and bottom of this arrow "is one unit", which shows current heading. But the middle part of this arrow is moving independently of the aircraft's heading. The middle of that arrow could be described as being "stand alone", and moves to the left if the aircraft is located to the right of localizer beam and to the right if the aircraft is located to the left of the localizer beam. When the arrow is "united" to a straight line, then the aircraft is following the localizer beam. (This second "arrow-indicator" is omitted in modern cockpits, but the main compass is still located below the artificial horizon.) The very first generation of localizer gauges had a different cockpit interface, and were not included in the artificial horizon nor any compass, but at a gauge of its own. The localizer was then represented as a dangling stick hanging from a fixed point at the top of a separate gauge, and the glideslope was represented by a similar, but horizontal, dangling stick, fixed at one of the sides of the gauge. When the aircraft was located exactly at the ILS-beam (or glidepath) the two sticks formed a cross. This interface resembles the flight director, which also forms a cross, but on the artificial horizon. This older ILS instrumentation system was omitted around the same time as jet airliners like Boeing 707 and DC 8 were introduced. The expression "catch the localizer" refers to runway approaches with the autopilot engaged. The angle between the aircraft heading and localizer beam should be less than 30 degrees, and the indicated airspeed at least below 250 knots (for jet airliners), then by pushing a button marked "APP" or "ILS", then the autopilot presumably will turn and then follow the localizer. The autopilot will then also automatically descend according to the glideslope. Normal procedure is to capture the localizer first and then follow the glideslope as well. If the angle is too large or the airspeed too high, capturing the localizer may be unsuccessful. Modern aircraft can land "themselves", provided the runway ILS is of sufficient standard (class III C) and the cross wind component is low. Autolandings are mostly done when the visibility is low. The cockpit ILS indicators are not to be confused with the flight director, which also places vertical and horizontal lines on the artificial horizon. A flight director only shows how the autopilot