On Thursday 17 Dec 2009, Curtis Olson wrote: > I had a squawk here from a (real) King Air pilot because on an > ILS approach, our glideslope indicator doesn't become > active/in-range until about 7-8 miles out. Beyond this range the > indicator just stays centered at zero. With a standard 3 degree > glide slope, 7 miles out equates to about 2000' AGL, outside of > this range the FlightGear glideslope does nothing. > > I see our database lists the GS ranges at 10nm usually. However, > our code seems to be clamping the range to something > significantly less than that. I've been poking around in > navdb.cxx and navradio.cxx but haven't been able to connect all > the dots yet. > > I don't have personal knowledge of what is correct, but this > change to glideslope range impacts our ability to practice ILS > approaches and I have a current King Air pilot complaining about > the behavior. Pulling out some old approach plates for KMSP here > I see a 14nm distance and 5000' MSL entry altitude (4000'+ AGL) > referenced in the approach to 30R. Is 7-8 miles a realistic > range for the glide slope? Is my King Air pilot contact smoking > something? > > Thanks, > > Curt.
I live beneath the turn-in point for clockwise approaches on 05 at Stanstead Airport (EGSS) and most airliners, up to 747s and MD-11s, are lined up on the glideslope by about 7.5 nm out from the threshold. The occasional AN-124s I've seen come in seem to be already on the glideslope quite a bit further out though - I'd estimate they're on the glideslope by the time they're about 10 nm out (I checked the distances using Google Earth). Iirc, when I last simulated these two types of approach at EGSS I was between 2500-3000ft asl (over ground that's about 200ft asl) as I turned in above my home for the more typical airliner approach, and around 4000ft when I got on the glideslope for a straight in approach using the AN-225 to mimic the AN-124s. In view of what seems to happen at EGSS, I would say that the 14nm range & 5000ft altitude seem about right. LeeE ------------------------------------------------------------------------------ This SF.Net email is sponsored by the Verizon Developer Community Take advantage of Verizon's best-in-class app development support A streamlined, 14 day to market process makes app distribution fast and easy Join now and get one step closer to millions of Verizon customers http://p.sf.net/sfu/verizon-dev2dev _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
