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Prc local controller described near midair collision at 6500 ft when a VFR arrival and VFR departure aircraft conflicted; likely due to ATC directed altitude assignments.
| Attributes | |
| ACN | 714401 |
| Time | |
| Date | 200610 |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | navaid : drk.vortac |
| State Reference | AZ |
| Altitude | msl single value : 6500 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tower : prc.tower |
| Operator | general aviation : personal |
| Make Model Name | Experimental |
| Operating Under FAR Part | Part 91 |
| Flight Phase | climbout : initial |
| Flight Plan | None |
| Aircraft 2 | |
| Controlling Facilities | tower : prc.tower |
| Operator | general aviation : personal |
| Make Model Name | Cessna 180 Skywagon |
| Operating Under FAR Part | Part 91 |
| Flight Phase | descent : approach |
| Flight Plan | VFR |
| Person 1 | |
| Affiliation | government : faa |
| Function | controller : local |
| Experience | controller limited radar : 10 controller radar : 9 |
| ASRS Report | 714401 |
| Person 2 | |
| Affiliation | other |
| Function | flight crew : single pilot |
| Events | |
| Anomaly | conflict : nmac conflict : airborne less severe |
| Independent Detector | atc equipment : conflict alert other controllera |
| Resolutory Action | controller : issued new clearance controller : issued alert |
| Miss Distance | horizontal : 0 vertical : 150 |
| Supplementary | |
| Problem Areas | ATC Human Performance Flight Crew Human Performance |
| Primary Problem | ATC Human Performance |
Narrative:
I departed the experimental on runway 21L and approved a right turn to the north (right downwind). I also had a skywagon inbound from the northwest instructed to enter 2 mi right 45 degree for runway 21R. I restr the skywagon to at or above 6500 ft because of another cessna in the pattern (pattern altitude 6000 ft). I realized that the experimental departed towards the drk VOR and that the inbound was more of a 90 degree entry than a 45 degree; and the 2 aircraft were in confliction. I issued traffic right away to the experimental who responded that he would expedite his climb. I then changed my plan with the inbound skywagon and had him expedite his descent to 6000 ft. The two passed with no horizontal and only 100-200 ft vertical. Scanning my airspace; tower radar display; quick action -- all prevented a possible incident.
Original NASA ASRS Text
Title: PRC LCL CTLR DESCRIBED NMAC AT 6500 FT WHEN A VFR ARR AND VFR DEP ACFT CONFLICTED; LIKELY DUE TO ATC DIRECTED ALT ASSIGNMENTS.
Narrative: I DEPARTED THE EXPERIMENTAL ON RWY 21L AND APPROVED A R TURN TO THE N (R DOWNWIND). I ALSO HAD A SKYWAGON INBOUND FROM THE NW INSTRUCTED TO ENTER 2 MI R 45 DEG FOR RWY 21R. I RESTR THE SKYWAGON TO AT OR ABOVE 6500 FT BECAUSE OF ANOTHER CESSNA IN THE PATTERN (PATTERN ALT 6000 FT). I REALIZED THAT THE EXPERIMENTAL DEPARTED TOWARDS THE DRK VOR AND THAT THE INBOUND WAS MORE OF A 90 DEG ENTRY THAN A 45 DEG; AND THE 2 ACFT WERE IN CONFLICTION. I ISSUED TFC RIGHT AWAY TO THE EXPERIMENTAL WHO RESPONDED THAT HE WOULD EXPEDITE HIS CLB. I THEN CHANGED MY PLAN WITH THE INBOUND SKYWAGON AND HAD HIM EXPEDITE HIS DSCNT TO 6000 FT. THE TWO PASSED WITH NO HORIZ AND ONLY 100-200 FT VERT. SCANNING MY AIRSPACE; TWR RADAR DISPLAY; QUICK ACTION -- ALL PREVENTED A POSSIBLE INCIDENT.
Data retrieved from NASA's ASRS site as of January 2009 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.