Service difficulty report · Pump · Dhav DHC4A

Difficulty date
April 30, 2006
Submitted
June 6, 2006
Operation
General aviation
Make and model
Dhav DHC4A
Aircraft time
15,800 hours
Part
Pump
Part number
6307901
Part serial
166344A
Condition
Failed
Location
Hydraulic Sys
Component
Hydraulic Sys
Stage of operation
CR
How discovered
O
Nature of condition
J, F
Precautionary procedure
O

As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.

What was found

AFTER REPLACING A PUMP DUE TO TIME-EX, NEXT 3 PUMPS INSTALLED FAILED. ALL FAILED DUE TO SHAFT SHEARING. FILTERS PULLED AFTER 1ST FAILURE, THERE WAS ONLY TRACE EVIDENCE OF METAL AND NOTHING ELSE. FILTER WAS CLEANED, REINSTALLED IAW MM. AFTER NEXT 2 FAILURES FILTERS PULLED AGAIN WITH NO METAL FINDINGS. FIRST FAILED PUMP, DISASSEMBLED IT TO TRY AND FIND CAUSE FOR FAILURE. DISASSEMBLY FOUND 2 OF PISTONS SEIZED DUE TO OVERHEATING AND SEPARATED FROM SWASH PLATE. 1 PISTON HAD END TORN OFF AND HAD GENERATED A FAIR AMT OF METAL CONTAM INTERNALLY TO PUMP. STILL INVESTIGATING CAUSE OF OVERHEATING THAT FAILED ORIG PUMP. UNABLE TO CHECK OTHER 2, SHIPPED ALREADY. AWAITING THE REPAIR SHOPS REPORT.