Insights

Sharp thinking yields great performance

The power-off, 180-degree accuracy approach and landing starts abeam a designated touchdown spot at 1,000 feet above ground level (agl) and terminates with a landing that's within 200 feet beyond that spot. All pilots benefit from practicing this maneuver, which is required for commercial pilot certification.

To fly the maneuver, imagine that you entered a deep-sea fishing contest and hooked a large fish that might be the winner. However, if you let the line get too tight, it will break; if you let the line get too loose, your fish will shed the hook. You must carefully play the fish until you get it next to the boat where it can be brought aboard.

In other words, if you travel too far from the designated touchdown spot, your line will break, and you'll land short. If you get too close, your line becomes too loose, and landing within 200 feet beyond the spot becomes impossible. Both situations are disqualifying, so you must carefully play the spot during the approach.

Elements to consider:

• A tailwind will shallow your glide angle. That could occur on the base leg.
• A headwind will steepen your glide angle. That could occur on the base or final legs.
• A dry, dark-colored surface on a sunny day will get hot, heat the adjacent air, and cause updrafts or thermals.
• A moist surface like grass or trees on a sunny day will get hot, but the moisture evaporates and cools the adjacent air, which may cause downdrafts.
• As you descend, wind velocity normally decreases and the wind direction moves counterclockwise.
• As a last resort when too low, you can increase glide distance by moving the prop control to the high-pitch, low-rpm position. Propeller drag can be a significant factor, and commercial pilot flight training is conducted in complex airplanes--with retractable landing gear and a controllable-pitch propeller.
• As a last resort when too high, you can decrease glide distance by executing a forward slip, but use caution. When the slip is terminated, you must immediately return to the approach attitude so that airspeed does not increase, a situation that will cause a long, disqualifying landing.
• You must use the correct airspeed. The pilot's operating handbook published airspeed is for maximum gross weight. Reduce airspeed 1 percent for every 2 percent below the airplane's maximum allowable gross weight. If the wind is gusting, add half the gust value.
• A short final approach is preferable to a long final approach, because you will encounter fewer variables.
• Do not aim for the spot. Aim short. The airplane will move to the spot during the landing flare. You must keep that spot in the same relative position on the windshield during final descent. One trick is to keep the bottom of the spot two inches above the top of the engine cowl. The spot's size will continually increase, but keep the bottom of it above the cowl. You can't do that with pitch, because airspeed will vary. You must do it with altitude control. Slip or extend flaps if high; use the prop's high-pitch setting if low.
• When everything looks correct and a normal wind gradient exists--wind velocity decreases during the descent--extend the next increment of flaps because you are about to go above your desired glidepath because of increasing groundspeed.
• Do not attempt a smooth landing. Ensure that the airplane is in a landing attitude--nosewheel above the main wheels--and allow the airplane to settle onto or just past the spot. Yes, it will be a firm landing.

With those factors in mind, play the spot by momentarily turning toward it once or twice while descending on the downwind and base legs. When it's obvious that you're too high, immediately turn away from the spot and continue the descent. That awareness will ensure that your line is not too tight or too loose. You've got the spot!

After you turn onto the base leg, monitor two visual distances: line A, your planned ground track to the approach end of the runway; and line B, the distance from the departure end of the runway to the horizon (the base of mountains).

For a normal power-on approach, your altitude is good when the apparent length of line A equals that of line B. You're too low when line A is longer the line B; you're too high when line A is shorter than line B.

For this maneuver, keep line A a little shorter than line B so that you're somewhat higher than a normal, power-on approach. As you approach the touchdown spot, you can always execute a moderate forward slip if necessary.

Ralph Butcher, a retired United Airlines captain, is the chief flight instructor at a California flight school. He has been flying since 1959 and has 25,000 hours in fixed- and rotary-wing aircraft. Visit his Web site.