On November 25, 2017, about 1515 Pacific standard time, an amateur-built Quicksilver GT-500, N599RA, was substantially damaged when it was involved in an accident near Willows, California. The flight instructor and the student pilot received minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. The student pilot, who was the pilot flying, reported that the accident flight was the third leg of a cross-country flight. He stated that after topping off both fuel tanks, the flight was departing from Willows-Glenn County Airport (WLW), Willows, California; when the airplane was about 70 ft above ground level and halfway down the runway, the engine momentarily sputtered and then experienced a total loss of power. He indicated that he attempted to land straight ahead but did not maintain proper airspeed, which, in his opinion, resulted in an aerodynamic stall and impact with terrain. Video from an onboard camera on the airplane’s left outboard wing showed the airplane lifting off about 4 minutes 25 seconds after the engine start. During the initial climb, the airplane was right of the runway centerline, and 22 seconds after liftoff, the engine lost power. The engine can be heard detonating about 15 seconds after full throttle application, and it started to seize until it completely lost power. The student pilot pulled back on the control yoke, and the airplane rapidly descended toward the runway and impacted the ground hard, which resulted in substantial damage to the fuselage and left-wing strut. A postaccident engine examination revealed that the radiator coolant level was low enough that the fluid was not visible through the radiator cap. Draining the remaining coolant from the system allowed investigators to estimate that about 1/4 of the antifreeze was missing from the cooling system before the accident. The radiator overflow and recovery bottle had fluid in it. However, the hose leading from the radiator to the recovery bottle was improperly attached at the top of the bottle instead of the bottom. The 90° fitting installed into the top of the recovery bottle extended into the bottle less than 1 inch (in), so the system could not replenish any lost coolant in between flights during the cool-down cycle. The normal hose connection nipple used for installation was plugged. A small leak was found on the water pump inlet hose, water pump housing, case halves, and motor mount plate on the exhaust side of the engine where the water pump and coolant hoses are mounted on. The hose that was attached to the water pump housing nipple measured 1 inch (in) in diameter, while the water pump housing nipple measured between 0.904 in and 0.978 in. Examination of both cylinders showed signs of lack of coolant. The intake port sides of the cylinders had antifreeze particles embedded in their surfaces consistent with overheating. Both spark plug electrodes on the No.1 cylinder were melted, indicative of preignition and subsequent detonation within that cylinder, and both spark plug electrodes on the No.2 cylinder showed signs of overheating. Black carbon deposits were observed around the perimeter on the spark plugs which indicated that the engine ran rich. The top portion of the No. 1 piston exhibited melted metal deposits (from the spark plug electrodes), indicative of preignition and detonation. In addition, the outside surface of the piston around the pin and the ring gap exhibited black burn marks consistent with preignition/detonation high-pressure/temperature gases escaping between the ring end gap and burning away the aluminum portion of the piston. The carbon build-up and the aluminum discoloration on the bottom side of the piston were consistent with exposure to excessive temperatures for a long period of time. The No. 2 piston exhibited discoloration and burnt-on carbon deposits consistent with the piston overheating for a period of time. Two vertical striations noted on the intake side of No. 2 piston indicated an area of high pressure consistent with a piston that overheated and expanded, reducing the cylinder-to-piston wall clearance to below tolerance. Both carburetors' needle jets, jet needles, and all the moving parts within the carburetor showed signs of significant wear. Inspection of the crankshaft, main bearings, and connecting rod bearings showed no anomalies.