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744 CAT 3B

Old 22nd May 2020, 16:50
  #21 (permalink)  
 
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I fail to understand how you can actually have a `DH of 0 ft`, [...] You would be on the runway (hopefully!) at this point anyway. What now forms the basis of your `decision`. [...]?
I would say the DH is the (final) point at which you elect to continue the autoland, or go-around, and even
with a DH of 0 ft there is still the rollout tracking and stopping part of the autoland left to go. If the aircraft landed way off to one side of the runway (or even the grass) instead of on the runway centreline, you might elect to go-around, even though you had "landed".
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Old 22nd May 2020, 21:53
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Cat 3B. The DH is either a positive number (and there aren’t many around anymore) or it’s no DH, not DH 0’. On my ac where we set 0’ because it doesn’t go any lower there are no auto calls of ‘approaching DH or minimums’ and 0’ actually means NO DH. So providing everything keeps working (ASA doesn’t say MANLAND, Flare annunciates) it will land with no requirement for any visual reference.
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Old 22nd May 2020, 21:57
  #23 (permalink)  
 
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Originally Posted by Uplinker View Post

I would say the DH is the (final) point at which you elect to continue the autoland, or go-around, and even with a DH of 0 ft there is still the rollout tracking and stopping part of the autoland left to go. If the aircraft landed way off to one side of the runway (or even the grass) instead of on the runway centreline, you might elect to go-around, even though you had "landed".
TBH the odd occasion I've done a CAT III B No DH landing as captain ( and I've done it on the 744 and the 777) my attention has been glued to the PFD ( especially the raw G/S and especially the raw Loc )right down until probably 60 knots or less.. I was sure as heck not looking up at "zero" or immediately thereafter for lights or grass if all the other annunciations were normal.
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Old 23rd May 2020, 07:47
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Thanks FD; its good to hear that some aircraft systems are being used with matching certification and operational approval. Also, that common sense is not yet flattened by 'training for the sake of training'.

What was the other aircraft type.

Uplink, 'off the runway'; a highly improbable scenario given system integrity requirements, and instrument displays and alerts, e.g. LOC deviation.
Operational thinking from 'the early days' has evolved with increasing experience and knowledge. Low DHs relating to visual cues became 'confirm a runway', which was more for the pilots peace of mind than operational practicability.
Also changes in procedure with more knowledge of realistic minimum visibilities, 50-70m RVR could be 00 met vis; personal experience lowest was 90-110m RVR (ATC / fire rescue may limit operations to 50/75 m)

GA from the runway might be muddled operational regulatory thinking about a mixed integrity auto-land and rollout systems; fail-op land, fail-passive rollout.
Not a lot of common sense in some operational regulation.

dh, wiggy; ok.
Why not look outside and enjoy the view; there is a lot to see, and many differences day/night, different runway surfaces/lighting.

LOC deviation on the runway - unlikely; yet in VMC practice it was quite a surprise when ATC switched runways and ILS while ground-roll was still engaged. (I think that LOC display remained centred, but the aircraft didn't).
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Old 23rd May 2020, 08:19
  #25 (permalink)  
 
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Originally Posted by Uplinker View Post

I would say the DH is the (final) point at which you elect to continue the autoland, or go-around, and even with a DH of 0 ft there is still the rollout tracking and stopping part of the autoland left to go. If the aircraft landed way off to one side of the runway (or even the grass) instead of on the runway centreline, you might elect to go-around, even though you had "landed".
If on a CAT3B fail operational approach and autoland, with no adverse annunciations, there still exists, for your ac type/autopilot technology, a `risk` from historical data of not landing on the centreline, then the pilot needs to be given a `casting vote` in the form of a DH>0. Even if its just 12 ft, which I believe was used by the Trident ac on occasions?
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Old 23rd May 2020, 09:42
  #26 (permalink)  
 
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PEI. I love a good view as much as anyone, but with 75R my concentration is elsewhere.

SE. Absolutely if there is a DH, otherwise the casting vote is based on cockpit indications alone(GS, LOC, ASA, FMAs etc). Today’s lockdown challenge is to find approaches with a 3B DH. My starter for ten is Brescia (30/100) as the only one on our list of lo vis airfields. Good luck !
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Old 23rd May 2020, 10:32
  #27 (permalink)  
 
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Interesting that some don’t want to look out of the window on 3b no DH. The basis of AWOPS training is one pilot heads out (normally PF) and one firmly heads down in (normally PM depending on operator SOP). Are you saying you see no value to seeking visual cues on a no DH approach ? A good unexpected visual cue forms another great resource if you’re lucky. Fog patches, midpoint significantly greater than 75m ? Perhaps you join the group of guys with newspapers In the windows to block out the sun or cockpit storm/ override light on in the dark because you’re IFR so there’s no need to look out.

Another lockdown question teeser. Why 75m for 3B no DH ?

Last edited by 8che; 23rd May 2020 at 10:59.
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Old 24th May 2020, 10:11
  #28 (permalink)  
 
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A320, fail-operational. Certified NO DH (min RVR 75m).
Only lurking in this thread but what does RVR 75 mean if there is no DH ? In effect does it still mean that if you don't see the runway at 75m you should go around ?
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Old 24th May 2020, 10:33
  #29 (permalink)  

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Originally Posted by atakacs View Post
Only lurking in this thread but what does RVR 75 mean if there is no DH ? In effect does it still mean that if you don't see the runway at 75m you should go around ?
Definitely no, as you suspected.

For no DH operations unless there is a failure the pilot takes no decisions and actions apart from operating non-automated stuff like the reversers.

The min value of RVR = 75 is an arbitrary limit to enable vacating the runway and taxing. In the sense you'd at least will be able to repot where you are after getting lost.

There are two other values of similar nature:

​​​​​​125 m is the min requirement for manual roll-out.
300 m for manual landing (IIRC used to be 350, happy to be corrected on this one).

A proposed fully autonomous landing under nil/0 conditions exists on paper for quite some time, search the interweb for ICAO CAT IIIC. The technology does not exist yet.

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