CAT II with DA(DH)
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From: On the Beach
longobard:
It happens in the U.S., too. Usually, the terrain is sufficiently irregular prior to the runway that the RA reading is either inaccurate or unreadable.
None, unless imposed in an operator's state authorization.
Anybody knows why YMML ILS 16 CAT II, and other asian airports, minima doesn't report RA but only DA(DH)?
Which operational consequences?
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From: Seattle KBFI
If RA is not approved, then DA(H) is determined by inner marker, and backed up with baro altitude.
So for the Europeans if DH must be established with RA, then can they not do Cat II approaches to places like KSEA, or others, where IM is used instead, due to the underlying terrain???
So for the Europeans if DH must be established with RA, then can they not do Cat II approaches to places like KSEA, or others, where IM is used instead, due to the underlying terrain???
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From: Vermont
The use of the inner marker in this case is the standard procedure for US operators; however, it must be approved in that carrier's Op Specs. Not all carrier's programs incorporate this. If they do not, the approach is not authorized.
AC 120-29A also references the use of the baro DA or the IM, whichever comes first. This is another option that must be included in the carrier's Op Specs.
In no case (that I am aware of) can a US operator use only the DA.
AC 120-29A also references the use of the baro DA or the IM, whichever comes first. This is another option that must be included in the carrier's Op Specs.
In no case (that I am aware of) can a US operator use only the DA.
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Manfield:
There was a time when a few operators that had done some modifications to their baro altimeters could fly to a 100-foot DA based on altimetry alone. But, those were "Jurassic" birds (727, DC-9, etc). I know my airline had that authorization but within a few years they installed radar altimeters. 
The use of the inner marker in this case is the standard procedure for US operators; however, it must be approved in that carrier's Op Specs. Not all carrier's programs incorporate this. If they do not, the approach is not authorized.
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From: Germany
AFAIK in EU-OPS you must have a RA for CATII . inner markers are practical nonexistend here. more, the glideslope must be 3 deg.
so when the terrain may give irratic RA readings in the vicinity of DH or a steep approach is needed the airport will simply not have cat II or more.
the aircraft must be quipped with an radar altimeter and two indepentend autopilots which must be approved and functional.
on the bae146 we did catII approaches and there is a light "CATII green" which signals that both autopilots are tuned properly and crosschecking each other. otherwise you are CATI limited for the app.
so when the terrain may give irratic RA readings in the vicinity of DH or a steep approach is needed the airport will simply not have cat II or more.
the aircraft must be quipped with an radar altimeter and two indepentend autopilots which must be approved and functional.
on the bae146 we did catII approaches and there is a light "CATII green" which signals that both autopilots are tuned properly and crosschecking each other. otherwise you are CATI limited for the app.
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From: _
PT6A - never seen that before. Does that imply the faster aircraft in categories C and D have a higher OCH and this puts them slightly further back at a point where the terrain profile isn't acceptable for this purpose? That doesn't seem consistent though because all Cat II/III approaches have to transit over this terrain as well, any ideas??
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From: My views - Not my employer!
Manch 05L has a valley just prior to the threshold. I'm guessing, but the slower approach speed of the CAT B aircraft means the rad alt ramping is judged to be acceptable, but in the faster aircraft it is not.
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From: _
Cough
Thanks for the reply but what I was eluding to earlier was how can any approach be allowed to continue past a point where the rate of rad alt change is unacceptably high without adequate visual reference? The EK 380 flight has most probably been conducting a CatIIIB approach onto this runway over the last few days whilst still barely able to see their own nose, can't see why the rules would have to change just because that point in space coincides with the location of the DH for CatII? The AIP cites the "terrain profile" as the reason but gives nothing else away, I'm not saying you're wrong only that it seems inconsistent to me.
Thanks for the reply but what I was eluding to earlier was how can any approach be allowed to continue past a point where the rate of rad alt change is unacceptably high without adequate visual reference? The EK 380 flight has most probably been conducting a CatIIIB approach onto this runway over the last few days whilst still barely able to see their own nose, can't see why the rules would have to change just because that point in space coincides with the location of the DH for CatII? The AIP cites the "terrain profile" as the reason but gives nothing else away, I'm not saying you're wrong only that it seems inconsistent to me.
