Narrative:

MEL 30-X-xx right wing valve fixed open. I went over the MEL line by line with dispatch and maintenance control after contract maintenance deferred the aircraft. I went over the MEL line by line with the first officer (first officer) to cover the configuration at the gate and for takeoff. Airborne; when the temperature was below 10 degrees C; we placed the engine bleed switch on as directed in the MEL. The right pack had been placed off for takeoff and remained off for the flight. We had both checked our configuration with the MEL; but had assumed that the pack switch needed to be off for takeoff. After placing the pack off for takeoff; at 10;000 feet; the right pack was correctly called (right pack off); but since that was the position we had it in for takeoff for the MEL; we didn't correct the pack position. Pressure held normally for cruise.nowhere in the MEL does it mention turning off the right pack. It is obvious to me now; the right pack switch should have been placed as in a normal flight. But the verbiage in proviso (I) led us to turn the pack off. Since the MEL does not have you turn the pack off; there is no mention to turn the pack back on. This was not a mistake because we didn't notice the pack off; it was a mistake in turning it off without specific guidance and not realizing the flaw in logic. A note referencing leaving the pack switch on (like a bleeds off takeoff) would have helped me avoid this error.

Related reports:

Google
 

Original NASA ASRS Text

Title: B737 Captain reports misunderstanding an MEL procedure and departing with the right pack off and the right bleed off for a right wing anti-ice valve fixed open. When the bleed valve is turned on; the pack valve is left off. The flight continued in single pack operation without difficulty. The pack should not have been turned off.

Narrative: MEL 30-X-XX Right Wing Valve Fixed Open. I went over the MEL line by line with Dispatch and Maintenance Control after Contract Maintenance deferred the aircraft. I went over the MEL line by line with the First Officer (FO) to cover the configuration at the gate and for takeoff. Airborne; when the temperature was below 10 degrees C; we placed the engine bleed switch ON as directed in the MEL. The right Pack had been placed OFF for takeoff and remained off for the flight. We had both checked our configuration with the MEL; but had assumed that the Pack switch needed to be off for takeoff. After placing the Pack off for takeoff; at 10;000 feet; the right Pack was correctly called (Right Pack Off); but since that was the position we had it in for takeoff for the MEL; we didn't correct the Pack position. Pressure held normally for cruise.Nowhere in the MEL does it mention turning off the right Pack. It is obvious to me now; the right Pack switch should have been placed as in a normal flight. But the verbiage in proviso (I) led us to turn the Pack off. Since the MEL does not have you turn the Pack off; there is no mention to turn the Pack back on. This was not a mistake because we didn't notice the Pack off; it was a mistake in turning it off without specific guidance and not realizing the flaw in logic. A note referencing leaving the Pack switch on (like a bleeds off takeoff) would have helped me avoid this error.

Data retrieved from NASA's ASRS site 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.