Low Visibility Procedures
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Low Visibility Procedures
I heard on the ATIS today "low visibility procedures in force". Is this included to inform the crew that the ILS is "protected"? If so, can the crew attempt a CAT II/III approach soley based on this, or is specific ATC clearance required?
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LVPs in force means that the airport is operating in accordance with the requirements laid down for such operations. One such requirement is for the ILS sensitive areas to be protected, another would be regarding power supplies etc.
The crew still require normal clearances for use of the ILS, the LVO procedures in force is what we need to hear to tell us that we can operate in accordance with our regulations to do such an approach.
PP
The crew still require normal clearances for use of the ILS, the LVO procedures in force is what we need to hear to tell us that we can operate in accordance with our regulations to do such an approach.
PP
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If so, can the crew attempt a CAT II/III approach soley based on this, or is specific ATC clearance required?
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Not necessarily nor systematically, although it is (nearly) true in Europe.
Most airport will declare LVO when the Wx is at or near Cat I minima.
If RVR is still Cat I, Cat I crew and craft will land normally; Would one want to do a Cat II, or Cat III with these conditions, he would have to request it, as it requires extra separation between approaching aircraft and extra protections and redundancies on the airport equipment.
Then the RVR goes Cat II and the Cat I folks are banned. Cat II/III pilots now have to "declare" they are authorized Cat II to be cleared for the approach. Same at Cat III RVR where Cat II are banned and Cat III have to be authorized to be cleared.
Just to confuse you a bit, once in Cat III, you still have to consider
Cat IIIA, CatIIIB with DH and CatIIIB without DH.
More confusion? In Cat IIIB, crew will have to remember the alert height and, whereas in usual IFR, the lower the authorized DH gives the better chance to land, the higher alert height will provide the better chance to land; figure that out!
And do not forget that if the airport is declared Cat III, and the RVR increases to Cat II or even I, no one under Cat III authorisation will be cleared to approach; one of the main reason being that in Cat III, the VASI/PAPI are switched off. Why would that be?
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Lemper, most of what you said makes sense. I have no idea what the "alert height" is though 
No idea, something to do with their inaccuracies at low altitude and the possible distraction of seeing 4 reds or 4 whites at DH?
If the crew were refused an approach due to a change in VIS/Cloud base, could they declare a new category of approach provided they haven't passed the IAF?
And do not forget that if the airport is declared Cat III, and the RVR increases to Cat II or even I, no one under Cat III authorisation will be cleared to approach; one of the main reason being that in Cat III, the VASI/PAPI are switched off. Why would that be?
If the crew were refused an approach due to a change in VIS/Cloud base, could they declare a new category of approach provided they haven't passed the IAF?
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When I started flying commercially it was company procedure to specifically request a CAT2 ILS and obtain that clearance before commencing descend below CAT1 minimums. Obviously you would get this clearance before starting the approach at all. However in recent days it is no longer required to get the "Cleared ILS CAT2 approach" to actually do the CAT2 approach in LV weather. The ATIS statement of LVP in force includes as stated previously that the ILS sensitive area is cleared, the number of A/C movements on ground is reduced and that the separation between airborn A/C's are increased to cater for CAT2 & 3 approaches. ATC doesn't care weather you descend to 200, 100 or 50' feet on the ILS before making a Go-Around. As long as the LVP is in force you as a pilot can be sure that adequate? separation is provided so that you can make the approach.
So the answer to your question is YES!
So the answer to your question is YES!
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Confusion between ATC LVPs and LV Safeguarding...
We found it necessary some time ago to split out the twin conditions of Low Vis Safeguarding being in place and ATC carrying out their Low Vis Procedures.
In order to protect the Localizer and Glideslope signals, we (aerodrome management) place barriers and issue warnings to prevent vehicles and aircraft from accidentally penetrating the Sensitive Areas - yes, Glideslopes have them, too. At LGW we do this as the RVR becomes 800m and is expected to fall to 600m and/or cloud ceiling becomes 300' and is expected to fall to 200'. We also assure that a standby power supply for the runway lighting and the ILS is capable of switching over within the timeframe required - one second normally.
Only once all the above is in place, can ATC declare that their Low Vis Procedures are in force, that is, they will increase the separation of aircraft to ensure that there is no preceding a/c within the Sensitive areas, whether approaching, vacating or departing, when a landing aircraft is within 2 miles.
Now, we used to hop about the airfield taking the safeguarding off every time the cloud lifted and causing delays whilst we put it back every time it went down again, when the Safeguarding and Procedures we all one and the same. By taking a common-sense approach, we now apply the safeguarding at the onset of poorer weather and only remove it when all danger of Low Vis has passed. Thus, ATC can move in and out of their procedures at will, knowing the aerodrome is Safeguarded. This means thay can take maximum advantage of every slight improvement in the IRVR, for instance, to move more traffic. Great!
The confusion comes from those who do not understand the difference between Safeguarding and Procedures. They hear a message saying 'ATC Low Visibility Procedures are cancelled' and think they can approach a CAT I bar instead of holding at the CAT III, or they can resume freeranging, if in a vehicle. Only they can't because the SAFEGUARDING is still in place. Hopefully our education programmes are reducing the instances of confusion. (Vehicle drivers, for instance, get a written test every 3 years around just this sort of scenario).
TheOddOne
In order to protect the Localizer and Glideslope signals, we (aerodrome management) place barriers and issue warnings to prevent vehicles and aircraft from accidentally penetrating the Sensitive Areas - yes, Glideslopes have them, too. At LGW we do this as the RVR becomes 800m and is expected to fall to 600m and/or cloud ceiling becomes 300' and is expected to fall to 200'. We also assure that a standby power supply for the runway lighting and the ILS is capable of switching over within the timeframe required - one second normally.
Only once all the above is in place, can ATC declare that their Low Vis Procedures are in force, that is, they will increase the separation of aircraft to ensure that there is no preceding a/c within the Sensitive areas, whether approaching, vacating or departing, when a landing aircraft is within 2 miles.
Now, we used to hop about the airfield taking the safeguarding off every time the cloud lifted and causing delays whilst we put it back every time it went down again, when the Safeguarding and Procedures we all one and the same. By taking a common-sense approach, we now apply the safeguarding at the onset of poorer weather and only remove it when all danger of Low Vis has passed. Thus, ATC can move in and out of their procedures at will, knowing the aerodrome is Safeguarded. This means thay can take maximum advantage of every slight improvement in the IRVR, for instance, to move more traffic. Great!
The confusion comes from those who do not understand the difference between Safeguarding and Procedures. They hear a message saying 'ATC Low Visibility Procedures are cancelled' and think they can approach a CAT I bar instead of holding at the CAT III, or they can resume freeranging, if in a vehicle. Only they can't because the SAFEGUARDING is still in place. Hopefully our education programmes are reducing the instances of confusion. (Vehicle drivers, for instance, get a written test every 3 years around just this sort of scenario).
TheOddOne
