NTSB Identification: NYC99LA139.
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Accident occurred Saturday, June 12, 1999 in WINDSOR LOCKS, CT
Probable Cause Approval Date: 06/22/2000
Aircraft: Aero Commander 500S, registration: N33PG
Injuries: 2 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

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.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

Hydraulic system contamination which prevented normal landing gear extension. A factor was the misjudged landing flare by the flying pilot.

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