China Civil UAV Theory Questions — Questions 193–202

A vented fuel tank balances pressure inside and outside the tank so fuel can flow smoothly into the fuel rail. A car fuel tank has two valves: an air valve and a vapor valve. The air valve eliminates vacuum in the tank (caused by fuel consumption). The vapor valve vents gasoline vapor formed by high temperatures, keeping tank pressure stable.

The downlink sends UAV information to the ground station; the uplink sends ground station information to the UAV. The UAV exiting ground station control mode means the UAV is not receiving ground station information — a possible consequence of uplink interruption. Rule out A. Being unable to obtain UAV status information means the ground station cannot receive UAV downlink data. B is correct. Being unable to replan route waypoints online and send mission commands means the UAV is not receiving ground station commands — a possible consequence of uplink interruption. Rule out C.

Manned aircraft actuators are all servo actuators, an important part of the navigation and flight control system. The control stick and rudder pedals are the control devices a manned aircraft pilot uses to control the aircraft.

C&C: command and control — the pilot controls the UAV's flight. ATC: air traffic control — the air traffic control unit manages and controls the UAV. S&A: sense and avoid — interaction between the UAV and other UAVs / manned aircraft / the external environment.

Study note: people are more reliable than machines. UAVs carry no people, so their reliability requirements are not as high as those of manned aircraft.

UAVs communicating within line of sight operate over short distances and do not need longer-range directional antennas. As the UAV flies, the relative position between the UAV and the control station changes quickly, so omnidirectional antennas, which have no directionality, are more suitable. A mushroom-head antenna is only one type of omnidirectional antenna; other omnidirectional antennas are also used on UAVs.

Textbook p. 45, §2.2.3.2, Flight control. Flight control means controlling the UAV's entire flight process in the air by remote control. Remote control is flight control manipulation of the UAV via the data link, generally including three modes: control-surface remote control, attitude remote control, and command remote control. ① Control-surface remote control: the control stick at the control station directly controls the UAV's control surfaces to remotely fly the UAV. ② Attitude remote control: on the basis of an attitude stabilization control mechanism, the control stick controls the UAV's pitch angle, roll angle and yaw angle, thereby changing the UAV's motion. ③ Command control: control commands are sent via the uplink; after the onboard computer receives the commands, it executes them under a predetermined control mode. This mode must be implemented on the basis of an onboard autopilot or an onboard flight management and control system under automatic control. Command modes generally include: pitch angle selection and control, altitude selection and hold, flight speed control, roll selection and control, heading selection and hold, and track control.

Turbojet engines and piston engines must draw air into the combustion chamber to burn and do work; combustion requires oxygen from the air. An electric motor drives the rotor with electric current and needs no air combustion to do work, so it needs no oxygen.

Navigation and flight control system composition: ① sensors; ② flight control computer; ③ actuators. A radio station is UAV onboard link equipment.

Aircraft fly within the atmosphere; a satellite flies in space and is not an aircraft but a spacecraft.