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ALC-34: Maneuvering: Approach and Landing
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Normal Approach

A perfect flying day!  Clear skies, good sunlight, little or no wind, and it’s directly down the runway.  A perfect airport - a long runway on miles of flat land with no obstacles.  Your airplane is in great shape with plenty of available power.

 

Under these conditions, the principles of normal approach and landing can be practiced easily.  But how often do you really encounter such a perfect mix of all these conditions?  It’s somewhat rare actually.

 

Later in this course we will go through the less-than perfect conditions and outcomes of approaches and landings.  But your ability to handle these situations require you to first have a thorough knowledge and mastery of the skills for ‘normal’ approaches and landings.

 

So let’s start with a  review (or an introduction if you are new student pilot) of what are considered ‘normal’ procedures for approach and landing.

 


It must be remembered that the manufacturer’s recommended procedures, including airplane configuration and airspeeds, and other information relevant to approaches and landings in a specific make and model airplane are contained in the FAA-approved Airplane Flight Manual and/or Pilot’s Operating Handbook (AFM/POH) for that airplane.

If any of the information in this chapter differs from the airplane manufacturer’s recommendations as contained in the AFM/POH, the airplane manufacturer’s recommendations take precedence.

 


 

The position of the base leg relative to the runway or landing area is one of the more important judgments made by the pilot in any landing approach. The pilot must accurately judge the altitude and distance from which a gradual descent will result in landing at the desired spot.

 

The distance from the runway or landing area will depend on the altitude of the base leg, the effect of wind, and the amount of wing flaps used. When there is a strong wind on final approach or the flaps will be used to produce a steep angle of descent, the base leg must be positioned closer to the approach end of the runway than would be required with a light wind or no flaps.

 

Normally, the landing gear should be extended and the before-landing check completed prior to reaching the base leg. 

 

8-1_Base to final.JPG 

 

After turning onto the base leg, the pilot should start the descent with reduced power and airspeed of approximately 1.4 Vso. (Vso—the stalling speed with power off, landing gears and flaps down.) For example, if Vso is 60 knots, the speed should be 1.4 times 60, or 84 knots.

 

Landing flaps may be partially lowered, if desired, at this time. Full flaps are not recommended until the final approach is established. 

 

Drift correction should be established and maintained to follow a ground track perpendicular to the extension of the centerline of the runway.

 

The base leg should be continued to the point where a medium to shallow-banked turn* will align the airplane’s flight path with the centerline of the runway. This descending turn should be completed at a safe altitude to properly clear terrain and any obstructions.

 

The turn to the final approach should also be sufficiently above the airport elevation to permit a final approach long enough to accurately estimate the point of touchdown, while maintaining the proper approach airspeed. This will require careful planning as to the starting point and the radius of the turn.

 

Normally, it is recommended that the angle of bank not exceed a medium bank because the steeper the angle of bank, the higher the airspeed at which the airplane stalls.

 

Since the base-to final turn is made at a relatively low altitude, it is vital that a stall not occur at this point.  Countless aircraft accidents have occurred during this ‘base-to-final’ turn.  Always remember that at this critical point in flight, you must not lose airspeed, over-bank the aircraft, or do anything else that could lead to a stall because you do not have sufficient altitude to recover from it!

 

If an extremely steep bank is needed to prevent overshooting the proper final approach path, it is advisable to discontinue the approach, go around, and plan to start the turn earlier on the next approach rather than risk a hazardous situation.

 

* A shallow-banked turn is one of less than 20 degrees bank angle and a medium-banked turn is from 20 to 45 degrees of bank angle.

 


 

After the base-to-final approach turn is completed, the airplane should be aligned with the centerline of the runway or landing surface, so that drift (if any) can be recognized immediately.

 

On a normal approach, with no wind drift, the longitudinal axis should be kept aligned with the runway centerline throughout the approach and landing.

 

After aligning with the runway, the final flap setting should be completed and the pitch attitude adjusted for the desired rate of descent. Slight adjustments in pitch and power may be necessary to maintain the descent attitude and the desired approach airspeed.

 

In the absence of the manufacturer’s recommended airspeed, a speed equal to 1.3 Vso should be used. If Vso is 60 knots, the speed should be 78 knots.

 

When the pitch attitude and airspeed have been stabilized, the airplane should be re-trimmed to relieve the pressures being held on the controls.

 

The descent angle should be controlled throughout the approach so that the airplane will land in the center of the first third of the runway. A common mistake of inexperienced pilots is to plan a landing at the approach end of the runway, sometimes leading to a last-minute addition of power to get to the runway, resulting in a non-stabilized approach and other problems discussed later.

 

The descent angle is affected by all four fundamental forces that act on an airplane (lift, drag, thrust, and weight). If all the forces are constant, the descent angle will be constant in a no-wind condition. The pilot can control these forces by adjusting the airspeed, attitude, power, and drag (flaps or forward slip).

 

The wind also plays a prominent part in the gliding distance over the ground. You need to correct for its effect on the airplane’s descent with pitch and power adjustments. 

