China Civil UAV Theory Questions — Questions 1012–1021

The engine manufacture date does not affect use, so it need not be checked. Further reading, pre-takeoff powerplant checks: (1) engine fuel quantity check; (2) engine fuel line check; (3) engine external looseness check; (4) idle RPM, vibration, and stability check after engine start; (5) high-power RPM and vibration check; (6) engine throttle, high/low fuel needles, and control cable (rod) check; (7) engine throttle-following check; (8) for micro UAVs, engine stability checks in different attitudes; (9) for electric motors, forward/reverse rotation check; (10) interference check between the powerplant after start and other systems.

During a long climb, the engine may overheat because of sustained high-power output. High temperature can harm engine performance and service life. Changing to level flight at a constant altitude gives the engine a chance to cool down, lowering the temperature. To reach the target climb altitude, quickly changing to a descent when the engine overheats is not the best solution.

In level flight at constant altitude, all the forces and moments acting on the aircraft should balance. But the aircraft's balance is often disturbed by various factors. The pilot must therefore spot and continuously correct deviations during flight. Main tasks: (1) judge the aircraft's pitch attitude and whether it is banked, from the attitude indicator; (2) judge the flight direction from the direction of the target point; (3) continuously check the airspeed, altitude, and heading indications; (4) watch the engine indications to understand how the engine is working.

A coordinated turn is a maneuver in the horizontal plane in which the ailerons, rudder, and other control surfaces are controlled sensibly so the aircraft holds a stable flight height and attitude through the turn, while reducing the sideslip angle for a smooth, efficient turn. During a turn, centrifugal force tends to make the aircraft sideslip outward. Adjusting the rudder offsets the centrifugal force and prevents sideslip.

When an aircraft turns, the outer airflow is faster than the inner airflow, so the lift on the two sides differs and a bank toward the turn develops. Opposite aileron must then be applied so the lift on both sides matches, keeping the wings level.

In a turn, because of the bank, the horizontal component of lift increases and the vertical component decreases, and the nose also pitches down under gravity, so speed increases.

Bank dominates turning. When the bank forms, the aircraft enters the turn; when the bank is leveled, the turn stops. Option C is therefore wrong: an efficient turn requires rudder participation together with a bank, which effectively reduces the turn radius and reduces sideslip.

Study note: nose low, pull diagonally aft; nose high, push diagonally forward. When the nose is too high, push the stick appropriately diagonally forward toward the turn side and twist the rudder slightly (pushing lowers the nose). When the nose is too low, increase the pull diagonally aft toward the turn side and ease the rudder slightly (pulling raises the nose).

Study note: nose low, pull diagonally aft; nose high, push diagonally forward. When the nose is too high, push the stick appropriately diagonally forward toward the turn side and twist the rudder slightly (pushing lowers the nose). When the nose is too low, increase the pull diagonally aft toward the turn side and ease the rudder slightly (pulling raises the nose).

When the speed is too high, it must be reduced by decreasing the glide angle, which increases the vertical component of lift. Increasing the pull raises the nose and decreases the glide angle.