CAT 3b after ABP
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CAT 3b after ABP
Hi ., I need some clarification on the matter!
Here is the scenario!
You are doing a CAT 3b approach with NO DH and the minimum RVR is 75 m
Now it is clear that if the RVR falls below the 75m before you have reached ABP you have to do a G/A.
But you have already passed the ABP and the RVR falls to 0m. What do you do? The key is in the wording NO DH! Do you continue to landing? Since you dont need any visual clue to land? Or do you discontinue the approach?
Here is the scenario!
You are doing a CAT 3b approach with NO DH and the minimum RVR is 75 m
Now it is clear that if the RVR falls below the 75m before you have reached ABP you have to do a G/A.
But you have already passed the ABP and the RVR falls to 0m. What do you do? The key is in the wording NO DH! Do you continue to landing? Since you dont need any visual clue to land? Or do you discontinue the approach?
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EASA OPS seems to be open for some interpretation on that particular topic. However in my outfit there is a crystal clear wording that requires a go around if the RVR drops below 75m even after the ABP.
If, after passing the outer marker or equivalent position the reported RVR/visibility falls below the applicable minimum, but in no case below 75m, the approach may be continued to DA/H or MDA/H.
EASA OPS seems to be open for some interpretation on that particular topic.
If, after passing 1000 ft above the aerodrome, the
reported RVR/VIS falls below the applicable
minimum, the approach may be continued to DA/H or
MDA/H.
reported RVR/VIS falls below the applicable
minimum, the approach may be continued to DA/H or
MDA/H.
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As far as i know the wording in our OM A was required by the local authority that argued that according to EASA you may continue to DH, but with a NO DH approach you do not have any DH therefore you may not continue as there is no DH to which you can continue. Additionally the required visual segment for rollout and taxying may not be available and therefore the safety case isn't valid anymore.
I know that quite a few countries in europe handle that differently, which may or may not be an economic advantage. Given the low count of real CAT IIIb days in europe (without the UK) it doesn't seem to be a major issue though.
As for the ABP itself, yes the main definition is the OM for us, but in the following notes it defines 1000ft in absence of an OM or other check point as the ABP.
I know that quite a few countries in europe handle that differently, which may or may not be an economic advantage. Given the low count of real CAT IIIb days in europe (without the UK) it doesn't seem to be a major issue though.
As for the ABP itself, yes the main definition is the OM for us, but in the following notes it defines 1000ft in absence of an OM or other check point as the ABP.
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In our outfit we can continue to landing. Taxiing is another issue. If you cant taxi off the runway. Stop on the runway. Nobody can descend below the ABP or take off anyway with the RVR below the cat 3b minima so u are not blocking the runway for anyone. When the vis increases. Taxi off the runway. I would rather be stopped on the runway than monitoring my fuel in the hold while waiting for the RVR to improve after a missed approach. The logic that there is no DH to descend to and therefore an immediate go around is required makes no sense to me. As long as the aircraft and ground facilities are operational i would Continue to landing. There is no decision to be made
Last edited by InSoMnIaC; 5th Dec 2014 at 00:04.
I would suspect that the procedure will vary according to local authority interpretation.
There should not be an operational issue with no DH, implying no visual confirmation required; however if visual confirmation is required (which normally defines the need for DH) then a GA might be specified.
Alternatively, if the RVR limit is due to airport operations - fire/crash rescue, then a GA would be expected for all operations because the airport is technically ‘closed’.
A change in visibility from such a low value (even if such a value can be archived) would be a very rare occurrrence due to the characteristics of stable fog; if the visibility is not due to fog … then think again before starting the approach.
The lowest vis which I encountered was daytime 90/110m RVR (= 90m Met vis) - GA from DH. At night a similar 90m Met vis gave 150 RVR which was operable … … until you tried to taxy in and park without the green centreline lights.
There should not be an operational issue with no DH, implying no visual confirmation required; however if visual confirmation is required (which normally defines the need for DH) then a GA might be specified.
Alternatively, if the RVR limit is due to airport operations - fire/crash rescue, then a GA would be expected for all operations because the airport is technically ‘closed’.
