Sunday, October 14, 2007

Hands-off flying

I had thought that today would be a great soaring day, because a cold front went through the area Saturday morning. Usually the post-frontal day is quite unstable and often has visible CU to fly. But it must have gone through quickly, and a building high warmed things up. The NAM forecast called for a strong inversion up to about 6000'. The temperatures aloft kind of reinforced that. So no one was expecting a great day, and in fact some pilots landed quickly. There was lift, but no one on the radio was getting above about 4000'. I planned to fly regardless, even if it was just a sled ride from a high tow above the inversion, because it had been quite a while since my last flight.

On tow, as soon as we got above the top of the visible muck in the air, all the light turbulence and lift disappeared... the air was silky smooth. I went up to 3800' AGL (5300' MSL) and released, because there was something I wanted to try out before beginning the work of thermalling. (I could see a couple of gliders thermalling not far away and below me, so I was pretty sure I could jump right in.)

In the November issue of AOPA Flight Training, an article by CFI Ralph Butcher talked about the need to learn to fly hands-off in order to free up one's hands for other cockpit tasks. I know that airplanes and gliders are basically stable, but more so in pitch (due to the trim) and yaw than in roll. But with no active roll inputs by the pilot, an aircraft will eventually roll one way or the other and end up in a spiral dive. Ralph's article crystallized something that I had half-learned some time ago: that small rudder inputs have a secondary effect of causing small roll effects. (This is mentioned somewhere in Stick and Rudder; maybe I'll look for the reference and add it later.) So in this smooth air, in straight flight, I tried it out. If a wing starts to come up, step on it - give light rudder pressure on the same side. That causes a slight yaw, which the airplane's dihedral turns into a slight roll. It works! I was able to fly the PW5 completely straight and level for 30-60 seconds (actually indefinitely). The PW5's pitch trim is in notches, not continuous, so I could not fly hands-off at any speed I want... but it definitely works, at least in relatively smooth air. So this can be used to free up my hands to deal with a chart, radio, PDA, or whatever. (It would be easy to get distracted with inside tasks and not keep a good lookout.)

Note to beginners: do not think for a moment that I am talking about turning the aircraft with the rudder. One can only really turn with the ailerons and coordinated rudder. These little rudder adjustments are intended to induce slight rolls to keep wings level without significantly changing the heading - a secondary effect of the rudder.

Down into the soup... amazing that it was so hazy just one day after a rainstorm. There was a clearly defined top to it, and once below the top, there were little bumps everywhere. I did find thermals of 1.0 to 2.0 knots, enough to work up to 3800' to 4000' MSL. But not high enough to go very far from the airport. It wasn't very strong, but it was wide enough and consistent enough that I could practice centering it using the vario, and the SeeYou "Thermal Indicator", and the seat of my pants. Some said that there was a shear line working, and I did kind of find some dispersed lift, but I could not visually see it. What I did find was generally big enough that I think it was all thermal. I flew with some crows for a while.

Eventually I got down fairly low and wasn't finding more lift, so I came back in rather than work hard on a marginal day. I ended up with exactly an hour in the air. My landing was one of the best I've had in the PW5: in the right spot, very smooth, and with enough speed to give me rudder control to roll off to the side. (The PW5, with its two fixed wheels and small rudder, usually does not steer well during the rollout.)

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