Arlington, VA, USA
Between approximately 0004 and 0028 local time, an air traffic control service interruption occurred at the Ronald Reagan Washington National Airport when two air carrier aircraft, a helicopter, an airport operations vehicle, and controllers at the Federal Aviation Administration's Potomac Terminal Radar Approach Control were unable to establish contact with the supervisory controller working alone in the control tower. Two air carrier aircraft landed during the period without tower contact. Postincident investigation revealed that the controller on duty had the necessary preconditions for the development of fatigue at the time of the event, specifically acute sleep loss in the 24 hours before the event and circadian disruption as a result of working the midnight shift.
On March 23, 2011, between approximately 0004 and 0028 Eastern daylight time, an air traffic control service interruption occurred at the Ronald Reagan Washington National Airport (DCA) when two air carrier aircraft, a helicopter, an airport operations vehicle and controllers at the FAA's Potomac Terminal Radar Approach Control (PCT) were unable to establish contact with the supervisory controller working alone in the control tower. Two air carrier aircraft landed during the period without tower contact. 1. History of Flight American Airlines flight 1012 (AAL1012) first contacted PCT at 2356 and was cleared direct to DCA after passing the OJAAY intersection. Further approach handling was routine. At 0003:49, the controller cleared AAL1012 to fly the Mount Vernon Visual Approach, a charted visual approach procedure to DCA. At 0004, the PCT controller instructed the pilot to contact DCA tower on frequency 119.1. At 0005, AAL1912 again contacted the PCT controller and reported that there had been no response from DCA. The controller responded, "that doesn't sound good...hold on, let me give them a call." AAL1012 continued toward DCA from the south, approximately straight-in to runway 1. The controller made two attempts to contact DCA on the phone line connecting the facilities, without success. At 0006, he instructed AAL1012 to attempt contact again on frequency 119.1. AAL1012 did so, and also attempted to contact the tower on frequency 121.5, which is an emergency frequency monitored by many air traffic control facilities. Again receiving no response, AAL1012 executed a go-around and notified PCT that they were still unable to contact the tower. The PCT controller instructed the pilot to fly heading 270 and climb to 3,000 feet. He advised the pilot that, "...we're making some phone calls here to see what we can find out." At 0008, the controller instructed the pilot to fly heading 190, and at 0010 he advised the pilot, "...[we] called a couple of times on the landline and the supervisor called on the commercial line and there's no answer." The pilot replied, "...we've got a little bit more gas we'd like to wait it out and see if we can get something worked out before we divert." The controller responded, "...[I] remember a while back uh a year or so ago a controller got locked out of the tower and the aircraft went in on uh taking it as an uncontrolled airport so you might want to uh think that over." The pilot responded, "OK we'd like to go in as an uncontrolled airport." The PCT controller told the pilot to fly heading 090 and descend to 2,000 feet. After confirming that the pilot had the (Potomac) river in sight, a requirement for aircraft flying the Mount Vernon procedure, the controller instructed the pilot to change to advisory frequency 119.1. However, the controller did not issue a new approach clearance. AAL1012 changed frequencies and began descending for landing. During the period that AAL1012 was approaching the airport, the PCT controller had activated a tunable transmitter/receiver site located in Suitland, Maryland, about 5 miles east of DCA. Using that site, he was able to transmit and receive on the DCA tower frequency. At 0015, AAL1012 reported on tower frequency that the flight was on 2 mile final. At 0018, AAL1012 reported having landed during the first of 2 unsuccessful attempts to contact DCA on 119.1. The crew continued making repeated attempts to contact the tower on ground, local, and clearance delivery frequencies without success, and also engaged in an extended discussion with an AAL maintenance crew aboard an aircraft occupying gate 32, which was assigned for use by AAL1012. At 0028, AAL1012 was able to get a response from the tower controller, and tower ATC services resumed. United Airlines flight 628 (UAL628T) first contacted PCT at 0010, and was instructed to descend via the ELDEE 5 terminal arrival route at 0011. At 0016, the PCT controller cleared UAL628T to proceed direct to DCA and advised the pilot, "...just so you're aware, we just had one aircraft go into DCA...the tower is apparently unmanned, we called on the phones and...nobody's answering so that aircraft (unintelligible.) The pilot responded, "that's interesting." UAL628T continued turning and descending toward the airport, and at 0020 the PCT controller transmitted, "United 628T you can plan on just going inbound to runway 1 uh with the airport being uncontrolled I'll switch you over to advisory on about a 5 mile final." The pilot responded, "OK - thank you." At 0021, UAL628T requested and was given the local altimeter setting, 29.96 inches of mercury, and at 0021:35 reported the (Potomac) river in sight. The PCT controller cleared UAL628T for the Mount Vernon Visual Approach to runway 1, and instructed the pilot to change to advisory frequency 119.1. He also told the pilot to report clear of the runway, and advised that he would be monitoring frequency 119.1. The