Narrative:

I was working the local control position in a limited radar approach control tower when a faster departure overtook a slower preceding departure resulting in a loss of IFR separation. Arrs and departures were utilizing runway 24R and runway 14, a nonstandard confign, due to wind. Runway 24L was closed for maintenance. I had 'automatic releases' for both runways. This meant I could use both runways for departures without requesting individual releases. Both aircraft were in a SID that required the aircraft to fly runway heading and to expect radar vectors on course. Both aircraft were initially issued an altitude of 4000 ft. The first departure, a DHC6, had departed and had been switched to departure control. Because of its route of flight, a wsw heading, the aircraft was under the control of the south radar sector. The second aircraft, a B737, was taxied into position. The aircraft was filed on a northerly route and would be under the control of the north radar sector. I coordinated with the north radar handoff position and requested a turn to a heading of 270 degrees for the B737. The north radar handoff controller denied the turn without providing a reason. I had aircraft waiting to depart on both runways. The aircraft departing runway 14 was a heavy aircraft. Because the departure flight paths of the 2 runways intersect at the ends, and because of wake turbulence issues, it was imperative that the runway 24R departure departed first. Without a westerly heading for the B737 I knew I would have to provide other separation. I held the aircraft in position as long as practical for in-trail spacing prior to issuing takeoff clearance. I dropped the departure half of the flight strip down the tube for north radar when I cleared the B737 for takeoff. Per our facility handbook, this indicates that the aircraft is rolling and contains aircraft identify, altitude and route information. When the aircraft became airborne, there was approximately 4 mi in-trail and 2000 ft of vertical separation. I immediately issued traffic and anticipated establishing visual separation when the aircraft reported the traffic in sight. In the same transmission, I inadvertently changed the aircraft to departure. The pilot replied, 'looking.' after other coordination and xmissions to other aircraft, I again issued traffic to the B737. This time I intentionally changed the aircraft to departure as I had observed the DHC6 turning southwest and observed that the B737 would pass well north of the DHC6 and that there was no traffic to the west or northwest that would prevent a timely turn in that direction. There was, of course, no reply as the pilot had already changed frequencys. As I continued to work other traffic, I observed that the B737 had not been turned but its course would take it north of and behind the DHC6 by 1 mi or more. I did not observe a safety issue so I did not call the radar position to determine why the aircraft was still on runway heading. When, a few mins later, I was relieved from the local control position for normal position rotation, I promptly explained to the supervisor what had taken place and headed to the TRACON to figure out what had happened. Review of the tapes indicated that the B737 reported the DHC6 in sight on initial contact while still 3 mi in trail. Congestion on the frequency prevented the controller, who was training on the position, from hearing the initial transmission from the B737 and thus maintaining IFR separation. After other xmissions on the frequency, the B737 again attempted to contact departure with the traffic in sight. The controller initially sounded confused as to who was calling. He later radar idented the aircraft and turned the aircraft to the north. When the pilot inquired as to whether the controller had received an alert between he and the DHC6, the controller advised him to maintain visual separation. At this point the B737 had already passed behind and right of the DHC6 by 1.09 mi and the loss of separation had already occurred. I believe that several factors contributed to this loss of separation. The first factor was the denial of the requested heading by north radar handoff. The request was valid and traffic was not a factor for denying the turn. The trainer and trainee both later told me that there was no reason to not turn the aircraft. The next factor was the lack of coordination about this aircraft to anyone by the north radar handoff controller. Upon receiving the requested turn and later receiving the flight strip for the faster aircraft, the controller knew the aircraft was rolling and could have done any number of things to ensure separation was maintained. An appropriate turn or altitude restr coordinated with me at any point prior to the frequency change would have ensured a smooth operation. Additionally, a heads up to the trainee or trainer that a faster aircraft was following a slower aircraft would have alerted the controller to the decreasing separation. The north radar handoff controller could have also alerted me to the fact that training was in progress and that sector saturation might prevent timely xfer and control instructions. Another factor was the training environment on north radar during an unusual runway confign. The trainee was receiving instruction on north radar sector combined with the north low sector and the final north sector. The north low sector is normally decombined during high traffic periods and final north is decombined when traffic warrants. The amount of traffic and frequency congestion likely contributed to the lack of awareness of north radar of the decreasing separation taking place in a 'cold spot,' an area of relative inactivity. The controller did not even seem to be aware that the B737 was there until the aircraft was finally able to check in. Therefore, he was unable to initiate communications and control instructions to the aircraft. The south radar controller asked the north radar controller if he was going to turn the aircraft. The north radar controller believed he was talking about another aircraft and replied that he had already changed the aircraft to tower. A final factor for the loss of separation was my lack of establishing visual separation by inadvertently changing the faster aircraft to departure before traffic was reported in sight. Had the aircraft reported the traffic in sight on my frequency, I would have been able to establish visual separation in a timely manner. Preventive measures to avoid this type of incident in the future may include reinforcing the 'team concept' where each controller strives to work together to maintain a safe operation and to alert others to potential conflicts. Additionally, perhaps towers and tracons should have a method of informing each other when training is taking place and operations may not move at a normal pace.

