Narrative:

My student and I were doing practice landings on runway 27 at carlisle municipal airport (4m3). 4m3 has two runways; 9-27 and 18-36; with the arrival ends of runways 36 and 27 crossing each other. We made our appropriate radio calls downwind; base; and final. There was no other traffic observed or heard over the radio. Upon reaching short final for runway 27; the following occurred.my student and I were on short final to runway 27; approximately 100-200 yards from the threshold at about 100-150 feet AGL. A crop duster was on a path to cross the threshold of runway 27 on an approximate heading of 020; 200 feet AGL; and 300 yards to our southwest. He was to our left. Due to his approach and speed to the airport and our traffic pattern position; we were unable to spot him earlier. Upon spotting the crop duster; the only feasible maneuver to avoid collision was to keep flying the approach; descend below the crop duster; and have him fly over us. We landed without any further incident or issue. The crop duster never reported its position around the airport; and it did not do any evasive maneuver to avoid us. After flying directly over us; he continued to drop his product on the field directly east of the airport. Based on the crop duster's position and speed in relation to us; continuing the descent seemed like the only reasonable option to avoid collision. If we climbed; we would cross over him; if we turned left or right we would go straight into his path.I believe this type of issue can be prevented in the future if all airplanes working in and around airports give timely position reports over the radio. Requiring radio communication around airports; regardless of the class of airspace; will greatly improve safety. If radios cannot be mandated; then ads-B for all airplanes regardless of airspace can also be beneficial.

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Original NASA ASRS Text

Title: Small aircraft flight instructor reported an NMAC with a crop duster on approach to 4M3; a non-towered airport.

Narrative: My student and I were doing practice landings on Runway 27 at Carlisle Municipal Airport (4M3). 4M3 has two Runways; 9-27 and 18-36; with the arrival ends of Runways 36 and 27 crossing each other. We made our appropriate radio calls downwind; base; and final. There was no other traffic observed or heard over the radio. Upon reaching short final for Runway 27; the following occurred.My student and I were on short final to Runway 27; approximately 100-200 yards from the threshold at about 100-150 feet AGL. A crop duster was on a path to cross the threshold of Runway 27 on an approximate heading of 020; 200 feet AGL; and 300 yards to our southwest. He was to our left. Due to his approach and speed to the airport and our traffic pattern position; we were unable to spot him earlier. Upon spotting the crop duster; the only feasible maneuver to avoid collision was to keep flying the approach; descend below the crop duster; and have him fly over us. We landed without any further incident or issue. The crop duster never reported its position around the airport; and it did not do any evasive maneuver to avoid us. After flying directly over us; he continued to drop his product on the field directly east of the airport. Based on the crop duster's position and speed in relation to us; continuing the descent seemed like the only reasonable option to avoid collision. If we climbed; we would cross over him; if we turned left or right we would go straight into his path.I believe this type of issue can be prevented in the future if all airplanes working in and around airports give timely position reports over the radio. Requiring radio communication around airports; regardless of the class of airspace; will greatly improve safety. If radios cannot be mandated; then ADS-B for all airplanes regardless of airspace can also be beneficial.

Data retrieved from NASA's ASRS site 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.