Narrative:

While working a DH8 inbound to mht at 4000 ft from the southwest, I issued traffic on a VFR target in his 1 O'clock position, approximately 6 mi, maneuvering at 4300 ft. He indicated he was looking. I updated the traffic call when both targets were about 2 mi apart. No vector was requested. When the targets were 1 mi to 1 1/2 mi apart, the DH8 turned north and descended approximately 500 ft. His turn put him in proximity of other VFR traffic indicating 3100 ft. At that time he (DH8) advised he was responding to several alerts. I issued a TA on the 3100 ft traffic. This situation was reported to the supervisor. I requested to report this situation on a TCASII form. I was advised this was no longer required. I feel a lateral deviation from an ATC clearance is unsafe and not the purpose TCASII was intended for. I received no training or guidance on handling aircraft that deviate laterally on a resolution or TA. I believe this to be an unsafe practice. I have reported this situation before and it seems to be ignored. The procedure or recommendation to request a vector around traffic has been around longer than TCASII. It seems to be forgotten.

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Original NASA ASRS Text

Title: FLC OF DH8 DEVIATED FROM RTE/ALT CLRNC DUE TO A TCASII RA. RPTR ALLEGES NO TRAINING OR GUIDANCE WAS RECEIVED ON LATERAL DEVS DUE TO TCASII RA'S.

Narrative: WHILE WORKING A DH8 INBOUND TO MHT AT 4000 FT FROM THE SW, I ISSUED TFC ON A VFR TARGET IN HIS 1 O'CLOCK POS, APPROX 6 MI, MANEUVERING AT 4300 FT. HE INDICATED HE WAS LOOKING. I UPDATED THE TFC CALL WHEN BOTH TARGETS WERE ABOUT 2 MI APART. NO VECTOR WAS REQUESTED. WHEN THE TARGETS WERE 1 MI TO 1 1/2 MI APART, THE DH8 TURNED N AND DSNDED APPROX 500 FT. HIS TURN PUT HIM IN PROX OF OTHER VFR TFC INDICATING 3100 FT. AT THAT TIME HE (DH8) ADVISED HE WAS RESPONDING TO SEVERAL ALERTS. I ISSUED A TA ON THE 3100 FT TFC. THIS SIT WAS RPTED TO THE SUPVR. I REQUESTED TO RPT THIS SIT ON A TCASII FORM. I WAS ADVISED THIS WAS NO LONGER REQUIRED. I FEEL A LATERAL DEV FROM AN ATC CLRNC IS UNSAFE AND NOT THE PURPOSE TCASII WAS INTENDED FOR. I RECEIVED NO TRAINING OR GUIDANCE ON HANDLING ACFT THAT DEVIATE LATERALLY ON A RESOLUTION OR TA. I BELIEVE THIS TO BE AN UNSAFE PRACTICE. I HAVE RPTED THIS SIT BEFORE AND IT SEEMS TO BE IGNORED. THE PROC OR RECOMMENDATION TO REQUEST A VECTOR AROUND TFC HAS BEEN AROUND LONGER THAN TCASII. IT SEEMS TO BE FORGOTTEN.

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.