On October 31, 2016, about 1620 eastern daylight time, a Cessna TR182, N4657S, was substantially damaged when the main landing gear collapsed while landing at Watertown International Airport (ART), Watertown, New York. The commercial pilot was not injured. No flight plan was filed for the personal flight that originated at Massena International Airport (MSS), Massena, New York. Visual meteorological conditions prevailed for the personal flight conducted under 14 Code of Federal Regulations Part 91.The pilot reported that, before landing, he observed a green light indicating that the landing gear were down. During landing, the right main landing gear collapsed, followed by the left main landing gear. The airplane veered off the left side of runway 28, resulting in substantial damage to the fuselage, elevator, and right horizontal stabilizer. A review of the maintenance records revealed that both down lock switches on the main landing gear were replaced approximately 29 hours, about 5 months, before the accident. The aircraft was placed on jacks and the landing gear were tested, all checks were normal. During a postaccident examination, the airplane was placed on jacks to facilitate inspection of the landing gear system. The landing gear was cycled normally several times, the emergency extension was also checked, and all operations were satisfactory. The landing gear warning horn was found to be inoperative due to a failure of the cabin speaker. The circuit breaker for the electrically-driven hydraulic power pack was found popped after the accident. Further investigation revealed the landing gear solenoid would intermittently stick closed and the power pack motor would continue to run without shutting off, tripping the circuit breaker. Replacement of the solenoid corrected the problem. The airplane was equipped with a Lycoming O-540 series, 235-horsepower engine. The airplane had been operated for about 61 hours since its most recent annual inspection, which was performed on November 17, 2015. The pilot reported 2,490 hours of total flight experience, of which 63 hours were in the accident airplane make and model. The weather conditions at ART reported at 1556, included wind variable at 5 knots; visibility 10 statute miles; sky condition, broken at 3,500 ft; temperature, 6° C; dew point, -2° C; and a barometric altimeter setting of 30.26 inHg.