Narrative:

Active runway 15. WX good VFR with varying wind form 150 to 230 degrees at 10 KTS, gusts to 18 KTS. Helicopter X approaching the airport from the west requesting to land at Z (facility) on the west side of the airport. Per SOP, I instructed 'helicopter X cleared to land on the parallel taxiway abeam Z. Remain west of the runway at all times for traffic.' aircraft Y subsequently called for departure from runway 15 to a n-erly direction. I replied, 'aircraft Y, left turn north departure approved. Runway 15 cleared fore takeoff.' this instruction would have initially put aircraft Y in a turn away from the inbound helicopter. I judged that the aircraft would not be a factor for each other. As the helicopter approached for landing, I observed aircraft Y at mid-field airborne make a sharp right turn directly at the helicopter. I immediately advised the helicopter pilot, who had simultaneously sighted aircraft Y. The helicopter took evasive action by turning hard right and descending to a safe landing at intended destination. Air carrier Y also returned to runway heading. When I questioned the pilot of aircraft Y, he said he had encountered a wind gust that had turned him and he momentarily lost control. The operation I described is routinely done at addison with no complications. I believe the wind conditions combined with the possible inexperience of the aircraft Y pilot were the cause of the conflict. An action I could have taken would have been to initially advise each aircraft of the other's position and intent; however, I don't believe this knowledge would have altered either of their actions, even though they would have been more away of the local traffic situation. As I said, this was a standard practice. I do believe future avoidance of this type situation could be achieved by keeping aware of the possibility of wind shear in varying surface wind conditions and the unexpected effect it could have on landing/departing aircraft. With this awareness a little more than normal sep could be applied.

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Original NASA ASRS Text

Title: ACFT Y FAILED TO FOLLOW ATC INSTRUCTIONS. PLT DEVIATION. CTLR FAILED TO EXCHANGE TRAFFIC INFORMATION. OPERATIONAL DEVIATION.

Narrative: ACTIVE RWY 15. WX GOOD VFR WITH VARYING WIND FORM 150 TO 230 DEGS AT 10 KTS, GUSTS TO 18 KTS. HELI X APCHING THE ARPT FROM THE W REQUESTING TO LAND AT Z (FAC) ON THE W SIDE OF THE ARPT. PER SOP, I INSTRUCTED 'HELI X CLRED TO LAND ON THE PARALLEL TXWY ABEAM Z. REMAIN W OF THE RWY AT ALL TIMES FOR TFC.' ACFT Y SUBSEQUENTLY CALLED FOR DEP FROM RWY 15 TO A N-ERLY DIRECTION. I REPLIED, 'ACFT Y, LEFT TURN N DEP APPROVED. RWY 15 CLRED FORE TKOF.' THIS INSTRUCTION WOULD HAVE INITIALLY PUT ACFT Y IN A TURN AWAY FROM THE INBND HELI. I JUDGED THAT THE ACFT WOULD NOT BE A FACTOR FOR EACH OTHER. AS THE HELI APCHED FOR LNDG, I OBSERVED ACFT Y AT MID-FIELD AIRBORNE MAKE A SHARP RIGHT TURN DIRECTLY AT THE HELI. I IMMEDIATELY ADVISED THE HELI PLT, WHO HAD SIMULTANEOUSLY SIGHTED ACFT Y. THE HELI TOOK EVASIVE ACTION BY TURNING HARD RIGHT AND DSNDING TO A SAFE LNDG AT INTENDED DEST. ACR Y ALSO RETURNED TO RWY HDG. WHEN I QUESTIONED THE PLT OF ACFT Y, HE SAID HE HAD ENCOUNTERED A WIND GUST THAT HAD TURNED HIM AND HE MOMENTARILY LOST CONTROL. THE OPERATION I DESCRIBED IS ROUTINELY DONE AT ADDISON WITH NO COMPLICATIONS. I BELIEVE THE WIND CONDITIONS COMBINED WITH THE POSSIBLE INEXPERIENCE OF THE ACFT Y PLT WERE THE CAUSE OF THE CONFLICT. AN ACTION I COULD HAVE TAKEN WOULD HAVE BEEN TO INITIALLY ADVISE EACH ACFT OF THE OTHER'S POS AND INTENT; HOWEVER, I DON'T BELIEVE THIS KNOWLEDGE WOULD HAVE ALTERED EITHER OF THEIR ACTIONS, EVEN THOUGH THEY WOULD HAVE BEEN MORE AWAY OF THE LCL TFC SITUATION. AS I SAID, THIS WAS A STANDARD PRACTICE. I DO BELIEVE FUTURE AVOIDANCE OF THIS TYPE SITUATION COULD BE ACHIEVED BY KEEPING AWARE OF THE POSSIBILITY OF WIND SHEAR IN VARYING SURFACE WIND CONDITIONS AND THE UNEXPECTED EFFECT IT COULD HAVE ON LNDG/DEPARTING ACFT. WITH THIS AWARENESS A LITTLE MORE THAN NORMAL SEP COULD BE APPLIED.

Data retrieved from NASA's ASRS site as of August 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.