Caravan 208A
Air Traffic Control Fully Certified
Training / Qualification; Time Pressure
ATC Issue All Types; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued New Clearance
Human Factors; Procedure; ATC Equipment / Nav Facility / Buildings
The following occurred while providing OJT in solid IFR conditions. A Caravan was cleared for an intersection take off from Runway XXL at Taxiway S. Pilot was instructed to make a close right turn heading 030; and to advise when established on the assigned heading. Pilot was also informed of traffic holding in position; with additional traffic on final. ASDE-X display indicated aircraft in a right turn. After the Caravan reported on the 030 heading; an MD80 was instructed to fly runway heading and cleared for take-off Runway XXL; full length. By this time; the ASDE-X tag for the Caravan dropped; further indicating aircraft was on assigned heading. While the MD80 was on take off roll or possibly airborne; ASDE-X tag for the Caravan reacquired and appeared to be moving in a northwest direction towards the XXL departure end. A partial Data Block was then acquired on the D-BRITE very close off the departure end of Runway XXL. The MD80 was then instructed to make an immediate left turn heading 300.
All positions in the Tower were staffed. The Local Controller and the Ground Controller were conducting On-the-Job-Training. The weather was IFR; Visibility approximately 1/4 mile and 200 FT ceiling. The Controller providing OJT on Local was a seasoned veteran controller with the FAA. I was standing with my headset plugged into the ETVS jack--alternately monitoring Ground Control and Local Control. The Local Controller asked me whether his understanding of a rule allowing him to position an aircraft for departure at the approach end of the runway with the intention of clearing another aircraft for take off from an intersection was OK as long as he wasn't simultaneously positioning both aircraft for departure on the same runway was correct. I informed him that his understanding of the rule was correct. At that point; I monitored the Local frequency exclusively. The Veteran Controller was writing something down on a legal pad. All arrivals and departures were utilizing Runway XXL with surface winds variable 010 to 030 at 14 KTS; occasionally gusting to 20+ KTS. IFR arrivals were established on final approach at approximately 2 miles and 7 miles respectively. An MD80 was approaching the ILS hold lines for Runway XXL and a cargo-hauling Caravan was approaching the intersection of Runway 1L and Taxiway S. The atmosphere in the Tower was all business. The Local Controller placed the legal pad in front of the Developmental Controller receiving OJT with instructions to position the MD80 on Runway XXL as soon as the first arrival passes the threshold. The Local Controller did not communicate his control actions to anyone in the Tower; however; he was instructing the Developmental Controller. The Developmental Controller observed the first arrival passing the runway threshold; via the ASDE-X; and transmitted instructions for the MD80 to line up and wait--reading directly from the legal pad. The instructor apparently wrote down what he wanted the Developmental to say as an aid due apparently to his recognition of her relative in-experience and his need to ensure her control instructions would be communicated clearly and followed promptly. The aircraft rolling out on Runway XXL stopped rather quickly and wanted to exit Runway XXL onto another runway; a turn of approximately 120 degrees to the left. The Local Controller approved the request with a sense of urgency. Once the runway was clear; the Caravan was cleared for an immediate take off from Runway XXL at Taxiway Sierra with instructions to turn right heading 030 and report established on the 030 heading. The next arrival was approximately 4 miles from the runway at this point. The instructor told the MD80 to come up on the power and be ready for an immediate departure. The Caravan departed Runway XXL from the intersection of Taxiway S and shortly thereafter; the pilot reported established on the 030 heading. I observed the Caravan tracking east of Runway XXL on a northeasterly course and I noticed the track disappeared from the ASDE-X display. The Caravan tagged up on the STARS display. The MD80 was cleared shortly thereafter for take off with the second IFR arrival approaching a two-mile final with a ground-speed read-out of 130 KTS. The Caravan was instructed to contact Departure. I observed a track for the Caravan reacquiring on the ASDE-X display; and to my surprise the track appeared at the departure end of Runway XXL tracking to the north as the track left the display. With IFR weather; it was impossible to see the aircraft from the Control Tower to verify the actual position. I immediately notified the Local Controller that I observed the track for the Caravan reappear at the departure end of Runway XXL. I looked at the STARS display and the Caravan appeared to be north of Runway XXL; in support of my concern that the Caravan was not tracking to the northeast. The Local Controller wasted no time taking action; instructing the MD80 to start an immediate left turn heading 300 degrees. Both aircraft were tracking on the STARS display; and Conflict Alert activated. The Local Controller called the East Departure Controller; and asked the