RE: [Flightgear-devel] GS needle sensitivity.
Ryan Larson writes: > This is worded weird. I would word it like this (this is from the diagram > in the FAA instrument rating written exam). > > The glideslope is a beam 1.4 degrees thick. It is pointed 3 degrees up from > the horizon starting at the 1000' foot mark down the runway from the > threshold. At 1300' from the threshold you are at an altitude of 100' above > touchdown zone. If you are off the GS by 2 dots at the 1300' mark you are > off by 28' (so either 72' or 128' above the touchdown zone). If you are > 5.6nm from the threshold (the Outer Marker) and you are off by 2 dots you > are off by 420' up or down. The target altitude at that point is 1500' > above the touchdown zone. > > Here is a table of what 1 dot or 2 dots mean at different distances. > > Distance from threshold Target Alt 1 Dot off 2 Dots >off Significance > 1300' 100'14' 28' > Inner Marker > 2600' (1/2nm) 200'28' 56' > Middle Marker > 1.9nm 500'70' 140' > 5.6nm 1500' 210'420' > Outer Marker The flight gear code cares about the deviation from the glide slope in degrees. The instrument panel code translates this difference into needle movement. Would someone with cvs access (base package and src code) be willing to test drive the most recent changes and double check that they are correct? Thanks, Curt. -- Curtis Olson IVLab / HumanFIRST Program FlightGear Project Twin Cities[EMAIL PROTECTED] [EMAIL PROTECTED] Minnesota http://www.menet.umn.edu/~curt http://www.flightgear.org ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] GS needle sensitivity.
>-Original Message- >From: [EMAIL PROTECTED] >[mailto:[EMAIL PROTECTED]]On Behalf Of Paul Deppe >Sent: Tuesday, July 09, 2002 4:31 PM >To: FGFS-Devel >Subject: RE: [Flightgear-devel] GS needle sensitivity. > > >> I had someone recently comment that they thought the glide slope >> needle was too sensitive in FG. Can anyone comment on this? What >> sort of needle range relative to how many degrees off the target glide >> slope should we be seeing? This person suggested 2 'dots' per degree >> off the glide slope (but they aren't a pilot and haven't flown any >> "real" instrument approaches.) I thought I had investigated this and >> had done it correctly when I first wrote the code, but it would be >> nice to verify that we are still doing this right since the question >> has come up (and given that the 2d panel instrument can also scale the >> values, there is more than one place an error could creep in.) > >Gents, > >Glideslope beams are designed to be 1.4 degrees "tall", that is, +/- 2 dots >(full scale) deviation on the gauge is equal to +/- 0.7 degrees glidesope >deviation, or 0.35 degrees per dot. This is the same for all standard >ILS's. This is correct. > >The localizer beam width is designed to produce +/- 2 dots deviation at +/- >700 feet deviation from centerline at the runway threshold. The localizer >scale sensitivity in degrees per dot is therefore a function of the distance >from the threshold to the localizer antenna. This is worded weird. I would word it like this (this is from the diagram in the FAA instrument rating written exam). The glideslope is a beam 1.4 degrees thick. It is pointed 3 degrees up from the horizon starting at the 1000' foot mark down the runway from the threshold. At 1300' from the threshold you are at an altitude of 100' above touchdown zone. If you are off the GS by 2 dots at the 1300' mark you are off by 28' (so either 72' or 128' above the touchdown zone). If you are 5.6nm from the threshold (the Outer Marker) and you are off by 2 dots you are off by 420' up or down. The target altitude at that point is 1500' above the touchdown zone. Here is a table of what 1 dot or 2 dots mean at different distances. Distance from threshold Target Alt 1 Dot off 2 Dots off Significance 1300' 100'14' 28' Inner Marker 2600' (1/2nm) 200'28' 56' Middle Marker 1.9nm 500'70' 140' 5.6nm 1500' 210'420' Outer Marker Ryan ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] GS needle sensitivity.
> The localizer beam width is designed to produce +/- 2 dots deviation at +/- > 700 feet deviation from centerline at the runway threshold. The localizer > scale sensitivity in degrees per dot is therefore a function of the distance > from the threshold to the localizer antenna. I agree with the summary, but would like to point out that the 700 number in the text is not a hard-and-fast rule and merely the usual default. It should be safe enough for the purposes of the simulation though. ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] GS needle sensitivity.
