ILS Descent Procedure

[Marty-Party]

If a procedural ILS has an turn inbound platform altitude of 2000' and the FAF (FAP) at 1700', do you have to descend to 1700' (e.g. in V/S mode) before taking the G/S? Or can you remain at 2000' inbound and then follow the G/S?

An example is the ILS approach into AUH rwy 31. I think it is OK to descend to 1700', fly level and then capture the glide but wouldn't it be more "elegant" to remain at 2000' and then capture the G/S. Is this legal?

I think the requirement for descent to 1700' is related to the LLZ only approach.

Any comments?????

Yes - those who work for the same Co as me will twig as this is in our current check.

[JustaFew]

We used to have a full ILS on one runway end, but a localiser-only
on the other end. The FAF/FAP for the ILS is expressed as a DME range, but for the localiser-only approach, the FAF/FAP was expressed as an altitude because that was the point at which the procedure began. The LLZ-only appraoach was only available when the DME was serviceable.

[oldebloke]

Marty, one always intercepts the G/S at the procedure turn Alt.The 1700' at the FAF is an altimeter check as well as a Non precision minimun alt to cross the FAF.as you say smoother' approach:O

And if one\'s lucky to get an early clearance one can \'follow\' the G/S from alt\'

[High Speed Descent]

I agree with Oldebloke. Alot of airports have FAF that start below 2000' and generally ATC will clear you to that altitude. If you choose to descent on a 3deg profile you will capture the ILS earlier so do remember the Height cross-check when captured. It is perfectly legal.

The approach chart caters for a LLZ (for alt-dme checks) as well as being noise sensitive (ie KIX FAF is at 1200' and there are height crossing restrictions) and of course obstacle clearance.

But i am not sure if beam strength has anything to do with it...stronger as you get closer?? or just more sensitive!!

HSD

[Marty-Party]

Thanks guys,

I'm glad I hadn't missed the point somewhere. I completely agree that there is nothing wrong with capturing the G/S from the procedure turn altitude (actually it's a base turn in this case). The FAF crossing altitude is there to cross-check the G/S.

For a LLZ only approach it would be necessary to descend to the FAF altitude after the base turn and then to potetially fly level until crossing the fix. There is no other way of determining your range from touch down (without DME).