A B737-291 had #1 and #2 engine driven hydraulic pump case drain filters installed incorrectly.

Attributes
ACN	347380
Time
Date	199609
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : zzz
State Reference	US
Altitude	agl bound lower : 0 agl bound upper : 0
Environment
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B737-200
Operating Under FAR Part	Part 121
Flight Phase	other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	other personnel other
Qualification	other other : other
ASRS Report	347380
Person 2
Affiliation	company : air carrier
Function	other personnel other
Qualification	other other : other
Events
Anomaly	aircraft equipment problem : critical non adherence : published procedure non adherence : far other anomaly other
Independent Detector	other flight crewa other other : unspecified cockpit
Resolutory Action	flight crew : overcame equipment problem other
Consequence	Other
Supplementary
Air Traffic Incident	other

Narrative:

On sep/sat/96 I was assigned to work on a B737 along with another mechanic. My first job was to replace the hydraulic pump on #1 engine. After going over the paperwork (the write-up and the maintenance manual), I went out to the aircraft and replaced the hydraulic pump. At the same time we were working pneumatic problems on both engines. I wasn't able to complete the installation without air pressure and an engine run. After helping change pneumatic components, I was able to get air on the system, run the engine and complete the pump installation. I read the maintenance manual before doing the job and thought I had followed it. I did not read where I had to replace the case drain filter. It was found later that both #1 and #2 engines hydraulic case drain filters had been installed incorrectly, creating a low pressure situation during a test flight.

Original NASA ASRS Text

Title: A B737-291 HAD #1 AND #2 ENG DRIVEN HYD PUMP CASE DRAIN FILTERS INSTALLED INCORRECTLY.

Narrative: ON SEP/SAT/96 I WAS ASSIGNED TO WORK ON A B737 ALONG WITH ANOTHER MECH. MY FIRST JOB WAS TO REPLACE THE HYD PUMP ON #1 ENG. AFTER GOING OVER THE PAPERWORK (THE WRITE-UP AND THE MAINT MANUAL), I WENT OUT TO THE ACFT AND REPLACED THE HYD PUMP. AT THE SAME TIME WE WERE WORKING PNEUMATIC PROBS ON BOTH ENGS. I WASN'T ABLE TO COMPLETE THE INSTALLATION WITHOUT AIR PRESSURE AND AN ENG RUN. AFTER HELPING CHANGE PNEUMATIC COMPONENTS, I WAS ABLE TO GET AIR ON THE SYS, RUN THE ENG AND COMPLETE THE PUMP INSTALLATION. I READ THE MAINT MANUAL BEFORE DOING THE JOB AND THOUGHT I HAD FOLLOWED IT. I DID NOT READ WHERE I HAD TO REPLACE THE CASE DRAIN FILTER. IT WAS FOUND LATER THAT BOTH #1 AND #2 ENGS HYD CASE DRAIN FILTERS HAD BEEN INSTALLED INCORRECTLY, CREATING A LOW PRESSURE SIT DURING A TEST FLT.

Data retrieved from NASA's ASRS site as of July 2007 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.