Experimenter is a magazine created by EAA for people who build airplanes. We will report on amateur-built aircraft as well as ultralights and other light aircraft.
Issue link: http://experimenter.epubxp.com/i/149316
F li g h t Te s t in g Te c hn i q u e s There's one more test to complete before you laminate your VY plot; namely, a flight to check your results. You can fly three climbs through a selected density altitude, one at VY (according to Figure 4), VY + 5, and VY – 5. The highest climb rate should occur at the VY indicated in Figure 4. If it doesn't, you'll have to check your data reduction for errors. If no errors can be found, and if the difference is large enough to concern you, another sawtooth climb test should resolve the discrepancy. Perhaps your airspeed wandered a bit too much, or the air was a little choppy, or setting the climb power was not performed as consistently as it should have been. Here's where those quality notes can come in handy. Considering the confidence levels we assigned during our testing, the engineering judgment we applied during the data reduction, and how well the curves overlay the data points (we didn't show you this), we expect our new tool to be accurate. That's it for VY. Next time, we'll take that same sawtooth climb data and create a similar plot for the best climb angle airspeeds (VX). Ed Kolano, EAA 336809, is a former Marine who's been flying since 1975 and testing airplanes since 1985. He considers himself extremely fortunate to have performed flight tests in a variety of airplanes ranging from ultralights to 787s. Correction to 'Angle of Attack and Maximum Range' Experimenter, March 2013 I goofed. In the March Experimenter article "Angle of Attack and Maximum Range," Figure 3 included a plot of lift coefficient and drag coefficient versus angle of attack and stated that the greatest vertical distance between the curves represents the maximum lift-todrag ratio. That's wrong. It represents the maximum difference between the curves—not the same thing, and not relevant to the maximum range discussion. Rather than enumerate the reasons for this error, I might just pen them as lyrics to a woe-is-me, countryand-western song. The bottom line is maximum range glide occurs at the unique angle of attack where drag is at its minimum and the ratio of lift to drag is at its maximum. My apologies for any confusion, and please disregard Figure 3 in my March column. – Ed Kolano 40 Vol.2 N o.8 /August 201 3