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Sna local controller described near midair collision when 2 aircraft in VFR traffic pattern lost sight of one another; citing facility procedures as contributory.
| Attributes | |
| ACN | 714537 |
| Time | |
| Date | 200610 |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | airport : sna.airport |
| State Reference | CA |
| Altitude | msl single value : 700 |
| Environment | |
| Flight Conditions | VMC |
| Light | Night |
| Aircraft 1 | |
| Controlling Facilities | tower : sna.tower |
| Operator | general aviation : instructional |
| Make Model Name | Yankee |
| Operating Under FAR Part | Part 91 |
| Flight Phase | cruise : level |
| Route In Use | approach : traffic pattern |
| Aircraft 2 | |
| Controlling Facilities | tower : sna.tower |
| Operator | general aviation : instructional |
| Make Model Name | Small Aircraft Low Wing 1 Eng Fixed Gear |
| Operating Under FAR Part | Part 91 |
| Flight Phase | cruise : level |
| Route In Use | approach : traffic pattern |
| Person 1 | |
| Affiliation | government : faa |
| Function | controller : local |
| Qualification | controller : non radar |
| Experience | controller limited radar : 6 controller non radar : 3 controller supervisory : 10 controller time certified in position1 : 16 controller time certified in position2 : 2 |
| ASRS Report | 714537 |
| Person 2 | |
| Affiliation | other |
| Function | flight crew : single pilot |
| Events | |
| Anomaly | conflict : nmac |
| Independent Detector | other controllera |
| Resolutory Action | flight crew : took evasive action |
| Miss Distance | horizontal : 100 vertical : 100 |
| Supplementary | |
| Problem Areas | FAA Flight Crew Human Performance ATC Human Performance Airport |
| Primary Problem | ATC Human Performance |
Narrative:
The 2 aircraft were operating in the runway 19L pattern practicing touch and goes. A B757 was arriving for runway 19R. Sna order 7110.5G; sep/xa/06; does not allow an aircraft to cross the runway 19L threshold when a B757 is operating on runway 19R between taxiway left and taxiway H. Because of this the 2 aircraft in the pattern could not turn base immediately and had to be re-sequenced instead of being allowed to complete their touch and go. During this re-sequencing the aircraft lost sight of each other and had to take evasive action. If this procedure had not been in place these aircraft would not have been so close in proximity and convergence. This procedure actually increases the aircraft's exposure to wake turbulence.
Original NASA ASRS Text
Title: SNA LCL CTLR DESCRIBED NMAC WHEN 2 ACFT IN VFR TFC PATTERN LOST SIGHT OF ONE ANOTHER; CITING FACILITY PROCS AS CONTRIBUTORY.
Narrative: THE 2 ACFT WERE OPERATING IN THE RWY 19L PATTERN PRACTICING TOUCH AND GOES. A B757 WAS ARRIVING FOR RWY 19R. SNA ORDER 7110.5G; SEP/XA/06; DOES NOT ALLOW AN ACFT TO CROSS THE RWY 19L THRESHOLD WHEN A B757 IS OPERATING ON RWY 19R BTWN TXWY L AND TXWY H. BECAUSE OF THIS THE 2 ACFT IN THE PATTERN COULD NOT TURN BASE IMMEDIATELY AND HAD TO BE RE-SEQUENCED INSTEAD OF BEING ALLOWED TO COMPLETE THEIR TOUCH AND GO. DURING THIS RE-SEQUENCING THE ACFT LOST SIGHT OF EACH OTHER AND HAD TO TAKE EVASIVE ACTION. IF THIS PROC HAD NOT BEEN IN PLACE THESE ACFT WOULD NOT HAVE BEEN SO CLOSE IN PROX AND CONVERGENCE. THIS PROC ACTUALLY INCREASES THE ACFT'S EXPOSURE TO WAKE TURB.
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.