NTSB Identification: SEA97LA058.
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Accident occurred Wednesday, February 05, 1997 in CEDAR CITY, UT
Probable Cause Approval Date: 05/29/1998
Aircraft: Cessna 421C, registration: N45MV
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 was on a night instrument approach in instrument meteorological conditions (IMC). When he put the gear handle down, the nose gear extended, but neither of the mains indicated down-and-locked. He recycled the gear a number of times, but still did not get a down indication of the main gear. The pilot then used the emergency blow-down gear extension system, but only the nose gear & left main indicated down. Since the gear could not be retracted once the blow-down system was used, & since severe weather was present, the pilot elected to continue the approach & land with the right main gear not fully extended. As the aircraft slowed during the landing roll, the right wing contacted the runway, & the aircraft began to slide sideways. While the aircraft was sliding, the nose gear and left main gear collapsed, and the right gear, which had come partially out of the wheel well, was torn from the wing. Postaccident inspection of the landing gear extension & retraction system revealed that hydraulic fluid in the right main gear actuator contained 30% water by volume. The surface temperature near the time of the landing was 23 degrees Fahrenheit, & the aircraft had been at altitude for over an hour before the approach. There was evidence that while en route, water in the actuator had frozen, & ice had kept the actuator from functioning properly when the pilot attempted to extend the gear. How or when the hydraulic system of the 19 year old aircraft had been contaminated was not determined.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: water contamination in the hydraulic system, which froze in the (right) main gear hydraulic actuator, and restricted movement of the (right) main gear retraction and extension system. Full narrative available
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