 |
37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
|
A B737-200 #2 engine pneumatic pre-cooler valve was replaced and prior to engine run it was discovered the high pressure valve was locked closed.
| Attributes | |
| ACN | 645280 |
| Time | |
| Date | 200501 |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | airport : zzz.airport |
| State Reference | US |
| Altitude | agl single value : 0 |
| Aircraft 1 | |
| Operator | common carrier : air carrier |
| Make Model Name | B737-700 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | ground : parked |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | maintenance : technician |
| Qualification | technician : airframe technician : powerplant |
| ASRS Report | 645280 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | maintenance : technician |
| Qualification | technician : airframe technician : powerplant |
| Events | |
| Anomaly | aircraft equipment problem : critical maintenance problem : non compliance with mel maintenance problem : improper maintenance maintenance problem : improper documentation non adherence : far non adherence : published procedure |
| Independent Detector | aircraft equipment other aircraft equipment : pneumatic bleed warning other other : 1 |
| Resolutory Action | none taken : detected after the fact |
| Consequence | other other |
| Factors | |
| Maintenance | performance deficiency : testing performance deficiency : non compliance with legal requirements performance deficiency : logbook entry performance deficiency : fault isolation performance deficiency : installation |
| Supplementary | |
| Problem Areas | Aircraft Chart Or Publication Environmental Factor Maintenance Human Performance Weather |
| Primary Problem | Maintenance Human Performance |
Narrative:
I was asked to help change out a pre-cooler control valve as per request of maintenance control. Chapter 36 history was researched and it was said that we have been experiencing a larger failure rate with these valves on -700's. Talked to the crew while I started opening #2 engine. We changed the pre-cooler control valve and a sense line. When actuating the valve; I could hear a diaphragm that sounded damaged and didn't feel right. Confident that this was at fault; we closed up for engine run-up. Before pushback; we noticed engine bleed air was on MEL; so we had to open the engine again and unlock the prsov. The high stage valve was misidented as the prsov. I don't know if that valve was locked out; but I did make sure it (high stage value) was open before closing the engine again for engine run-up. This could have been prevented if a complete maintenance manual check-out of right&right of pre-cooler control valve would have been performed allowing the MEL to be cleared correctly. Also; the run-up pad had partial snow cover on it causing the aircraft to slide forward approximately 10 ft when throttles were advanced. Due to this distraction; the bleed system was not correctly isolated; had it been; this problem would have been prevented.
Original NASA ASRS Text
Title: A B737-200 #2 ENG PNEUMATIC PRE-COOLER VALVE WAS REPLACED AND PRIOR TO ENG RUN IT WAS DISCOVERED THE HIGH PRESSURE VALVE WAS LOCKED CLOSED.
Narrative: I WAS ASKED TO HELP CHANGE OUT A PRE-COOLER CTL VALVE AS PER REQUEST OF MAINT CTL. CHAPTER 36 HISTORY WAS RESEARCHED AND IT WAS SAID THAT WE HAVE BEEN EXPERIENCING A LARGER FAILURE RATE WITH THESE VALVES ON -700'S. TALKED TO THE CREW WHILE I STARTED OPENING #2 ENG. WE CHANGED THE PRE-COOLER CTL VALVE AND A SENSE LINE. WHEN ACTUATING THE VALVE; I COULD HEAR A DIAPHRAGM THAT SOUNDED DAMAGED AND DIDN'T FEEL RIGHT. CONFIDENT THAT THIS WAS AT FAULT; WE CLOSED UP FOR ENG RUN-UP. BEFORE PUSHBACK; WE NOTICED ENG BLEED AIR WAS ON MEL; SO WE HAD TO OPEN THE ENG AGAIN AND UNLOCK THE PRSOV. THE HIGH STAGE VALVE WAS MISIDENTED AS THE PRSOV. I DON'T KNOW IF THAT VALVE WAS LOCKED OUT; BUT I DID MAKE SURE IT (HIGH STAGE VALUE) WAS OPEN BEFORE CLOSING THE ENG AGAIN FOR ENG RUN-UP. THIS COULD HAVE BEEN PREVENTED IF A COMPLETE MAINT MANUAL CHK-OUT OF R&R OF PRE-COOLER CTL VALVE WOULD HAVE BEEN PERFORMED ALLOWING THE MEL TO BE CLRED CORRECTLY. ALSO; THE RUN-UP PAD HAD PARTIAL SNOW COVER ON IT CAUSING THE ACFT TO SLIDE FORWARD APPROX 10 FT WHEN THROTTLES WERE ADVANCED. DUE TO THIS DISTR; THE BLEED SYS WAS NOT CORRECTLY ISOLATED; HAD IT BEEN; THIS PROB WOULD HAVE BEEN PREVENTED.
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.