Technique / The Power Curve

1. Level off your trainer

at a typical round-number airspeed, say 100 knots indicated airspeed (IAS). Wait until the condition has stabilized, note the power setting, and write it down. In the Cessna 172N used here for demonstration that is 2,400 rpm. Next, decelerate to 90 KIAS while maintaining level flight. When ready, write down the new power setting. The 172N’s is 2,250 rpm. Continue this process down through 80 (2,000 rpm), 70 (1,750 rpm), and 60 (1,700 rpm). Now you’re deep into the slow-flight realm, approaching VS. At 50 KIAS, it took increasing the power to 2,000 rpm to maintain level flight—this is the region of reversed command. 

2. To make the graph

during the postflight session take graph paper or a lined piece of notebook paper, and draw two axes at right angles. Set airspeeds from left to right in increasing increments on 
the horizontal axis. Arrange power settings on the vertical axis, with highest power used at the top. 

3. Plot each point

from your in-flight notes. A U-shape graph will emerge. As you study it, note where the power settings begin to increase; this marks the region of reversed command, so called because you must increase—not decrease—power to maintain level flight as airspeed decreases. The left side of the U also illustrates the idea that any power setting between minimum power used in the exercise and power at VS produces two airspeeds in level flight, each resulting from a different power-and-pitch combination. As an example, see the two points plotted at 2,000 rpm for the Skyhawk.