NTSB Identification: MIA88LA027.
The docket is stored on NTSB microfiche number 35571.
Accident occurred Wednesday, November 04, 1987 in CLEARWATER, FL
Probable Cause Approval Date: 02/14/1989
Aircraft: LEARJET 35A, registration: N900JE
Injuries: 3 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.

DURING TAXI UP TO HANGAR UNDER DIRECTION OF LINEMAN AFTER ARRIVAL THE FLT EXPERIENCED LOSS OF HYDRAULIC PRESSURE AND BRAKES. THE PLT COULD NOT ACTIVATE THE EMERGENCY BRAKES PRIOR TO ROLLING INTO THE HANGAR AND COLLIDING WITH TWO ACFT PRIOR TO COMING TO REST. EXAMINATION OF THE ACFT REVEALED THE SPOILERON CONTROL VALVE ASSEMBLY SUFFERED FRACTURE OF A NAS1351-4H-24P SCREW DUE TO HYDROGEN EMBRITTLEMENT CRACKING WHICH CAUSED THE SCREW HEAD TO SEPARATE FROM THE SCREW SHANK. THE SCREW IS ONE OF THREE WHICH RETAINS THE SELECTOR VALVE TO THE MANIFOLD ASSEMBLY. WHEN THE SCREW FAILED THE VALVE BODY SEPARATED ALLOWING LOSS OF ALL USABLE HYDRAULIC FLUID. THE SOURCE OF THE MIGRATING ELEMENTAL HYDROGEN INTO THE FRACTURE AREA COULD NOT BE DETERMINED. THE VALVE ASSEMBLY HAD BEEN INSTALLED IN THE ACFT SINCE MANUFACTURE IN 1977 AND HAD ACCUMULATED 5,642 HOURS. THE VALVE IS MAINTAINED ON CONDITION.

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

FLT CONTROL SYST,BOOST SYSTEM..FAILURE,PARTIAL

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

FLUID,HYDRAULIC..LOSS,TOTAL

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

LANDING GEAR,NORMAL BRAKE SYSTEM..LOSS,TOTAL

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

BRAKES(NORMAL)..NOT POSSIBLE

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

BRAKES(EMERGENCY)..NOT ATTAINED


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