|CHAPTER 11. Approaches and Landings
For situations in which an increase in the descent angle is needed for the intended landing spot, the normal procedure is to increase speed above the best LD speed in order to descend. The greater the speed is, the greater the parasitic drag and descent angle.
Each design has different descent rates based on the parasitic drag of the wing and carriage. For example, a single surface with an exposed crossbar wing and a stick carriage (no streamlined cowling) increases the descent angle quickly because of the dramatic increases in drag with increased speed. A double surface wing with a streamlined carriage does not develop parasitic drag as fast with increased speed and is less able to achieve a steep angle with increased speed. The pilot should understand that this characteristic is unique to the make/model being fl own. This steep angle technique is the optimum steep approach procedure because the aircraft is lined up on the runway and the pilot can easily judge the glideslope using the stabilized approach method covered earlier. [Figure 11-29]
Increase speed as required to obtain the descent angle for the intended touchdown point. Use the stabilized approach technique to obtain the increased angle for the aiming point. At the higher speeds and greater descent, slow to the normal approach speed, intersect the normal fi nal approach path, and perform the landing required for that particular situation (calm air/crosswinds/turbulent air). As the student gains profi ciency at steep approach techniques, the altitude to transition from the high speed steep angle to the normal approach speed can be lowered and eventually combined into one continuous roundout for landing started at a higher altitude than the normal approach and roundout. For this situation, note that with the increased speed the roundout covers additional distance that should be accounted for as the speed is decreased.
If at a height at which a steep approach is necessary, but the aircraft is too high to obtain an angle steep enough to make the intended landing area, alternating turns can be made to decrease altitude to a point at which the steep angle technique could be applied for the remainder of the descent. These alternating turns should be performed no lower than 400 feet above ground level (AGL). The turns should be an equal distance from the runway centerline extension to keep track and maintain the relative position on the runway centerline. The bank and direction of turns across the runway centerline should be determined by how much altitude must be lost to position the WSC aircraft for utilization of the steep angle technique for the remainder of the steep approach, if required. [Figure 11-30]
Power-Off Accuracy Approaches
Power-off accuracy approaches are made by gliding with the engine idling through a specifi c pattern to a touchdown beyond and within 200 feet of a designated line or mark on the runway. The objective is to instill in the pilot the judgment and knowledge of procedures necessary for accurate fl ight, without power, to a safe landing. This simulates procedures for an emergency engine-out situation. The ability to estimate the distance an aircraft glides to a landing is the real basis of all power-off accuracy approaches and landings. This largely determines the amount of maneuvering that may be done from a given altitude. In addition to the ability to estimate distance, the ability to maintain the proper glide while maneuvering the aircraft is required.
With experience and practice, altitudes up to approximately 1,000 feet can be estimated with fair accuracy, while above this level the accuracy in judgment of height above the ground decreases since features tend to merge. The best aid in perfecting the ability to judge height above this altitude is altimeter indications and associating them with the general appearance of the Earth.
The judgment of altitude in feet, hundreds of feet, or thousands of feet is not as important as the ability to estimate gliding angle and its resultant distance. The pilot who knows the normal glide angle of the aircraft can estimate with reasonable accuracy the approximate spot along a given ground path at which the aircraft lands, regardless of altitude. The pilot who also has the ability to estimate altitude accurately can judge how much maneuvering is possible during the glide, which is important to the choice of landing areas in an actual emergency.
Unlike a normal approach in which power is available when needed, for a power-off approach the power is fi xed at the idle setting. Pitch attitude is adjusted to control the airspeed, which also changes the glide or descent angle. As discussed in the basic fl ight maneuvers descents and the steep approach maneuver, lowering the nose to a speed above the best glide angle causes the descent angle to steepen. If the airspeed is too high, raise the nose, and when the airspeed is too low, lower the nose. If the pitch attitude is raised too high, the aircraft settles rapidly due to low airspeed and insuffi cient lift. For this reason, never try to stretch a glide to reach the desired landing spot.
Uniform approach patterns such as the 90°, 180°, or 360° power-off approaches are described further in this chapter. Practice in these approaches provides the pilot with a basis on which to develop judgment in gliding distance and in planning an approach. The 180° power-off approach from pattern altitude should be the normal landing procedure in calm winds. This should become routine and develop the ability to accurately judge the landing for an engine-out situation. Remember, the steep approach technique can always be used if the aircraft is a little high, but do not stretch a glide by lowering the speed if too low.
The basic procedure in these approaches involves closing the throttle at a given altitude and gliding to a key position. This position, like the pattern itself, must not be allowed to become the primary objective; it is merely a convenient point in the air from which the pilot can judge whether the glide safely terminates at the desired spot. The selected key position should be one that is appropriate for the available altitude and the wind condition. From the key position, the pilot must constantly evaluate the situation. It must be emphasized that, although accurate spot touchdowns are important, safe and properly executed approaches and landings are vital. The pilot must never sacrifi ce a good approach or landing just to land on the desired spot.
All power-off approaches must be practiced to avoid interfering with normal traffi c fl ow at busy airports, so the place and timing must be evaluated by the instructor to prevent airport traffi c confl icts. This is especially important for the 360° power-off approach.
|ŠAvStop Online Magazine Contact Us Return To Books|
Grab this Headline Animator