Narrative:

On a training flight to vti for touch-and-goes at vti on runway 16. Private pilot rated student was flying while I was providing instruction and watching for traffic. The student announced our position on the CTAF for each leg of the pattern except upwind leg. We did our first 2 touch-and-goes with no event. After we took off from the second landing; I noticed a crop duster land on runway 16 as we turned crosswind. There was no announcement on the CTAF. As we proceeded on downwind; I noticed another crop duster departing runway 27. Again; there were no announcements on the CTAF besides us. I watched the crop duster turn out towards the south. I turned back to watch for more traffic on base and final. As we turned final at approximately 500 ft AGL; I noticed the crop duster that had departed runway 27 was now flying low down runway 9. It looked as if he was over the south side of the runway spraying the grass. I'm not sure if it was training or if there was actual aerial application being done at the airport or if it was showboating for the other aerial applicators temporarily located on the field (I saw at least 4 other crop dusters on the ramp). We made our call for final as the other aircraft passed in front of us from our left to right. I made another call that we were on final. The crop duster pulled up sharply but didn't initiate an immediate turn. We mistakenly thought the crop duster noticed us and was going to let us complete our landing before coming back in. However; the crop duster did make a turn at an altitude of about 500 ft AGL. It began a dive back down toward the runway. We were at approximately 100 ft AGL at the time. I took control of the airplane from the student and immediately initiated a go around. I felt it prudent to veer to the left toward the crop duster in order to pass behind and above it. A right turn would've kept us on a collision course and could've possibly caused us to lose sight of it. We passed within 200 ft of the other airplane. I returned control of the airplane to the student and we continued on around in the pattern for another attempt at making a landing. I instructed the student to make a wide pattern in case the crop duster made another pass so that we would be outside of the crop duster's turn. Sure enough; the crop duster continued to make aerial application passes along the runway in both directions. There was never any acknowledgement of other traffic or announcements on the radio. We continued with our approach as far as about 400 ft AGL on final and then decided to break off the landing and departed the airport to the west.

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Original NASA ASRS Text

Title: A C172 EXPERIENCED AN NMAC WITH A CROP DUSTER AT VTI.

Narrative: ON A TRAINING FLT TO VTI FOR TOUCH-AND-GOES AT VTI ON RWY 16. PVT PLT RATED STUDENT WAS FLYING WHILE I WAS PROVIDING INSTRUCTION AND WATCHING FOR TFC. THE STUDENT ANNOUNCED OUR POS ON THE CTAF FOR EACH LEG OF THE PATTERN EXCEPT UPWIND LEG. WE DID OUR FIRST 2 TOUCH-AND-GOES WITH NO EVENT. AFTER WE TOOK OFF FROM THE SECOND LNDG; I NOTICED A CROP DUSTER LAND ON RWY 16 AS WE TURNED XWIND. THERE WAS NO ANNOUNCEMENT ON THE CTAF. AS WE PROCEEDED ON DOWNWIND; I NOTICED ANOTHER CROP DUSTER DEPARTING RWY 27. AGAIN; THERE WERE NO ANNOUNCEMENTS ON THE CTAF BESIDES US. I WATCHED THE CROP DUSTER TURN OUT TOWARDS THE S. I TURNED BACK TO WATCH FOR MORE TFC ON BASE AND FINAL. AS WE TURNED FINAL AT APPROX 500 FT AGL; I NOTICED THE CROP DUSTER THAT HAD DEPARTED RWY 27 WAS NOW FLYING LOW DOWN RWY 9. IT LOOKED AS IF HE WAS OVER THE S SIDE OF THE RWY SPRAYING THE GRASS. I'M NOT SURE IF IT WAS TRAINING OR IF THERE WAS ACTUAL AERIAL APPLICATION BEING DONE AT THE ARPT OR IF IT WAS SHOWBOATING FOR THE OTHER AERIAL APPLICATORS TEMPORARILY LOCATED ON THE FIELD (I SAW AT LEAST 4 OTHER CROP DUSTERS ON THE RAMP). WE MADE OUR CALL FOR FINAL AS THE OTHER ACFT PASSED IN FRONT OF US FROM OUR L TO R. I MADE ANOTHER CALL THAT WE WERE ON FINAL. THE CROP DUSTER PULLED UP SHARPLY BUT DIDN'T INITIATE AN IMMEDIATE TURN. WE MISTAKENLY THOUGHT THE CROP DUSTER NOTICED US AND WAS GOING TO LET US COMPLETE OUR LNDG BEFORE COMING BACK IN. HOWEVER; THE CROP DUSTER DID MAKE A TURN AT AN ALT OF ABOUT 500 FT AGL. IT BEGAN A DIVE BACK DOWN TOWARD THE RWY. WE WERE AT APPROX 100 FT AGL AT THE TIME. I TOOK CTL OF THE AIRPLANE FROM THE STUDENT AND IMMEDIATELY INITIATED A GAR. I FELT IT PRUDENT TO VEER TO THE L TOWARD THE CROP DUSTER IN ORDER TO PASS BEHIND AND ABOVE IT. A R TURN WOULD'VE KEPT US ON A COLLISION COURSE AND COULD'VE POSSIBLY CAUSED US TO LOSE SIGHT OF IT. WE PASSED WITHIN 200 FT OF THE OTHER AIRPLANE. I RETURNED CTL OF THE AIRPLANE TO THE STUDENT AND WE CONTINUED ON AROUND IN THE PATTERN FOR ANOTHER ATTEMPT AT MAKING A LNDG. I INSTRUCTED THE STUDENT TO MAKE A WIDE PATTERN IN CASE THE CROP DUSTER MADE ANOTHER PASS SO THAT WE WOULD BE OUTSIDE OF THE CROP DUSTER'S TURN. SURE ENOUGH; THE CROP DUSTER CONTINUED TO MAKE AERIAL APPLICATION PASSES ALONG THE RWY IN BOTH DIRECTIONS. THERE WAS NEVER ANY ACKNOWLEDGEMENT OF OTHER TFC OR ANNOUNCEMENTS ON THE RADIO. WE CONTINUED WITH OUR APCH AS FAR AS ABOUT 400 FT AGL ON FINAL AND THEN DECIDED TO BREAK OFF THE LNDG AND DEPARTED THE ARPT TO THE W.

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