Just as it takes special skills to safely drive a fast car, flying fast calls for certain advanced skills. The perceptions are different when you fly fast, time is compressed, and you have to anticipate and think further ahead to stay on top of the flight ("Think Fast," AOPA Flight Training, December 1999).
Fast airplanes don't go fast all of the time, however. In fact, even in a fast airplane there's a fair amount of time spent in slow flight. In the context of primary flight training, the term "slow flight" usually means an exercise in which you fly at an airspeed just above stall. The exercise helps build good stick-and-rudder skills and knowledge of the handling qualities of the airplane. It requires vigorous use of the rudder to keep the ball centered, and good coordination of pitch and power to maintain altitude at the targeted slow airspeed. Excess power results in altitude gain or a higher airspeed, depending on pitch. Incorrect pitch attitude results in loss of altitude or erosion of airspeed and, potentially, an aerodynamic stall.
In everyday flying, however, slow flight takes on a different meaning. We could even define "slow" flying as anything done below the normal range of cruise speeds. If that's the case, then we fly slow quite a bit of the time.
Slow flight carries special concerns. When we're slow, we're closer to stall speed, control surfaces are not as effective, and the engine doesn't cool as well as at higher indicated airspeeds. In effect, the margin of safety narrows. If the engine loses power when you're cruising at 8,500 feet, you have ample time to get set up for an emergency landing and still troubleshoot the problem. If the engine loses power in the initial climb, you have neither sufficient airspeed nor altitude to hesitate while you figure out what to do. You must react instinctively by lowering the nose to avoid stalling; picking out a landing site; and, hopefully, running through a few quick troubleshooting procedures, such as switching fuel tanks and turning on the fuel pump.
Takeoff and climb speeds may be higher in a heavier, faster airplane, but the techniques for accomplishing those "slow" phases aren't all that much different. On takeoff, apply back pressure to the control yoke while accelerating on the runway to raise the nose and achieve a positive angle of attack for a smooth liftoff. In climb, adjust the pitch attitude to achieve the appropriate climb speed for the conditions and mission-best rate to get to cruise altitude as quickly as possible; cruise climb for maximum speed over the ground and good engine cooling and over-the-nose visibility; or some compromise speed between the two.
Where pilot technique usually diverges, when comparing slow airplanes with fast ones, is in slowing down. Slowing down in a typical light trainer or basic four-place single isn't much of a problem. These are relatively high-drag machines. When you pull back the throttle or raise the nose, the airplane sheds speed as though it's on some sort of new Atkins low-horsepower diet.
Speed control becomes more of an issue when you move up the performance ladder. The combination of more power and lower drag yields higher airspeeds, but it also makes slowing down more difficult. With the exception of some speedy little pocket-rocket homebuilts, most high-performance singles are heavier than their slower counterparts. That means the pilots also have increased inertia conspiring against their desire to slow down.
One way we don't slow down is to yank the throttle back. That technique just doesn't yield much in the way of significant, immediate results, especially if the airplane already is descending. Gross throttle reductions should be avoided in any air-cooled, piston-engine airplane, slow or fast. The sudden reduction in heat generated in the cylinders and transmitted to the cooling fins, combined with the increased airflow through the engine plenum in a descent, is known as shock cooling.
Shock or sudden cooling can lead to expensive problems. Textron Lycoming cites excessively worn piston ring grooves or broken rings, warped exhaust valves, bent pushrods, and sparkplug fouling as possible consequences of shock cooling. The company recommends a maximum cylinder-head cooling rate of 50 degrees Fahrenheit per minute. Increasingly, aircraft operators are installing engine monitors that display engine temperatures, including the amount and rate of cooling.
A big reduction in power almost always is the result of poor planning-of waiting too late to begin a descent or to configure the airplane for final approach. You end up high and perhaps too fast as well. As the runway looms in the windshield, you grow increasingly anxious about getting down, so you reach for the throttle and pull it back almost all the way to idle. Bad idea!
To begin a descent at cruise airspeed, reduce the throttle by about three inches of manifold pressure or, if it's a fixed-pitch propeller, about 300 rpm. The airplane will gradually nose over and descend. During the descent, enrich the mixture and periodically reduce the throttle because the power will build as you descend into increasingly dense air.
If you find that you haven't planned your arrival well and need to descend quickly, reduce the throttle to 20 inches, or 2,000 rpm for a fixed-pitch prop, while maintaining altitude. The airplane gradually will slow down, and at that power setting there's no danger of shock cooling. If you find that's still not enough to initiate a steep descent without the airspeed creeping up to the top of the green arc, reduce the throttle further. Hold your altitude until indicated airspeed drops into the white arc, then extend the flaps for added drag.
If it's a complex airplane, extend the landing gear. The drag from the flaps and gear will be more than enough to slow the aircraft for a rapid descent. Be sure to monitor airspeed on the way down, and adjust pitch attitude if necessary to keep the airspeed from straying outside the white arc.
Some airplanes, notably Mooneys, can be modified by installing spoilers. The devices stow inside the wing behind the leading edge. When activated, they extend a few inches up into the slipstream to add drag. They're marvelous tools on go-fast airplanes that just don't like to slow down.
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