Paul Deppe writes: > Glideslope beams are designed to be 1.4 degrees "tall", that is, +/- 2 dots > (full scale) deviation on the gauge is equal to +/- 0.7 degrees glidesope > deviation, or 0.35 degrees per dot. This is the same for all standard > ILS's. > > The localizer beam width is designed to produce +/- 2 dots deviation at +/- > 700 feet deviation from centerline at the runway threshold. The localizer > scale sensitivity in degrees per dot is therefore a function of the distance > from the threshold to the localizer antenna. Ok, we were way off. We don't handle changing the 'cone' shape depending on the position of the transmitter relative to the threshold, but that's something that wouldn't hurt to put on the todo list todo some day. Curt. -- Curtis Olson IVLab / HumanFIRST Program FlightGear Project Twin Cities[EMAIL PROTECTED] [EMAIL PROTECTED] Minnesota http://www.menet.umn.edu/~curt http://www.flightgear.org ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] GS needle sensitivity.
Paul Deppe writes: > Glideslope beams are designed to be 1.4 degrees "tall", that is, +/- 2 dots > (full scale) deviation on the gauge is equal to +/- 0.7 degrees glidesope > deviation, or 0.35 degrees per dot. This is the same for all standard > ILS's. That makes an awful lot of sense. On a three-degree glidepath, you'll be at around 520 feet AAE on a 2 mile final; with a two-degree error, you could be around 175 feet AAE, otherwise known as the concierge level of the airport hotel. All the best, David -- David Megginson, [EMAIL PROTECTED], http://www.megginson.com/ ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] GS needle sensitivity.
> I had someone recently comment that they thought the glide slope > needle was too sensitive in FG. Can anyone comment on this? What > sort of needle range relative to how many degrees off the target glide > slope should we be seeing? This person suggested 2 'dots' per degree > off the glide slope (but they aren't a pilot and haven't flown any > "real" instrument approaches.) I thought I had investigated this and > had done it correctly when I first wrote the code, but it would be > nice to verify that we are still doing this right since the question > has come up (and given that the 2d panel instrument can also scale the > values, there is more than one place an error could creep in.) Gents, Glideslope beams are designed to be 1.4 degrees "tall", that is, +/- 2 dots (full scale) deviation on the gauge is equal to +/- 0.7 degrees glidesope deviation, or 0.35 degrees per dot. This is the same for all standard ILS's. The localizer beam width is designed to produce +/- 2 dots deviation at +/- 700 feet deviation from centerline at the runway threshold. The localizer scale sensitivity in degrees per dot is therefore a function of the distance from the threshold to the localizer antenna. Regards, Paul Paul R. Deppe Veridian Engineering (formerly Calspan) Flight & Aerospace Research Group 150 North Airport Drive Buffalo, NY 14225 (716) 631-6898 (716) 631-6990 FAX [EMAIL PROTECTED] ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] GS needle sensitivity.
Curtis L. Olson wrote: > I had someone recently comment that they thought the glide slope > needle was too sensitive in FG. Can anyone comment on this? I think the glideslope needle is too sensitive in FG. :) I don't have any harder evidence either, but I'll throw in my 2¢ anyway. I've been practicing constant AoA landings in the A-4 over the last week or so (getting really good at them now, gonna have to code up arrestor wires pretty soon...), and using the ILS receiver to train my eyes to recognize the right glideslope. It's definitely very touchy, even 2-3 miles out. My sense is that maximum deflection of our instrument is only a small fraction of a degree, when it should* be something more like 1° or so. Andy * Where "should" means "what other simulators seem to do" and not "what real equipment does". -- Andrew J. RossNextBus Information Systems Senior Software Engineer Emeryville, CA [EMAIL PROTECTED] http://www.nextbus.com "Men go crazy in conflagrations. They only get better one by one." - Sting (misquoted) ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
[Flightgear-devel] GS needle sensitivity.
I had someone recently comment that they thought the glide slope needle was too sensitive in FG. Can anyone comment on this? What sort of needle range relative to how many degrees off the target glide slope should we be seeing? This person suggested 2 'dots' per degree off the glide slope (but they aren't a pilot and haven't flown any "real" instrument approaches.) I thought I had investigated this and had done it correctly when I first wrote the code, but it would be nice to verify that we are still doing this right since the question has come up (and given that the 2d panel instrument can also scale the values, there is more than one place an error could creep in.) Thanks, Curt. -- Curtis Olson IVLab / HumanFIRST Program FlightGear Project Twin Cities[EMAIL PROTECTED] [EMAIL PROTECTED] Minnesota http://www.menet.umn.edu/~curt http://www.flightgear.org ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
