Descent ... FSX

FSX gauges at descent

The Descent phase of your flight contains three segments: Cruise Descent, Initial Approach, and Final Approach. Here is the Cruise Descent segment.

Maintain your cruise speed while descending to the initial approach point. Plan to end your cruise descent about 10 NM from the field and at an altitude of 3000 ft above the ground. "Ten and three" are easy numbers to remember. Also be aware that if you are making an ILS approach that you must be below the Glide Slope to properly capture it.

But when do we start our descent? Plan a descent rate of 500 fpm for all your descents unless circumstances dictate differently. So at 500 fpm eleven minutes will elapse to descend from 5500 ft down to Provincetown's near sea-level elevation. At 135 kts cruise, you will cover 25 NM in 11 minutes. I usually subtract out about 3 NM from that estimated descent distance since the Initial Approach and Final Approach segments are flown at slower speeds and less ground will be covered.

So begin this descent at 22 NM from the field. It will take five minutes to descend from 5500 ft down to 3000 ft.

Note that if you have a 10 kt headwind during your approach that your Ground Speed will reduce to 125 kts, and in 11 minutes you will cover only 23 NM. For that case, begin descent 20 NM from the field after subtracting out the 3 NM.

At 22 NM from the field reduce the Manifold Pressure to 20 in.—with the throttles—but leave the props at 2050 RPM. Adjust the throttles as needed to maintain your desired air speed as you descend.

From the Piedmont flight manual: "Never exceed 500 fpm rate of descent, except when necessary to stay on the glide slope during an ILS approach."

Reduce your power settings before beginning the descent to keep your airspeed under control.

Whenever flight conditions require a large reduction in power, reduce RPM as well as manifold pressure. As a rule of thumb, remember that each 100 RPM requires at least 1 inch Hg manifold pressure; for example, 18 inches Hg at 1800 RPM. Operation at high RPM and low manifold pressure should be kept to a minimum.

Never exceed 2325 RPM during descent.