Parachute is a kind of deployable pneumatic reducer made of flexible fabric. It spreads out in the air to increase the movement resistance, reduce the speed of people or objects, stabilize the posture, and land safely from the air to the ground. Parachutes are mainly used for airdrop, aerospace life-saving, parachute jumping, aircraft deceleration and recovery, etc.
Parachutes are usually composed of guide parachutes, umbrella covers, main parachutes, umbrella bags and straps / straps. After the parachute cover is fully opened and falls stably for a period of time, its descent rate will be a fixed value. Under the ideal condition that there is no wind and the parachute system has good stability, the landing point of airdrop personnel and goods can be calculated according to the flight speed and altitude of the aircraft.
Affected by the actual meteorological conditions and parachute technology, the accuracy of the plane circular parachute used in the early stage is not very high. Each airdrop can only delineate an approximate target area. Even so, the personnel and materials dropped by air will still be widely dispersed, and even some paratroopers and materials dropped by air will be blown down to a long distance by the airflow. In several large-scale airborne operations in World War II, it was very difficult to assemble airborne troops and equipment. "The longest day", "the distant bridge" and other war films have true descriptions of this.
In order to meet the needs of military struggle and scientific and technological development, countries around the world have strengthened the scientific research of parachutes. At present, great progress has been made in parachute technology such as inflation characteristic control, application of new materials, stable descent and safe landing. In addition, the improvement of airdrop Technology (low altitude parachute jumping, hollow parachute jumping - low altitude parachute opening, ultra-low altitude parachute traction airdrop, etc.) greatly improves the accuracy of airdrop personnel and materials. In particular, the emergence of an airfoil parachute with horizontal gliding function has raised the accuracy of airdrop to a new height.
The airfoil parachute is also called ram parachute. The umbrella is wing shaped rather than traditional round. The upper and lower wing surfaces are made of airtight fabric, the middle is connected with wing shaped fins, and the front edge is cut to facilitate the entry of air, so that the parachute can form a wing shape after inflation. Parafoil can generate lift in gliding, with good maneuverability and landing performance. Well trained athletes or paratroopers can control the parafoil to fly over the dangerous area, avoid obstacles, and accurately land to the designated target point. At present, the automatic airdrop system under development, such as the "snow geese" and "Sherpas" developed by Canada's Mister mobile integrated system technology company, can automatically send goods to places tens of thousands of meters away by using the wing umbrella of GPS satellite positioning, and the landing accuracy can reach 100 meters left and right. Wing parachute is the most promising high-performance parachute in the parachute field. It has made great progress in parachute jumping, airdrop, aviation life-saving, aircraft recovery and other application fields.