pilot acknowledged. After changing to 119.1, UAL628T reported turning base for runway 1, 5-mile final for runway 1, and clear of the runway at 0026. DCA tower resumed service about 2 minutes later and UAL628T taxied to the gate. Radar Data The PCT approach controller used radar sites located at Washington Dulles International Airport (IAD) and DCA to monitor the progress of AAL1012 and UAL628T. After landing, the aircraft were tracked by an Airport Surface Detection Radar-X (ASDE-X) ground movement radar system. Graphics depicting AAL1012's first and second approaches, and UAL628's approach, have been entered in the docket for this case along with the Mount Vernon Visual Approach chart and the DCA airport diagram. Personnel Statements NTSB investigators interviewed the PCT supervisor and the radar controller on duty at the PCT KRANT position during the incident, as well as the DCA midnight shift supervisor (who was alone and working as a controller at the time of the incident), an evening-shift DCA controller and a supervisor who interacted with the midnight shift supervisor after he arrived in the tower cab, and the day shift controller who relieved the DCA midnight shift supervisor on the morning after the incident. PCT Radar Controller The PCT radar controller stated that there were no unusual conditions affecting operations when the midnight shift started. He had worked a day shift earlier, going off duty at 1345. He slept from 1500 until 2000, which was his normal practice for the midnight shift. His work schedule typically included two evening shifts, two day shifts, and either another day shift or a midnight shift. The PCT radar controller first realized that something was wrong when AAL1012 reported being unable to establish contact with DCA tower. He then attempted to contact the DCA controller using the phone lines at the KRANT position but was unable to do so. He suggested that AAL1012 reattempt contact, but the pilot was unsuccessful and executed a go-around. The PCT radar controller began following the normal procedures for handling a go-around, and once AAL1012 was reestablished on downwind he advised the supervisor, who was also qualified on the KRANT sector, about the aircraft's lack of contact with the tower and the go-around, adding that it seemed that there was no one in the tower. The PCT radar controller advised AAL1012 that PCT was unable to contact DCA, and suggested to the pilot that he might want to continue to the airport but handle the approach and landing as an uncontrolled airport. The PCT radar controller stated that this came to mind because of an earlier incident that occurred in 2007, where the DCA tower controller locked himself out of the tower cab. The PCT radar controller recalled that aircraft landed under uncontrolled airport procedures in that event also. After vectoring AAL1012 from downwind to base leg, the PCT radar controller again instructed the pilot to change to DCA tower frequency. The PCT radar controller stated that he set the tunable radio available at the KRANT position to the DCA tower frequency so he could monitor the aircraft. After AAL1012 landed, the PCT radar controller heard AAL1012 on the ground calling AAL maintenance to discuss gate information. The maintenance crew was also apparently having difficulty getting in contact with the tower. The PCT radar controller stated that he assumed AAL1012 was off the runway because, "... that's what they're supposed to do, and I heard the pilot talking to the maintenance people." The next arrival was UAL628T, who at the time was descending through 15,000 feet west of DCA. The PCT radar controller cleared UAL628T for the ELDEE standard terminal arrival. The pilot subsequently asked to deviate around some precipitation, which took the aircraft off the arrival route. The PCT radar controller then assigned the pilot a descent to 8000 feet, followed by a descent to 4000 feet. He advised the pilot of the communication difficulties being experienced with DCA and the possibility of treating it as an uncontrolled airport. Once UAL628T descended below the clouds and reported the river in sight, the PCT radar controller cleared the flight for the charted Mount Vernon Visual Approach. He stated that he would not have cleared UAL628T for approach if he thought that AAL1012 was still on the runway. Asked why he specifically instructed UAL628T to report clear of the runway but did not do so for AAL1012, the PCT radar controller replied that he didn't know. After AAL1012 had landed, but before UAL628T arrived, the PCT supervisor came to the KRANT position to find out what was happening. The radar controller informed the supervisor that AAL1012 had landed, UAL628T was cleared for approach, and as far as he could tell there was no one in the tower. The PCT radar controller noted that he had earlier asked the supervisor if anyone else was trying to reestablish communications, and the supervisor responded that he and the FAA technical operations staff had both been trying to contact the tower. The PCT radar controller stated that he first became aware that DCA tower was back in service when he heard, via the tunable radio, AAL1012 talking to somebody, possibly the tower. He then heard UAL628T definitely talking to the tower controller. At that point, he called the tower on the "shout line" to confirm that they were back in service. The PCT radar controller did not have any other conversations with the tower controller about what had occurred, but may have had some coordination exchanges during the night. After the situation apparently returned to normal, the PCT radar controller walked over to the PCT supervisor's position to inquire about the incident. By then, the