A learjet 60 experienced loss of main hydraulic system pressure and quantity. Primary cause was incorrect installation of main reservoir bleed air check valve.

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Attributes
ACN	688233
Time
Date	200602
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : zzz.airport
State Reference	US
Environment
Light	Daylight
Aircraft 1
Operator	common carrier : charter
Make Model Name	Learjet 60
Operating Under FAR Part	Part 135
Flight Phase	cruise : level ground : maintenance
Person 1
Affiliation	other
Function	maintenance : inspector
Qualification	technician : airframe technician : powerplant
Experience	maintenance technician : 10
ASRS Report	688233
Person 2
Affiliation	other
Function	maintenance : technician
Qualification	technician : airframe technician : powerplant
Experience	maintenance technician : 5
ASRS Report	688232
Events
Anomaly	aircraft equipment problem : critical maintenance problem : improper maintenance maintenance problem : improper documentation non adherence : far non adherence : published procedure
Independent Detector	aircraft equipment other aircraft equipment : main system - press qty and indications other other : 1
Resolutory Action	none taken : detected after the fact
Consequence	other other
Factors
Maintenance	contributing factor : schedule pressure performance deficiency : inspection performance deficiency : installation performance deficiency : logbook entry performance deficiency : non compliance with legal requirements performance deficiency : scheduled maintenance performance deficiency : testing
Supplementary
Problem Areas	Maintenance Human Performance Chart Or Publication Aircraft
Primary Problem	Maintenance Human Performance

Narrative:

Learjet 60 experienced a loss of main hydraulic pressure in-flight. Found pressure hose (main) at right engine pump blown (failed). Learjet field service was contacted and had suggested checking main hydraulic reservoir for head pressure; investigation found no head pressure in reservoir due to bleed air check valve for hydraulic reservoir being installed backwards during maintenance. Installed 2 new engine driven hydraulic pumps; new reservoir check valve; and pressure relief valve; 4 hoses (hydraulic at the pumps) and both pressure and return hydraulic filter. Svced and cycled all hydraulic system with no defects noted. Note; no metal was found in main hydraulic system. How the problem arose: as the inspector; I didn't see the regulator/check valve assembly before it was installed on the aircraft reservoir. I couldn't see the check valve due to accessibility. I should have removed the assembly to check for correct installation.

Original NASA ASRS Text

Title: A LEARJET 60 EXPERIENCED LOSS OF MAIN HYD SYS PRESSURE AND QUANTITY. PRIMARY CAUSE WAS INCORRECT INSTALLATION OF MAIN RESERVOIR BLEED AIR CHK VALVE.

Narrative: LEARJET 60 EXPERIENCED A LOSS OF MAIN HYD PRESSURE INFLT. FOUND PRESSURE HOSE (MAIN) AT R ENG PUMP BLOWN (FAILED). LEARJET FIELD SVC WAS CONTACTED AND HAD SUGGESTED CHKING MAIN HYD RESERVOIR FOR HEAD PRESSURE; INVESTIGATION FOUND NO HEAD PRESSURE IN RESERVOIR DUE TO BLEED AIR CHK VALVE FOR HYD RESERVOIR BEING INSTALLED BACKWARDS DURING MAINT. INSTALLED 2 NEW ENG DRIVEN HYD PUMPS; NEW RESERVOIR CHK VALVE; AND PRESSURE RELIEF VALVE; 4 HOSES (HYD AT THE PUMPS) AND BOTH PRESSURE AND RETURN HYD FILTER. SVCED AND CYCLED ALL HYD SYS WITH NO DEFECTS NOTED. NOTE; NO METAL WAS FOUND IN MAIN HYD SYS. HOW THE PROB AROSE: AS THE INSPECTOR; I DIDN'T SEE THE REGULATOR/CHK VALVE ASSEMBLY BEFORE IT WAS INSTALLED ON THE ACFT RESERVOIR. I COULDN'T SEE THE CHK VALVE DUE TO ACCESSIBILITY. I SHOULD HAVE REMOVED THE ASSEMBLY TO CHK FOR CORRECT INSTALLATION.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.