+1. Reversible approaches should be configured like any other ATC controlled ground system - such as runway lighting. I have no objections to an automatic selector for which ILS end to enable, but it should be based on surface wind (for example) and not the aircraft position.
John Denker <[email protected]> wrote: >Back in the 2nd week of September there was discussion of >reversible ILSs. > >Maybe I missed something, but I thought there was rough >consensus around the following ideas: > >a) FG behavior should be reasonably realistic. We should > not make artificial assumptions that make approaches > unflyable, when better alternatives are readily available. > Conversely, we should not require FG to implement features > that are not available in real life. > >b) An instrument approach procedure generally contains a > "missed approach segment". There is a maxim that says > "If you are not prepared for the miss, you are not prepared > for the approach." The FAA says that half the time, > a practice approach should include flying the missed > approach segment. Real-world pilots take this seriously. > Lives are at stake. > >c) You cannot show up at a real-world airport and expect > both ends of a reversible ILS to be active simultaneously. > The physics doesn't permit it. The signals would interfere. > If runway 11 is active and you would prefer runway 29, > you can ask Tower to reverse the ILS. They might or might > be able to grant your wish. > >d) For years, FG has attempted to divine which end of the > reversible ILS the pilot wants to use based on aircraft > position and/or heading. This is both unrealistic (see > item c) and impossible. There is no objective way to > determine whether an aircraft is flying the "upwind leg" > for runway 11 or the "downwind leg" for runway 29; the > only difference between the two is the pilot's intentions. > You've heard of problems that are so hard that they are > classified as NP-complete ... well, this problem is much > worse than that. It is ESP-complete. > >e) The current code is even more broken than that. At > some airports, it gets the wrong answer 100% of the time, > so that you cannot fly the inbound segments, never mind > the missed approach segment. Bug reports on this issue > have been discarded without comment. > >f) Code to fix all these problems has been available since > September. It uses a "preferred-approach-deg" value > in the property tree to decide which end of the ILS to > activate. If you prefer the other end, you can easily > change this property. All segments of the approach are > flyable. Everything is predictable and well behaved. > > The same words that described the ILS service volume > apply here: This is a significant departure from past > FG behavior, but it is not wrong. It is feature, not > a bug. > > This code was not committed. It was discarded without > comment. > >=========== > >I was recently told [off list] that there was a >"requirement" within FG to permit simultaneous approaches >to both ends of a reversible ILS. This came as a surprise >to me. I do not recall anybody suggesting this, even as >a joke, much less any consensus in this direction. > >Let's be clear: We all agree it is important for both >ends of the ILS to be available without undue hassle, but >they don't need to be available at the same time. And >"without undue hassle" doesn't mean without any pilot >input at all, especially when the problem is ESP-complete. >Most real-world instrument-rated pilots are content to >fly the approach that Tower says is the active approach; >they don't show up at an airport with inflexible pre- >conceptions about which approach will be active. > >I was also informed [off list] that the code to make >reversible ILSs usable had been "ignored" because it was >"not good enough". That is not very informative, not >very constructive. No clarification has been forthcoming >as to what makes it "not good enough". > >Perhaps some folks on this list would be kind enough >to look at the code and make constructive comments. >Take a look at > http://gitorious.org/~jsd/fg/sport-model/commits/sport >in particular the item that speaks of "reversible ILS". > >If there are some requirements that I am not aware of, >requirements that make unflyable approaches preferable >to flyable approaches, please explain. > >------------------------------------------------------------------------------ >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 >[email protected] >https://lists.sourceforge.net/lists/listinfo/flightgear-devel ------------------------------------------------------------------------------ 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 [email protected] https://lists.sourceforge.net/lists/listinfo/flightgear-devel
