What is a passenger plane blind landing?

ILS (Instrument Landing System) is a common name for ILS. Because the instrument landing system can guide the aircraft to approach and land in low weather standards or in weather where the pilot can't see any visual reference, people call it blind landing. Instrument landing system is an international standard system for aircraft approach and landing guidance. It is an international standard landing equipment confirmed by ICAO in 1947 after World War II. The instrument landing system all over the world adopts the technical performance requirements of ICAO, so any aircraft equipped with blind landing equipment can get unified technical service at any airport equipped with blind landing equipment all over the world. The instrument landing system usually consists of a VHF heading beacon, a UHF glide beacon and several VHF beacons. The heading beacon gives the heading plane aligned with the center line of the runway, and the glide beacon gives the glide plane with an elevation of 2.5-3.5. The intersection of these two planes is the accurate route given by the instrument landing system for aircraft approaching and landing. The pointer provides the key calibration point along the approach route, that is, the height check at a certain distance from the runway entrance and the distance from the entrance. In the final landing stage of the aircraft from the establishment of blind descent, if the aircraft falls below the glide line provided by blind descent, the blind descent system will give an alarm. The role of blind descent is particularly prominent in bad weather and low visibility. It can provide a reliable approach and landing channel for the aircraft when it is difficult for the pilot to find the runway or sign with the naked eye, so that the pilot can master the position, orientation and descending height and land safely. According to the precision of blind descent, the approach and landing standards provided by blind descent are different, so blind descent can be divided into ⅰ, ⅱ and ⅲ standards. The weather standard for Class I blind descent is that the visibility in front is not less than 8 meters (half a mile) or the runway visual range is not less than 55 meters, and the decision height of the minimum landing standard is not less than 6 meters (2 feet). That is to say, the Class I blind descent system can guide the aircraft to automatically descend to the height of 6 meters from the runway elevation. If the pilot can see the runway clearly at this altitude, he can land, otherwise he will have to go around. The standard of Class II ILP is that the visibility in front is 4 meters (1/4 mile) or the runway visual range is not less than 35 meters, and the decision height of the minimum landing standard is not less than 3 meters (1 feet). Like Class I, autopilot descends to the decision height of 3 meters. If the pilot can see the runway visually, he can land, otherwise he will have to go around. The weather standard of Class III blind descent means that the runway can't be seen effectively at any altitude, and the pilot can only make the decision of landing by himself, and there is no decision on altitude. Class ⅲ blind descent can be subdivided into three subclasses: Ⅲ A, Ⅲ B and Ⅲ C. The weather standard for Class ⅢA is that the visibility in front is 2m (7ft), the decision height is lower than 3m or no decision height, but sufficient stopping distance should be considered, and the runway visual range should not be less than 2m; The weather standard for Class ⅢB is that the visibility in front is 5m (15ft), the decision height is less than 15m or no decision height, and the runway visual range is less than 2m but not less than 5m, so that there is enough allowable taxiing distance after grounding; Class ⅢC has no limit of decision height and runway visual range, that is to say, under the condition of "reaching out and not seeing five fingers", it can automatically drive and land safely with the guidance of blind descent. At present, ICAO has not approved Class ⅢC operation. At present, airports at or above the provincial (district) bureau level and most terminals in China have been equipped with blind descent, and airports newly built and expanded in recent years have been equipped with two-way blind descent, among which only Beijing, Guangzhou and Shanghai airports have reached Class II operation standards, and the rest airports are open according to Class I standards. In the early days of Xiamen Airport, only runway 5 in the main descent direction was opened for Class I blind descent. After the completion of the airport expansion project started in 1993, it has been opened for bidirectional Class I blind descent. Runway 5 in the main descent direction is equipped with Class II blind descent equipment, but it is now opened according to Class I standards. It played a huge role in actual operation. On New Year's Eve in 1998, the visibility of Xiamen Airport was always around 1,5 meters, and the weather was not too bad. However, due to the unavailability of the blind landing system at that time, the airport was actually closed that day, and only one plane landed all day, and all other flights were alternated or cancelled. This happened on New Year's Eve, and we can imagine how great its impact on airport operation and airport image was. At present, blind descent is the most ideal and reliable auxiliary approach and landing system.