Piper PA28 accident near San Juan, Puerto Rico, July 4, 2017

The NTSB's narrative final · quoted from the NTSB record

The private pilot reported that, before the local, personal flight, the airplane was fueled and that he performed a preflight inspection and an engine run-up with no issues noted. The takeoff was normal; however, during the initial climb, about 250 ft above ground level, the engine started to run roughly and lose power. The engine did not respond to throttle inputs. The pilot contacted the air traffic control tower and stated that he intended to return to the departure airport to land. He did not recall the remainder of the accident sequence. A passenger, who was also a certificated pilot, stated that, as the pilot was turning the airplane left back to the airport, he saw that the airspeed was decreasing and that the stall warning light was flashing. Subsequently, the airplane entered an aerodynamic stall and spun into a canal. A review of a video taken by a witness corroborated the passenger's account.   Examination of the airframe and engine did not reveal any preaccident mechanical malfunctions or failures that would have precluded normal operation. Sound spectrum analysis of onboard video revealed that the engine rpm decreased by about 300 and then increased by about 300 twice but then remained steady near full power for about 6 seconds before impact. The reason for the rpm changes could not be determined.

The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.