CAT 3B with 15 ft decision hieght
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? when it is the lowest approved minima for an approach?
It will then be used, when required, in preference to higher minima?
I'm sorry, but I don't understand the question? If the weather is such that it requires those limits, then it will be used, if approved????
It will then be used, when required, in preference to higher minima?
I'm sorry, but I don't understand the question? If the weather is such that it requires those limits, then it will be used, if approved????
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For example at CDG 08L, DH 22 ft with RVR 75m, this is a state minimum and completeley unpractible at least for the type I am flying (A 330). Because at 22 ft with RVR 75 m, there will be no visual clue to make a decision.
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So, we haven't progressed much since the Trident in the 60's (or was it the Varsity in the 50's) due to nonsensical DH's, rather than lack of aircraft capability. As prev poster said, not much point in a DH, if you will have no visual cues to enable the decision making process.
I know from practical experience, that 175m vs 200m looks very different from 50'DH (RVR dropped after 1000'/FAF , as you asked) so I am guessing that the relation of RVR/DH/Cut off angle would make any DH with RVR 100m or less, a bit of a theoretical nonsense , with no practical purpose. If they are trying to argue it is the last moment to check all is OK , & if so land, I would suggest that is what is being done constantly on a Low Vis appr by the monitoring ( & handling ! ) pilot, so no reason for applying a DH there either.
AFAIK BA had 75m No DH on the 757 ( & no doubt other fleets) surely the only sensible limit for an aircraft with automated after landing centre-line guidance avail. Would take a while to find you in the event of some emergency after /during landing, but that is a whole new discussion topic.
I know from practical experience, that 175m vs 200m looks very different from 50'DH (RVR dropped after 1000'/FAF , as you asked) so I am guessing that the relation of RVR/DH/Cut off angle would make any DH with RVR 100m or less, a bit of a theoretical nonsense , with no practical purpose. If they are trying to argue it is the last moment to check all is OK , & if so land, I would suggest that is what is being done constantly on a Low Vis appr by the monitoring ( & handling ! ) pilot, so no reason for applying a DH there either.
AFAIK BA had 75m No DH on the 757 ( & no doubt other fleets) surely the only sensible limit for an aircraft with automated after landing centre-line guidance avail. Would take a while to find you in the event of some emergency after /during landing, but that is a whole new discussion topic.
Would take a while to find you in the event of some emergency after /during landing, but that is a whole new discussion topic.
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DH-25
There it comes where the individual person at the regulatories buddy has no technical clue nore any practical understanding what are the consequences of issueing these none sensed restrictions.
CAT IIIb was implemented for fail safe operation where the Autopilot is satiesfying the requirements for safe touchdown and rollout. Now with DHīs implemented of 25 feet, 22 feet, 15 feet or whatever the Regulatory Authority is excercising the "right" to do so, mainly to show that they are concerned of safety.
In the reality it jeopardizes and undermines that effort. Mostly at or below 27ft, 25ft, depends on Type, the Autothrottle walks back to idle and the flare mode starts. That is the moment the Airplane will touch the RWY, now you have that moment where you "decide" to Go-around. Pushing TO/GA button and the acceleration of the Engines takes much longer with, in most cases, the main wheels touching the RWY momentarily and then taking off again to. It does not demage the Airplanes, they are built to do so. TMīs tell you that, in some SIM-excercises you can also demonstrate that.
The common PAX will be the one who is not convinced by the fact that the wheels touched and we could not "land".
The surprised Pilot can revert his decission that the ground is reached and disconnects the Autopilot to "stay" on the ground and starts to fight with a out of trim plane that shows the nose into the sky and Centerline getīs lost quickly. Situation like that getting dynamic quickly and then out of hand / ability. Yes I know, when one Crew Member calls Go Around we do that and stick to the maneuver with a missed approach followed that bulked landing but the human is still the weakest part in the chain and there is, at least until today, not maintenance programm invented that integrates the human into the closed loop.
