NTSB Identification: LAX97FA069.
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Scheduled 14 CFR operation of ALOHA ISLANDAIR INC. (D.B.A. ISLAND AIR )
Accident occurred Sunday, December 15, 1996 in HONOLULU, HI
Probable Cause Approval Date: 03/31/1998
Aircraft: de Havilland DHC-8, registration: N801WP
Injuries: 13 Uninjured.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

Hydraulic fluid was leaking from a deteriorated O-ring in the landing gear selector solenoid valve, rendering the normal landing gear extension system inoperative. The crew actuated the alternate gear extension system and was unable to extend the right main landing gear. The first officer pulled the main landing gear alternate extension cable until it stopped and the right main landing gear uplock actuator did not release. On advice from company maintenance, after completing the alternate gear extension procedure, the crew retracted the nose gear and the left main gear using the normal system and then attempted another normal extension. Only the left main landing gear extended. The airplane's number 2 hydraulic system was depleted with 1.5 quarts of fluid remaining. The crew attempted another retraction to raise the left main landing gear without success. The captain then landed the airplane with only the left main landing gear extended. Examination of the alternate gear system revealed the main gear extension cable would bind after the left main landing gear uplock actuator would release. Subsequent testing of the system while the airplane was on jack stands reduced the binding, but in all tests the left main landing gear uplock actuator would release before the right uplock actuator. Examination of the main landing gear alternate extension cable revealed the plastic coating was missing in two places adjacent to a pulley. The right main landing gear wheel well was excessively dirty with areas of exfoliated white paint, exposing the underlying primer.

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

A failure of the normal landing gear extension system due to a hydraulic leak, and the failure of the airplane's emergency landing gear extension system due to inadequate servicing by company maintenance personnel. Factors were the emergency landing gear extension systems dirty and binding condition, a worn emergency landing gear extension cable, and the training simulator's lack of fidelity concerning the force required to operate the emergency gear extension T-handle.

Full narrative available

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