|
In aviation, autoland describes a system that fully automates the landing procedure of an aircraft's flight, with the flight crew supervising the process. Such systems enable aircraft to land in weather conditions that would otherwise be dangerous or impossible to operate in. ==Description== Autoland systems were designed to make landing possible in visibility too poor to permit any form of visual landing, although they can be used at any level of visibility. They are usually used when visibility is less than 600 meters Runway Visual Range and/or in adverse weather conditions, although limitations do apply for most aircraft—for example, for a Boeing 747-400 the limitations are a maximum headwind of 25 kts, a maximum tailwind of 10 kts, a maximum crosswind component of 25 kts, and a maximum crosswind with one engine inoperative of five knots. They may also include automatic braking to a full stop once the aircraft is on the ground, in conjunction with the autobrake system, and sometimes auto deployment of spoilers and thrust reversers. Autoland may be used for any suitably approved Instrument Landing System (ILS) or Microwave Landing System (MLS) approach, and is sometimes used to maintain currency of the aircraft and crew, as well as for its main purpose of assisting an aircraft landing in low visibility and/or bad weather. Autoland requires the use of a radar altimeter to determine the aircraft's height above the ground very precisely so as to initiate the landing flare at the correct height (usually about ). The localizer signal of the ILS may be used for lateral control even after touchdown until the pilot disengages the autopilot. For safety reasons, once autoland is engaged and the ILS signals have been acquired by the autoland system, it will proceed to landing without further intervention, and can be disengaged only by completely disconnecting the autopilot (this prevents accidental disengagement of the autoland system at a critical moment) or by initiating an automatic go-around. At least two and often three independent autopilot systems work in concert to carry out autoland, thus providing redundant protection against failures. Most autoland systems can operate with a single autopilot in an emergency, but they are only certified when multiple autopilots are available. The autoland system's response rate to external stimuli work very well in conditions of reduced visibility and relatively calm or steady winds, but the purposefully limited response rate means they are not generally smooth in their responses to varying wind shear or gusting wind conditions – i.e. not able to compensate in all dimensions rapidly enough – to safely permit their use. The first aircraft to be certified to CAT III standards, on 28 December 1968,〔(Slat Retraction During Reverse Thrust? 747-400 Tech Ops Forum | Airliners.net )〕 was the Sud Aviation Caravelle, followed by the Hawker-Siddeley HS.121 Trident in May 1972 (CAT IIIA) and to CAT IIIB during 1975. The Trident had been certified to CAT II on 7 February 1968. Autoland capability has seen the most rapid adoption in areas and on aircraft that must frequently operate in very poor visibility. Airports troubled by fog on a regular basis are prime candidates for Category III approaches, and including autoland capability on jet airliners helps reduce the likelihood that they will be forced to divert by bad weather. Autoland is highly accurate. In his 1959 paper 〔W. J. Charnley (1959). Blind Landing. Journal of Navigation, Vol. 12, No.2, April 1959, p 128 http://journals.cambridge.org/abstract_S037346330001794X〕 John Charnley, then Superintendent of the UK Royal Aircraft Establishment's (RAE) Blind Landing Experimental Unit (BLEU), concluded a discussion of statistical results by saying that "It is fair to claim, therefore, that not only will the automatic system land the aircraft when the weather prevents the human pilot, it also performs the operation much more precisely". Traditionally autoland systems have been very expensive, and have been rare on small aircraft. However, as display technology has developed the addition of a Head Up Display (HUD) allows for a trained pilot to manually fly the aircraft using guidance cues from the flight guidance system. This significantly reduces the cost of operating in very low visibility, and allows aircraft which are not equipped for automatic landings to make a manual landing safely at lower levels of look ahead visibility or runway visual range (RVR). Alaska Airlines was the first airline in the world to manually land a passenger-carrying jet (Boeing 737) in FAA Category III weather (dense fog) made possible with the Head-Up Guidance System.〔("Alaska Air Group Almanac, November 2004" page 3 )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Autoland」の詳細全文を読む スポンサード リンク
|