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June 23, 2011

flying: 2nd take on the 150M

The wind was much lower today, only 10 knots. I was able to experiment freely with the back side of the power curve and I think I am getting it now. The thing about the 150 is how sharp the curve is. Once you got it slowing beyond Vy, it immediately starts slowing even more, and will quickly run out of airspeed. It also develops truly disconcerning sink rate and angle. The earlier you catch it, the quicker you put nose down, the less is the speed loss before recovery. I think a sharp pilot should be able to exploit it for short field landings, by balancing the plane on the back side of the curve. Cherokee, by contrast, has a reasonably flat top to its power curve and does not require anywhere near as sharp reactions. Just power it up and down as you want, and it extends or shortens the approach in a predictable way.

Can't say I'm an ace in 150 now, and in fact I ended completely lazing it by flying in with 10 to 20 degrees of flaps and then touching down at 60 mph. Oh well, it will have to do.

P.S. Why are we talking about the power curve if airplane glides down? That is because the loss of potential energy is tantamount to power over the same period. There is, however, a little trick to it: when a pilot sets RPMs or manifold pressure, that is pretty much it, but the power derived from descent depends on the rate of descent. If the back of the power curve is not steep, this can create a stable system: as airplane steepens its descent, the "power" grows and it extends the glide. But 150 is not like that.

There's an explanation of power curve in John Denker's See How It Flies. But to the best of my recollection, he does not make a connection of descept rate to power and thus the position of airplane on the power curve.

Posted by: Pete Zaitcev at 10:00 PM | No Comments | Add Comment
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