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/118927
1 Airspeed (knots) 30 40 50 60 70 80 90 Flight Path Angle (degrees) 0 -1 -2 -3 -4 -5 -6 Figure 3 speed, they'd realize markedly different changes in flight path angle. path corrections by adjusting power rather than by changing airspeed. Airspeed deviations in Airplane Y result in large changes in descent angle, making airspeed control a significantly more critical task than in Airplane X. Because small airspeed variations in Airplane Y result in comparatively large flight path changes, its pilot must diligently control airspeed to remain on the desired glideslope. On the other hand, pilot Y can make minor, short-term glideslope corrections using just the stick and not have to adjust, and then reset, the throttle. The reality is most pilots don't fly one-handed approaches. We manipulate the throttle and the stick to control the vertical flight path. Flight path stability curves provide an indication of how much of each you'll have to use to make glideslope adjustments. Airplane X's descent angle is not as sensitive to airspeed variations, and to make an effective flight path correction its pilot would have to deviate a lot further from the proper approach speed. The flatness of Airplane X's curve can lead to sloppy airspeed control because the pilot can maintain a near-proper glideslope over a range of airspeeds. If pilot X doesn't notice—and correct—an airspeed deviation, he will likely see one of two outcomes. Airplane X may land hard because it doesn't have enough airspeed left for a proper flare. Or it will float down the runway in the flare, dissipating its excess airspeed. In Airplane X, you'd most likely make flight The Dark Side Figure 3 shows the flight path stability curve for another airplane with a 75-knot approach speed. Notice how sharply Figure 3's descent angle increases as the airspeed drops below about 70 knots. Trying to stretch a glide in this airplane can result in the bottom falling out too close to the ground to recover, even with power. There's another insidious deception with some airplanes. Unless you're flying an instrument approach, you won't have a vertical flight path angle indicator. You'll have airspeed and vertical speed indicators, and you do the math to establish the desired descent angle. Some final approaches give you approximate glideslope indications through VASI and PAPI systems, but at many VFR airports pilots must visually assess their descent EAA Experimenter 43