Hi Rat,
Completely agree with your post.
It is interesting, however, that us "old school" folks can be also mislead by trying to "aviate" the more modern aircraft that are not so much designed to be "aviated".
This thread is a case in point with several posters suggesting techniques such as putting a different cruise altitude into the pressurisation system, or climbing above the set cruise altitude.
These techniques won't work on the 737NG, although they may have worked on the older 737's.
Unfortunately, as the SOP chapter widens, the systems description chapter narrows. FCOM Vol 2 is still fat, but these days it doesn't really tell you how the system really works. It just tells you the minimum you need to know.
As I pointed out in my earlier post, Vol 2 doesn't tell me how many cabin altitude sensors there are, and whether they are shared between gauges and systems.
It also doesn't tell those suggesting the alternative techniques why those techniques won't work.
I recall once (new to the NG, but not new to the 737), hearing the airconditioning go suddenly deathly quiet climbing through 8-9000 feet. We looked at the cabin climb rate and saw close to zero. We expected to see 300-500 fpm climb, as that was what we were accustomed to seeing. We leveled out at 10,000' thinking something must be wrong with the pressurisation, but couldn't work out what. Eventually we continued climb and all came back to normal.
It turned out that the NG didn't climb the cabin in the same way as the older 737's. The NG maintains close to zero cabin climb until above 10,000 feet. The older 737's didn't behave the same way. The Vol 2 didn't bother to point out that little nugget.
The deathly quiet was just a chunk of ice clearing from the duct, which was making the cockpit much noisier than normal, and the deathly quiet was actually just a noisier than normal cockpit resuming normal noise.
Boeing says do the checklist, and don't try to troubleshoot, unless the problem becomes more complex than the scope of the checklist. So that's my next question to the OP: what you saw shouldn't have happened, so what did it turn out to be?
Last edited by Derfred; 1st May 2017 at 15:41.