Fsbuild-2 Flight Planner

My apologies if this has been addressed; I searched for "Mach" in this forum and found only two messages which did not answer my question.

If I may ask the readers indulgence, I want to briefly describe a "routine" I follow which will set the background an context for the answers I seek.

After takeoff, once I have enabled the autopilot, if I am flying without any active ATC, I'll have my altitude set for my desired cruise. I climb at 250 IAS until passing 10,000, then set 280 IAS until I get up around FL250 or so when I change to Mach, generally around 0.70. At this point I also reduce my v/s from +1800fpm to +1500, +1000, and if I'm climbing up near the aircrafts limit, I may even have to drop to about +600 fpm to maintain speed by keeping the AOA around +5 or 6 deg.

I set Mach 0.80 or 0.78 as the aircraft levels off.

Beginning my descent, I switch back to IAS mode, and if the resulting speed is >250 I reduce it to 250 IAS. If <250, I wait while the descent brings me into denser air, and the Vne increases safely above 250 IAS.

General observation
First, it appears that the airspeeds I can set for various things within the Smith's FMS (and from what I've read, in the .cfg) use IAS regardless of whether or not a Mach value was entered (and subsequently translated into IAS). I did find one exception to this (exactl which setting escapes me right now) where TAS was the mode of representation.

My point is that somewhere between FL200 and FL300, it no longer makes sense to use IAS in a dynamic flight configuration, that is, where a climb is going to change density and therefore a given IAS is going to be an increasingly higher TAS (and Mach), with the possibility of exceeding Vne. If however one changes to Mach hold, Vne will not (or should not) ever be exceeded (turbulence notwithstanding).

The Climb, Cruise, and Descent modes all appear to use IAS. I am thinking this at least needs to have two settings for each - an IAS for below, say, FL250, and a Mach value for above that FL. Ideally, the transition height should be user-configurable.

I mentioned that when descending, I use 250 IAS unless that would exceed Vne. I do this deliberately because this results in a gradual slowing of the aircraft as I descend. Again, this is most relevant when I'm flying without any ATC; this may not make as much sense in a stepped climb/descent under ATC control.

It is probably apparent by now that I am not knowledgeable about FMCs; it occurs to me that the way the FMS works is how they work in real life. If so, it seems odd. If not, perhaps this is worthy of consideration.

I have a lot of questions, so expect more posts soon. (I can almost hear Ernie sigh in exasperation

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The glass is twice as big as it needs to be.

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The glass is twice as big as it needs to be.

Ernie,

Thank you for help thus far. I am slowly learning what I need.

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The glass is twice as big as it needs to be.