Food for thought, I am open to take another sight as well and be happy if someone could educate me further.
Fly safe and land happy
NG
CAT IIIb was implemented for fail safe operation where the Autopilot is satiesfying the requirements for safe touchdown and rollout. Now with DHīs implemented of 25 feet, 22 feet, 15 feet or whatever the Regulatory Authority is excercising the "right" to do so, mainly to show that they are concerned of safety.
In the reality it jeopardizes and undermines that effort. Mostly at or below 27ft, 25ft, depends on Type, the Autothrottle walks back to idle and the flare mode starts. That is the moment the Airplane will touch the RWY, now you have that moment where you "decide" to Go-around. Pushing TO/GA button and the acceleration of the Engines takes much longer with, in most cases, the main wheels touching the RWY momentarily and then taking off again to. It does not demage the Airplanes, they are built to do so. TMīs tell you that, in some SIM-excercises you can also demonstrate that.
The common PAX will be the one who is not convinced by the fact that the wheels touched and we could not "land".
The surprised Pilot can revert his decission that the ground is reached and disconnects the Autopilot to "stay" on the ground and starts to fight with a out of trim plane that shows the nose into the sky and Centerline getīs lost quickly. Situation like that getting dynamic quickly and then out of hand / ability. Yes I know, when one Crew Member calls Go Around we do that and stick to the maneuver with a missed approach followed that bulked landing but the human is still the weakest part in the chain and there is, at least until today, not maintenance programm invented that integrates the human into the closed loop.
Food for thought, I am open to take another sight as well and be happy if someone could educate me further.
Fly safe and land happy
NG
Dog Tired
Quote:
Would take a while to find you in the event of some emergency after /during landing, but that is a whole new discussion topic.
That is indeed the reason for the 75m RVR requirement. In the early Cat III discussions, the fire services at LHR argued that they would have difficulty in finding an aircraft in distress if the visibility was any less.
Would take a while to find you in the event of some emergency after /during landing, but that is a whole new discussion topic.
That is indeed the reason for the 75m RVR requirement. In the early Cat III discussions, the fire services at LHR argued that they would have difficulty in finding an aircraft in distress if the visibility was any less.
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Hi 737NG,
Not quite sure what you mean .... but in the old days on TriStars, we could only do CAT IIIB No DH AutoLands in the UK. Everywhere else (e.g. Paris, Frankfurt etc.) we did CAT IIIB with a mini DH of about 15ft. We had to see "One centre line light or marking" in order to continue to AutoLand. There is no way you could do a manual landing from it, due to the absence of the visual clues - so once you'd pressed the TOGA switch at DH - you were going around and would most times kiss the runway with the wheels.
Yes I know, when one Crew Member calls Go Around we do that and stick to the maneuver with a missed approach followed that bulked landing but the human is still the weakest part in the chain and there is, at least until today, not maintenance programm invented that integrates the human into the closed loop.
In the early Cat III discussions, the fire services at LHR argued that they would have difficulty in finding an aircraft in distress if the visibility was any less.
Agree with B737NG, these DHs of circa 15 ft are pointless and indeed counterproductive to safety IMHO
It was one of the reasons. Also, the minor matter of the aircraft being able to taxi to the gate.
Taxying to the gate at Heathrow was facilitated by a combination of green centre-taxiway lights, ground movement radar and compass headings. The airline would have probably have liked something like 50m - although how practical that would have been for later wide-body aircraft is for others to say.
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I taxied out from the old circular space station terminal (still T1 ? can't remember ) once at CDG for departure on 09L. RVR was above the 125 we needed to go (although probably not by much) Taxying uphill from satellite 3 we had to stop, as (even in a 737) we literally couldn't see enough to continue. I imagine 75m in a 757, never mind a 777/747/A380 doesn't give much in the way of slant angle/vis to proceed anywhere at any rate at all.
