Date: 202008
Flight conditions: VMC
Weather elements / visibility: 10
Light: Daylight
Aircraft: Light Transport; High Wing; 2 Turboprop Eng
Operator: Air Taxi
Operating under: Part 135
Flight plan: VFR
Mission: Cargo / Freight / Delivery
Flight phase: Final Approach
Airspace: Class D BET
ATC / advisory: Tower BET
Reporter organization: Air Taxi
Reporter function: First Officer; Pilot Flying
Reporter qualification: Flight Crew Commercial; Flight Crew Instrument; Flight Crew Multiengine
Human factors: Communication Breakdown
Anomaly: ATC Issue All Types; Inflight Event / Encounter Loss Of Aircraft Control; Inflight Event / Encounter Wake Vortex Encounter
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Regained Aircraft Control
Contributing factors: Environment - Non Weather Related; Procedure
Primary problem: Procedure

Narrative: Entering the left downwind leg of the traffic pattern for 19R at BET. Tower instructed us to extend downwind and he would call our base due to a landing 737 on final. Tower cleared us to land number 2 behind the 737. Just after we were abeam the 737; I (Pilot Flying) turned base to follow them in. I verbalized my intent to the PM (Pilot Monitoring) to stay high in case we needed to add full flaps and make a slower; steeper descent for spacing. We turned final and were in a stabilized descent with approach flaps at 110 Kts.The plane suddenly rolled violently to the left; about 60deg; with a loud bang that sounded like a shotgun blast from the area of the left wing. I immediately corrected back to wings level and within 3 seconds it rolled to the left again; almost 75deg; with another loud bang. The Captain took controls and corrected back to wings level.We briefly discussed requesting priority handling but opted not to since it would increase the workload and we were less than a minute to landing already. The Captain landed the plane normally and taxied to the ramp while I performed control checks and found no anomalies. Post-flight inspection found no visible damage. Our initial theories were a control malfunction or engine problem; but after more discussion we concluded that we were most likely caught in the wake turbulence of the 737. Further research showed us that wingtip vortices can make a loud whip-crack or gunshot sound; and I believe this is what we heard; rather than a mechanical malfunction. While we intended to stay higher than the 737's flight path; ADSB data showed that we were approximately on the same descent profile; or only slightly above. I believe that the light winds and thermals of the afternoon assisted in keeping the vortices from drifting down and away.One of our company managers called the Tower after the fact to get more information and the Controller stated that he instructed us to go around because he was concerned about the separation between us and the 737. [Neither] the Captain nor I heard any such instruction; and since there was no actual loss of separation or violation; we were not aware of this until hearing second hand from our manager. A close-in base turn behind the 737; as well as not staying above their flight path; created a hazard for encountering wake turbulence. Another plane was cleared to land number 3 behind us and this created pressure to land faster and avoid delaying the other aircraft.Allowing more space between aircraft when landing; being cognizant of the flight paths of larger planes; and knowledge of how various atmospheric conditions can affect wingtip vortices are all good practices that could prevent similar incidents or accidents.In conclusion; following a larger jet closely on landing and complacency regarding wake turbulence avoidance resulted in an unusual attitude at low altitude during a critical phase of flight.




Synopsis: First Officer reported encountering wake turbulence on approach to BET in trail of a B737 that resulted in violent uncontrolled rolls.