Runway Status Lights System - RWSL - How It Works: RELs and THLsRELs

This site is hosted by MIT Lincoln Laboratory in support of the FAA/ATO-P RWSL DFW Operational Evaluation. MIT Lincoln Laboratory has been tasked by FAA/ATO-P to implement the evaluation system at DFW, design and execute the Operational Evaluation, and develop an assessment of the operational suitability of Runway Status Lights (RWSL).

How It Works: DFW Recorded Data of RELs and THLs

For departures, THLs illuminate whenever there is a target in position on the runway and another target is simultaneously "on" the runway; such as holding on the runway for an intersection departure (that is 2500 feet or less in separation) or crossing the runway and going past the taxi position hold line at any intersection ahead of the target in position. The THLs are turned off once when any such conditions is no longer met. In this instance, first EGF263 is cleared for takeoff by ATC and begins to depart without any conflicting target ahead of it on the runway; therefore, the THLs do not illuminate. Next, EGF205 is cleared and taxis into position for an intersection departure, and the intersection THLs illuminate red in front of it for a brief time during which the separation between the two departures is less than 2500 feet on the runway. The full-length departure, AAL 1223, is cleared and proceeds to taxi into position and hold, and the full-length THLs illuminate red in front of it for a brief time during which the separation between the two departures is less than 2500 feet on the runway. Then AAL1644 is cleared to cross by ATC and proceeds "on" the runway, having started to taxi across ahead of the holding departures, thereby illuminating the intersection THLs red in front of EGF205. Once the crossing aircraft is clear, then the intersection THLs are turned off. EGF205 is cleared for the intersection takeoff by ATC and departs. Once it is safely separated away from the target holding in position for a full-length departure, then the full-length THLs are turned off. Finally, AAL 1223 is cleared for takeoff by ATC and departs.

THL_DFW_Departure.mov (QuickTime Format)