The radio alt antennas point vertically downward. Just as pitch angle affects the displayed RA, so does bank angle. This effect increases with bank/pitch angle --- you can work out the trigonometry easily.
RA is calibrated to read 0 at main gear touchdown (nose up pitch angle perhaps 5 to 8 degrees). When nose gear touches down, the RA would read some -6 feet. With a heavily loaded jet (greater gear strut compression), the RA reads -8 feet. On 15/07/2010, Thorsten <bre...@googlemail.com> wrote: > On Sun, Jul 11, 2010 at 7:45 PM, Victhor wrote: >> Em Dom, 2010-07-11 Ã s 18:33 +0200, Thorsten escreveu: >> > Hi, >> > >> > I've been working on some smaller issues with the Ground Proximity >> > Warning System. Is someone currently maintaining or actively working >> > on the mk-viii module, or is any help wanted? >> > >> > * The "Bank angle!" warning wasn't working. It's because the module >> > reads the planes angle from >> > /instrumentation/attitude-indicator/indicated-roll-deg >> > However, with the planes I have tested (B737, B747, B777, A380) this >> > value is never updated (value is constant at 40 degrees). This >> > sometimes triggers an incorrect "Bank angle!" warning (at lower >> > heights, where 40 degrees is outside the allowed range). Changing the >> > input property to >> > /orientation/roll-deg >> > made the feature work for me. I'm not familiar with this attitude >> > indicator. Is anything broken so the property above isn't updated? Or >> > could we just change the module's input property? Alternatively, a >> > configuration property could be added, so the location of the input >> > property isn't hard-wired in the sources and could be configured for >> > every plane... >> This instrument needs vacuum to work, as in piston powered GA aircraft >> and some others. /systems/vacuum/suction-inhg is what you're looking >> for. A vacuum pump RPM source can be defined in case you want the pump >> to be powered by something other than /engines/engine/rpm, however I >> don't know where to find this. IIRC the Citation X uses this, it's no >> nasal. > > Ok, I'll also give this a try. But I could still try to make this input > source configurable. Those who like modelling all the details can then > select the output of this vaccuum driven device. But to me it seems not > every plane developer goes to this detail. And in this case they could > still get this module to work properly by using the input from > /orientation/roll-deg, e.g. as the module's default input source, since > it always seems to provide valid data. And the module is already reading > other data from such general sources (e.g. altitude from /position/... > see below). Does an option to configure the input source make any > sense? I'm new to FlightGear though... > >> > "A properly calibrated radio altimeter indicates zero feet at the >> > moment the aircraft contacts ground. This requires taking into account >> > the height of the antennas above ground (at touchdown) [...] After >> > touchdown, the weight of the aircraft may cause the radio altimeter to >> > read slightly below ground level". >> > So I guess the radio altimeter isn't perfectly accurate right now - or >> > are there already configuration settings to tune/adapt the altimeter >> > to a specific plane? Maybe that's where the problem is... >> The "radio-altimeter" instrument never worked properly with me, it has >> considerable lag. Radar altimeter instruments in FG are instead driven by >> /position/altitude-agl-ft, which updates in real time. > > You're right, the mk-viii module is directly reading > /position/altitude-agl-ft. I have changed this to /position/gear-agl-ft > - and it certainly is the gear that matters on touchdown... When using > this property the altitude callouts seem really precise to me - > including the 10ft callout moments before touchdown. Anyone knows > details on gear-agl-ft? Could we just change the mk-viii's input source > to this property, or are there objections / reasons why altitude-agl-ft > still is a better source? > And maybe the HUD could also use gear-agl-ft as its source - instead of > showing 15ft agl when taxiing...? > > I'll be working bit on some of the EGPWS issues and then also try to > update the wiki page with some more information. For example there are > already configuration options in the module to disable specific warnings > in case they don't apply to a specific type of plane... > > Thorsten > > ------------------------------------------------------------------------------ > This SF.net email is sponsored by Sprint > What will you do first with EVO, the first 4G phone? > Visit sprint.com/first -- http://p.sf.net/sfu/sprint-com-first > _______________________________________________ > Flightgear-devel mailing list > Flightgear-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/flightgear-devel > ------------------------------------------------------------------------------ This SF.net email is sponsored by Sprint What will you do first with EVO, the first 4G phone? 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