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Original NASA ASRS Text

Title: ANC LCL CTLR EXPERIENCED OPERROR WITH 2 SUCCESSIVE DEP ACFT.

Narrative: I WAS WORKING THE LCL CTL POS IN A LIMITED RADAR APCH CTL TWR WHEN A FASTER DEP OVERTOOK A SLOWER PRECEDING DEP RESULTING IN A LOSS OF IFR SEPARATION. ARRS AND DEPS WERE UTILIZING RWY 24R AND RWY 14, A NONSTANDARD CONFIGN, DUE TO WIND. RWY 24L WAS CLOSED FOR MAINT. I HAD 'AUTO RELEASES' FOR BOTH RWYS. THIS MEANT I COULD USE BOTH RWYS FOR DEPS WITHOUT REQUESTING INDIVIDUAL RELEASES. BOTH ACFT WERE IN A SID THAT REQUIRED THE ACFT TO FLY RWY HDG AND TO EXPECT RADAR VECTORS ON COURSE. BOTH ACFT WERE INITIALLY ISSUED AN ALT OF 4000 FT. THE FIRST DEP, A DHC6, HAD DEPARTED AND HAD BEEN SWITCHED TO DEP CTL. BECAUSE OF ITS RTE OF FLT, A WSW HDG, THE ACFT WAS UNDER THE CTL OF THE S RADAR SECTOR. THE SECOND ACFT, A B737, WAS TAXIED INTO POS. THE ACFT WAS FILED ON A NORTHERLY RTE AND WOULD BE UNDER THE CTL OF THE N RADAR SECTOR. I COORDINATED WITH THE N RADAR HDOF POS AND REQUESTED A TURN TO A HDG OF 270 DEGS FOR THE B737. THE N RADAR HDOF CTLR DENIED THE TURN WITHOUT PROVIDING A REASON. I HAD ACFT WAITING TO DEPART ON BOTH RWYS. THE ACFT DEPARTING RWY 14 WAS A HVY ACFT. BECAUSE THE DEP FLT PATHS OF THE 2 RWYS INTERSECT AT THE ENDS, AND BECAUSE OF WAKE TURB ISSUES, IT WAS IMPERATIVE THAT THE RWY 24R DEP DEPARTED FIRST. WITHOUT A WESTERLY HDG FOR THE B737 I KNEW I WOULD HAVE TO PROVIDE OTHER SEPARATION. I HELD THE ACFT IN POS AS LONG AS PRACTICAL FOR IN-TRAIL SPACING PRIOR TO ISSUING TKOF CLRNC. I DROPPED THE DEP HALF OF THE FLT STRIP DOWN THE TUBE FOR N RADAR WHEN I CLRED THE B737 FOR TKOF. PER OUR FACILITY HANDBOOK, THIS INDICATES THAT THE ACFT IS ROLLING AND CONTAINS ACFT IDENT, ALT AND RTE INFO. WHEN THE ACFT BECAME AIRBORNE, THERE WAS APPROX 4 MI IN-TRAIL AND 2000 FT OF VERT SEPARATION. I IMMEDIATELY ISSUED TFC AND ANTICIPATED ESTABLISHING VISUAL SEPARATION WHEN THE ACFT RPTED THE TFC IN SIGHT. IN THE SAME XMISSION, I INADVERTENTLY CHANGED THE ACFT TO DEP. THE PLT REPLIED, 'LOOKING.' AFTER OTHER COORD AND XMISSIONS TO OTHER ACFT, I AGAIN ISSUED TFC TO THE B737. THIS TIME I INTENTIONALLY CHANGED THE ACFT TO DEP AS I HAD OBSERVED THE DHC6 TURNING SW AND OBSERVED THAT THE B737 WOULD PASS WELL N OF THE DHC6 AND THAT THERE WAS NO TFC TO THE W OR NW THAT WOULD PREVENT A TIMELY TURN IN THAT DIRECTION. THERE WAS, OF COURSE, NO REPLY AS THE PLT HAD ALREADY CHANGED FREQS. AS I CONTINUED TO WORK OTHER TFC, I OBSERVED THAT THE B737 HAD NOT BEEN TURNED BUT ITS COURSE WOULD TAKE IT N OF AND BEHIND THE DHC6 BY 1 MI OR MORE. I DID NOT OBSERVE A SAFETY ISSUE SO I DID NOT CALL THE RADAR POS TO DETERMINE WHY THE ACFT WAS STILL ON RWY HDG. WHEN, A FEW MINS LATER, I WAS RELIEVED FROM THE LCL CTL POS FOR NORMAL POS ROTATION, I PROMPTLY EXPLAINED TO THE SUPVR WHAT HAD TAKEN PLACE AND HEADED TO THE TRACON TO FIGURE OUT WHAT HAD HAPPENED. REVIEW OF THE TAPES INDICATED THAT THE B737 RPTED THE DHC6 IN SIGHT ON INITIAL CONTACT WHILE STILL 3 MI IN TRAIL. CONGESTION ON THE FREQ PREVENTED THE CTLR, WHO WAS TRAINING ON THE POS, FROM HEARING THE INITIAL XMISSION FROM THE