Matt Fienberg writes: > For an IFR interested VFR student, what's an MDA, and what does it > mean to bust it by 20 ft? I'd guess at "minimum designated > altitude?"
MDA is Minimum Descent Altitude. Non-precision approaches (such as NDB, VOR, LOC, LOC-BC, and GPS) provide only horizontal course guidance. For altitude, you pass a series of step-down fixes (such as a DME distance or a radial from another navaid), where you're allowed to descend to a new altitude limit before levelling off again. The last levelling-off altitude is the MDA, and you cannot go below that until you actually see the runway. 500 ft AGL is a typical MDA, but it can vary by an enormous amount. Precision approaches (such as ILS) have a decision height (DH) instead -- that's the lowest you're allowed to go on the glidescope without seeing the runway. When you hit DH without visual contact, you go missed immediately, without any levelling off. DH is usually 200 ft AGL, lower for a specialized Cat II approach. Here's an easy way to remember: from the side, a precision approach looks like a ramp, while a non-precision approach looks like a staircase. > Maybe if I ask enough questions, I'll have you on the road to CFI/CFII... Nope. 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
