|Quoting LTU932 (Thread starter):|
For example, if the ILS is a CATIIIb, would it be required to have a DME? And if a DME equipped ILS is required for a CATIIIb or CATII ILS, which categories require the DME equipment for the ILS overall?
is not required, however it becoming more of the norm, its a cost saving to have one DME
serving both ends of a runway than having multiple markers. Some countries allow the use of GPS in lieu of DME
|Quoting Philsquares (Reply 3):|
Just a minor technicality, there is no FAF with an ILS. The "maltese cross" is the FAF for the Localizer only portion. I do agree about the altitude check, although I don't believe it's actually required.
This is from the ICAO Procedures for Air Navigation Services, Volume II
, you can in extreme cases have a FAF on an ILS. You are correct in most cases you do not, you have a FAP. Most FAFs depicted on charts are not for the ILS approach, they are the LLZ,, they are a ILS/LLZ charts with both approaches overlaid.
1.4 PRECISION SEGMENT
The precision segment is aligned with the localizer course and contains the final descent for landing as well as the initial and intermediate phases of the missed approach segment See Figure 11-1-1-5.
The precision segment starts at the final approach point (FAP), that is, the intersection of the nominal glide path and the minimum altitude specified for the preceding segment. The FAP should not normally be located more than 18.5 km (10.0 NM
) before threshold, unless adequate glide path guidance beyond the minimum specified in Annex 10 is provided.
1.4.3 Descent fix
220.127.116.11 A descent fix may be located at the FAP to overcome certain obstacles located before the FAP as an alternative to increasing the glide path (GP) angle. When so located, it becomes the final approach fix. The extension of the precision surfaces into the precision segment is then terminated. . The descent fix should not normally be located more than 18.5 km (10.0 NM
) before threshold, unless adequate GP
guidance beyond the minimum specified in Annex 10 is provided. The maximum fix tolerance is +/- 0.9 km ( +/- 0.5 NM
). Where DME
is used to identify the fix, the range shall he stated in tenths of kilometres (nautical miles).
Note.- Guidance material for determining the distance to the descent fix froom the threshold is contained in Appendix D.
18.104.22.168 Obstacle clearance at the descent fix
22.214.171.124.1 When a descent fix is provided , the precision approach surfaces start at the earliest point of the FAF tolerance area (see Figure 11-1-1-2). The provisions of Part 1, Section 3, Chapter 2, 2.7.4, "Obstacle close to a final approach fix or stepdown fix" which allow obstacles close to the fix to be ignored, apply in the area below the 15 per cent gradient within the precision surfaces (Cat H, 15 per cent gradient or the nominal gradient multiplied by 2.5,
whichever is greater).
126.96.36.199.2 Where a descent fix is not provided at the FAP, no curtaibnent of the precision surfaces is permitted (see Figure 11-1-1-3).
188.8.131.52.3 if the precision surfaces are extended into the preceding segment, they shall not be extended beyond the intermediate approach segment.
1.4.4 Glide path verification check A fix (outer marker or DME
) is necessary so as to permit comparison between the indicated glide path and the aircraft
altimeter information. The fix shall not have a fix tolerance exceeding i 0.9 km (A 0.5 NM
). When DME
is used to identify the fix, the range shall be stated in tenths of kilometres (nautical miles).
Note.- Guidance material for determining the height crossing the outer marker is contained in Appendix D
1.4.5 Missed approach
The missed approach point is defined by the intersection of the nominal glide path and the decision altitude height (DNH). The DNH is set at or above the OCAIH, which is determined as specified in 1.4.7 to 1.4.9 and 1.5.
The precision segment normally terminates at the point where the final phase of the missed approach commences (see Part I, Section 4, Chapter 6,6.1.2, "Phases of missed approach segment") or where the missed approach climb surface Z (starting 900 m past threshold) reaches a height of 300 m (984 ft) above threshold, whichever is lower.
|Quoting Ralgha (Reply 7):|
Yes there is, the FAF on an ILS is on the glideslope at the lowest intercept altitude, however it is not marked with the cross as non-precision approaches are.
I think your referring to the FAF on the LLZ, most ILS approaches do not have a FAF, most only have a FAP. A FAF is normally only included on an ILS where extreme terrain exists.
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