"How can I predict how early to reduce power when slowing down to enter the pattern or preparing to descend on an instrument approach? I always seem to start too soon or too late." — Andrzej S.
“Here’s an exercise that’s especially helpful when stepping up to a high-performance airplane, but useful in any aircraft. Do this drill only with an instructor or safety pilot on board to keep a lookout for traffic.
Set normal cruise power and configuration. If you have an autopilot, turn it on in heading and altitude hold modes. Note your indicated airspeed. In fact, use your phone to take a ‘panel selfie’ to record the power setting, pitch attitude, and speed for normal cruise in level flight. Start a timer (and optionally, if the winds are light, set your GPS to track to a fix directly ahead and note the distance to the waypoint).
Smoothly reduce power to slow down for the speed you prefer for your initial approach or traffic pattern entry. I call this the ‘happy place’ in my Bonanza. It’s 17 to 18 inches of MP and 2300-2500 RPM, depending on the aircraft weight. In a Cessna 172 or similar type, set power at 2000 to 2100 RPM.
When the airplane stabilizes at the new airspeed (125 to 130 KIAS, clean, in a typical Bonanza; about 90 KIAS in a C172) stop the timer and note how long it took you to slow down. Take another panel selfie to record the new figures. If you want to average the times, return to the initial cruise settings and repeat the exercise.
You now know how much time and distance you need to slow down as you begin an approach or prepare to join the pattern. Or how long you can comply with ATC requests to keep the speed up until you need to slow down on an approach. You can also repeat this procedure to learn the power settings and configurations for other transitions, such as normal descents. The phone photos help you remember the key Pitch+Power+Configuration=Airspeed combinations for your airplane.
I had a new Bonanza A36 pilot run through this exercise the other day. It really helped him manage the airplane.
And now he knows it takes about one minute and 30 seconds to go from 2300 RPM and 23 inches MP in normal cruise … to the happy place.”
Do you use specific power/configuration settings to yield certain airspeeds (in level flight)?