The Approach
I have, on more than one occasion, watched a pilot have all the variables of a landing into the air at the same time. Power up then down, airspeed down then up, approach path high to low and back again. Runway alignment moving side to side and the nose swinging back and forth. As an instructor, I find it difficult not to provide salvaging information. However, a recent pilot asked that I give him a pattern without saying anything. The approach was a revelation to the student as to his procedures as well as a revelation to me that letting the pilot get into trouble was certainly one way to get his attention focused on my instruction.
The stabilized approach begins from a high-speed descent and ends at the tiedown. At every intermediate point the pilot is reducing the variables that he is expected to juggle one by one. Normal entry into downwind is when the pilot begins to configure the aircraft for the pattern. the pre-landing checklist, including gear down is completed. At the numbers the power is set for a pre-determined constant. A reduction that will give 1500 rpm or 15 inches are acceptable settings. Further power changes should be made to maintain power constants as necessary. The entire landing to touchdown can be accomplished with no changes to this power setting.
A pilot whose initial training did not include emphasis on the stabilized approach is more likely to make compound corrections. Power will be added at the same time the nose is raised when low on the glide path. The nose may be lowered to bring up the airspeed and correct being high on the glide path. These procedures often fail to correct the problem and must be repeated several times. Above the glidepath and fast requires both a power reduction or additional drag along with a higher pitch attitude.
Making decisive correction of airspeed, attitude and configuration means that the student must know what element of glide slope control is going to be decisive. The early detection of small errors allows either small adjustments or, as in the case of flaps, a delay until a full increment can be used to make the correction more permanent. The stabilized approach is the antithesis of the compound correction. The only solution for being low on the glide slope is a full power correction while maintaining approach speed with yoke pressure for an estimated time period or until the nose touches the far end of the runway. There are three ways to correct being high. First, flaps as conditions allow. Second, power reductions that will allow interception of the glide path. Third, reduce airspeed to increase rate of sink over distance flown.
The constant airspeed means that the controls will perform in a constant manner. The stabilized approach is the basis upon which a hands-off landing can be made down to the flare. Being able to trim accurately for the airspeed stabilized approach gives you the final useful constant. Knowing how the controls will behave reduces the likelihood of excessive or improper control movement.
The flap settings are made according to wind conditions with trim adjusted for hands-off airspeed. (Flap changes are best never made below 200' AGL because the variables will once again will be in the air and the stabilized approach lost.) With all configurations constant and on final, the airspeed (Pitch attitude) is set and trimmed for the final approach. Airspeed is energy. Too much airspeed causes float and wasted runway.
Too little airspeed will increase the sink rate and perhaps a short or hard landing. The POH airspeed is based on gross and may be lower if the approach is flown below gross. Even slight changes in airspeed make large differences in the way the float and flare react to elevator movements.
By maintaining a constant indicated airspeed the pilot is able to make considered judgment as to the glide path. Knowing the glide path's relationship to the runway is a stabilized approach enables the pilot to determine the expected landing. Once established you have two points in mind. There is an aiming point at which point you will flare and a touchdown point a distance beyond. The pilot still has several variables that allow him to vary the distance between the aim point and the touchdown point.
Runway alignment can be visually determined by reference to the centerline of the runway. If the runway does not make a vertical line on the windshield, then the airplane is not lined up properly.
Flaring high and reducing the power to off quickly can cause the plane to settle abruptly, so abruptly that the one-second human reaction time is just enough delay to allow ground contact. Depending on the remaining kinetic energy the plane may stay on the ground or rebound back into the air. Any attempt by the pilot to salvage the landing is likely to result in severe aircraft damage. The go-around is the best option if the aircraft is not firmly on the ground.
Flaring low can greatly extend the touch down range by keeping the power at 1500. The low flare takes advantage of the drag reducing capabilities of ground effect. This capability is a seldom-used capacity by those pilots who have never taken glider training. Several glider lessons will greatly improve your use of ground effect and rudder.
