On Tuesday, June 11, 2002, at 02:27 pm, Jim Wilson wrote:
> If I'm not mistaken (and I easily could be) the FMC would usually just > feed > the autopilot heading and speed data when using non-radio-stack "NAV" > modes. > The FMC monitors the course and the AP only needs to follow the > commands from > the FMC (heading select, flight level and speed select). Generally AP's > aren't all that smart which is why we have computers on board on some > aircraft. I think we're actually in total agreement about the basics, we just need to thrash out some specifics. > Even landing modes are basically just rolling to a angle of > attack, holding the heading and rolling out on the ground. Well ... basically, but some of the landing modes get pretty involved. For example, you need to calculate the roll angle to counter-act the crosswind, and then prior to touch-down you need to convert roll into crab to avoid an engine scrape. Even DC-10 autopilots (which are presumably an analog electronic nightmare, not digital) do this, IIRC. > It'll work and the config file won't be that bad. I would suggest that > FGBowingFLCHMode would be a single command from the FMC to the > autopilot. It > is a pretty basic autopilot function. The autopilot's xml > configuration would > define the major attributes for "FL CH" mode: that we're flying to > selected > altitude and controlling pitch to maintain the speed selected. Other > details > such as whether a mode is arm type or takes over the axis immediately > would be > hardcoded for the mode's implementation (they tend not to vary). Err, I wouldn't make too many assumptions about what tends not to vary :-), but we have to start somewhere, so it's not a big deal. > I'm a little fuzzy though on who's going play the thrust computer and > set the > flight gear "throttle" value for climb mode. Perhaps we should have an > autothrottle class and the FMC would tell the autopilot to do "FL CH" > and tell > the autothrottle we want climb thrust. Well, this is where it gets interesting :-) We really need to define the auto-throttle property nodes, so that the FMC/MCDU can set (some of ) those. Or, on the 757/767, this is done via a physical panel, apparently (if I understand Thomas' comments). (the 777 uses a THRUST LIM page). And on the airbuses (at least the A320) it's again done via the MCDU. Presumably John W is going to need to be able to set this too, from his external FMC impl. I would figure on the FMC (or some other source, like a panel) computing the appropriate EPR values internally, and setting them via properties. Then the auto-throttle code just needs to track those. H&H James -- Anyone who considers arithmetical methods of producing random digits is, of course, in a state of sin. -- John Von Neumann, 1951 _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
