Be-300 captain reported near mid-air collision after takeoff.

Attributes
ACN	1682664
Time
Date	201909
Local Time Of Day	0601-1200
Place
Locale Reference	SAT.Airport
State Reference	TX
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Make Model Name	Super King Air 300
Operating Under FAR Part	Part 91
Flight Phase	Climb
Route In Use	Vectors
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Person 1
Function	Pilot Flying Single Pilot Captain
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument Flight Crew Flight Instructor Flight Crew Flight Engineer Flight Crew Multiengine
Experience	Flight Crew Last 90 Days 50 Flight Crew Total 28000 Flight Crew Type 500
Events
Anomaly	Conflict NMAC Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy Deviation - Track / Heading All Types
Miss Distance	Horizontal 1 Vertical 300

Narrative:

At takeoff clearance; given turn left 040; then on roll given runway heading 127 as previous traffic was turned northeast. Climbing off airport boundary given turn left 060. Ap (autopilot) on so commanded turn to 060. Then ap chimes off so I re-engage. I missed resetting heading bug so ap continued turning left thru assigned 060 before I recognized error. Immediately turned off ap and hand flew back to 060. Departure called and inquired heading as I re-established heading. At this moment got a RA (resolution advisory) to climb 2000+ to solve conflict. I was already doing near this amount of rate of climb. My estimate was I passed over traffic 300 ft. At the moment did not get a good recollection of the actual altitude.I got behind airplane with heading changes; ap failing off at inopportune time; and slow recognition response. I have not flown this aircraft in 30 days and it showed. Rest of the day went well. Called sat TRACON upon arrival at destination and was told nothing came up post event. No excuses; I just was behind the departure and airplane at this moment.

Original NASA ASRS Text

Title: BE-300 Captain reported near mid-air collision after takeoff.

Narrative: At takeoff clearance; given turn left 040; then on roll given runway heading 127 as previous traffic was turned northeast. Climbing off airport boundary given turn left 060. AP (Autopilot) on so commanded turn to 060. Then AP chimes off so I re-engage. I missed resetting heading bug so AP continued turning left thru assigned 060 before I recognized error. Immediately turned off AP and hand flew back to 060. Departure called and inquired heading as I re-established heading. At this moment got a RA (Resolution Advisory) to climb 2000+ to solve conflict. I was already doing near this amount of rate of climb. My estimate was I passed over traffic 300 ft. At the moment did not get a good recollection of the actual altitude.I got behind airplane with heading changes; AP failing off at inopportune time; and slow recognition response. I have not flown this aircraft in 30 days and it showed. Rest of the day went well. Called SAT TRACON upon arrival at destination and was told nothing came up post event. No excuses; I just was behind the departure and airplane at this moment.

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.