On 01/03/2007 01:01 AM, Dave Perry wrote: > The ILS minimums for non CAT II or CAT III approaches are usually no > less than 200 1/2 (200 ft AGL decision height and 1/2 mile visibility). > It is not legal to do a 0-0 ILS in the C172P with this autopilot. If you > do not have the runway environment well in sight at the decision height > (usually the GS intersects the DH at the middle marker), you are > required to execute a missed approach.
That seems unhelpful on several levels. (A more helpful approach is suggested below.) 1) First of all, visibility (etc.) regulations are irrelevant to the design and simulation of low-end autopilots. The autopilot isn't looking out the window. 2) That isn't a correct statement of the regulations. FAR 91.175(c) is quite a bit more intricate than that. Pilots have enough trouble keeping track of the real regulations; it doesn't help to have made-up pseudo-regulations bandied about. *) To say the same thing another way: There is no law against coupling an autopilot to an ILS signal in good weather and flying it as low as autopilot (and pilot) performance permits. You don't need an IFR clearance, or even an instrument rating. *) There are /some/ situations where regulations are designed around hardware limitations, and/or hardware is designed to meet regulations, but this is not one of those situations. Trying to connect KAP140 performance to Cat-I ceiling and visibility has no basis in legality or practicality. So let's rephrase the question. Autopilot designers should be asking, among other things: -- How accurate is the autopilot? -- How do things like left/right accuracy and sensitivity change as the aircraft gets nearer and nearer to the localizer antenna? -- How do things like up/down accuracy and sensitivity change as the aircraft gets nearer and nearer to the glideslope antenna, which will be approached very closely indeed during a normal landing. Also remember that some people (not all, but quite a few) are interested in _realistic_ simulations. An autopilot that does a fair-to-poor jobs of tracking NAV signals is not particularly unrealistic :-). ===================================== In a real aircraft, if the autopilot is controlling the ailerons, you shouldn't be forcing the yoke left or right, and the autopilot will resist you if you try. You can overpower the autopilot if you try hard enough ... but this is not normal procedure. Similarly, in a real airplane, if the autopilot is controlling the elevator, you shouldn't be forcing the yoke in the pitchwise direction. Modelling this is tricky. Ideally we would have force-feedback and position-feedback on our joysticks, but not all of us can afford that. Ignoring joystick input on each autopilot-controlled axis is the most sensible option I've seen proposed. Note: Be sure that the cockpit model shows the yoke moving in response to autopilot inputs. This is particularly important when it comes time to disengage the autopilot; the astute user will position the joystick to match the position of the yoke before transferring control. ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