PCT supervisor had spoken to the DCA midnight shift supervisor, who had reported that, "he didn't know what happened." At 0105, the PCT supervisor instructed the PCT radar controller to fill out a controller statement, adding that "...this was going to be a big deal." Asked to explain his decision to treat DCA as an uncontrolled airport, the PCT radar controller stated that under the circumstances it fit the definition of uncontrolled and that the tower appeared to be out of service. He specifically noted that he didn't tell AAL1012 to do anything, but simply provided information relevant to a situation that was similar to the previous 2007 incident. The PCT radar controller thought that the pilot should make the decision on how to handle the situation. To the controller's knowledge, there was nothing prohibiting an aircraft from landing at DCA with the tower out of service. Investigators reviewed a replay of the approach conducted by AAL1012, and noted that radar contact was lost with AAL1012 on final approach, just before the aircraft landed. Asked how he handles that, the PCT radar controller stated that he would sometimes change radar sites when aircraft are conducting instrument approaches in order to provide better monitoring and ensure the availability of minimum safe altitude warning service. He would not necessarily do that for aircraft conducting visual approaches. PCT Supervisor The PCT supervisor reported no unusual operational or equipment issues when he assumed responsibility for the shift. He first realized something was wrong when the KRANT radar controller reported that he could not contact DCA tower. The supervisor then tried to reach the tower through the commercial administrative phone and also by using the direct "shout" line. Neither attempt worked. While the supervisor was attempting to make contact with DCA, a technical operations technician reported that they were trying to coordinate a "cold start" of the radar data processing system (which requires coordination with all affected facilities) but could not contact DCA tower. The supervisor then called DCA airport operations to see if they could assist. The airport operations staff had unsuccessfully been trying to contact the tower for their own purposes. After some discussion, the airport operations staff stated that they would send emergency responders to the tower. The supervisor requested that they advise him of their findings. The supervisor continued attempting to contact the tower. He consulted with technical operations to see if they were aware of any equipment issues that might have been affecting communications with DCA. The technical operations staff reported that to their knowledge all equipment was operating normally. The supervisor stated that because it was so early in the shift he wasn't really considering the possibility that someone had fallen asleep. He considered an equipment issue to be a more likely explanation. About 20 minutes after their initial conversation, DCA airport operations called to report that the tower was back in normal operation. The PCT supervisor then contacted the DCA supervisor on the phone, and was told, "We've been here the whole time." The DCA supervisor did not comment further about what had happened to cause the loss of contact. The call was conducted on an unrecorded line. The PCT supervisor had no further contacts with DCA tower during the shift, and was not aware of any other PCT personnel discussing the incident with the DCA supervisor during the remainder of the shift. About 0230, he notified the Regional Operations Center and the PCT air traffic manager about what had occurred. Following the notifications, the PCT supervisor began receiving phone calls from FAA management and others requesting information on the incident. Asked to provide an evaluation of how the situation was handled, the PCT supervisor stated that in hindsight he could have provided more direction. At the time, he neither approved nor disapproved of the KRANT controller's plan, but should have "vetoed or co-signed" the decisions made. He thinks the situation was handled as safely as it possibly could have been, but under the circumstances, the KRANT controller was left to operate in "sketchy, uncharted territory." In retrospect, the PCT supervisor thought that perhaps the situation could have been handled differently, for example by holding the flight instead of letting it land. He said the plane would likely have diverted within 10 minutes. The PCT supervisor stated that he had no training about what to do in the event of losing contact with a major tower. He was not familiar with the 2007 loss of communications with DCA tower. DCA Evening Shift Supervisor The DCA evening shift supervisor stated that on the evening of the incident, the midnight shift supervisor came to the cab about 2145 and had a brief discussion with the controller working the local control position. After that discussion ended, the two supervisors had a conversation about a personnel issue. That discussion continued until about 2220. The DCA evening shift supervisor was within 5 to 10 feet of the midnight shift supervisor, and noticed nothing unusual about him that would indicate fatigue or a medical issue. The midnight shift supervisor did not discuss his daily activities or make any references to how he was feeling during the conversation with the evening shift supervisor. The evening shift supervisor ha
The tower controller's loss of consciousness induced by lack of sleep, fatigue resulting from working successive midnight shifts, and air traffic control scheduling practices.
Source: NTSB Aviation Accident Database
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