in particular that I very much want to make is out west to Darke Co. in order to visit the corporate offices of Schmetterling Corp. I had hoped to make such a trip yesterday, but the morning forecast showed winds at 11 knots gusting to 15, and afternoon winds of an even more prohibitive 17 gusting to 22. Even back in the halcyon days of RV-6 piloting, the afternoon winds would have been more than I was comfortable with. The morning winds, on the other have, would hand been  acceptable. Not so in the 12, at least not yet. I have not yet practiced in winds that high. So, rather than sit at home moping about my inability to comfortably fly in winds that are relatively common, I decided to devote the morning to practicing crosswind landings. It is time to adjust to the newer, lighter airplane.

Speaking of adjustments, there were two more that I was interested in. First of all, I wanted to address the issue of the propensity of the airplane to want to bank to the right when flying hands-off. This new turning tendency is a direct result of having added the trim tab on the rudder to make the airplane fly straight without having to constantly have my right foot pushing on the rudder pedal. I wasn't sure that I was going to be able to fix the rolling tendency without the addition of yet another trim tab, but I thought it worthwhile to at least try the Van's black magic solution before adding another ugly protuberance to the plane.  Van's approach is to crimp down the trailing edge of the flaperon on the "light" wing, which in my case was the left side.  I don't know the aerodynamic theory behind it, but there are people that swear that it works.  Being as how it is easier to add more squeeze that it is to remove too much, I very cautiously worked my way down the length of the left flaperon using a pair of sheet metal seaming pliers ever so gently squeezing the trailing edge radius.

The results can be seen here:

video

Surprisingly, even that minor crimping was enough to remove the rolling tendency entirely.

The other thing I wanted to adjust was the lackadaisical way in which the autopilot would turn the plane. It seemed as if it really wasn't trying very hard at all. I dug out the calibration instructions that came with the Skyview and found that there was a setting that told the autopilot to limit itself to a user-defined number of degrees per second to turn, or to limit itself to a given bank angle. The default setting was 3.5 degrees per second, or nearly a minute to make a 180 degree course reversal. Lollygagging, that is.  I changed it to target a bank angle of 35 degrees.  This too was quite a satisfactory change:

video

Having determined that my two adjustments were adequate, I proceeded on course to MadCo where I would practice a few crosswind landings and refuel against the day when I can finally make the trip out to Darke Co.  The winds at altitude were an indication of what I would be facing as I tried to land. As the winds were out of the south, I got a notably high cruise speed when heading north.  About 20 knots of the indicated 138 is due to the wind.


Before too very long, I was entering the left downwind for my first attempt:


Naturally you are wondering at this point how it went. Well, I'm here to tell you that your first landing in an LSA with a 15 knot crosswind is.... eye opening. Other orifices, on the other hand, may pucker to an appreciable degree.  Being as light as it is, the bumpiness of the air plays a significant factor. It also takes quite a bit of wing-down-into-the-wind combined with opposite rudder to maintain a straight line towards the runway. None of this is all that unusual, but having taught myself to let the plane get lower and slower than I was used to in the RV-6, I did find that I had to remind myself to add sufficient power to overcome the additional drag from the displaced flaperons and rudder.  

The other tricky thing was dealing with the turning tendency caused by the wind pushing against the vertical stab once on the runway. The swiveling nose wheel just doesn't help at all. I found myself zig-zagging a little bit as I tried to roll straight down the runway. Now that I have had some time to reflect on it, this zig-zagging might be an indication of another adjustment I need to make. When I was finishing up the plane, I torqued the breakout force of the nose wheel (the side force required to move it away from center) to the specified 26 ft-lbs. I've read that Van's has reduced that value. I think what might be happening is that I am making directional corrections that don't have any effect until the pressure gets high enough to overcome the breakout force. When it gets to the point that the nose wheel will swivel, it lunges into the correction to the degree that I have to catch it with an opposing input. Which then causes the same problem in reverse. The net result of which is my zig-zagging down the runway.

In theory.

The testing of that hypothesis will give me something to try next time the weather is a tetch windy.

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