Mechanics cross 2 sense lines which rendered engine bleed air inoperative.

Attributes
ACN	234464
Time
Date	199302
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : den
State Reference	CO
Altitude	agl bound lower : 0 agl bound upper : 0
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Person 1
Affiliation	company : air carrier
Function	other personnel other
Qualification	other other : other
ASRS Report	234464
Events
Anomaly	aircraft equipment problem : critical non adherence : far non adherence : published procedure
Independent Detector	other flight crewa
Resolutory Action	none taken : detected after the fact
Consequence	Other
Supplementary
Air Traffic Incident	other

Narrative:

The aircraft was operating with an MEL placard for #2 engine bleed air inoperative. While en route to reno, bad WX was encountered and, per placard, aircraft diverted to sfo. During troubleshooting of the #2 engine pneumatic system it was discovered 2 sense lines to the pressure regulating shutoff valve were cross-connected rendering engine bleed air inoperative. Prior to this incident on feb/93, den maintenance competed a pylon modification requiring removal/installation of the #2 engine. It was during this maintenance that the lines were inadvertently installed incorrectly. All work was competed per air carrier engine removal/install form and corresponding engine trim form. Currently, neither work card includes a step to operate affected systems (bleed air, generator, hydraulic, disturbed during engine removal. Air carrier is in the process of revising the work cards to include system operational checks. In addition, manufacturer, has issued a service bulletin dated mar/87 for replacement of sense lines to prevent cross-connecting. Revisions to work cards, compliance with the service bulletin, and increased awareness of this problem will prevent future occurrences of cross connecting the sense lines.

Original NASA ASRS Text

Title: MECHS CROSS 2 SENSE LINES WHICH RENDERED ENG BLEED AIR INOP.

Narrative: THE ACFT WAS OPERATING WITH AN MEL PLACARD FOR #2 ENG BLEED AIR INOP. WHILE ENRTE TO RENO, BAD WX WAS ENCOUNTERED AND, PER PLACARD, ACFT DIVERTED TO SFO. DURING TROUBLESHOOTING OF THE #2 ENG PNEUMATIC SYS IT WAS DISCOVERED 2 SENSE LINES TO THE PRESSURE REGULATING SHUTOFF VALVE WERE CROSS-CONNECTED RENDERING ENG BLEED AIR INOP. PRIOR TO THIS INCIDENT ON FEB/93, DEN MAINT COMPETED A PYLON MODIFICATION REQUIRING REMOVAL/INSTALLATION OF THE #2 ENG. IT WAS DURING THIS MAINT THAT THE LINES WERE INADVERTENTLY INSTALLED INCORRECTLY. ALL WORK WAS COMPETED PER ACR ENG REMOVAL/INSTALL FORM AND CORRESPONDING ENG TRIM FORM. CURRENTLY, NEITHER WORK CARD INCLUDES A STEP TO OPERATE AFFECTED SYSTEMS (BLEED AIR, GENERATOR, HYD, DISTURBED DURING ENG REMOVAL. ACR IS IN THE PROCESS OF REVISING THE WORK CARDS TO INCLUDE SYS OPERATIONAL CHKS. IN ADDITION, MANUFACTURER, HAS ISSUED A SVC BULLETIN DATED MAR/87 FOR REPLACEMENT OF SENSE LINES TO PREVENT CROSS-CONNECTING. REVISIONS TO WORK CARDS, COMPLIANCE WITH THE SVC BULLETIN, AND INCREASED AWARENESS OF THIS PROB WILL PREVENT FUTURE OCCURRENCES OF CROSS CONNECTING THE SENSE LINES.

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.