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.
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.
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.
>Due to the complexity of ILS localizer and glide slope systems, there are some limitations. Localizer systems are sensitive to obstructions in the signal broadcast area like large buildings or hangars. Glide slope systems are also limited by the terrain in front of the glide slope antennas. If terrain is sloping or uneven, reflections can create an uneven glidepath causing unwanted needle deflections. Additionally, since the ILS signals are pointed in one direction by the positioning of the arrays, glide slope supports only straight-line approaches with a constant angle of descent. Installation of an ILS can be costly because of siting criteria and the complexity of the antenna system.
>ILS critical areas and ILS sensitive areas are established to avoid hazardous reflections that would affect the radiated signal. The location of these critical areas can prevent aircraft from using certain taxiways[3] leading to delays in takeoffs, increased hold times, and increased separation between aircraft.
You don't think that the ILS system could be vulnerable to an attack similar to this? The main point of the article is that we rely on tech that is insecure to give us our location and that can be influenced by an outside source. If that outside source is nefarious in nature then we can experience some real issues.
Yes, you can indeed hijack an ILS system. At least during WW2.
For more information regarding what happens if someone alters the altitude of a plane, see [2].
For example ultralights are pretty much "You're small and light enough not to cause much damage when you crash; don't do anything stupid". So yes, I am quite sure there are heavier-than-air flying machines carrying humans and a GPS unit as their sole navigational tool. As if you need advanced tools for what a ultralight can actually handle in practice, LOL.
On the other hand if you go to the E-CFR and look at FAA reg 91.205 if you want to climb above/thru FL240 you need a working DME or RNAV kinda implies any commercial operation must have VOR-type gear installed.
Note that the same playback hack that works really well on GPS works even better and easier on old fashioned VOR gear.
Merely being required to have operational gear doesn't mean a little angel is perched on each pilot's shoulder making sure they actually do have the gear, and they know how to use it, and they are actually using it.
(Scroll up to 1-1-19. Global Positioning System (GPS). The FAA's links are all wacky.)
This is the FAA's Aeronautical Information Manual.
http://aeronav.faa.gov/content/aeronav/acfstatus/Presentatio...
Yes, I'm sure that pilots routinely ignore the altimeter, air speed indicator, climb rate indicator, compass ....
GPS is useful, but no competent pilot ignores all of the other sensors and uses GPS alone.