ILS Category I: Provides for approach to a height above touchdown of not less than 200 feet, and with runway visual range of not less than 1,800 feet.The ALS provides lights that will penetrate the atmosphere far enough from touchdown to give directional, distance, and glide path information for safe visual transition.Ĭategories of instrument approach procedures allowed at airports equipped with the following types of instrument landing systems: At this point, the approach should be continued by reference to the runway touchdown zone markers. As the runway threshold is approached, the visual glide path will separate into individual lights. The most critical period of an instrument approach, particularly during low ceiling/visibility conditions, is the point at which the pilot must decide whether to land or execute a missed approach. Approach Lighting Systems (ALS). Normal approach and letdown on the ILS is divided into two distinct stages: the instrument approach stage using only radio guidance, and the visual stage, when visual contact with the ground runway environment is necessary for accuracy and safety.For example, the outer locator at Dallas/Love Field (DAL) is identified as “DA.” The middle locator at DAL is identified by the last two letters “AL.” The coding identification of the outer locator consists of the first two letters of the three-letter identifier of the associated LOC. When used in conjunction with an ILS front course, the compass locator facilities are collocated with the outer and/or MM facilities. Compass Locator. Compass locators are low-powered NDBs and are received and indicated by the ADF receiver.The back-course marker, where installed, indicates the back-course FAF. It indicates the point at which an aircraft is at the decision height on the glide path during a Category II ILS approach. The inner marker (IM), where installed, is located on the front course between the MM and the landing threshold. The OM is located on the localizer front course 4 to 7 miles from the airport to indicate a position at which an aircraft, at the appropriate altitude on the localizer course, will intercept the glide path The MM is located approximately 3,500 feet from the landing threshold on the centerline of the localizer front course at a position where the glide-slope centerline is about 200 feet above the touchdown zone elevation.A marker beacon may also be installed to indicate the FAF on the ILS back course. A third beacon, the inner, is used where Category II operations are certified. Marker Beacons. Two VHF marker beacons, outer and middle, are normally used in the ILS system.At 10 NM from the point of touchdown, this represents a vertical distance of approximately 1,500 feet, narrowing to a few feet at touchdown. The system provides no vertical guidance for approaches on the back course. Unlike the localizer, the glide-slope transmitter radiates signals only in the direction of the final approach on the front course.At locations where standard minimum obstruction clearance cannot be obtained with the normal maximum glide-slope angle, the glide-slope equipment is displaced farther from the approach end of the runway if the length of the runway permits or, the glideslope angle may be increased up to 4°. The glide-slope projection angle is normally adjusted to 2.5° to 3.5° above horizontal, so it intersects the MM at about 200 feet and the OM at about 1,400 feet above the runway elevation. The course projected by the glide-slope equipment is essentially the same as would be generated by a localizer operating on its side.The glide-slope equipment is housed in a building approximately 750 to 1,250 feet down the runway from the approach end of the runway, and between 400 and 600 feet to one side of the centerline.The glide path is the straight, sloped line the aircraft should fly in its descent from where the glide slope intersects the altitude used for approaching the FAF, to the runway touchdown zone. Glide Slope. Glide slope (GS) describes the systems that generate, receive, and indicate the ground facility radiation pattern. With no more than one-quarter scale deflection maintained, the aircraft will be aligned with the runway. This sensitivity permits accurate orientation to the landing runway. With this course width, a full-scale deflection shows when the aircraft is 2.5° to either side of the centerline. The localizer course is very narrow, normally 5°.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |