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01/08 - Slow Flight!

By Steve Krog

Flying an airplane safely and confidently involves much more than cruising around looking at the beautiful scenery below. Do you recall when you first learned how to drive a car? Whether it was your father or a driver’s training school teaching you, different skills had to be learned as well as developing judgment so that you could drive safely and earn an official driver’s license.

Learning to fly is quite similar. To fly safely we must learn the various skills to operate the airplane, and also develop judgment. Thus, there are different maneuvers we must learn.

In previous Reach For The Sky articles, we discussed the first flight experience and attitude flying. Once we’ve demonstrated the ability to climb, descend and turn the airplane using coordinated control inputs, the next challenge is slow flight.

What is slow flight?

Much has been written about slow flight in flight training textbooks and verbally stated in video/DVD training programs. Yet for all the verbiage, slow flight is still misunderstood by student pilots, and even by a lot of flight instructors.

If this maneuver is first understood, and then demonstrated and practiced properly, a student will find slow flight a “fun challenge”. Further, through understanding and practice, you will become a much more safe, competent and confident pilot.

Slow flight can be defined as flight at any airspeed that is less than normal cruise airspeed. Taking that definition to the next level: flying the airplane at the slowest possible airspeed while still able to maintain full directional and altitude control of the airplane. This airspeed is usually about 5 mph above the aircraft’s known stall speed.

Why do we want to practice and become competent in slow flight? The objective of maneuvering during slow flight is to develop the pilot’s sense of feel of the airplane and ability to use the controls correctly, and to improve proficiency in performing maneuvers that require slow airspeeds such as during takeoffs, climbs, descents, go-arounds, and approaches to landing.

For example purposes, let’s compare flying an airplane to riding a bicycle. The airplane we fly normally cruises at approximately 100 mph, climbs out at 60 mph and lands at 70 mph. When riding your bike at a normal speed of 10-15 mph, control inputs to remain upright and ride in a straight line requires very little movement. But if you slow down and ride your bike as slow as you can at 2-3 mph, greater inputs are required to remain upright and balanced. The control movements of the airplane are similar and will feel quite different at each of these airspeeds as well.

Let’s assume we’ve made our take off and have climbed to a safe altitude of 2,500 feet above the ground (AGL), and are now flying in a straight and level cruise attitude. Your instructor will now demonstrate the slow flight maneuver.

The airplane will be transitioning from cruise speed to a much slower speed of approximately 45 mph, so we must first practice flight safety. The very first thing we will do before beginning slow flight is to clear the flight practice area for any other flying traffic. We accomplish this by making a medium bank turn 90 degrees in one direction, then 90 degrees back to our heading.

Once we have cleared the area for other traffic, we are ready to begin the maneuver. Note the altitude and the heading of the airplane, as we will strive to maintain both during slow flight. (I like to use an indicated altitude of 3,500 feet and one of the four cardinal headings - north, south, east or west - so that the student also has roads for directional reference.)

Attitude Controls Airspeed, Power Controls Altitude

Apply carburetor heat and begin reducing power to a fast idle. Simultaneously, begin applying backpressure on the yoke (or stick) to maintain altitude. Remember our last flight where we learned about attitude flying? Position the nose of the aircraft on the horizon in an attitude similar to the 60 mph climb. The airspeed begins to slow, and then stabilize at let’s say 50 mph. However, we’re striving for 45 mph. Raise the nose just a fraction of an inch on the horizon and again let the airspeed stabilize. Once we’ve reached 45 mph, note and maintain that attitude.

The maneuver also requires that we maintain a constant altitude as well, and power controls our altitude. A quick glance at the altimeter may indicate that your altitude is decreasing. Smoothly add power increasing your RPM’s by approximately 200. Do not fixate your vision on the altimeter. Rather, look out over the nose allowing airspeed and altitude to stabilize for a few seconds. Then quickly glance at the altimeter again. If you are still losing altitude, add another 100 RPM’s and repeat the process until both airspeed and altitude have stabilized.

Once both have stabilized you’ll be holding quite a bit of backpressure on the yoke. Holding the yoke in one hand, use the other to adjust the trim in a “nose up” configuration, until you feel the back pressure neutralize, requiring little or no back pressure to maintain both attitude and altitude.

