Vans rv pilot reported a twin turboprop aircraft overflew them resulting in evasive action maneuver.

Attributes
ACN	1603181
Time
Date	201812
Local Time Of Day	0601-1200
Place
Locale Reference	AFO.Airport
State Reference	WY
Environment
Flight Conditions	VMC
Aircraft 1
Make Model Name	Vans Aircraft Undifferentiated or Other Model
Operating Under FAR Part	Part 91
Flight Phase	Takeoff
Route In Use	None
Flight Plan	None
Aircraft 2
Make Model Name	Small Transport Low Wing 2 Turboprop Eng
Flight Phase	Initial Climb
Flight Plan	VFR
Person 1
Function	Pilot Flying Single Pilot
Qualification	Flight Crew Private
Experience	Flight Crew Last 90 Days 10 Flight Crew Total 1500 Flight Crew Type 450
Events
Anomaly	Conflict Ground Conflict Critical Deviation - Procedural Published Material / Policy
Miss Distance	Horizontal 0 Vertical 150

Narrative:

I completed my run-up at the departure end of runway 34 at afo; verified visually that there was no traffic in the pattern; and announced on the CTAF (122.8); 'afton traffic; [aircraft X] departing 34; afton'. I had not heard any calls on the CTAF of traffic in the area. I taxied onto [runway] 34 and began the take-off roll when a twin turboprop aircraft flew directly over my aircraft at an estimated height of 150-200 ft. I applied brakes and watched the turboprop execute a missed approach. The turboprop executed a left crosswind turn to 34; then a turn to a left 34 downwind after which I resumed my take-off. There was no CTAF communication from the turboprop (that evidently was executing a straight-in approach to 34) either prior to the approach; during the missed approach or the crosswind; downwind; base; or final legs of the turboprop landing after the potential conflict. Lack of communication from the turboprop as to its position and intent for landing at afo contributed to the potential conflict as did its apparent use of a straight-in approach to runway 34. Potential events like this could be prevented by communication on the CTAF; landing aircraft executing a standard approach pattern rather than a straight-in approach; and by the pilot of departing aircraft double checking for traffic on final prior to taxing onto the active runway.

Original NASA ASRS Text

Title: Vans RV pilot reported a twin turboprop aircraft overflew them resulting in evasive action maneuver.

Narrative: I completed my run-up at the departure end of Runway 34 at AFO; verified visually that there was no traffic in the pattern; and announced on the CTAF (122.8); 'Afton Traffic; [Aircraft X] departing 34; Afton'. I had not heard any calls on the CTAF of traffic in the area. I taxied onto [Runway] 34 and began the take-off roll when a twin turboprop aircraft flew directly over my aircraft at an estimated height of 150-200 ft. I applied brakes and watched the turboprop execute a missed approach. The turboprop executed a left crosswind turn to 34; then a turn to a left 34 downwind after which I resumed my take-off. There was no CTAF communication from the turboprop (that evidently was executing a straight-in approach to 34) either prior to the approach; during the missed approach or the crosswind; downwind; base; or final legs of the turboprop landing after the potential conflict. Lack of communication from the turboprop as to its position and intent for landing at AFO contributed to the potential conflict as did its apparent use of a straight-in approach to Runway 34. Potential events like this could be prevented by communication on the CTAF; landing aircraft executing a standard approach pattern rather than a straight-in approach; and by the pilot of departing aircraft double checking for traffic on final prior to taxing onto the active runway.

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.