Narrative:

At the completion of the after start checks; we began taxiing to runway 36 from the passenger terminal area. I announced on CTAF that we were taxing to runway 36 at mason city for departure. This initial call was made on comm 1. We initiated taxi to runway 36. Midway through the before takeoff checks; I called minneapolis center; on comm 1 to get our clearance. During this time I simultaneously monitored the CTAF on comm 2. During this time I heard no aircraft announcing their position in the mason city area. When I had obtained the clearance I placed the CTAF in the active frequency on comm 1 and the minneapolis center frequency on standby on comm 2. We completed the before takeoff checks. We were now short of runway 36 for departure. The captain cleared the left side of the aircraft; and I cleared the right side of the aircraft; and noted no observed traffic. On CTAF I announced our intention to depart mason city on runway 36; and that we would be turning a left crosswind departure and would be departing the area to the southwest. We heard no other traffic in the area. As we taxied onto the runway centerline we completed the runway items checklist. The captain transferred control of the aircraft to me. I looked down the runway one last time and seeing no traffic advanced the power levers for takeoff. The takeoff roll was completely normal and per the normal takeoff profile. At the positive rate call I called for gear-up heading IAS. While the captain was performing these duties I was crosschecking my instruments making certain that we were at V2 + 10. In this case V2 + 10 was higher than vclean. When I noted that the radar altimeter was above 400 AGL; I called for flaps up; after takeoff check. The captain initiated the after takeoff check. I initiated a shallow bank to the left and scanned outside for traffic. I immediately noticed an airplane slightly higher than our altitude (approximately 100 ft); and very close horizontally (I would guess between 500-1;000 ft). I immediately stated traffic; and reversed my turn to approximately 15 degrees of right bank; and lowered the nose to stay below the aircraft and gain additional airspeed. The other aircraft appeared to be in a steep; climbing right turn. The aircraft appeared to be white in color; and I believe had a twin tail similar to a vans style aircraft. We received neither a TA; nor an RA from the TCAS system. When we visually verified we were clear of the aircraft we continued climbing at vmm; and executed a left turn on course. We verified that the transponder was selected to altitude; and the TCAS was selected to automatic. When we checked on with msp center we queried him if there was other traffic in our area. Center stated that the nearest aircraft on his radar was 35 miles away. Our TCAS still showed no aircraft; not even a primary target.we proceeded on course. As we climbed out I called back to the operations frequency and asked them to keep an eye out for any GA airplane that landed very shortly after our departure and attempt to get a tail number. They radioed back after approximately 5 to 10 minutes and noted that no one had landed. The remainder of the flight was without incident. The next morning when we landed I recognized the fuel truck operator from the night before. I gave him a description of an aircraft and inquired if there was one based on the field. He said there was one. I asked if he had arrived shortly after we departed. He stated no. He also noted that he had seen that we had almost been hit shortly after take-off. He stated that he believed the aircraft to be transient due to the fact that after he saw the incident he looked and waited for the aircraft to land so he could talk to the pilot. He said he never saw the airplane land. He also stated that transient aircraft flying over mcw with no radio calls was a fairly common occurrence. This event occurred because while I believe that we used due diligence in reporting our position and intentionson the mcw CTAF a low flying transient aircraft was not using radios and flew over the top of the mason city airport very near traffic pattern altitude. I have noticed lately that I have been spending a lot of time looking inside the aircraft on instruments even on VFR days. I look out quickly to check for traffic then go back on instruments to assure that I am meeting the climb profile; following the flight director; etc. This day I had made a conscientious decision to spend more time outside the aircraft when climbing in VFR conditions. Thankfully I spent a great deal of time scanning outside the aircraft in that climb or I may not have seen the aircraft until it was too late. I think that perhaps placing an emphasis on flying the airplane visually in visual conditions with slightly less emphasis on extreme profile accuracy would encourage more people to get their eyes outside of the flight deck.another question to ponder is what quantifies as a near midair collision event? There is little in the fom for guidance (although I may have missed it); to spell out an incident such as this. We received no TA or RA from the TCAS system; which did not even show a primary target. The distances that I related in my description are a guess at best; although the general size of the other aircraft in the window does lead me to believe that we were beyond to close for comfort. What constitutes evasive action? Yes; I could have 'yanked and banked' the aircraft to avoid the traffic. However my situational awareness was such that I knew I was still below vmm; and 1;000 AGL or less. I did not want to worry about accelerated stalls; or the shaker so I chose swift but controlled reaction. The fact that I had to make an immediate turn reversal makes me wonder if that was or was not evasive action; and if that is the sole hard evidence I have; was or was not the entire encounter a near midair collision event? In the end the tipping point I believe for me was that as I talked with the fuel truck driver at mason city; he had seen the events unfold and thought we were going to collide.

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Original NASA ASRS Text

Title: An SF340 had a close encounter with an unannounced aircraft while departing an uncontrolled airport.

