Narrative:

In cruise at FL410; I noticed that the cabin press differential needle was in the middle of the amber band at about 8.5 psi. Had the first officer look at it and he had never seen it that high in the band before either. The first officer called up maintenance control to discuss this indication. In the mean time; ATC told us that there would be moderate turbulence at FL410 ahead and recommended FL390 instead; so I asked for FL390 and just after we started out of FL410 we got the number 2 pack bleed trip light on. We followed the QRH on it; hit the reset button; light went out; we continued on to our destination and wrote up the 8.5 and the trip light up in the same write up.they worked on the problem for 2.5 hours doing this and that. We had a long discussion with the mechanics and maintenance control about the 8.5 psi. They told us that the 8.5 was within acceptable limitations according to their books. So off we went on the next leg. We did not get a trip light this time; however the cabin differential was still showing 8.5 psi. Not sure wither this was normal (based on maintenance numbers; or our flight operations numbers with 8.35 being normal and at the base of the arc; and 9.1 being maximum for an ng) so we decided to wait till we got on the ground and would again ask maintenance control if in fact this 8.5 psi was acceptable. After landing maintenance again said that; based on the previous research and the write up that cleared our write up; the 8.5 psi was normal and no write up was needed. I still questioned how that 8.5 psi was 'normal' and volunteered to make the write up again. In the mean time; our aircraft was scheduled to block out after only 24 minutes after we arrived and there was a shift change going on within maintenance. But I was again told that 'no' the write up was not wanted as the 8.5 psi was considered normal. Again; all of this happened with the oncoming captain listening to the discussion. So off I went to go home. While on the crew bus; I got a call from crew scheduling saying that maintenance wanted to talk with me on the issue. I had a long talk with maintenance in the parking lot bus shelter; told them everything that I saw and knew. Since it now seemed to me that there was in fact something more then this is 'normal'; I asked if this plane was still departing on time. That was when he informed me that no; this plane was going nowhere as it was grounded. Great! So I called the base chief pilot; who told me he just came back from that gate with our plane. From what I understand; the oncoming maintenance shift decided that 8.5 psi was indeed 'not normal'; that they wanted to ground the aircraft; but refused to make the write up. As I was no longer there; the oncoming captain was asked to [and agreed to] make the write up based on the discussions he had witnessed. This incident illustrates three problems. It is difficult dealing with what we as pilots; via our manuals; think is a limitation or not normal; when that is in conflict with what maintenance thinks is a limitation or not normal. We make a write up because we think it is wrong; but maintenance tells us that in their manuals or procedures it is acceptable. This happens all the time. And I did not want to make a write up if it was considered 'okay' and nothing would be done. Also; with the ever present 'got to get this flight out on time come hell or high water' attitude (note only 24 minutes between our block in and scheduled block out) everyone is 'rush; rush; rush' and 'lets do the minimum so we can get this thing out of here'. No time to think a problem through and do what is right. Finally; the fact that we were in the middle of a shift change and the outgoing mechanics did not want to speak for the oncoming shift. And the oncoming guys sure had a different view point then the two previous shifts; since they ended up grounding the aircraft.

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Original NASA ASRS Text

Title: a B737-700 Captain expressed his concerns which resulted from a dispute with Maintenance about differences between published flight operations versus maintenance aircraft pressurization differential limits.

Narrative: In cruise at FL410; I noticed that the cabin press differential needle was in the middle of the amber band at about 8.5 PSI. Had the First Officer look at it and he had never seen it that high in the band before either. The First Officer called up Maintenance Control to discuss this indication. In the mean time; ATC told us that there would be moderate turbulence at FL410 ahead and recommended FL390 instead; so I asked for FL390 and just after we started out of FL410 we got the number 2 pack bleed trip light on. We followed the QRH on it; hit the reset button; light went out; we continued on to our destination and wrote up the 8.5 and the trip light up in the same write up.They worked on the problem for 2.5 hours doing this and that. We had a long discussion with the mechanics and Maintenance Control about the 8.5 PSI. They told us that the 8.5 was within acceptable limitations according to their books. So off we went on the next leg. We did not get a trip light this time; however the cabin differential was still showing 8.5 PSI. Not sure wither this was normal (based on Maintenance numbers; or our Flight Operations numbers with 8.35 being normal and at the base of the arc; and 9.1 being maximum for an NG) so we decided to wait till we got on the ground and would again ask Maintenance Control if in fact this 8.5 PSI was acceptable. After landing Maintenance AGAIN said that; based on the previous research and the write up that cleared our write up; the 8.5 PSI was normal and no write up was needed. I still questioned how that 8.5 PSI was 'normal' and volunteered to make the write up again. In the mean time; our aircraft was scheduled to block out after only 24 minutes after we arrived and there was a shift change going on within Maintenance. But I was again told that 'NO' the write up was not wanted as the 8.5 PSI was considered normal. Again; all of this happened with the oncoming Captain listening to the discussion. So off I went to go home. While on the crew bus; I got a call from Crew Scheduling saying that Maintenance wanted to talk with me on the issue. I had a long talk with Maintenance in the parking lot bus shelter; told them everything that I saw and knew. Since it now seemed to me that there was in fact something more then this is 'normal'; I asked if this plane was still departing on time. That was when he informed me that no; this plane was going nowhere as it was grounded. Great! So I called the Base Chief Pilot; who told me he just came back from that gate with our plane. From what I understand; the oncoming maintenance shift decided that 8.5 PSI was indeed 'not normal'; that they wanted to ground the aircraft; but refused to make the write up. As I was no longer there; the oncoming Captain was asked to [and agreed to] make the write up based on the discussions he had witnessed. This incident illustrates three problems. It is difficult dealing with what we as pilots; via our manuals; think is a limitation or not normal; when that is in conflict with what Maintenance thinks is a limitation or not normal. We make a write up because we think it is wrong; but Maintenance tells us that in their manuals or procedures it is acceptable. This happens all the time. And I did not want to make a write up if it was considered 'okay' and nothing would be done. Also; with the ever present 'got to get this flight out on time come hell or high water' attitude (note only 24 minutes between our block in and scheduled block out) everyone is 'rush; rush; rush' and 'lets do the minimum so we can get this thing out of here'. No time to think a problem through and do what is right. Finally; the fact that we were in the middle of a shift change and the outgoing Mechanics did not want to speak for the oncoming shift. And the oncoming guys sure had a different view point then the two previous shifts; since they ended up grounding the aircraft.

Data retrieved from NASA's ASRS site as of April 2012 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.