Hi there,

 

There's no end to my issues with the 737, and I'm evidently still learning Today, after takeoff, I was climbing with LNAV and VNAV onto FL370. The maximum FMC could handle was FL378, so I entered 37000 ft in the INIT REF page, activated and departed. I began to climb, everything was fine, AP activated, it was going all damn smooth. Eventually at around TOC, speed started to fall until I received BUFFET ALERT.

 

Presumably, there has been a lot of topics about the buffet alert, fine, but why does my speed fall to a critical 170kts and below when I did absolutely nothing different to my previous flights where the VNAV has been functioning properly? The wind is also null, 0kts, and I'm wondering what I could be doing wrong, and how can I fix my probably terrible and simple PMDG mistakes? I'm fed up flying at 230kts, with speed dropping 99% of the time, while maintaining my altitude with no winds.

You have to check some things:

1) engines-thrust, make sure engines are working and (if in VNAV) make sure the AT is engaged and working (look at the FMA)

2)When you're sure that the engines/thrust are good, check the outside temperature (probably you will see an high temperature due to a wrong setting of the wheater engine)

3) At fl370 it is better to speak about mach number and not in knots.

 

The maximum FMC could handle was FL378, so I entered 37000 ft in the INIT REF page, activated and departed.

 

It's not the max the FMC can handle.  It's the max your engines and wings can handle.  Take a look at your OPT altitude instead.  That will give you better performance, and your wings and engines will thank you for it.

 

To me, it just seems like there's a little missing in the background detail - no offense meant.

 

If you want realistic performance and behavior out of a realistic simulation, you should treat it like the real plane is treated.  Proper loads for fuel and passengers, along with proper routing should be used.  That's not to say it's going to behave terribly if you don't, but if you want it to act like you're expecting it to, make sure you're giving it what it expects.  Based on what you wrote, it seems like you may have just quickly loaded up and departed.  While that's not optimal, the plane should be able to make it up to MAX without too much issue (essentially, without being in any yellow bands).

 

My second thought would be your hardware.  If you have a throttle, and your options setting isn't either "override the throttle any time the AT is on," or "override except in [these modes]," you should set that option (the introduction manual explains where to find these options).  It seems like your throttle may not be fully forward, and the AT isn't overriding it.

 

Hopefully that helps some.

wind is not a factor, OAT may be.

 

EDIT: Tested if you have inversed temperature lapse rate, it would result in behavior you described.