With no ident on the glide path the only check you have is the altimeter check height. Pilots who do not vigilantly cross check outer maker or DME check heights on the ILS or ILS DME are foolishly risking their lives, and the lives onboard they carry. The flag in the aircraft will not show error on the glide path in the case of false glide slope capture. The ILS has a ident code on the LLZ signal only, no Morse identification is transmitted on the glide path. Also an Air New Zealand 767 captured a false glide slope on an ILS transmitter that was radiating in test mode. I can think of an incident in Canada where altimetry procedures resulted in a hull loss while the aircraft was track for final approach. read 500’ whilst at ground level), or the case of false glide slope capture. The markers in an ILS approach are used to cross check the aircraft altimeters to the glide path, this is a gross error check for cold temperature operations where altimeter can dangerously over read (i.e. In an ILS or ILS/ DME approach the final approach commences at the glide path intercept point and ends at the decision height/altitude. The final segment on a non-ILS approach begins at the final approach fix or point and ends at the missed approach point or fix. I have to agree that the ILS or ILS/ DME approach does not have a Final Approach Fix (FAF), it does however have under ICAO rules a Final Approach Point (FAP). Otherwise, there will be a repeat of the KAL accident. However, if you are flying a Loc only, then for situational awareness it's something to brief. Since you are using the localizer and G/S it makes no difference. You would see the DME decrease to your altitude in miles (.2 or so) and then increase. You'll see there the VOR/ DME is actually prior to the runway. In some approaches, the DME is not colocated with the ILS or the end of the runway, or there is another DME associated with the miss approach procedure. In this case, the approach would be labeled as a VOR/ILS or ILS/ DME. (In the very old days, it was timing from the OM to the MAP) There are still some approaches around the world that don't have a DME associated with the ILS. ![]() The DME and FAF comes into play should you lose the G/S now if you have the DME you can continue to the localizer only minimum. All of those aren't dependent on the DME. There are all sorts of criteria for the controller to turn you onto the final and a minimum distance from the runway. In some cases, you will intercept the G/S outside of the FAF (for a localizer only) and you fly the approach like a normal ILS. What the ILS has is a glideslope intercept altitude. See the Durban (FADN VORDME ILS RWY 06, you will notice there is no Loc only and thus no "maltese cross"). ![]() (Stand by everyone, we can debate that point later. Technically speaking an ILS has no Final Approach Fix (FAF). I used it more than 30 years ago when I went through UPT. If you can try to get a copy of AFM 51-37 and that will give you a very good tutorial on ILS/VOR/ DME approaches. OK, I will try to give my explanation as I have understood it for a number of years. Distance really doesn't enter the equation unless there are step down fixes farther out on the approach, in which case they are identified by distance from the DME station so it still doesn't matter where the station is located. Basically the approach boils down to keeping two needles (or their equivilant) centered until reaching the decision altitude, at which point you either have the requirements to continue the descent met, or you don't. It's really not that hard to subtract the length of the runway, and besides the distance just isn't very important on an ILS. Which is probably why they don't exist in the US. The problem with offset DMEs is they will always read a reduced distance whatever angle you approach them from You're assuming the airport in question has a VOR DME on field. If it's an ILS without DME, distance can be read approximately by tuning the VOR/ DME on the airfield.
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