February 13, 2010

Changing Gears - Continued

Last week I posed the question, "Why would you need to change gears while flying?" and provided a list of reasons why I though you would have to. Tony Condon, a Cherokee II pilot (who's soaring blog can be read here) also provided his own reasons for changing gears. Below I address a few of those reasons and provide anecdotal evidence from my own flying.

Good Reasons for changing gears:

The sky ahead is blue.

I imagine this is the most common reason for changing gears during flight, and the easiest to see coming. It happened to me on a 500km triangle task on my way to the first turn point; the last 50km was out in the blue after a leg under good cloud development and reliable lift. The approach was simple because it was easy to see the problem coming, which is important to realize in addressing the other reasons for changing gears - if you are aware of the changes ahead you can start to plan early. In this instance, the solution was to climb as high as possible before heading out into the blue and switch from flying cloud references to following ground references. Dial back the MacCready and turn around and retreat before you are too low to make it back into an area of known good lift. Keep in mind when flying into the blue there are three reasons why the sky is blue; 1) the lift doesn't go as high as it did in the area of clouds, 2) the dew point is lower and the lift goes just as high, 3) there is little or no lift. On my flight, it turned out that the lift was just stopping 500' lower than in the area of clouds. That portion of the leg was still slower but I made the turnpoint.

The last thermal was broken at 8000'.

This one came form a very interesting learning experience; it required connecting a lot of different information together to develop a good reason to change gears and slow down. The sky was clearly rocking, good cu all over with good vertical development but no hint at over development. The cloud tops were leaning to the north east but I was showing wind more out of the north west. Cloud base appeared to be at 9500'-10,000', but climbing through 8000' the lift was broken and weak, about 2-3 knots below the rest of the climb. I realized, after ignoring the sings for an hour, that there was a shear layer at 8000' and if I could break through 8000' the lift would be much better and as an added bonus the wind would be better aligned with my leg. So I changed gears by slowing down and struggling through the shear layer, once above 8000' the lift picked up markedly. I was then forced to shrink my working band so that I would not drop below 8000'.

I am nervous.

Death Valley has an intimidating name which conjures up images of a very formidable place for a glider pilot to fly over. When your landing options are Furnace Creek or Stove Pipe Wells you consider all other options seriously. On a straight out flight from Tehachapi, Ca for the 2010 Dust Devil Dash, I had to make an even more difficult decision. I needed to cross the valley north east of Death Valley - 35 miles of inaccessible desert with the retrieve option being a helicopter for you and a 3 day expedition for the glider on ATVs and 4 wheel drive trucks. In this situation, no matter how good the clouds look are how strong the lift is, it's reasonable to change gears, slow down and stay high.

Bad reasons for changing gears:

I needed to make up lost time.

This happens to me more than I would like to admit. If you set a goal for your flight, and maybe it's a bit reaching or an over call for the day, it easy to blame yourself for falling behind and try to make up for it by doing the completely wrong thing in poor conditions; change gears and fly faster. There is only one optimal speed for every condition, and that speed doesn't change because you are flying poorly or because you need to fly faster to make your turnpoint or goal.

The final point is that there are good and bad reasons to change gears - good reasons are based on lots of information gathered from all resources available, bad reasons often come from internal emotions or rational independent of all the information available to the pilot. If you only eliminate all the bad reasons for changing gears from your flying you will be making a significant improvement.

Keep soaring, no matter what gear you're in!


  1. Good examples! I especially like the point about shear, as I've never really thought about that, but have probably experienced it. So while it took you an hour to read the signs it has apparently taken me 5 years :)

    Goal flights are interesting in the potential for adding the pressure of wanting to achieve the goal. On a long ago flight that I recently posted on my blog here: http://cherokeesailplanes.blogspot.com/2010/02/another-flight-report.html
    I chose to keep bombing away into pretty obviously non soarable conditions with the hope that I would get lucky and make my goal instead of changing direction and staying in the sunlight. I wasn't over Death Valley but there was a lot of corn down there, not a lot of really good landable areas. It all worked out in the sense that i didn't break the glider, but I didn't make the goal either.

  2. Tony,

    Thanks for the comment! That's another good "bad" reason for pushing - though not that bad. Pushing to achieve a goal in bad conditions is what flying an east coast contest is all about, so it's good to develop that skill set.


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