19990612022039A

On June 12, 1999, about 1330 eastern daylight time, an aero commander 500S, N33PG, was substantially damaged while landing at the Bradley International Airport (bdl), Windsor Locks, Connecticut. The two certificated airline transport pilots were not injured. Visual meteorological conditions prevailed for the local instructional flight. No flight plan had been filed for the flight that was conducted under 14 CFR part 91. The pilot reported that he was engaged in a local proficiency flight which originated from westchester county airport (hpn), white plains, new york, and was planned to terminate there. During one of the approaches the landing gear selector was placed in the down position, and the nose landing gear extended; however, the main landing gear failed to extend. The pilots elected to retract the landing gear and diverted to bdl due to its better weather. The owner/pilot who had been receiving instruction elected to allow the other pilot to make the landing. At the request of the pilot/owner, the runway was foamed for the landing. On short final both engines were shut down, and both propellers feathered. The airplane struck the runway about 60 feet short of the foam and slid into the foamed area. The touchdown was described as hard. An inspector from the federal aviation administration (FAA) reported that he interviewed witnesses who reported that the airplane appeared to drop in from about 50 feet. Examination of the airplane revealed that the lower aft fuselage was crushed upward. The crushing was visible on the lower 1/2 of the aft fuselage. After the accident, the airplane hydraulic system was examined and found to be full of fluid. The airplane was placed on jacks and hydraulic power applied. The landing gear which had been previously extended was retracted with no problems noted. The landing gear selector was then placed in the down position, and the nose landing gear extended; however, the main landing gear failed to extend. Further examination of the landing gear selector valve is planned. According to FAA records, the pilot/owner had in excess of 3,300 hours, and the flight instructor had in excess of 8,400 hours. (-23) according to the pilot, attempted to lower the aircraft landing gear. The landing gear did not extend. The pilot declared an emergency. The aircraft landed with the aircraft landing gear in the up position . The aircraft sustained substantial damage. (.4) the pilot in command was flying the airplane with a safety pilot onboard. After multiple approaches, when the landing gear was extended, only the nose landing gear extended. Unable to extend the main landing gear, the pilot in command requested that the second pilot perform the gear up landing, because of his greater experience. The propellers were feathered prior to touchdown, and the airplane touched down hard, crushing the lower aft fuselage. Examination of the hydraulic system revealed contamination in the system. According to the mechanic who worked on the airplane, '...the contamination caused the main gear uplock cylinder not to release and allow the gear to extend....' The airplane is not equipped with an alternate gear extension system, therefore, if the hydraulic uplock valve cannot be released, the main gear cannot be extended.