Narrative: At the completion of the After Start Checks; we began taxiing to Runway 36 from the passenger terminal area. I announced on CTAF that we were taxing to Runway 36 at Mason City for Departure. This initial call was made on COMM 1. We initiated taxi to Runway 36. Midway through the before takeoff checks; I called Minneapolis Center; on COMM 1 to get our clearance. During this time I simultaneously monitored the CTAF on COMM 2. During this time I heard no aircraft announcing their position in the Mason City area. When I had obtained the clearance I placed the CTAF in the active frequency on COMM 1 and the Minneapolis Center frequency on standby on COMM 2. We completed the before takeoff checks. We were now short of Runway 36 for departure. The Captain cleared the left side of the aircraft; and I cleared the right side of the aircraft; and noted no observed traffic. On CTAF I announced our intention to depart Mason City on Runway 36; and that we would be turning a left crosswind departure and would be departing the area to the Southwest. We heard no other traffic in the area. As we taxied onto the runway centerline we completed the runway items checklist. The Captain transferred control of the aircraft to me. I looked down the runway one last time and seeing no traffic advanced the power levers for takeoff. The takeoff roll was completely normal and per the normal takeoff profile. At the positive rate call I called for gear-up heading IAS. While the Captain was performing these duties I was crosschecking my instruments making certain that we were at V2 + 10. In this case V2 + 10 was higher than Vclean. When I noted that the radar altimeter was above 400 AGL; I called for flaps Up; After Takeoff check. The Captain initiated the after takeoff check. I initiated a shallow bank to the left and scanned outside for traffic. I immediately noticed an airplane slightly higher than our altitude (approximately 100 FT); and very close horizontally (I would guess between 500-1;000 FT). I immediately stated traffic; and reversed my turn to approximately 15 degrees of right bank; and lowered the nose to stay below the aircraft and gain additional airspeed. The other aircraft appeared to be in a steep; climbing right turn. The aircraft appeared to be white in color; and I believe had a twin tail similar to a Vans style aircraft. We received neither a TA; nor an RA from the TCAS system. When we visually verified we were clear of the aircraft we continued climbing at Vmm; and executed a left turn on course. We verified that the transponder was selected to ALT; and the TCAS was selected to AUTO. When we checked on with MSP center we queried him if there was other traffic in our area. Center stated that the nearest aircraft on his radar was 35 miles away. Our TCAS still showed no aircraft; not even a primary target.We proceeded on course. As we climbed out I called back to the Operations frequency and asked them to keep an eye out for any GA airplane that landed very shortly after our departure and attempt to get a tail number. They radioed back after approximately 5 to 10 minutes and noted that no one had landed. The remainder of the flight was without incident. The next morning when we landed I recognized the fuel truck operator from the night before. I gave him a description of an aircraft and inquired if there was one based on the field. He said there was one. I asked if he had arrived shortly after we departed. He stated no. He also noted that he had seen that we had almost been hit shortly after take-off. He stated that he believed the aircraft to be transient due to the fact that after he saw the incident he looked and waited for the aircraft to land so he could talk to the pilot. He said he never saw the airplane land. He also stated that transient aircraft flying over MCW with no radio calls was a fairly common occurrence. This event occurred because while I believe that we used due diligence in reporting our position and intentionson the MCW CTAF a low flying transient aircraft was not using radios and flew over the top of the Mason City Airport very near traffic pattern altitude. I have noticed lately that I have been spending a lot of time looking inside the aircraft on instruments even on VFR days. I look out quickly to check for traffic then go back on instruments to assure that I am meeting the climb profile; following the flight director; etc. This day I had made a conscientious decision to spend more time outside the aircraft when climbing in VFR conditions. Thankfully I spent a great deal of time scanning outside the aircraft in that climb or I may not have seen the aircraft until it was too late. I think that perhaps placing an emphasis on flying the airplane visually in visual conditions with slightly less emphasis on extreme profile accuracy would encourage more people to get their eyes outside of the flight deck.Another question to ponder is what quantifies as a NMAC event? There is little in the FOM for guidance (although I may have missed it); to spell out an incident such as this. We received no TA or RA from the TCAS system; which did not even show a primary target. The distances that I related in my description are a guess at best; although the general size of the other aircraft in the window does lead me to believe that we were beyond to close for comfort. What constitutes evasive action? Yes; I could have 'yanked and banked' the aircraft to avoid the traffic. However my situational awareness was such that I knew I was still below Vmm; and 1;000 AGL or less. I did not want to worry about accelerated stalls; or the shaker so I chose swift but controlled reaction. The fact that I had to make an immediate turn reversal makes me wonder if that was or was not evasive action; and if that is the sole hard evidence I have; was or was not the entire encounter a NMAC event? In the end the tipping point I believe for me was that as I talked with the fuel truck driver at Mason City; he had seen the events unfold and thought we were going to collide.

Data retrieved from NASA's ASRS site as of April 2012 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.