Acceleration Offsets Clarification

[ark1320]

Hello Pete,

 Offset 0x31C8 is described as vertical acceleration relative to the world axes. Am I correct in understanding that this acceleration is a measure of the time rate of change of an aircraft's vertical velocity, as we normally think of it,  relative to the earth's surface? For example, this would be a measure of how an aircraft's vertical velocity is changing with time during landing.

And offset 0x3068 is described as vertical acceleration relative to the body axes. I assume the body in this case is the aircraft. So if the aircraft is flying 'level' (meaning not pitched up or down), I assume this acceleration value would be the same as the 0x31C8 value, but would otherwise differ with the pitch of the aircraft since, for example, in a steep climb the vertical axis of the aircraft is no longer vertical relative to the earth's surface.

I would also like to ask about how often, on average, would you estimate these values, or offsets in general, get updated? My understanding is values in FSX nominally get updated about 18 times per sec, or about once every 56 milliseconds. Is this a reasonable number for the typical update rate of an offset?

Thanks,

Al

 

[Pete Dowson]

3 hours ago, ark1320 said:

 Offset 0x31C8 is described as vertical acceleration relative to the world axes. Am I correct in understanding that this acceleration is a measure of the time rate of change of an aircraft's vertical velocity, as we normally think of it,  relative to the earth's surface? For example, this would be a measure of how an aircraft's vertical velocity is changing with time during landing.

Probably. Sorry, it is a value I read from FS. I'm not all that knowledgeable about what everything means. I would see if you can contact Herve Sors about it if you need to know more. Same for the other value. But you could always monitor them yourself, see how they behave.

3 hours ago, ark1320 said:

I would also like to ask about how often, on average, would you estimate these values, or offsets in general, get updated? My understanding is values in FSX nominally get updated about 18 times per sec, or about once every 56 milliseconds. Is this a reasonable number for the typical update rate of an offset?

I request SimConnect to supply values when they change by more than a certain amount. How often specific values may change by less I don't know -- 18 Hz does sound familiar --  but there's little point in flooding the system with thousands of messages telling me about minute changes. 

For the body accelerations the "Delta" (minimum change seen) is 0.0001 (of the units used), and for the World accelerations it is 0.001. I've no idea why they are different -- I think i took advice, long long ago.

Pete