737 - Missed Approach Altitude on Type B Approaches
 

Regarding 737:

On an ILS (or IAN) approach, you can set the missed approach alt on the MCP any time after GS (GP for IAN) capture.
1) Is it possible to set it before? Not that you would want to be but is it still possible somehow?

2) On an NPA and APV approach, when do you set the missed approach altitude? Let's say you're using any of the guidance modes like V/S or VNAV. Will adjusting the altitude on the MCP not cause ALT HOLD?

1) Yes, if you were flying level in ALT HOLD then you could set it. You could also theoretically set it and then use VS (don’t do this)!
2) Good question. It’s good practice to set MDA initially, engage VS or VNAV in a descent towards it. Once more than 300ft below the missed approach alt you can set the missed approach altitude. But wind it up using 1000s, and then back down using auto to avoid a capture. Bear in mind that the only thing now preventing you flying into the ground is YOU, especially in VS (or VNAV with a mis-set QNH etc). And EGPWS won’t save you in the landing configuration close to the runway - several 737s have crashed short of the runway doing this (Lion air flight 904 into the sea). If you have a spare few minutes in the sim try it. Repos to a 3nm final. Increase the VS by just 100-200fpm and release the freeze. See what happens. It’s scary.

I guess that's why they call it non-precision and give you a much higher minima...
In my (similar) Boeing for an ILS you can set the MAA when in ALT hold or on the Glideslope (or when the other guy reaches for the checklist and reminds you to set it!)
For a V/S or VNAV approach you would set the first hundred below the minima then follow it down, setting the MAA once you're 300 ft below the MAA. I usually ask for gear down, flap 20, arm the speed brake and set MAA at the same time.