Large Airplanes
Pilots of larger airplanes with higher stall speeds may find the speed they maintain on the instrument approach is near
1.3 VSO, putting them near point C (in figure 2-7) the entire time the airplane is on the final approach segment. In this case, precise speed control is necessary throughout the approach. It may be necessary to overpower or underpower in relation to the target power setting in order to quickly correct for airspeed deviations.
For example, a pilot is on an instrument approach at 1.3 VSO, a speed near L/DMAX, and knows that a certain power setting will maintain that speed. The airplane slows several knots below the desired speed because of a slight reduction in the power setting. The pilot increases the power slightly, and the airplane begins to accelerate, but at a slow rate. Because the airplane is still in the “flat part” of the drag curve, this slight increase in power will not cause a rapid return to the desired speed. The pilot may need to increase the power higher than normally needed to maintain the new speed, allow the airplane to accelerate, then reduce the power to the setting that will maintain the desired speed.
One of the more difficult tasks that a pilot must routinely execute occurs during the brief transition between the final approach and first contact with the landing surface. This transition is known as the landing flare. The flare process requires that the pilot adjust the aircraft attitude and power settings from those maintained during final approach to values which are appropriate for landing. To be successful, these adjustments must occur at a height above the landing surface that will vary based on the size, weight and performance criteria of the aircraft and the prevailing environmental conditions. In many aircraft, pilots are required to make all height assessments based solely on external visual clues. A radio altimeter, when fitted, will provide an accurate height above the runway and can aid the pilot in determining the appropriate point at which to initiate the flare.
If executed correctly, the flare will result in the aircraft achieving the appropriate landing attitude with power at or near idle, a reduced rate of descent and a decaying airspeed, all at a height varying from several inches to several feet above the landing surface (dependant upon aircraft type). If not executed correctly, the flare could result in a hard landing, the collapse of the landing gear, a tailstrike or in a runway overrun or excursion.
Flare technique, and the amount of time prior to touchdown that the aircraft is maintained in the landing attitude to allow the speed to decay, varies from aircraft to aircraft. At one end of the spectrum are landings on an aircraft carrier in which the aircraft maintains the approach attitude and rate of descent until touchdown. For all intents, there is no flare and the landing gear design must be robust enough to ensure that no damage occurs because of the high rate of descent. At the other extreme are many light, general aviation, aircraft in which proper landing technique requires that the aircraft be held off the runway in the landing attitude until the speed decays almost to the point of aerodynamic stall. The majority of aircraft fall in between these extremes with touchdown occurring after the flare, power reduction and a brief hold off, at a speed well above Vs. Note that for these aircraft, intentionally holding the aircraft off of the runway for a protracted period in an attempt to achieve a smooth touchdown will result in a significant increase in landing distance and could lead to a tailstrike.
Once the main landing gear is in contact with the runway, de-rotation should occur without delay and before decaying airspeed results in the loss of elevator authority. In all cases, appropriate roll out and deceleration procedures should be initiated immediately following the touchdown as dictated by the calculated stopping distance and the available runway.
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