A change in visibility from such a low value (even if such a value can be archived) would be a very rare occurrrence due to the characteristics of stable fog; if the visibility is not due to fog … then think again before starting the approach.
The lowest vis which I encountered was daytime 90/110m RVR (= 90m Met vis) - GA from DH. At night a similar 90m Met vis gave 150 RVR which was operable … … until you tried to taxy in and park without the green centreline lights.
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Land.
75m is really just for taxiing. Land, then stop on the runway and get a follow me or a tug. The runways blocked but who cares, no one else can make an approach anyway.
75m is really just for taxiing. Land, then stop on the runway and get a follow me or a tug. The runways blocked but who cares, no one else can make an approach anyway.
Only half a speed-brake
Just a feeling. Are we not mixing apples with oranges?
The approach RVR limit is set for 1000 ft (used to be OM or equivalent), to achieve a certiain thing. In my eyes, that is to increase system-wide safety level by reducing human, fallible component/involment.
The hazard:
. get-home-itis
. being overly mission oriented (busting minima)
The risk
. bending aluminum due to having no means to ascertain wheter you are just a cowboy getting lucky or plain sucidal (IMC with no vis reference). < no more safety stops (cheese slices) to keep all alive.
The aim of the rule, as I understand it, is to statistically reduce the exposure to above mentioned hazards, thus - in the greater scheme of things - avoid the associated risks. If the WX is not favourable by 1000 ft, let's forbid ourselves from even trying as we wish to avoid the dark side of what trying may bring.
Before continuing I confess that the safest flying is no flying at all. Yet the industry needs to be practical, hence - for instance - the wet/contaminated allowance for reversers, screen height of 15 ft and TORA-to-lift-off relationaship for instance.
My point being: with C3 fail-operational system, the landing is "never" compromised. No need then to set gates against a misguided attempt, because the un-acceptable risks are just not there anymore since the "attempt" is in fact (AP) guided.
To conclude, the APB rule is good, useful and badly needed, but for C3 APCH w/NO DH, do the reasons for the rule ever materialise and come together in a 4D world?
The approach RVR limit is set for 1000 ft (used to be OM or equivalent), to achieve a certiain thing. In my eyes, that is to increase system-wide safety level by reducing human, fallible component/involment.
The hazard:
. get-home-itis
. being overly mission oriented (busting minima)
The risk
. bending aluminum due to having no means to ascertain wheter you are just a cowboy getting lucky or plain sucidal (IMC with no vis reference). < no more safety stops (cheese slices) to keep all alive.
The aim of the rule, as I understand it, is to statistically reduce the exposure to above mentioned hazards, thus - in the greater scheme of things - avoid the associated risks. If the WX is not favourable by 1000 ft, let's forbid ourselves from even trying as we wish to avoid the dark side of what trying may bring.
Before continuing I confess that the safest flying is no flying at all. Yet the industry needs to be practical, hence - for instance - the wet/contaminated allowance for reversers, screen height of 15 ft and TORA-to-lift-off relationaship for instance.
My point being: with C3 fail-operational system, the landing is "never" compromised. No need then to set gates against a misguided attempt, because the un-acceptable risks are just not there anymore since the "attempt" is in fact (AP) guided.
To conclude, the APB rule is good, useful and badly needed, but for C3 APCH w/NO DH, do the reasons for the rule ever materialise and come together in a 4D world?
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An aircraft using LAND 3 was designed to have RVR advisory
The answer on the "Required RVR" can depend on the applicable "Authority", authorization (e.g., Op-Spec) and the specific authorization for that aircraft, crew, and runway, ...and to some extent even the aircraft and system type, such as if SBs apply. However note that from a safety perspective, aircraft designed with "LAND 3" capability and demonstrated to meet FAA AC120-28D, with all relevant systems operating normally, and operating within limits such as for wind components, typically are fully capable from a technical perspective of safely landing with TD, MID, and RO RVR used only as advisory, regardless of report value. It is only a matter of time before some regulatory authorities catch up to the capability of the technology being used, when using properly protected modern ILSs, and especially GLS, which is already vastly better than ILS.