 

8-02_HdWnd_Final.JPG

 

Considering the factors that affect the descent angle on the final approach, for all practical purposes at a given pitch attitude there is only one power setting for one airspeed, one flap setting, and one wind condition.

 

A change in any one of these variables will require an appropriate coordinated change in the other controllable variables.  For example, if the pitch attitude is raised too high without an increase of power, the airplane will settle very rapidly and touch down short of the desired spot.

 

You should never try to stretch a glide by applying back elevator pressure alone to reach the desired landing spot. This will shorten the gliding distance if power is not added simultaneously.

 

The objective of a good final approach is to descend at an angle and airspeed to reach the desired touchdown point at an airspeed which will result in minimum floating just before touchdown; in essence, a semi-stalled condition.  To accomplish this, both the descent angle and the airspeed must be accurately controlled.

 

On a normal approach, the power and pitch attitude should be adjusted simultaneously to control the airspeed and descent angle, or to attain the desired altitudes along the approach path. By lowering the nose and reducing power to keep approach airspeed constant, a descent at a higher rate can be made to correct for being too high in the approach.

 

This is one reason for performing approaches with partial power; if the approach is too high, merely lower the nose and reduce the power. When the approach is too low, add power and raise the nose.

 


 

The lift/drag factors may also be varied to adjust the descent through the use of landing flaps.

 

Flap extension during landings provides several advantages by:

 

• Producing greater lift and permitting lower landing speed. 

• Producing greater drag, permitting a steep descent angle without airspeed increase. 

• Reducing the length of the landing roll. 

 

Flap extension has a definite effect on the airplane’s pitch behavior. The increased camber from flap deflection produces lift primarily on the rear portion of the wing, producing a nose-down force.  This pitch behavior varies on different airplane designs.

 

Flap deflection of up to 15° primarily produces lift with minimal drag. The airplane has a tendency to balloon up with initial flap deflection because of the lift increase. The nose down pitching moment, however, tends to offset the balloon.

 

Flap deflection beyond 15° produces a large increase in drag.  In high-wing airplanes, a significant nose up pitching moment can occur because the resulting downwash increases the airflow over the horizontal tail. 

 

When the flaps are lowered, the airspeed will decrease unless the power is increased or the pitch attitude lowered. On final approach, therefore, you must estimate where the airplane will land through discerning judgment of the descent angle.

 

If it appears that the airplane is going to overshoot the desired landing spot, more flaps may be used or the power reduced, and the pitch attitude lowered. This will result in a steeper approach.

 

If the desired landing spot is being undershot and a shallower approach is needed, both power and pitch attitude should be increased to readjust the descent angle.

 

8-03_Flaps_ldg_point.JPG

 

Never retract the flaps to correct for undershooting since that will suddenly decrease the lift and cause the airplane to sink even more rapidly.

 

The airplane must be re-trimmed on the final approach to compensate for the change in aerodynamic forces. With the reduced power and with a slower airspeed, the airflow produces less lift on the wings and less downward force on the horizontal stabilizer, resulting in a significant nose-down tendency.

 

 8-04_Flaps_Apprch_Angl.JPG

 

The elevator must then be trimmed more nose-up. It will be found that the roundout, touchdown, and landing roll are much easier to accomplish when they are preceded by a proper final approach with precise control of airspeed, attitude, power, and drag resulting in a stabilized descent angle.

 


 

During the approach, roundout, and touchdown, your head should be in a natural, straight-ahead position. Visual focus should be changing slowly from a point just over the airplane’s nose to the desired touchdown zone and back again, while maintaining awareness of distance from either side of the runway with peripheral vision.

 

Speed blurs objects at close range. For example, most everyone has noted this in an automobile moving at high speed. Nearby objects seem to merge together in a blur, while objects farther away stand out clearly. The driver subconsciously focuses the eyes sufficiently far ahead of the automobile to see objects distinctly.

 

The distance at which the pilot’s vision is focused should be proportionate to the speed at which the airplane is traveling over the ground. Thus, as speed is reduced during the roundout, the distance ahead of the airplane at which it is possible to focus should be brought closer accordingly.

 

If you attempt to focus on a reference that is too close or look directly down, the reference will become blurred, and your reaction will be either too abrupt or too late. In this case, the tendency will be to over-control, round out high, and make full-stall, drop-in landings. Not good!

8-05_Close_Focus_Blur.JPG

When you focus too far ahead, accuracy in judging the closeness of the ground is lost and the consequent reaction will be too slow since there will not appear to be a necessity for action. This will result in the airplane flying into the ground nose first.

 

The change of visual focus from a long distance to a short distance requires a definite time interval and even though the time is brief, the airplane’s speed during this interval is such that the airplane travels an appreciable distance, both forward and downward toward the ground. 

 

If the focus is changed gradually, being brought progressively closer as speed is reduced, the time interval and the pilot’s reaction will be reduced, and the whole landing process smoothed out.