OPS11IA401

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.

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 c