height" (or "You're gonna fly all night") (too high) RED on WHITE – "You're all right" RED on RED – "You're dead" (too low) until they are used to the lights' meaning. The PAPI is a light array positioned beside the runway. It normally consists of four equi-spaced light units color-coded to provide a visual indication of an aircraft's position relative to the designated glideslope for the runway. An abbreviated system (APAPI) consisting of two light units can be used for some categories of aircraft operations. The international standard for PAPI is published by the International Civil Aviation Organization (ICAO) in Aerodromes, Annex 14 to the Convention on International Civil Aviation, Volume 1, Chapter 5. National regulations generally adopt the standards and recommended practices published by ICAO. An earlier glideslope indicator system, the visual approach slope indicator (VASI) is now obsolete and was deleted from Annex 14 in 1995. The VASI only provided guidance down to heights of whereas PAPI provides guidance down to flare initiation (typically ). PAPIs are calibrated relative to the Minimum Eye Height over Threshold (MEHT). Pilots in certain aircraft may see a "slightly low" indication even though they are on the ILS glideslope, when pilot eye height is above the ILS receiver antenna. The PAPI is usually located on the left-hand side of the runway at right angles to the runway center line. The units are spaced 9 meters apart with the nearest unit 15 meters from the runway edge. A PAPI can, if required, be located on the right-hand side of the runway. The red lights are always on the side closest to the runway. If the PAPI is on the right-hand side of the runway (non-standard), the red lights will be on the left. At some locations PAPIs are installed on both sides of the runway but this level of provision is beyond the requirements of ICAO. The light characteristics of all light units are identical. In good visibility conditions the guidance information can be used at ranges up to by day and night. At night the light bars can be seen at ranges of at least . Each light unit consists of one or more light sources, red filters and lenses. Each light unit emits a high-intensity beam. The lower segment of the beam is red, and the upper part is white. The transition between the two colours must take place over