CAT 3 B with DH

[JammedStab]

Originally Posted by Check Airman

Originally Posted by eckhard

It's also an 'American thing'.

A quick look through a major EASA airline's manuals reveals that Los Angeles LAX, Chicago ORD and New York JFK do not allow Cat3B No DH, whereas they do allow Cat3B with a DH.

However, Denver DEN does allow it!

Not sure where you looked, but I just looked at the CAT II/III plated for LAX and ORD, and none of them had a DH associated with any of the CAT III approaches.

Time to make some clarifications in this thread. The post by Ekhard was not written clearly, but I interpret it as saying that LAX and ORD do not have a CAT III approach with a DH but EASA allows CAT III with DH. But then the same post says that Denver allows CAT III with DH. I checked the Denver charts in my Jeppesen manual and I did not see this at all. However, keep in mind that we do not all get the same approach plates from Jeppesen, so if anybody has different, please post. But, I suspect that the CAT III DH thing is only an EASA thing.

Originally Posted by Mansfield

I realize that few operators allow manual CAT II landings anymore, but that is what the visual references are predicated on. Note that in the States, we now have waivers allowing CAT II approaches with diminished lighting as long as we autoland.

I think this CAT II landing approval without autoland may be what Horizon Air uses on their Dash-8-400 out in Seattle which subject to confirmation, is also, I believe, done with manual throttle. Concerning the requirement for autoland when doing a CAT II reduced visibility approach, this is not accurate. The ops spec I have says that autoland or HUD to touchdown is required.

Originally Posted by Denti

For france we used a blanket 20ft DH for airbii and 50ft for Boeings. But apparently the french have changed their way and we can now use the normal no DH.

We still have a DH of 14 feet. But, I am reading that from a company manual(which is always subject to being out of date), not official French CAA documentation.

Originally Posted by eckhard

I looked at the 'Company Specific' minima page for 24R and 25L. On the actual Lido approach charts it gives minima for Cat1 and Cat2. For Cat3 it says, 'Company' and then you have to refer to the Company Specific page. I guess it's an Ops Specs thing but still curious as to why Cat3B No DH would be allowed in a company's Ops Specs for DEN and not for LAX, given that the capability exists at both airports?

This appears to be different than Jeppesen charts I have which show CAT IIIA or B minima for airports in the US. In EU, they only show CAT IIIA and in that case, a company specific page has to be referenced to see if there is even CAT III approval and for the CAT IIIB minima.

[quote=Rick777;9276617]It must be an opspecs thing. I live in Denver and have been based here and LAX well as flying into ORD hundreds of times in A320, 767, and 757. We used an Alert Height of 50 feet for Cat III approaches. It was not a

[JammedStab]

Originally Posted by _Sundown_

Very nice thread guys...

Let me ask you something. For B-737 Ng, the FCTM states that, for fail operational autoland approaches, above Alert Height if a mode change occurs e.g. from Land 3 to Land 2 or to No Autoland, set new minima or go-around. At least I understand it that way.

Pretend that, for a CatIII B approach after self test Land 3 announciated but above 200' AH it changed to LAND 2, shall we set a new minima e.g. CAT III A minima of 50' ?

We continue. There seems to be different methods on what to do. But 50' RA can be pre-set and blanked on my aircraft type. So, if this happens prior to the FAF, reset the appropriate switches to 50' RA. If it happens beyond the FAF, the captain will simply say something such as "Fail-passive, RA 50, call 100 to minimums and minimums" with no switches being moved.

So all the F/O has to do for this is look at the RA and make the appropriate calls at 150 and 50 feet.

[7478ti]

This is all explained in AC120-28D !!!

This is all well explained in FAA AC120-28D (issued 13 June , 1999).

See section 4.3 of the AC in particular, reference use of an AH vs. a DH, for Fail-Op versus Fail-Passive. It also matters whether with or without rollout capability (e.g., note the original triple channel SPZ-1 B747s had FAIL-OP capability, but NO rollout system even installed [thus the Op-Spec visual confirmation requirement before TD], ...until later rollout systems were added via the "rollout special condition" which was used for their initial certifications.

Derek Helmore (UK CAA inspector) and I (for FAA) first sorted out the use of Fail Op and Fail Passive systems for Cat III, with Fail Op using only an alert height [and no need any more for a (low) DH] many decades ago, back when we were negotiating TWA's L1011 minima into the UK, ...versus Concorde minima to be used into KJFK and KIAD... as well as when we later wrote the first drafts of ICAO Doc 9365AN/910 (ICAO Manual of All Wx Ops).

Further we (the FAA/JAA AWO HWG) addressed addressed these subjects again extensively, over the decade of the '90s, before and leading up to issuing the [somewhat] harmonized revised versions of AC120-28D and AC120-29A, when they were published. This was also the period when we [the AWO HWG] globally dropped any further used of the concept of MABH.

Bottom line is that [under US rules] for LAND3 mode [i.e., Fail Op], an alert height is typically used [usually set at either 100' HAT or 50' HAT], and no DA(H) is necessary. For Fail passive systems and ops [i.e., LAND2 or equivalent] a DH is applied (with some minor exceptions for certain specific irregular terrain airports where an IM or DA may still apply), primarily to accommodate the possibility of a fail passive AP disconnect.

A minor special case has evolved recently, using AC120-28D (section 5.8) provisions for a "Hybrid System", by combining use of an autoland system, monitored with a suitable AIII mode capable HUD. Per the AC, this combination can theoretically be considered as a Fail-Op system, and used with an AH [and without a DH] if AP LAND 3 mode is used as baseline, ...or used with a low DH, if the AP mode used is LAND 2 or equivalent. In either case, the AP is backed up by a suitable AIII capable HUD, for the [contingency] continuation case, or balked landing GA case.

[_Sundown_]

Thank you very much for your feedback...

[7478ti]

That's also why we dropped MABH way back in the '80s

That's also why we dropped MABH way back in the '80s.

Low DHs below 50' HAT (e.g., 15 ft), where you're below the adjacent taxiway tail heights, and obstacles "fixed by their aeronautical purpose" still make no sense at all. To get below 50' HAT one needs to be sure you're over the TDZ, period. Further, the aircraft are (required) assured to still have safe characteristics in the event of an inadvertent TD in the event of initiation of a low altitude GA.

That's why the AWO HWG long ago agreed that MABH is irrelevant (and JJ LaBlonde, Jacques Rosay, and Gerard Marin were each there for the deliberations), and was not needed. Further, applying any low DH below 50' HAT to any Fail Op A/L was simply an unnecessary distraction at a critical time in flare, ..and that to get below 50' HAT one ought to be Fail-Op or equivalent anyway.

The only few exceptions to this day, were the special cases using a Fail-Op system without a rollout system installed (e.g., some early B747s), which required confirmation of a safe TD and adequate visibility for the initial transition to rollout, ...before committing to a TD,... Or the more recent case of a "Hybrid" Fail-Op system situation, using HUD AIII mode (with reversion rollout capability) to monitor an AP FP autoland as the primary means of control.