User Guide

Learning To Fly with Rod Machado
151
7
The Constant-rate Descent
For a typical ILS approach flown at 90 knots, a 500-foot-per-minute (FPM) descent rate is required to
remain on glideslope. Of course, if you fly the approach at a faster speed, you must increase your
descent rate. Glideslope angle and wind are two factors that affect the precise descent rate required
to center a glideslope needle. But we’ll use a ballpark descent rate of 500 FPM for our example.
Okay, enough talk. Time for a little action, Jackson. Let’s practice flying a descent at this rate.
Shucks, you probably thought I was going to let you off without doing another one of those
experiments, didn’t you? That’s not going to happen as long as I’m your instructor. Fortunately, this
experiment is fun.
From the Flights menu, click Select Flight, and choose Tutorial 15, Situation 1.
The autopilot’s altitude hold is off and the airplane is paused in level flight at an airspeed of 90 knots.
I’ve also hidden the heading indicator, altimeter and turn coordinator for this lesson to help you focus
on the appropriate instruments for a constant-rate descent.
Here’s what I want you to do. Fly a descent at a constant rate of 500 FPM at 90 knots. Do this by
radial scanning the VSI and airspeed indicator, starting with the attitude indicator. You’ll do this by
reducing power from its present setting to a little less than 10 inches of MP and letting the nose
naturally pitch down slightly. Adjust the pitch as necessary to maintain a descent rate of 500 FPM
and adjust the power to maintain 90 knots of airspeed. Yes, this is a reversal of the control functions
we used in Tutorial 7. Using the controls in this manner allows you to maintain precise control of the
descent rate required for an ILS approach. Give it a try.
1. Press P to activate the simulation.
2. Adjust power to maintain 90 knots in level flight (approximately 14
inches of MP as shown in Figure 5). Notice that 90 knots requires a
pitch attitude of approximately 5 or 6 degrees nose-up pitch.
3. Reduce power to a little less than 10 inches of MP, let the nose pitch
forward naturally, and adjust the pitch to maintain a 500 FPM descent
rate. This requires approximately 1 degree of nose-up pitch on the
attitude indicator (AI).
4. Trim to maintain the attitude for this descent rate.
5. Make small adjustments in pitch to maintain 500 FPM and a small
adjustment in power to maintain 90 knots. (Airplanes have inertia so it
may take a few seconds to change speed when moving the throttle. Be patient.)
6. Once you’re established at this rate, press P to pause the simulation.
Believe it or not, you’ve just learned what to do when intercepting the glideslope. Since glideslopes
are normally intercepted from below, you’ll fly level at 90 knots until the needle lowers to a center
Figure 5