Small Aircraft; High Wing; 1 Eng; Fixed Gear
Flight Crew Commercial; Flight Crew Multiengine
Flight Crew Last 90 Days 158; Flight Crew Total 417; Flight Crew Type 383
Situational Awareness; Distraction
ATC Issue All Types; Conflict NMAC
Flight Crew Took Evasive Action
Human Factors
During an aerial survey mission; another aircraft flying near our same altitude came within 100-200 feet of our aircraft; while traveling the opposite direction. No notification was given to either aircraft by ATC and this incident almost resulted in a Midair Collision. Evasive action was taken on our part once the aircraft was spotted; however by then the aircraft was too close for evasive action to be effective and the aircraft passed below our aircraft. Earlier during this flight we had coordinated with Ft. Wayne Indiana's airport approach controller to receive air traffic advisories while we operated near their airspace. We were then handed over to Indianapolis approach control in order to continue the traffic advisories as we grew closer to their airspace. We were acknowledged by Indianapolis Approach on Frequency 120.650 with our full tail number and asked to report any altitude changes; to maintain our own navigation and we maintained the squawk code. Approximately 45 to 60 minutes after being handed over to Indianapolis approach; while continuing our aerial survey flight at a constant altitude of 4700 MSL; is when the other aircraft involved passed dangerously close to our aircraft; headed southwesterly; while we maintained a north heading. The other aircraft never made any indication as to the proximity they had just flown to us; either by evasive action or by notification to ATC about the incident. We were unable to see the aircraft heading in our direction due to a small window of time during survey collection where we need to be inside the aircraft; operating our survey equipment and ensuring everything is working properly so that we may complete our mission. By the time we were able to continue scanning our outside surroundings; the other aircraft was under ours.I have since talked with Indianapolis TRACON and we have determined that due to a fault of their controller system; sometime after our aircraft was recognized by the assigned approach controller; their system accidentally dropped our beacon code and they were no longer being notified as to our location. This accompanied by a lack of situational awareness by the controller personnel; led to our two aircraft being allowed to continue on a course that nearly resulted in a near midair collision.
The non-flying pilot reported a near-miss while receiving traffic advisories from IND Approach.