China Civil UAV Theory Questions — Questions 173–182

Installing a supercharger increases engine intake pressure, raising oxygen content, so that an engine of the same displacement produces 20% to 50% more horsepower.

Study note: ignition — CDI. Capacitor discharge ignition (CDI) is an electronic ignition system widely used in motorcycles, lawn mowers, chainsaws, small engines, turbine-powered aircraft and some cars. To shorten the time needed for the ignition coil (high-voltage coil) to generate secondary voltage, so the ignition system suits high-speed engines (such as small engines, racing engines and rotor engines), a capacitor is charged to store the required electricity and discharges it all at once through the ignition coil, generating high voltage to trigger the spark plug.

Fixed-wing UAV servos — rudder, elevator, ailerons, flaps, etc. — generally have an output travel of ±20°.

Civil UAVs mainly use electric servo actuators. Further reading: advantages of electric servo actuators: ① easy to manufacture and maintain; ② same energy source as the flight control system; ③ easy signal transmission and control; ④ simple system composition; ⑤ convenient wiring.

Study note: UHF, L and C. Currently, UAV spectrum use worldwide is mainly concentrated in the UHF, L and C bands. Further reading: regulations on radio frequency band use for UAV systems in China.

Study note: piston + electric. For example, most multirotor UAVs sold on the market are battery-powered and use electric motors.

This question tests UAV classification. Since the stem already lists single-rotor and multirotor, it tests knowledge of aircraft platforms.

Study note: with air-cushion, choose the advantages. Advantages of air-cushion landing: ① the UAV can land on unprepared ground, mud, ice and snow fields or water, without terrain restrictions (the biggest advantage); ② not limited by UAV size or weight, with a high recovery rate; ③ reportedly up to 1 sortie per minute, while air recovery achieves 1 sortie per hour.

Point 1: What is 'backfire'? In a gasoline engine, the phenomenon of the combustible mixture burning in the intake pipe or at the carburetor mouth is called backfire. This happens because the mixture is too lean, so combustion is slow, and burning continues as exhaust nears its end and the intake valve opens, igniting the fresh mixture in the intake pipe or carburetor with an explosive sound. Point 2: Why is backfire likely when starting in cold conditions? When starting an engine in cold conditions, low air temperature makes gasoline hard to vaporize, so the mixture easily becomes excessively lean; rotational speed is low and gas flow in the intake pipe is slow. In this situation, flame propagation speed easily exceeds gas flow speed, causing carburetor backfire.

The downlink sends UAV information to the ground station; the uplink sends ground station information to the UAV. If the UAV is set to exit ground station control mode when it stops receiving ground station commands, it may leave ground station control mode during an uplink interruption, but that is not inevitable. Rule out A. Being unable to obtain UAV status information means the ground station cannot receive UAV downlink data. Rule out B. Being unable to replan route waypoints online and send mission commands means the UAV cannot receive ground station commands — a possible consequence of uplink interruption. C is correct.