The normal flare occurs with the wheels near hip high above the ground with 1500 RPM. Once the round-out speed has reduced we feel a slight singing-elevator sensation. We begin to increase the back and up movement of the yoke while at the same time in 100-RPM increments we reduce the power. One effective procedure is to fix the nose on the far end of the runway and wait for ground contact. The ideal is that at the moment the yoke is full back and the power all the way off, ground contact occurs. In the less than ideal landing the ground contact is made with the main gear and the nose wheel held clear of ground contact. Any power remaining is removed at moment of ground contact.
Generic Landing Pattern
The landing climaxes at the point of touchdown but will not end there. Furthermore, the beginning of a particular landing occurred at some past landing where a lesson was learned when the pilot was high, low, fast, slow or out of control. The mistake of the past is avoided, corrected and blended into a successful landing. Not perfect, just satisfactory.
The satisfactory landing begins with aircraft control. Aircraft control is the pilot's ability to perform the four basics of climb, descent, level, and turns within a predetermined tolerance level. Aircraft control also includes the ability to use the four basics to position the aircraft in the landing pattern within another predetermined tolerance level of distance and altitude. The last element of aircraft control has to do with configuration. The pilot to select the optimum configuration for the situation uses wind and terrain. The so-called stabilized approach to landing begins far before turning final. The amount of tolerance allowed by an instructor is a variable based on how close you are to doing solo landings.
On downwind you should make a preliminary decision as to the flap configuration you will use. The POH standard is to land with full flaps if wind conditions allow. Just how you set the power, apply flaps, and trim for an airspeed is multi-task variable. Whatever you choose to do should have a consistency. Only in simulated emergency or short-short approaches should power be taken all the way off. Shock cooling the engine is a relatively dangerous practice. Accumulative engine damage. (See 4.7) Whatever the power and flap setting the trim should be adjusted for the hands-off airspeed desired. Do not accept trimmed airspeeds off the desired speed. Most trainers use the same approach speed from the key position, to base, to final, to the round-out. Beyond the trainer, aircraft will use two or three different speeds from downwind, base, and final.
One variable that often occurs in downwind is an ATC call or situation that puts you as #3 to land or a need that you extend your downwind. In both cases you initiate the slow-flight procedure immediately even before using the radio. You want to avoid getting too far from the airport if possible. You hand-fly the slow-flight by using the same trim as you would have but add about 500 rpm to hold altitude and 10 degrees of flap to improve over the nose visibility. Resumption of the approach requires only reduction of power.
My preference is to reduce power to whatever setting will give me 1500 rpm when I reach the key position. The 'key' is a 45-degree angle to your rear toward the runway threshold. At the key position I will have maintained altitude and trimmed for my base approach speed, I put in one notch of flaps hold that airspeed with forward yoke and retrim while turning base. I have learned to put in flaps, apply forward pressure, and trim without looking any place except over the nose of the aircraft. I have begun my descent and am trimmed hands-off. Once my aircraft is under control I look to see the airport. A major fault of those who lose control is mixing up their priorities.
I make most of my approach adjustments on base. I may add a second notch of flaps, fly a wider base, or one closer in. Occasionally, ATC may ask you to make an adjustment by asking that you, "square your base" or "fly directly to the runway". Regardless of what you do, do it at a constant airspeed. Only by having a constant airspeed can you develop the skills needed in determining a stabilized approach angle. On final and on final approach airspeed I use the nose as a sight to make my high/low decisions. By aiming short of the runway a hundred feet you can become experienced in the use of ground effect. Being high offers the most corrective options; I can add flaps to maximum for wind conditions; I can reduce power in increments of 100 rpm or more; or, I can reduce my approach speed to cover less ground for altitude lost. Runway permitting I assume normal approach speed just prior to round-out. The universal solution for being low consists of adding full power while holding approach speed for an estimated time needed to intercept normal glide path.
Other opinions to the contrary, small additions of power can cause a pilot to enter into a condition known as 'the constantly decelerating approach'. As the power is added, the speed drops until there is not enough power to maintain altitude. You are behind the power curve and with the ground close by you have run out of options. The worst thing that could happen to a low-time pilot is to 'get away' with additions of power that lead to the decelerating approach. Next time you may not get away with it. (See decelerating approach)
Continue To Next Page