On 3 Jan 2009, at 17:12, John Denker wrote: > Is there anything unrealistic about item (B)? Is there > any instrument/system in the world that expects the > nav tuner to put out the GS angle in degrees? > > The only MK-VIII known to me is a GPWS, and I very much > doubt it needs to know any GS info beyond the usual > position within the GS beam as a fraction of the > peg-to-peg sector.
When I write 'Mk -VIII' I was assuming everyone realised I was talking about the GPWS unit, since it's what I'm trying to fix, and the only thing we have with that name in FG. And what it actually uses is mV CDI deflection if driven by analogue volts, or ARINC 429 words expressing DDM. The problem is driving this sensibly from what we have at present from navradio.cxx. If I add a gs-deviation-norm, I'll assume (based on the INSTALL docs for the Mk-VIII, and the ICAO spec) that their 'dots' correspond to the half- and full- sector deviations for both LOC and GS purposes, i.e two dots to full-sector. But that's entirely a problem for me and the GPWS code :) That would be absolutely fine - as you say, the fraction of peg-to-peg is what's needed - but we don't have that at this moment. I greatly dislike working in 'peg-to-peg percentage multiplied by 3.5', which is what we sort of have right now, for the GS, and 'peg to peg multiplied by 10' for the LOC. Especially when people then *think* that those numbers correspond to degrees, when we have pretty clearly established that quite often they do not :) The Mk-VIII is guilty of all of the above - assuming degrees, *and* being oblivious to the factor of 5 multiple. Since the author was clearly not a fool, I don't think better documentation is a 'sufficient' fix, but normalising to -1..1 is. (And letting the actual panel instrument clamp, i.e remove the clamping in navradio.cxx ... but that needs to be done with considerable care, lest we break something) James ------------------------------------------------------------------------------ _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
