HN39;
Originally Posted by Post #1200
That's another intriguing thing. The ADR's calculate Mach and CAS quasi-simultaneously from the same pitot and static pressures. Why would there be a delay of two seconds between Mach and CAS?
Yes, intriguing indeed. I doubt if it's "polling" in nature, as these values would be in continuous calculation, but "polling", (so to speak...it doesn't quite work that way, but close), does affect flight data due to recording rates-per-second. Between the two, I'm not sure what the ADR "saw". Is the two second apparent delay merely just that? ...the time it took for BITE processes to assess/decide and the first test was Mach No.?
We have only limited resources from which to build theories and create tentative conclusions; it has been my experience that one cannot rely upon the flight data, (
meaning, one must take into account parameter recording rates), for these things because of polling rates, whereas, as you observe, Mach, CAS, etc are "quasi-simultaneously" calculated and (one assumes), sent to the "users", (the ADRs) for use.
Here, I'm not sure about the notion of "quasi-simultaneous" - are these calculations truly parallel and "held in memory" until all processes are finished and data can be sent onwards, or are they series and the data is sent as it becomes available, and if so, at what point in the calculation is a decision made, for example, if quasi-simultaneous calculations result in one Mach value of M0.26, does the process stop there and bifurcate into a "can the AFS remain engaged?" loop, or is it more recursive than this, "just to make sure" of data correctness and a decision to disengage is confirmed? From my reading of the AMM, it seems a lot simpler than this, and I wonder if the two-second "delay" is actually a delay or is it the nature of flight data itself?