"Good approaches make good landings." You've heard this adage many times in your flying life. And it's true: If you're all set up on the final approach leg of the pattern, the job of gracefully touching down is much, much easier. For the purposes of this article, we'll talk about the segment of the traffic pattern between the turn from base to final and a point just short of the runway threshold. We're talking about a controlled descent along a straight track, from approximately 800 to 1,000 feet agl to approximately 100 feet agl.
There are several key aspects to properly managing the approach. But first things first. You've flown a near-perfect pattern up to this point, correct? You've been making the recommended radio calls over the CTAF (common traffic advisory frequency) or unicom frequency (nontowered fields), or communicating and complying with ATC (towered airports), right? You've determined the proper direction of turns in the pattern, yes? And you haven't committed any of the blunders mentioned in my recent article on traffic pattern manners, have you? (See " Pattern Perfection," May Pilot.)
The first step in making a good approach is knowing how to control pitch, power, and configuration to achieve an optimal airspeed and descent profile. The target airspeed is published in your airplane's pilot's operating handbook (POH). It's usually very near an airspeed that's 1.3 times the power-off stall speed in the landing configuration — meaning with full flaps and landing gear extended, in the case of retractable-gear airplanes. With gusty winds, add half the gust factor to your 1.3 V SO target, as protection against shear-induced stalls. For example, if the winds are 10 gusting to 20 knots, that's a gust factor of 10 knots. So add half that — 5 kt — to your target speed.
You want a nice, gradual descent — one that lets you concentrate on the runway touchdown point and watch your ground track for signs of drift. You can't do that if you're constantly monkeying with the throttle or flaps. This is a time when seconds count, and a time for staying well ahead of the airplane.
You should have a good handle on how to quickly set up the airplane for landing. The combination of values is different for each airplane, but for light singles the following variables work pretty well:
- Power — 15 inches manifold pressure (for airplanes with constant-speed propellers) or 1,500 to 1,700 rpm (fixed-pitch propellers).
- Pitch — The attitude indicator's symbolic airplane should be one to one and a half bar widths down from the indicator's horizon.
- Flaps — Second increment.
- Landing gear — Down.
This should yield an airspeed somewhere around 70 to 80 knots, and a descent rate in the 500- to 700-fpm range. With a little practice, you can jot down the exact settings for your airplane. They may vary a little bit with weight or wind conditions — more power or less flap deflection may be required at heavier weights or with strong headwind components, for example.
With the settings firmly in mind, all you need to do after turning final is to go right to the values you've noted, then turn your attention to the threshold. Does this mean that you can relax? Of course not!
The target values are a starting point, a reference guide to be used as a baseline. They're for use immediately after turning onto final. We all know that thermal activity, turbulence, and strong head- or tailwind components can require changes in power and pitch as the flight progresses to the runway. This segment of the flight should be flown with one hand on the control yoke and the other on the throttle. Sinking on final? Apply enough power to arrest the descent. Thermals pushing you high above the ideal glidepath? Then reduce power to drift back down to the correct altitude. Wind shear causing dangerous variations in airspeed or altitude? Then execute a go-around, no matter where you may be on final.
Apart from reducing power, there are some other time-honored methods of losing altitude quickly — without diving to the runway and building up a huge surplus of airspeed. One is to cross the controls (i.e., right aileron and left rudder) and slip. This creates a lot of drag, and down you go. Two caveats are in order. One is to be sure you don't let your airspeed drop below your target value. You don't want to stall the airplane close to the ground — especially with the controls crossed. That's a recipe for a spin. And of course you should check your airplane's POH to see if slips are not recommended under certain conditions. Some airplane manufacturers warn that slipping an airplane with partially full fuel tanks can cause unporting. This happens when the fuel level sloshes away from the fuel line standpipes in the tanks. When that happens, fuel lines can admit air, and cause the engine to surge — or quit altogether. And other manufacturers warn against slipping with full flaps because airflow over the horizontal stabilizer can be blanketed. This can cause a tailplane stall.
The airlines teach that stabilized approaches are best. By this, they mean constant, rock-steady profiles with strictly defined parameters. Airspeed, for example, cannot waver by more than 10 knots over the target value to zero knots below it. Descent rates can't be greater than 1,000 fpm. Wings must be level below 400 feet agl.
Goals like these are admirable, but they're intended for turbofan-powered airplanes operating at higher speeds and weights. Compared to light singles, these airplanes take longer to respond to changes in power and aren't usually as maneuverable. For this reason, the pilot of a light single is in a much better position to react to minor upsets in pitch and roll when fighting turbulence on final. (Then again, the light single's relatively light wing loading makes it more susceptible to turbulence anyway.)
Even so, we can draw a lot from the stabilized-approach concept. Though you might be able to "save" a wild approach with skillful jockeying of power and controls, it's always best to stick to a target configuration and power setting for each and every "normal" approach. Make sure you have target values for short-field, soft-field, and spot landings in your bag of tricks, too.
Of all the factors affecting final approach, crosswinds can be the most vexing. They can really shake up the approach, and there are two main techniques for dealing with them.
One is to crab the airplane into the wind, then fly the approach crabbed. The other is to slip the airplane: Use ailerons to bank the upwind wing into the wind, and opposite rudder to prevent a turn. Slips cause uncoordinated flight and can make passengers uneasy if they're subjected to too much in the way of yawing forces. For this reason, many pilots prefer to crab down final.
Either way, once you're within a wingspan's altitude of the runway elevation it's time to kick out the crab or slip and prepare to align the airplane's longitudinal axis with the runway centerline. You want the airplane pointed in the same direction as the runway right before you touch down, or you may pay a price! But getting ready for touchdown is another story, one we'll cover in an upcoming issue.
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