IAP Questions

[brns2]

I have just a few questions regarding rules that I was taught, and have just accepted until now going through the rule book. From reading through my jepps none of these rules are published? are these old rules that old instructors still think exist and are still being tought.

Regarding the ILS:
1) If you are conducting an ILS and you pass the FAF above the published altitude, you need to add that altitude to the DA.

2) If at the FAF the altimeter underreads then you use the same DA. (JEPP TERMINAL Instrument Approach/takeoff 2.7.3.1, states any unexplained descrepancy, then conduct a MA)

3)If you are more than half scale deflection you conduct a missed approach. (Jepp Instr app/takeoff procedures 2.7.3.1, states anytime the LOC or GS indicates full scale deflection a MA SHOULD be conducted)

Regarding DGA:
4) If you have a raim warning below the MSA you may continue at that altitude to the MAP. ( I think this is an old rule, as JEPP DGA procedures, 1.5.1.f states if there is a raim warning or any doubt off the gps information, a MA must be conducted)

Other:
5) You must join an instruments approach at of before the IAF. Never found a rule for that one, and I dont see why it is not safe to join after if you are not descending below the MSA.

[muffman]

1) If you are conducting an ILS and you pass the FAF above the published altitude, you need to add that altitude to the DA.

2) If at the FAF the altimeter underreads then you use the same DA. (JEPP TERMINAL Instrument Approach/takeoff 2.7.3.1, states any unexplained descrepancy, then conduct a MA)

This used to be the rule in Australia quite a few years ago but was never a part of the ICAO docs as far as I know. It has been replaced with the requirement for a missed approach in line with ICAO.

3)If you are more than half scale deflection you conduct a missed approach. (Jepp Instr app/takeoff procedures 2.7.3.1, states anytime the LOC or GS indicates full scale deflection a MA SHOULD be conducted)

From the AIP/Jepp terminal:
"A missed approach must be executed if:
a. during the final segment of an instrument approach, the aircraft
is not maintained within the applicable navigation tolerance for
the aid in use"

4) If you have a raim warning below the MSA you may continue at that altitude to the MAP. ( I think this is an old rule, as JEPP DGA procedures, 1.5.1.f states if there is a raim warning or any doubt off the gps information, a MA must be conducted)

Sounds like a more practical interpretation of the rules than a technically correct one. I guess in theory if you've descended to your current altitude with RAIM available and then it drops out, the altitude you're at is definitely still safe because you got there using valid distance information. The steps always get lower on a DGA so your current altitude would continue to be safe until you reach the missed approach point.

[john_tullamarine]

your current altitude would continue to be safe until you reach the missed approach point.

.. would you be entirely comfortable about your nav solution position/tracking integrity ?

[eocvictim]

4) If you have a raim warning below the MSA you may continue at that altitude to the MAP. ( I think this is an old rule, as JEPP DGA procedures, 1.5.1.f states if there is a raim warning or any doubt off the gps information, a MA must be conducted)
Sounds like a more practical interpretation of the rules than a technically correct one. I guess in theory if you've descended to your current altitude with RAIM available and then it drops out, the altitude you're at is definitely still safe because you got there using valid distance information. The steps always get lower on a DGA so your current altitude would continue to be safe until you reach the missed approach point.

It does also state (and I dont think you'll find anyone who will argue with this) 1.5.2 e. In the event of a significant disparity between the NDB or VOR track, and the GPS track indication, the pilot must discontinue the arrival procedure.

Without raim you have "no" track indication so as far as I'm concerned thats a significant disparity.

Interesting note though it does say you much discontinue the arrival, for which there is no deffinition, however the Missed approach procedure is defined as

The procedure to be followed if the approach cannot be continued.

If you are discontinuing the arrival then surely that meets the deffinition above and hence you must conduct the missed approach. Why it doesn't just say that? I dont know.

Other:
5) You must join an instruments approach at of before the IAF. Never found a rule for that one, and I dont see why it is not safe to join after if you are not descending below the MSA.

This has an approach specific answer however its the only approach that gives reference to it.
(from my old AIP because my jepps are at work)
DME arc:

ENR 1.5 2.8.1 DME arcs must be joined at or before an IAF and at an altitude not below the relevent MSA or the appropriate sector DME arrival step

Obviously if its a reversal you have to fly over the fix but with regard to DME arrivals (track specific) the only significance I've found is for your speed limitations. Finally an RNAV has an Initial waypoint and thus a part of the procedure.

[Zoomy]

Jepps Terminal 1.6.1

Except when complying with the requirements for a visual approach, when conforming to a published DME or GPS arrival procedure, or when identified and assigned an altitude by ATC, an aircraft approaching an aerodrome must not descend below the LSALT or the MSA for the route segment being flown until it has arrived over the IAF or Facicility.

So unless DME/GPS arrival, then fly over the aid or IAF before starting the APP.