Is it because a published ILS approach is not just the bit from the FAP to the TDZ.
Agree you just follow the horizontal line on the GP and you can cross check altitudes in your head if there are no markers and providing you know where the TDZ = 0 on the GPS.
But what about the rest of the approach, if it is not an overlay in the database.
I have to admit in all the ILS approaches I have made to minima 550m vis and 200’ AGL I have always been surprised at how little you see when getting visual. Often the approach lights are about it and even they look like a sodium street light on a foggy day. I I wouldn’t want to be worrying about whether or not I was 0.3nm or 600m short or long of TDZ. I think it would be long normally but mathematical brain a bit foggy this morning🙂
Przemek wrote:
I tried it and I find that I can’t setup gtn to show always distance to fixed point (for example dme from map)
The answer is: You can’t
Only way to do it is a second GTN that is not synced with the first one where you enter a fligtplan with a direct to the fix you want to know the distance to. Then you can see the distance as the distance to the next waypoint on default nav page of this GTN.
Ibra wrote:
Why? if you have the glidepath & altimeter, why you need DME on straight-in ILS? what is the logic?
You need it for the glidepath check. Originally marker and/or locator beacons were used for that, but they are increasingly being replaced by DME.
What about the “direct to” or “waypoint info” pages of the GTN? These show distance to waypoint, don’t they?
lionel wrote:
What about the “direct to” or “waypoint info” pages of the GTN? These show distance to waypoint, don’t they?
Those only help for waypoints which are on the active flight plan – the DME is typically not…
Ibra wrote:
if you have the glidepath & altimeter, why you need DME on straight-in ILS?
Btw: Altimeter is useless without any form of lateral position indicator like the DME. So in that case you have glidepath. No redundancy…
No redundancy…
Why 3D LPV does not have a separate redundancy requirement? (other than RAIM/SBAS satellites)
On 3D ILS, the DME reading at FAP or navigatiom fix is yoyr sort of “ILS RAIM” once that checked you will slide untill DH no matter what happens
You can still cross-check distance & altitude on ILS every 1nm but realistically, one only do that during exams…once happy with glidepath at FAP you just fly ILS neddles
On LOC, it’s different you have to maintain CDFA profile, keep MDH on step altitudes and go missed at MAPT…
Malibuflyer wrote:
Those only help for waypoints which are on the active flight plan – the DME is typically not…
I meant “nearest” instead of “direct to”. The “waypoint info” page can be opened for any arbitrary waypoint as far as I remember.
Ibra wrote:
once happy with glidepath at FAP you just fly ILS neddles
It’s not like that at least not for me. I always crosscheck DME and altitude during ILS approach because one always have to be prepared for losing GP. It’s just a habit related to good airmanship.
Do you degrade to LOC minina on losing glide path or go missed?
Do you degrade to LOC minina on losing glide path or go missed?
Degrade to LOC minima if above, go missed if below and no RW in sight (happened once in 12 years of IFR flying).
