D-4 NPU (Xian NPU)

The D-4 is a small UAV operated by remote control. The contractor is Xian Pilotless Research and Development Center, located at the Northwestern Polytechnical University in China. Other similar craft are BAZ (Iran) and LG 17 (CIS). The D-4 drone's wings are high-mounted, straight to the midsection, and tapered from midwing to tips. The engine is a single, prop-driven engine in the nose section. The fuselage is round and tapers to front and rear, with fixed landing pads. The tail flats are high-mounted on the body and equally tapered. The fin is equally tapered.

To meet the requirements of aerial survey to small area but in large scale and aerial physical exploration the NPU began its exploratory study based on a miniature model drone. The conceptual definition study and ground and flight tests of the flying quality, autopilot, high precision navigation, small area but large scale aerial survey and mineral prospect and remote sensing equipment were carried out in a nature of advanced R&D so that the precious firsthand information and data were obtained. The formal development of the miniature RPV D4 began in March 1981. The persons in charge of technical issues were Xue Mingxian, etc. The successful first flight of the D4 was made in February 1982 and its technical certification was awarded in December 1983.

The D4 is a low altitude, low speed miniature pilotless aircraft with wing span of 4.3 m, fuselage length of 3.3 m and maximum takeoff weight of 140 kg. It is the smallest and the lightest Chinese pilotless aircraft. It can carry 28 kg payload of special instruments and equipment. The power plant is a gasoline piston engine developed by the NPU. An engine-driven two rotors generator supplies the electricity to the aircraft control system and special instruments and equipment. The aircraft is flown by an autopilot and is controlled and guided to fly on a predefined course through a radio remote controlling, telemetering and locating system. The action radius is 40 km. It can also flown by a programable control system if high precision of flight path is not required.

The D-4 is of glass fibre reinforced plastic construction. It is launched from a zero-length launcher by a rocket booster which uses solid fuel and is automatically disconnected after takeoff and can be repeatedly utilized. The takeoff process is automatically performed according to the programme. A parachute is used for recovery. The oleo-pneumatic shock absorbers were installed at two sides of the fuselage belly to absorb landing impact. The wing and tailplane can be rapidly dismantled for transportation.

In October 1984, the NPU set up a Pilotless Aircraft Design and Research Institute. Some experimental studies were carried out to extend range of the D4. In addition to the main application in aerial photography now the RPVs have also been used in survey of terrains, cities and towns, railways and rivers, exploration of mines and oil fields, output forecast of forests, agriculture and fishery, water and soil conservation, water regimen observation and archaeological survey. In addition it can also be retrofitted into front line reconnaissance aircraft and electronic-jamming aircraft.

The approach to develop the pilotless aircraft is featured with Chinese characteristics, i.e. all the development activities of the pilotless aircraft have been exclusively carried out in three universities and colleges owned by the MAI. This approach is beneficial in improving teachers' ability in solving pratical problems and in running the universities and colleges both as an education center and as a R&D center to obtain the research achievements and at the same time to train qualified students. The universities and colleges have comparablly complete disciplines, various professional people and capabilities to develop products which are advanced but need less man powers. Therefore, it is appropriate to undertake the task of developing pilotless aircraft by them. The technology development in the field of the pilotless aircraft will be more rapid with the deepening of the worldwide technology revolution. The cause of Chinese pilotless aircraft must further advance and the minimum altitude flying drones and the supersonic drones must be developed in order to better serve our national defence and national economy.