Flight Training - November 2012 - 21

CHECKRIDE

By Bob Schmelzer

SLOW FLIGHT 101

FLIGHT AT MINIMUM CONTROLLABLE AIRSPEED

ne of the first flight maneuvers your designated pilot examiner (DPE) will ask you to perform on your checkride will be slow flight—or, flight at minimum controllable airspeed. This maneuver requires you to reduce to and maintain an airspeed that is slightly above stall speed, while maintaining heading control, a specified altitude, and proper rudder coordination throughout. The tricky part is that at very slow airspeeds, flight control effectiveness and aircraft maneuverability are drastically reduced. In addition, flight control responsiveness becomes quite “mushy” when compared with flight at higher, normal operating speeds.
Flying at cruise speed is easy, but it takes real skill and coordination (and solid practice) to consistently perform this slow-flight task properly. Learning this valuable skill yields several additional beneficial side effects. Topping that list is developing an acute awareness of how the aircraft handles at speeds very close to the stall speed. Developing this sensitivity—often referred to as “stall awareness”—cannot be overemphasized. Another important benefit is effective rudder coordination over a wide range of airspeeds. Remembering your basic aerodynamics lessons, when the wing’s angle of attack is high, the angle of the relative wind to the propeller axis is also increased, thereby increasing the effects of p-factor. Recall that p-factor is the result of the descending (right-hand) propeller taking a bigger “bite” of the air, thus tending to yaw the nose of the aircraft to the left. Proper coordination requires that this front-end-alignment issue be countered with right rudder—not right aileron, as is too often observed during checkrides. While practicing slow flight, notice that when you’re applying enough right rudder to keep the wings level, your ailerons will be nearly neutral, thus yielding the desired result of proper rudder coordination—centered ball in the turn coordinator. Yeah! A third benefit will be a high degree of pitch/airspeed control. As we say in airline flying, “Speed is life.” Speed control, therefore, is life insurance. The ability to accurately control airspeed within a knot or two—especially at speeds just above a stall—is critical to safely flown takeoffs and landings, which are always accomplished close to the ground where accurately controlled airspeed is most critical. With very fine adjustments to the pitch during slow flight, you will be able to develop a keen sense of exactly when

PRACTICAL TEST STANDARDS
Task: Maneuvering during slow flight Objective. To determine that the applicant: 1. Exhibits knowledge of the elements related to maneuvering during slow flight. 2. Selects an entry altitude that will allow the task to be completed no lower than 3,000 feet (920 meters) agl. 3. Establishes and maintains an airspeed at which any further increase in angle of attack, increase in load factor, or reduction in power, would result in an immediate stall. 4. Accomplishes coordinated straight-andlevel flight, turns, climbs, and descents with landing gear and flap configurations specified by the examiner. 5. Divides attention between airplane control and orientation. 6. Maintains the specified altitude, plus or minus 100 feet (30 meters); specified heading, plus or minus 10 degrees; airspeed, plus 10 knots/minus 0, and specified angle of bank, plus or minus 10 degrees.

the onset of a stall would occur. And with that awareness comes the ability to tickle the edge of the stall using very small and timely elevator inputs, resulting in highly accurate speed control. The only remaining element is altitude control. And with proper practice, this is the easiest of all to master. Simply adjust power to control altitude. It is extremely helpful to have a good idea what approximate power setting provides the desired performance. As soon as your airspeed approaches the slow flight speed you are attempting to maintain, immediately increase power to that known value and then make subsequent power adjustments small and timely to maintain your desired altitude. Do not adjust pitch attitude to control altitude as you would during normal straight-and-level flight, because that would throw off your beautifully established airspeed control. Instead, at the first sign of a climb or descent away from your examiner-specified altitude, immediately adjust power to compensate. And make your power adjustments proportional to the relative rate of the observed altimeter needle movement. Finally, don’t forget to carefully clear the area for other traffic before beginning this maneuver. Slow flight requires a prolonged nose-high attitude that hinders your normal view ahead of the aircraft; clearing turns during slow flight are especially important, as well. Make these turns at a relatively shallow bank (around 10 degrees) to prevent an inadvertent stall caused by increasing load factor. When the maneuver is completed, simply advance power and revert to your normal pitch-controls-altitude elevator inputs while raising the flaps incrementally and, as appropriate, carburetor heat to Cold. Excellent! Next maneuver….
Bob Schmelzer is a Chicago-area designated pilot examiner, a United Airlines captain, and Boeing 777 line check airman.

NOVEMBER 2012 FLIGHT TRAINING

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Flight Training - November 2012

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