B737 AND THUS MAINTAINING IFR SEPARATION. AFTER OTHER XMISSIONS ON THE FREQ, THE B737 AGAIN ATTEMPTED TO CONTACT DEP WITH THE TFC IN SIGHT. THE CTLR INITIALLY SOUNDED CONFUSED AS TO WHO WAS CALLING. HE LATER RADAR IDENTED THE ACFT AND TURNED THE ACFT TO THE N. WHEN THE PLT INQUIRED AS TO WHETHER THE CTLR HAD RECEIVED AN ALERT BTWN HE AND THE DHC6, THE CTLR ADVISED HIM TO MAINTAIN VISUAL SEPARATION. AT THIS POINT THE B737 HAD ALREADY PASSED BEHIND AND R OF THE DHC6 BY 1.09 MI AND THE LOSS OF SEPARATION HAD ALREADY OCCURRED. I BELIEVE THAT SEVERAL FACTORS CONTRIBUTED TO THIS LOSS OF SEPARATION. THE FIRST FACTOR WAS THE DENIAL OF THE REQUESTED HDG BY N RADAR HDOF. THE REQUEST WAS VALID AND TFC WAS NOT A FACTOR FOR DENYING THE TURN. THE TRAINER AND TRAINEE BOTH LATER TOLD ME THAT THERE WAS NO REASON TO NOT TURN THE ACFT. THE NEXT FACTOR WAS THE LACK OF COORD ABOUT THIS ACFT TO ANYONE BY THE N RADAR HDOF CTLR. UPON RECEIVING THE REQUESTED TURN AND LATER RECEIVING THE FLT STRIP FOR THE FASTER ACFT, THE CTLR KNEW THE ACFT WAS ROLLING AND COULD HAVE DONE ANY NUMBER OF THINGS TO ENSURE SEPARATION WAS MAINTAINED. AN APPROPRIATE TURN OR ALT RESTR COORDINATED WITH ME AT ANY POINT PRIOR TO THE FREQ CHANGE WOULD HAVE ENSURED A SMOOTH OP. ADDITIONALLY, A HEADS UP TO THE TRAINEE OR TRAINER THAT A FASTER ACFT WAS FOLLOWING A SLOWER ACFT WOULD HAVE ALERTED THE CTLR TO THE DECREASING SEPARATION. THE N RADAR HDOF CTLR COULD HAVE ALSO ALERTED ME TO THE FACT THAT TRAINING WAS IN PROGRESS AND THAT SECTOR SATURATION MIGHT PREVENT TIMELY XFER AND CTL INSTRUCTIONS. ANOTHER FACTOR WAS THE TRAINING ENVIRONMENT ON N RADAR DURING AN UNUSUAL RWY CONFIGN. THE TRAINEE WAS RECEIVING INSTRUCTION ON N RADAR SECTOR COMBINED WITH THE N LOW SECTOR AND THE FINAL N SECTOR. THE N LOW SECTOR IS NORMALLY DECOMBINED DURING HIGH TFC PERIODS AND FINAL N IS DECOMBINED WHEN TFC WARRANTS. THE AMOUNT OF TFC AND FREQ CONGESTION LIKELY CONTRIBUTED TO THE LACK OF AWARENESS OF N RADAR OF THE DECREASING SEPARATION TAKING PLACE IN A 'COLD SPOT,' AN AREA OF RELATIVE INACTIVITY. THE CTLR DID NOT EVEN SEEM TO BE AWARE THAT THE B737 WAS THERE UNTIL THE ACFT WAS FINALLY ABLE TO CHK IN. THEREFORE, HE WAS UNABLE TO INITIATE COMS AND CTL INSTRUCTIONS TO THE ACFT. THE S RADAR CTLR ASKED THE N RADAR CTLR IF HE WAS GOING TO TURN THE ACFT. THE N RADAR CTLR BELIEVED HE WAS TALKING ABOUT ANOTHER ACFT AND REPLIED THAT HE HAD ALREADY CHANGED THE ACFT TO TWR. A FINAL FACTOR FOR THE LOSS OF SEPARATION WAS MY LACK OF ESTABLISHING VISUAL SEPARATION BY INADVERTENTLY CHANGING THE FASTER ACFT TO DEP BEFORE TFC WAS RPTED IN SIGHT. HAD THE ACFT RPTED THE TFC IN SIGHT ON MY FREQ, I WOULD HAVE BEEN ABLE TO ESTABLISH VISUAL SEPARATION IN A TIMELY MANNER. PREVENTIVE MEASURES TO AVOID THIS TYPE OF INCIDENT IN THE FUTURE MAY INCLUDE REINFORCING THE 'TEAM CONCEPT' WHERE EACH CTLR STRIVES TO WORK TOGETHER TO MAINTAIN A SAFE OP AND TO ALERT OTHERS TO POTENTIAL CONFLICTS. ADDITIONALLY, PERHAPS TWRS AND TRACONS SHOULD HAVE A METHOD OF INFORMING EACH OTHER WHEN TRAINING IS TAKING PLACE AND OPS MAY NOT MOVE AT A NORMAL PACE.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.