You are now flying in a slow flight configuration. However, you’ll note that the airplane has turned about 30 degrees to the left of your assigned heading while you were busy adjusting attitude, power, trim, etc. When the airplane is in a nose high attitude and you are carrying any amount of power, engine torque and propeller “P” factor enter into the equation trying to turn the airplane to the left. To hold a constant heading while performing slow flight we must also apply slight but constant right rudder to offset the torque and “P” factor.

The first half-dozen times you transition from cruise flight to slow flight you’ll feel like the proverbial “one-armed paper hanger.” But after several tries you’ll be able to simultaneously raise the nose, adjust the back pressure and trim, and adjust your power until you can establish and maintain an assigned constant altitude, airspeed and heading.

We’ve described the step-by-step procedure for transitioning from cruise flight to slow flight. Now let’s take a detailed look at making the transition from slow flight back to cruise flight.

The very first step is to begin applying power until we’re back at the approximate normal cruise power setting. You’ll have a tendency to fixate or stare at the tachometer while doing so. Rather, you will want to continue looking out over the nose with only a few quick glances at the tachometer. Simultaneously, as the power is applied the nose will have a tendency to pitch further upward due to the amount of “nose up” trim we had applied. This will require forward pressure on the yoke to prevent the airplane from climbing. While holding forward pressure with one hand, use the other to adjust the trim “nose downward” relieving the pressure. In doing so, keep your eyes on the nose attitude with quick glances at your altimeter. Slowly lower the nose back to the straight and level attitude as airspeed begins to build. Relax the pressure you have been holding on the right rudder. Remember, we want to make the transition back to cruise flight without changing our altitude or heading.

After positioning the nose to the straight and level flight attitude, push the carburetor heat off, fine tune your power setting, and trim for cruise. Congratulations! You’ve just completed a satisfactory transition from slow flight to cruise.

Making the transition will again feel like you have a dozen things happening and time for only a half dozen. However, with practice the procedure will become much easier. After several practice sessions you’ll wonder how it initially was so complicated.

After successfully accomplishing the transition to and from slow flight, there are several more things your instructor will have you do while demonstrating slow flight. He or she will also teach you how to make turns to a new heading while in slow flight.

Making turns while in the slow flight configuration requires a bit of finesse. For discussion purposes, let’s make a slow flight turn to the left from a heading of west to south (90 degrees). While maintaining a constant nose high attitude and 45 mph, gently turn the yoke to the left and relax the rudder pressure you are holding with your right foot. Establish a bank angle of about 10 degrees and return the yoke to the centered or neutral position. The airplane is now in a shallow bank turn to the left but our altimeter is indicating a very slow descent. We’ve lost a slight amount of lift due to the bank angle of the wings, so we need to compensate by applying slight backpressure on the yoke, increasing our lift. However, as we increase lift our airspeed shows a slight decrease. We adjust for our airspeed by adding slight power, approximately 50-100 RPM’s. Now we’re comfortably established in a slow flight turn to the left and we’re maintaining our constant altitude of 3,500 feed and our airspeed of 45 mph.

As we approach our assigned heading of south, we must stop the turn and return to a wings level, nose high attitude. When we are about 5 degrees from our heading, we will turn the yoke slightly to the right and apply slight right rudder pressure. The airplane is now coming out of the shallow 10-degree bank. Approaching the wings level position we will return the yoke to the center or neutral position and relax the pressure we are holding on the right rudder.

Once back in the nose high wings level position we will need to readjust the power to prevent the airplane from climbing. Remember, we added power for the turn, now we must reduce that increased power. While doing so, we will again need to add very slight right rudder pressure to prevent torque and “P” factor from pushing the airplane further to the left of our desired heading of south.

There, you’ve just completed a slow flight turn to the left while maintaining a constant altitude and airspeed. Slow flight right turns are done in a similar manner.

While in the slow flight configuration, your instructor will point out how slow and sluggish the control inputs react compared to when you are flying at a normal cruise speed. You will want to note and remember this, as you will experience the slow and sluggish control reaction again when you begin practicing take offs and landings.

Every different make and model aircraft that you will fly in the future will have a different feel when flown in the slow flight configuration. It is important to understand and know the flight handling characteristics to fly the airplane safely and confidently.

As your flight training advances, your flight instructor will have you demonstrate slow flight again, but this time with primary reference to the airplane’s instruments. It won’t be hard, provided you’ve learned the basics as described.

In the next issue of Reach For The Sky we will discuss and demonstrate stalls.