On June 17, 2024, about 1415 eastern daylight time, an experimental, amateur-built Vans RV-6A airplane, N715PA, was substantially damaged when it was involved in an accident near Methuen, Massachusetts. The private pilot was fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. A preliminary review of air traffic control communications and radar data revealed the airplane was cleared for takeoff from runway 23 at the Lawrence Municipal Airport (LWM), Lawrence, Massachusetts, about 1411. The pilot planned to stay in the traffic pattern and practice full stop landings. After takeoff, the airplane climbed to 1,650 ft mean sea level (msl) before entering a wide right turn and entering the downwind leg of the airport traffic pattern for runway 23. About 1411, an air traffic controller cleared the airplane to land, and the pilot acknowledged. Less than 1 minute later, the pilot said he was having a “problem”, and the controller cleared the airplane to land on any runway. The pilot transmitted “oh, oh”, and there were no further communications from airplane. Several witnesses reported that the airplane was experiencing engine trouble after it took off. One witness was outside his office when he heard the airplane departing. The engine was at “full throttle” before it abruptly stopped. The witness said the airplane leveled and made a right turn (north to east) at an altitude of about 1,500 to 2,000 ft msl. He thought the pilot was having a fuel issue or he was practicing a simulated “engine out” in the traffic pattern. He never heard the engine restart. The witness said the airplane looked “in control” the entire time before it disappeared from his view behind trees and buildings. Another witness was working near the airport when he heard the airplane’s engine sputter and “quit” before it reached traffic pattern altitude. Less than 1 minute later the witness heard the engine restart, sputter and quit again. The airplane was flying east toward the Merrimack River before it disappeared from his view. A helicopter pilot, who had just landed at LWM, observed the airplane on downwind in a controlled descent over the Merrimack River. He told the controller that the airplane was not going to make it back to the airport. The helicopter pilot departed and located the airplane in the river. The airplane came to rest inverted in about 3 ft of water. There was no postimpact fire. The airplane was recovered from the river to a secure salvage facility for further examination.