China Civil UAV Theory Questions — Questions 982–991

When the airport temperature is high, rising air is produced, the aircraft's lift increases, and the glide distance and float distance become longer, easily producing a visually high estimate. When the airport temperature is low, descending air is produced, lift decreases, and the glide distance and float distance become shorter, easily producing a visually low estimate.

There are four main causes of landing deviation: (1) excessive nervousness and worry about the landing, leading to misallocated attention and hesitant, inappropriate control actions; (2) poor landing conditions, for example: a visually high estimate easily leads to a high flare; a visually low estimate with low speed easily leads to a low flare; throttle not fully closed with high speed easily leads to a high flare or ballooning; a poor glide direction easily distracts attention from watching the ground; (3) inconsistent timing, angle, and distance for shifting the gaze to the ground; (4) other causes, such as a mechanical pull or a rough, abrupt pull causing landing deviation.

With strong wind and low temperature, the external weather affects the aircraft more and requires greater power output. If visually low, more throttle is needed, and the amount added should be large. If visually high, the throttle should be reduced, but not by much.

Closing the throttle a bit earlier is more proactive, allowing timely adjustment as conditions develop, so option C is correct.

Stretching out the throttle-closing process gives enough time and favors precise operation.

Bouncing is the phenomenon of the aircraft leaving the ground after touchdown. Correction method: (1) When the aircraft bounces off the ground, hold the stick steady and quickly judge the height above ground and the aircraft's state. (2) If the bounce does not exceed 0.5 m and the pitch angle is not large, hold the stick lightly, wait for the aircraft to sink, and make a normal landing. (3) If the bounce is trending over 0.5 m or the pitch angle is large, promptly push the stick or ease it appropriately so the aircraft does not bounce too high or pitch too much. When the aircraft sinks, gently pull the stick and make a normal landing. (4) If the bounce follows an improper crosswind correction with a drifted touchdown, besides handling the bounce, bank appropriately opposite the drift (that is, toward the crosswind) and apply slight opposite rudder, to avoid touching down with drift again.

Ballooning is the phenomenon of the aircraft rising during the flare or float. Correction method: (1) On discovering ballooning, immediately and gently push the stick or ease it to stop the aircraft from rising further. (2) After stopping the rise, quickly judge the height. At 0.5 m or below with a small pitch angle, hold the stick steady, wait for the aircraft to sink, then gently pull the stick and make a normal landing. (3) After stopping the rise, quickly judge the height. Above 0.5 m or with a large pitch angle, gently push the stick or ease it to reduce the pitch angle, let the aircraft sink slowly, and then make a normal landing.

Study note: too low, pull more; too high, pull less. A flare ending below 0.5 m in height is a low flare. Correction method: (1) During the flare, on discovering a low-flare tendency, appropriately increase the pull so the aircraft enters the float at 0.5 m in height. Because the pull is fast and large, the aircraft may balloon just as it enters the float; guard against this and correct it promptly. (2) For a low flare with height above 0.3 m, land by the normal method. (3) For a low flare with height below 0.3 m, pay special attention to judging height and sink accurately. When the aircraft shows a sinking tendency, without causing ballooning, pull the stick timely and moderately to increase the pitch angle so the aircraft touches down in the normal two-point attitude. (4) If the aircraft descends quickly and touches down in a small two-point attitude, hold the stick slightly to keep the two-point attitude and prevent the nosewheel from striking the ground, but also avoid pulling too much at touchdown and causing a bounce. (5) If the flare ends too low with high speed, pull a bit more to avoid a three-point touchdown. If a three-point touchdown has already occurred, hold the stick steady promptly to avoid bouncing.

Study note: too low, pull more; too high, pull less. A flare ending above 0.5 m in height is a high flare. Correction method: (1) During the flare, on discovering a high-flare tendency, stop pulling or decrease the pull and let the aircraft sink. Based on the aircraft's height above ground, sink rate, and pitch attitude, pull the stick gently and evenly so the aircraft enters the float at 0.5 m in height. (2) For a high flare, if the aircraft then sinks, hold the stick steady, wait until it sinks to 0.5 m, then gently pull the stick and make a normal landing. (3) For a high flare, if the aircraft does not sink, ease the stick slightly (noting that the throttle is fully closed) so the aircraft sinks slowly to 0.5 m, then make a normal landing. (4) If the flare height is above 3 m and is not corrected in time, go around.

A flare ending below 0.5 m in height is a low flare. Correction method: (1) During the flare, on discovering a low-flare tendency, appropriately increase the pull so the aircraft enters the float at 0.5 m in height. Because the pull is fast and large, the aircraft may balloon just as it enters the float; guard against this and correct it promptly. (2) For a low flare with height above 0.3 m, land by the normal method. (3) For a low flare with height below 0.3 m, pay special attention to judging height and sink accurately. When the aircraft shows a sinking tendency, without causing ballooning, pull the stick timely and moderately to increase the pitch angle so the aircraft touches down in the normal two-point attitude. (4) If the aircraft descends quickly and touches down in a small two-point attitude, hold the stick slightly to keep the two-point attitude and prevent the nosewheel from striking the ground, but also avoid pulling too much at touchdown and causing a bounce. (5) If the flare ends too low with high speed, pull a bit more to avoid a three-point touchdown. If a three-point touchdown has already occurred, hold the stick steady promptly to avoid bouncing.