DFW controller described a loss of separation event between departures when a CRJ200 departing Runway 17R failed to turn onto the RNAV SID; the flight crew indicating FMS did not capture course.
Synopsis
DFW controller described a loss of separation event between departures when a CRJ200 departing Runway 17R failed to turn onto the RNAV SID; the flight crew indicating FMS did not capture course.
Narrative
While working Local East 1; I cleared Air Carrier X for takeoff on Runway 17R for a RNAV departure and issued 'Air Carrier X; RNAV to NAVYE; Runway 17R; cleared for takeoff'; which the pilot acknowledged. As soon as an ARTS data tag acquired on Air Carrier X; I switched the aircraft to Departure Control; basing my separation on the succeeding aircraft with Air Carrier X's mileage south of DFW Airport. Shortly thereafter; I observed that Air Carrier X was not turning left to join the RNAV departure and I immediately contacted Departure Radar 1 at D10 and asked 'Is Air Carrier X turning left to join the RNAV departure?' The DR1 Controller hesitated briefly and then issued a heading of 080 to Air Carrier X. At the time; there was traffic abeam Air Carrier X which had departed DFW's West Complex; but I do not recall the exact altitude of either aircraft; only the lateral proximity which appeared to be decreasing as Air Carrier X appeared to drift slowly right of course. Recommendation; it would have been helpful to lengthen my scan toward the departure end of the runway to ensure that Air Carrier X was indeed commencing the appropriate slight left hand turn toward the RNAV fix. It would also have been of assistance to have the Local Assist position staffed to assist with my scanning responsibilities; as this is the regular configuration during a day shift such as this; but due to staffing; that position was not staffed. We seem caught in a contradictory arrangement with the RNAV departures; i.e.; we must switch the departures to the Departure Controller as soon as possible; but also attempt to ensure that the aircraft IS actually turning in the correct direction. Sometimes; due to aircraft climb performance; the timing of the ARTS data tag acquire; and scan of the entire airport; accomplishing this simultaneously can be awkward; hence; the reason for staffing the Local Assist 1 position. But; primarily; my attempted solution in the future will be to maintain a visual scan ON the RNAV departure to attempt to ensure a turn.
Second reporter narrative
At the gate; the Captain loaded the FMS while I conducted the walk around. I verified the FMS upon returning to the cockpit; and the correct Departure Procedure and route was programmed; all way points on the Departure Procedure were programmed. On taxi out we verified that 17R (the correct departure runway) was loaded in the FMS. The radio tuning units were both set to 'auto tune;' and everything appeared normal. The Tower cleared us for takeoff; RNAV to NAVYE; which I verified by glancing at the FMS/CDU. After rotation; at 400' the NAV mode was called for and selected. Upon climbing through approximately 1800'MSL the Captain switched to Departure Control; checking on at 2200'. We both recognized that something was amiss when the FD did not capture the RNAV route to begin the turn (I was still hand flying with the aircraft centered in the FD bars which were still straight and level; never turning since leaving the runway). This may have been recognized sooner however I unknowingly had the 5mile scale set on my MFD (I normally have the 2.5 mile scale set); which made me think I had more room to give the FD a chance to capture the course; since the FMA indicated that it was tracking. Climbing through 2500' MSL I engaged the autopilot so I could better manage the situation; and after adjusting the scale on the MFD to 2.5 miles; I recognized that the lead-arrow which indicates a turn (in this case indicating a left turn to join the RNAV) was extending in front of the aircraft (on the MFD display) and indicating that we should continue straight ahead with a turn abeam NAVYE. I have never seen anything like this before; and knowing that we needed to turn to NAVYE I was in the process of switching to HDG mode at which time ATC recognized the deviation; asked which departure procedure we were flying; and then issued us a heading. While in heading mode; I then noticed that in the NAV information box (the one which tells us TERM; GPS APPR; and distance remaining information on the PFD) had a message which said 'SEQ INHIBIT.' Checking all of the switches which may inhibit the FMS sequencing; they were all in their normal positions. I saw nothing that would inhibit the FMS sequencing. The aircraft flight director did not capture the course. I have no recommendations for preventing this event. It should not have occurred and as far as I can tell; it was an aircraft issue or computer glitch of some sort.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.