Narrative:

Was in position and holding for takeoff on runway 33 at btv. Light aircraft was in the pattern on runway 01 doing left patterns. After light aircraft completed his touch and go on runway 01, he was given clearance for another pattern with a right turn to a right base, and we were cleared for takeoff with the copilot making the takeoff. As we were passing 100 KTS I noticed the light aircraft making a left turn toward the departure end of our runway at an altitude of 400-500' AGL. As we were moving rapidly and I had clear visibility contact, I notified the first officer of the problem, told him to continue and make a very shallow climb out. As we lifted off tower notified the light aircraft of this wrong turn and verified that we had visibility sep. We passed directly underneath the other aircraft by about 200'. If visibility contact had not been established, a midair would have been a high probability. From my observation point, all parties were complying with standard procedures, up till the time that the light aircraft turned to a left instead of right base. I suspect training was going on and being a quiet sunday morning the other aircraft was used to left turnouts and unconsciously continued in its established routine. Fortunately for us, it was a clear day and we saw the other aircraft with plenty of time to spare. There is also a strong possibility that tower's call would also have helped us if we had not noticed the other aircraft a few seconds earlier. The key here was situational awareness. We were very much aware of the other aircraft with tower, however the other party not only made a wrong turn, but also the clear for takeoff calls on runway 33 which should have warned him that turning that way at 500' AGL would be a problem.

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Original NASA ASRS Text

Title: SMA PLT DID NOT COMPLY WITH INSTRUCTIONS FROM TWR LCL CTLR. HE TURNED LEFT DOWNWIND INSTEAD OF A RIGHT DOWNWIND PATTERN. PREVIOUS PATTERN WAS LEFT DOWNWIND--HOWEVER, TWR CHANGED TO RIGHT PATTERN TO ALLOW THE MLG TO DEPART TO THE NORTHWEST. RIGHT DOWNWIND WOULD HAVE TAKEN THE SMA BEHIND THE DEP.

Narrative: WAS IN POS AND HOLDING FOR TKOF ON RWY 33 AT BTV. LIGHT ACFT WAS IN THE PATTERN ON RWY 01 DOING LEFT PATTERNS. AFTER LIGHT ACFT COMPLETED HIS TOUCH AND GO ON RWY 01, HE WAS GIVEN CLRNC FOR ANOTHER PATTERN WITH A RIGHT TURN TO A RIGHT BASE, AND WE WERE CLRED FOR TKOF WITH THE COPLT MAKING THE TKOF. AS WE WERE PASSING 100 KTS I NOTICED THE LIGHT ACFT MAKING A LEFT TURN TOWARD THE DEP END OF OUR RWY AT AN ALT OF 400-500' AGL. AS WE WERE MOVING RAPIDLY AND I HAD CLR VIS CONTACT, I NOTIFIED THE F/O OF THE PROB, TOLD HIM TO CONTINUE AND MAKE A VERY SHALLOW CLBOUT. AS WE LIFTED OFF TWR NOTIFIED THE LIGHT ACFT OF THIS WRONG TURN AND VERIFIED THAT WE HAD VIS SEP. WE PASSED DIRECTLY UNDERNEATH THE OTHER ACFT BY ABOUT 200'. IF VIS CONTACT HAD NOT BEEN ESTABLISHED, A MIDAIR WOULD HAVE BEEN A HIGH PROBABILITY. FROM MY OBSERVATION POINT, ALL PARTIES WERE COMPLYING WITH STANDARD PROCS, UP TILL THE TIME THAT THE LIGHT ACFT TURNED TO A LEFT INSTEAD OF RIGHT BASE. I SUSPECT TRNING WAS GOING ON AND BEING A QUIET SUNDAY MORNING THE OTHER ACFT WAS USED TO LEFT TURNOUTS AND UNCONSCIOUSLY CONTINUED IN ITS ESTABLISHED ROUTINE. FORTUNATELY FOR US, IT WAS A CLEAR DAY AND WE SAW THE OTHER ACFT WITH PLENTY OF TIME TO SPARE. THERE IS ALSO A STRONG POSSIBILITY THAT TWR'S CALL WOULD ALSO HAVE HELPED US IF WE HAD NOT NOTICED THE OTHER ACFT A FEW SECS EARLIER. THE KEY HERE WAS SITUATIONAL AWARENESS. WE WERE VERY MUCH AWARE OF THE OTHER ACFT WITH TWR, HOWEVER THE OTHER PARTY NOT ONLY MADE A WRONG TURN, BUT ALSO THE CLR FOR TKOF CALLS ON RWY 33 WHICH SHOULD HAVE WARNED HIM THAT TURNING THAT WAY AT 500' AGL WOULD BE A PROB.

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.