4 ms·
There is more airports in US that have GPS only approaches than airports that have ILS approaches. For example: http://155.178.201.160/d-tpp/1308/05879R25.PDF h
by hedgie13 13y ago
There is more airports in US that have GPS only approaches than airports that have ILS approaches. For example: http://155.178.201.160/d-tpp/1308/05879R25.PDF http://155.178.201.160/d-tpp/1308/05879R25.PDF
500 ft altitude with GPS only (without vertical guidance). LPV minimum is 300 ft.
Category III ILS minimum is 200 ft, Cat II -- 100 ft. But there are a lot of airports where ILS is not available.
- mikeash 13y agoA lot of small airports with very little traffic. Counting airports doesn't give you an accurate picture, because just about any airport can have a GPS approach, since the whole point is that it doesn't require any ground equipment. That doesn't mean those approaches get much use, because people don't fly into those airports all that much, especially not on instrument approaches. I fly out of an airport with a published GPS approach and no ILS, and people use the GPS approach on well under 1% of the total landings there. Any reasonably busy airport will have ILS.
- hedgie13 13y agoTrue, they are less busy, but it does not mean GPS is not used for instrument approaches (as parent implied). I fly airplane without IFR GPS (IFR student), but ATC is trying to assign us GPS approach all the time (when coming into airport with ILS). As far as I understand, GPS approaches are used, even if they are less critical in busier airports. Besides, sometimes ILS is not available in bigger airports as well.
- toomuchtodo 13y agoILS was not available on the SFO runway the Asiana aircraft crashed on ~2 weeks back: http://en.wikipedia.org/wiki/Asiana_Airlines_Flight_214 http://en.wikipedia.org/wiki/Asiana_Airlines_Flight_214
- hedgie13 13y agoYes, but the weather was clear. No need for ILS in such weather.
- toomuchtodo 13y agoUnless of course you've never landed at SFO before in an aircraft you're barely type-rated on.
- mikeash 13y agoNeither should matter. A visual landing at any airport is pretty much the same, and the basics don't change for different aircraft. There's nothing at all tricky about a visual approach into SFO.
- jnsaff2 13y agoYou've got it backwards: CAT I is 200ft Decision Height (btw, not Minimum Descent) Cat II is 100ft Cat III is 0ft (with differing horizontal visibilities for IIIa/IIIb/IIIc
- hedgie13 13y agoI am wearing paper bag for the rest of the day. Not enough caffeine in the morning.