A.J.On your third question - V/S is fine in descents, you just have to watch your airspeed, make sure it doesn't overspeed etc. A very common technique for hitting restrictions in real life if you're not using VNAV is to use the V/S wheel to position the green arc on the restriction waypoint. The plane will capture the altitude set in the MCP in V/S - there's no issue with that. (on planes like our J41 it will NOT though unless you've armed ALT CAP mode) The issue I've referred to in the past is using V/S in climbs - If you took off and set 3000 feet per minute V/S and then didn't touch it, you're eventually going to stall, even with the engines firewalled. The air thins as you get higher and your IAS starts decreasing. If you watch closely during a climb in VNAV or LVL CHG this can't happen because it's pitching to maintain an airspeed or mach number - the resultant V/S decreases as you get higher so that it stays on speed.

Thanks for the clarification Tabs, the distinction between using v/s with climbs as opposed to descents makes the theory clearer for me now (in fact, you mentioned the disadvantage of using v/s as a climb technique very recently in another topic).Happy 4th of July to you and everyone at PMDG, and to all!

Hi Greg.I would like to ask you:Which are the differences between the CMD button and CWS button? I have heard that CWS is to maintain your pitch configuration. But, is it the only function of that?And the last question: are the fuel pumps essential to hold the APU on? Because in a graphic I have seen that APU has its own fuel pump. What this APU fuel pump is for? Thanks.

Hey AJ. The NG can go through your selected altitude if you arep not familiar with the FMA annunciations. Normally on a descent from cruise this is not a problem. It can bite you, for example, on oa ndb approach.i will explain.Different companies have different procedures but I will explain a scenerio which could catch you. The preferred method of descent on an ndb approach is V/S. Lets day you pass the FAF and now are on descent to the MDA (for our example is 600 feet and missed approach altitude is 2000 feet ). As you reach MDA is is quite often procedure to set the missed approach altitude. But as you are reaching the MDA, the FMA will indicate ALT ACQ indicating it is acquiriing the altitude set in the MCP. So now what some pilots msy do is set the missed approach altitude in the MCP and if you aren't paying attention the plane will continue to descend nto the ground. The key here is to WAIT ntil the FMA indicates ALT HLD and NOT ALT ACQ. The ALT HLD will annunciate shortly after the ALT ACQ. Once that happens ou can now set the missed approach altitude now that the autopilot is locked into maintain MDA of 600 feet. JackColwill