There seems to be a bit of confusion here amongst different operators as to exactly what it is that Boeing recommends - and I'll start by rejecting Skyjob's assertions regarding pressurization cycles because there is simply no basis for it from Boeing. If there is (with respect Skyjob), please provide a reference.
First of all, when Boeing recommends (in the FCTM) setting the "final" cruise altitude, if you read the context in which this is written in the FCTM, what they are saying is do not set intermediate level-off altitudes that may be assigned by ATC during short term delays to reach your requested cruise altitude.
For example, if you have planned to cruise at FL370 (that is your top of climb - perhaps your flight plan suggests a step climb to FL390 in 3 hours' time - that is irrelevant), you would have FL370 set in the FMC and the pressurization panel. If ATC clear you to FL310, and advise to expect to be cleared higher soon after passing under crossing traffic, then FL310 is not your final cruise altitude so you would not set that in the pressurization panel. You would leave it at FL370. After a few minutes at FL310, ATC tell you to climb to FL350, FL370 will not be available due traffic. Now FL350 has become your final cruise altitude, so you would set that in both the FMC cruise page and also the pressurization panel. This is the point of the FCTM reference to "final" cruise altitude. If you happen to get lucky and get a higher altitude down track, then you would amend both FMC and the pressurization panel at that time.
So, "final" cruise altitude obviously means the altitude you finally expect to cruise at, at the completion of climb. It does not mean the altitude you expect to be at at top of descent. It also does not mean the highest expected cruise altitude for the entire flight (which may not even be the same thing - your flight plan may recommend a descent for wind reasons later down track - would you set that?). If that was what they wanted, then that would have been what they said.
There is no way anyone in my airline would cruise for 3 hours at FL370 with FL390 in the pressurization panel, purely on the basis that the flight plan suggested a step climb 3 hours into cruise (on ANY aircraft type, not just 737). And no (Skyjob), the cabin does not descend at 1000fpm when climbing from FL370 to FL390, it descends at around 400 fpm. I've been watching it do that for years. And also no (de facto), the descent procedure does not ask you to check that you have actually reached some imaginary highest cruise altitude that you happened to set in the pressurization panel some 5 hours ago, and all sorts of things have happened since, and you never got there... So getting an "Off Schedule Descent" warning is quite likely in the event you never made it to the altitude set in the pressurization panel, so off we go into a QRH checklist.
The FCOM pre-flight says "set cruise altitude". If they wanted you to set the highest expected cruise altitude for the flight, they would have written "set highest cruise altitude expected"... Unless you really believe they are that incompetent that they accidently left that bit out all these years.
Furthermore, the FCOM Supplementary procedure for Step Climb (and Step Descent) includes the following: "FLT ALT indicator... Set new level-off altitude". Why would it say that if the intention was anything other than to have the pressurization panel reflect the actual cruise altitude?
In summary, the reference to "final" cruise altitude in the FCTM can be mis-interpreted if you miss the context in which it is written. Obviously Boeing could have worded it better. It is a relatively recent addition which, if you go back and read it again, is obviously intended to address an inclination by some operators to set intermediate level-off altitudes in the pressurization panel - a practice that was never intended and they are trying to stamp it out. It is not a change of long standing policy which has always been to set intended top of climb cruise altitude. If you subsequently change cruise altitude, you change the pressurization panel, as you always did.
Lastly, to the best of my knowledge, this has been the same procedure for every pressurized airliner Boeing has ever built. Why would the 737NG be any different?
Last edited by Derfred; 1st Dec 2015 at 13:49.