Narrative:

Air carrier X's aircraft fleet X, arrived ZZZ approximately XA10 local, with #2 engine anti-ice 'light' written up as 'illuminated on departure, but extinguished just prior to level out.' after consulting with air carrier X maintenance control in ZZZ1, decision was made to defer per air carrier X MEL 30-3F. This entailed opening #2 engine fan cowls and #2 engine (right hand) thrust reverser 'C' duct. Drawing provided in MEL for cowl tai valve, and high stage (9TH) bleed valve, were vague and did not match confign of aircraft. Maintenance controller was unable to facsimile us correct maintenance manual. Instead received unrelated technical material. Was able to successfully deactivate and lock tai (thermal anti-ice) valve in open position. Then proceeded, after discussing with maintenance control, to lock out, in closed position, what I believed to be the 9TH stage engine bleed valve. Aircraft logbook was signed off and aircraft released for service. Approximately 2 hours later, while reviewing another airline's component locator guide and maintenance manual, I was horrified to see that I had not locked out the 9TH stage bleed valve, but the pressure regulator and shut off valve, leaving the engine unable to provide pneumatic pressure to the aircraft. I immediately notified maintenance control of the error. The aircraft landed safely at ZZZ1, where maintenance opened the prsov, and locked closed the 9TH (high) stage bleed valve. In discussing with the maintenance controller on duty, (a different one than had assisted me with the MEL earlier), we determined that the aircraft still had nose cowl anti-ice, as the tap off for nose cowl tai is up-stream of the prsov. The only difficulty the crew experienced was, with the right air conditioning pack operating, right hand duct pressure dropped to zero. (No air from #2 engine.) the crew shut off #2 right air conditioning pack. When they did this, the bleed air isolation valve which was in 'automatic' position, opened pressurizing the right hand pneumatic duct, and provided tai bleed air for wing anti-ice right hand side. The left air conditioning pack was sufficient to maintain cabin pressure, based on aircraft altitude and routing. Aircraft proceeded to intended destination without incident, and company maintenance insured proper deactivation of anti-ice and pneumatic system. Poorly written instructions in the MEL. For instance, 9TH stage bleed valve, and high stage bleed valve are both referenced, but not together to make it clear they are in the same valve. Poor drawings in the MEL which fail to reflect the confign of the B737-700, and which fail to properly locate the 9TH stage bleed valve. Note: both 9TH stage and prsov valves are close to each other, and lock out identically. The maintenance manual provided by the manufacturer is far superior to the MEL used in this case.

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Original NASA ASRS Text

Title: A B737-700 WAS DISPATCHED IN NON COMPLIANCE WITH THE #2 ENG PRESSURE REGULATOR AND SHUTOFF VALVE RENDERED INOP IN CONFLICT WITH THE MEL.

Narrative: ACR X'S ACFT FLEET X, ARRIVED ZZZ APPROX XA10 LCL, WITH #2 ENG ANTI-ICE 'LIGHT' WRITTEN UP AS 'ILLUMINATED ON DEP, BUT EXTINGUISHED JUST PRIOR TO LEVEL OUT.' AFTER CONSULTING WITH ACR X MAINT CTL IN ZZZ1, DECISION WAS MADE TO DEFER PER ACR X MEL 30-3F. THIS ENTAILED OPENING #2 ENG FAN COWLS AND #2 ENG (R HAND) THRUST REVERSER 'C' DUCT. DRAWING PROVIDED IN MEL FOR COWL TAI VALVE, AND HIGH STAGE (9TH) BLEED VALVE, WERE VAGUE AND DID NOT MATCH CONFIGN OF ACFT. MAINT CTLR WAS UNABLE TO FAX US CORRECT MAINT MANUAL. INSTEAD RECEIVED UNRELATED TECHNICAL MATERIAL. WAS ABLE TO SUCCESSFULLY DEACTIVATE AND LOCK TAI (THERMAL ANTI-ICE) VALVE IN OPEN POS. THEN PROCEEDED, AFTER DISCUSSING WITH MAINT CTL, TO LOCK OUT, IN CLOSED POS, WHAT I BELIEVED TO BE THE 9TH STAGE ENG BLEED VALVE. ACFT LOGBOOK WAS SIGNED OFF AND ACFT RELEASED FOR SVC. APPROX 2 HRS LATER, WHILE REVIEWING ANOTHER AIRLINE'S COMPONENT LOCATOR GUIDE AND MAINT MANUAL, I WAS HORRIFIED TO SEE THAT I HAD NOT LOCKED OUT THE 9TH STAGE BLEED VALVE, BUT THE PRESSURE REGULATOR AND SHUT OFF VALVE, LEAVING THE ENG UNABLE TO PROVIDE PNEUMATIC PRESSURE TO THE ACFT. I IMMEDIATELY NOTIFIED MAINT CTL OF THE ERROR. THE ACFT LANDED SAFELY AT ZZZ1, WHERE MAINT OPENED THE PRSOV, AND LOCKED CLOSED THE 9TH (HIGH) STAGE BLEED VALVE. IN DISCUSSING WITH THE MAINT CTLR ON DUTY, (A DIFFERENT ONE THAN HAD ASSISTED ME WITH THE MEL EARLIER), WE DETERMINED THAT THE ACFT STILL HAD NOSE COWL ANTI-ICE, AS THE TAP OFF FOR NOSE COWL TAI IS UP-STREAM OF THE PRSOV. THE ONLY DIFFICULTY THE CREW EXPERIENCED WAS, WITH THE R AIR CONDITIONING PACK OPERATING, R HAND DUCT PRESSURE DROPPED TO ZERO. (NO AIR FROM #2 ENG.) THE CREW SHUT OFF #2 R AIR CONDITIONING PACK. WHEN THEY DID THIS, THE BLEED AIR ISOLATION VALVE WHICH WAS IN 'AUTO' POS, OPENED PRESSURIZING THE R HAND PNEUMATIC DUCT, AND PROVIDED TAI BLEED AIR FOR WING ANTI-ICE R HAND SIDE. THE L AIR CONDITIONING PACK WAS SUFFICIENT TO MAINTAIN CABIN PRESSURE, BASED ON ACFT ALT AND ROUTING. ACFT PROCEEDED TO INTENDED DEST WITHOUT INCIDENT, AND COMPANY MAINT INSURED PROPER DEACTIVATION OF ANTI-ICE AND PNEUMATIC SYS. POORLY WRITTEN INSTRUCTIONS IN THE MEL. FOR INSTANCE, 9TH STAGE BLEED VALVE, AND HIGH STAGE BLEED VALVE ARE BOTH REFED, BUT NOT TOGETHER TO MAKE IT CLR THEY ARE IN THE SAME VALVE. POOR DRAWINGS IN THE MEL WHICH FAIL TO REFLECT THE CONFIGN OF THE B737-700, AND WHICH FAIL TO PROPERLY LOCATE THE 9TH STAGE BLEED VALVE. NOTE: BOTH 9TH STAGE AND PRSOV VALVES ARE CLOSE TO EACH OTHER, AND LOCK OUT IDENTICALLY. THE MAINT MANUAL PROVIDED BY THE MANUFACTURER IS FAR SUPERIOR TO THE MEL USED IN THIS CASE.

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.