controller to turn the Caravan further right to a 050 heading. The Departure Controller advised Local that he was not talking with the Caravan. The Local Controller attempted to contact the Caravan; and the pilot responded even though he earlier acknowledged instructions to contact Departure. The MD80 was tracking northwest and the aircraft were tracking on diverging courses. The Local Controller turned the Caravan right to a heading of 050 and coordinated the newly assigned heading with the East Departure Controller. The MD80 was instructed to contact Departure. Neither pilot reported receiving a TCAS RA. In retrospect; I recall feeling uncomfortable with the decision to use only 20 degrees of divergence; however; the event played out very quickly; allowing me only a few seconds to recommend or insist on additional steps to ensure more positive control of the situation. My immediate thought; recalling previous experience with the Caravan pilots; was at least two incidents where a Caravan deviated from an ATC clearance resulting in a loss of separation. I checked the wind to see what role if any the winds might have factored into this incident. The wind was blowing down the runway. I looked at the TDWR and ITWS products to check the winds aloft as well. The winds aloft were coming from the northwest; therefore; both the surface wind and the winds aloft should have pushed an aircraft assigned to fly a 030 heading farther east. The two IFR aircraft clearly came too close from my perspective. I checked the flight plan of the Caravan; and I learned [where] his destination was. Using a controller-tool available on the STARS system; I checked to see what heading a pilot might fly if cleared direct from here to there--this typically happens shortly after departure when traffic permits. I learned that his destination is due north of our airport. Of course it's always very easy to consider what could or should have happened when one has the luxury to consider all of the facts with ample time to form an opinion. The technique employed by the Local Controller works well in VFR weather when the Local Controller can wait longer to clear the turbo-jet departing behind the Caravan; needing the departure merely to be airborne 6;000 FT or more from the arriving traffic when the arrival crosses the landing threshold; and when the Caravan is visible from the Tower. In such cases; I have seen; and I personally prefer; assigning a bigger turn initially and maintaining two-way contact with the pilot of the slower plane. A heading of 050 would have been more appropriate; and arguably would have provided much more margin for error--whether from the wind or a pilot anxious to navigate directly to a downstream GPS waypoint. The Controller chose to utilize a RADAR form of separation which permits aircraft to fly diverging courses of 15 degrees or more in lieu of using another approved form of RADAR or non-RADAR separation. He needed to take the weather and significant differences in performance characteristics into account when planning and executing his plan. I recommend training all ATCS personnel as soon as practical on the application of both RADAR and non-RADAR separation standards and how to correctly apply each rule; include a discussion about factors such as weather; differences in performance characteristics; the effects of prevailing winds and the impact of OJT. Looking at my own performance as the Operational-Supervisor-In-Charge (FLM/CIC); I already mentioned the fact that I really only had a few seconds to suggest or insist on alternate instructions to ensure greater positive control and a higher measure of safety. I'll look at my performance from a positive and critical standpoint. From a positive perspective; I was actively engaged in the operation. I was standing; observing and actively listening on-frequency. Although ASDE-X cannot be used like RADAR as a tool to establish approved IFR separation between successive IFR departures; it is nevertheless a useful tool for Tower controllers providing greater awareness of the location of departing; arriving and taxiing aircraft.  This is particularly true when poor visibility precludes visual surveillance of the airport. I noticed the reacquired track of the Caravan before anyone else working in the Tower; and I advised the Local Controller immediately. From a critical perspective; Front-Line Managers continually need to be reminded of the importance of the responsibility they bear when assigned Operational oversight authority. Controllers are certified to work traffic under 'general supervision.' What that looks like often depends on the situation at hand; the level of experience present on various operational positions; whether or not OJT is being conducted; and the impact of factors not under the team's control; such as weather; equipment limitations; policy and procedural demands; etc. My reluctance to micro-manage or dictate control actions unless I am convinced I have no other choice hurt me here. I should have trusted my own discomfort and insisted on another 20 or 30 degrees east for the Caravan. I don't like 'come up on the power' as a technique.
Tower Controller described a conflict event between two successive IFR departure aircraft during reduced visibility when the first aircraft failed to turn as cleared. A supervisory report on the event provided an additional perspective.