Fort Lauderdale, FL, USA
N587NK
AIRBUS A321 231
The runway incursion occurred during the early morning hours when traffic was light, and when the airport authority usually conducted maintenance activities on the airfield. The air traffic controller approved a request by an airport maintenance vehicle to operate on the runway; however, there were no standard operating procedures or standard phraseology regarding how airfield vehicle operators were to reference the specific runway end when requesting permission to enter a runway. This lack of standard procedure resulted in four hear back/read back errors between the operator of the vehicle and the air traffic controller immediately prior to the runway incursion event. After the airport vehicle had been approved by the air traffic controller to operate on the runway, the crew of the A321 requested a clearance to taxi to the same runway for departure and was subsequently cleared for takeoff. The airport runways and taxiways were equipped with the Runway Status Light (RWSL) system. As the crew of the A321 aligned with the runway centerline for departure, the Takeoff Hold Lights (THL) portion of the RWSL activated, displaying red lights on the runway surface. The crew continued the takeoff over the illuminated RWSL system. The RWSL system was operating correctly and the THL portion of the system deactivated when the A321 reached a predetermined speed consistent with an aircraft continuing departure. As the A321 was departing, the Airport Surface Detection Equipment Model X (ASDE-X) alerted and the air traffic controller responded by cancelling the takeoff clearance when the A321 was near takeoff speed. The A321 stopped on the runway about 500 feet from the airport vehicle.
HISTORY OF FLIGHTAt 0153:50, the driver of Truck54 requested permission to enter runway 10L at taxiway D. The local controller responded "Truck54 roger, understand you're clear runway 28 to eight left." The driver of Truck54 read back the clearance "proceeding on 10L, we'll stay clear of all aircraft." The local controller responded "Truck54 roger, proceed on runway 28L." Neither the truck operator nor the air traffic controller corrected the runway error or requested clarification. When Truck 54 went into position at runway 10L and taxiway D, the ASDE-X system depicted the target as a diamond symbol with no relative speed. At 0155:30, the pilot of NKS371 requested to taxi from the gate to runway 28R for departure. The tower controller instructed the pilot to taxi via taxiways T4 and B. At 0159:06, the pilot of NKS371 advised the tower controller that he was "approaching holding short ah runway two eight right, ready to go." At 0159:14, the tower controller issued the pilot a departure heading of 275 and cleared the flight for takeoff. The pilot correctly read back the takeoff instructions. At 0200:00, as NKS371 taxied onto the runway and began lining up with the runway centerline, the runway status lights (RWSL) takeoff hold lights (THLs) activated. Once aligned with the runway centerline, NKS371 immediately went from taxi to takeoff roll without stopping. At 0200:24, the ASDE-X generated aural and visual logic alerts to the tower controller indicating there was a vehicle on the runway. At 0200:36, the tower controller cancelled the takeoff clearance for NKS371 and the pilot acknowledged at 0200:42 and aborted his takeoff. The ASDE-X data indicated NKS371 came to a stop at 0200:52. At 0200:57, the tower controller transmitted "Spirit Wings three seventy one, you can taxi back to runway two eight right." the pilot responded "ok taxi back two eight right Spirit Wings three seventy one." At 0201:31, the local controller asked who the vehicle was on runway 28R stating "who's that?" The driver of Truck54 responded "Truck five four." The tower controller said "Truck five four, you said you wanted to go on runway two eight left"; the driver of Truck54 did not respond. At 0202:16, the pilot of NKS371 advised the tower controller that he would need to hold in position to allow the brakes to cool down; the tower controller replied "no problem." At 0210:22, the driver of Truck54 reported "clearing runway one zero left," and the tower controller acknowledged. At 0218:04, the pilot of NKS371 advised the tower controller that he would need to return to the gate to allow maintenance to inspect the brakes. The tower controller issued taxi instructions to gate 14 and a short time later the flight cancelled the intended flight. There were no further recorded communications from the pilot. Airport Runway Status Lights System FLL runway 28R was equipped with RWSLs, a "fully automated system that provides runway status information to pilots and surface vehicle operators to clearly indicate when it is unsafe to enter, cross, takeoff from, or land on a runway." When operational, RWSLs have two states; ON (lights are illuminated red) and OFF (lights are off), and are switched automatically based on input from the ASDE-X system and independent of air traffic controllers. The RWSL system is made up of two sub-systems; runway entrance lights (RELs), installed where taxiways and runways intersect, and THLs installed on the approach end of runway centerlines. RELs are "flush mounted, in-pavement, unidirectional light fixtures that are parallel to and focused along the taxiway centerline and directed toward the pilot at the hold line." They are designed to warn pilots and vehicle operators operating on taxiways when there is an aircraft operating at high speed on the intersecting runway. THLs are "flush mounted, in-pavement, unidirectional light fixtures in a double longitudinal row aligned either side of the runway centerline lighting." THLs are designed to warn pilots of departing or landing aircraft when there is an aircraft or vehicle occupying the same runway. The FLL runway 28R THL system lights extended from the runway threshold down the runway centerline 1,497.85 feet toward the departure end of the runway. They are installed as 16 pairs of flush mounted double red light-emitting diode (LED) lights spaced every 100 feet. The FLL RWSL system derived its operational data from the ASDE-X system; although they remain two independent systems. To activate the THLs, an aircraft or other airport vehicle must be on the runway and detected by ASDE-X with an aircraft preparing to depart in the runway threshold. The THLs are designed to extinguish when the RWSL system determined an aircraft was departing (aircraft speed dependent). There was up to a 2 second delay from when the RWSL system received the ASDE-X data indicating there was a vehicle on the runway, and when the THLs were activated. To deactivate the THLs, the RWSL system would determine by the ASDE-X that the aircraft or airport vehicle that was on the runway was no longer there; or, the RWSL system had determined the aircraft in the runway threshold had reached a pre-determined speed consistent with that of a departure. The RWSL system would consider an aircraft to be a departure when the aircraft reached a minimum speed of 48.5 knots with an acceleration rate of 3.8 knots per second. At 0200:27, the FLL RWSL system extinguished the THLs when the ASDE-X system determined NKS371 had met these parameters. Spirit Airlines Pilot RWSL Training The locally based crew of the A321 had received initial and recurrent training on the RWSL systems, and had been provided with airport information and textual descriptions of airports equipped with RWSL's. According to the Director, Regulatory Compliance and Internal Evaluation Programs of Spirit Airlines, pilots were provided training in RWSL and he stated that "for both recurrent and initial [training] we use the FAA.gov website for our training of runway status light" including the "RWSL Animation" and "RWSL Demonstration Video." During initial training the pilots are provided additional PowerPoint slides on THLs. One of the slides titled "Pilot Interaction with THLs" stated: If holding in position and THLs illuminate: Continue holding in position If takeoff roll has begun and THLs illuminate: Stop. If aborting the takeoff is impractical for safety reasons: Proceed according to your best judgment Understand that the THLs indicate the runway is unsafe. If on short final and THLs are illuminated red: Go around In all cases, advise ATC.
The air traffic controller's failure to ensure the runway surface area was clear of vehicles before clearing an aircraft for takeoff. Also causal was the flight crew's decision to initiate a takeoff while the Runway Status Lights (RWSL) Takeoff Hold Lights (THLs) were activated. Contributing to the incident was the lack of a standard procedure for vehicle operators to request runway clearances and resultant "hear back/read back" error between the vehicle operator and the air traffic controller.
Source: NTSB Aviation Accident Database
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