SAN Recorded Data
RELs at SAN (includes audio)
The movie clip is from a test conducted at SAN in May 2006, in which live data drove RELs displayed in the tower (RELs on the airport surface were not turned on). The clip demonstrates RELs turning on first for a departure and then for an arrival and turning off before a waiting aircraft is cleared to cross by air traffic control.
For arrivals, as shown, all RELs are simultaneously illuminated based on distance from the runway threshold. The distance is one nautical mile for most arrivals and three-quarter nautical miles for any infrequent relatively slow arrivals (with a velocity of less than 110 knots). When the aircraft decelerates through approximately 80 kts, RELs downfield are turned off except at the intersection the aircraft is approaching. All the RELs are turned off when the aircraft slows towards taxi speed.
In this instance, KHA881 was instructed by ATC to hold short of crossing the runway at TWY B4 on RWY 27 while SWA562 is approaching to land. The yellow diamond on the horizontal green line displayed at the approach end of the runway symbolizes the a/c on final approach. The scale is approximately 5 nm. At one nautical mile all the RELs turn on. Once the arrival lands, the RELs turn off at the far end of the runway and then at the taxiway intersections the lander approaches as it decelerates to a landing roll out and finally a taxi speed. For departures, all RELs in front of the aircraft are illuminated when an aircraft transitions from a taxi to a departure at approximately 30 knots. All RELs are turned off when the aircraft transitions from a departure to an airborne status (wheels off ground and positive rate of climb). For departure aborts, when the aircraft decelerates below 34 knots, RELs will be turned off.