CAT II/III and the requirement for LVP's

[Wonder Boy]

The airport I most often operate into offers CAT II approaches without enforcing LVP's when cloud base is at or above 200' and vis is at or above 550m.

For example: weather is broken 200' and vis of 10K.....

ATC offer the CAT II approach and apply procedures for protection of CAT II equipment (stop bars, separation, equipment redundancy...etc). However, because the entire airfield is visible from the tower below the cloud, ATC can visually confirm that gates are locked and there are no vehicles/aircraft infringing the protected zones.

It is only when the vis/cloud base conditions deterioriate below 200'/550m that they enforce LVP's.

Essentially, they view procedures for protection of CATII approaches as separate from LVP's. They see CATII protection as a 'high-vis' procedure when vis is at or above 550m and a low vis procedure when vis is below this.

My question is; are they correct?

The ATC section in the Jeppy (section 7.11.4) does refer to CATII/III protection procedures and low vis procedures as separate things. However, my understanding was that LVP's were originally introduced (1988 I think?) with the primary intention of protecting CATII/III approaches and facilitating low vis takeoffs.

I appreciate clarification.

[411A]

My question is; are they correct?


Yes, generally speaking.

IF you fly an L1011, it would not make a difference anyway...little disruption for non-compliant airfields..IE, The 'ole TriStar is simply a better product.:ok:

[White Knight]

LVP's incorporate 'protection'.. They also have extras such as designated taxi routes, flow control, closed airport roads etc etc..

[Wonder Boy]

I also believe they are correct. However, I'm aware that many airlines (my own included) have SOP's which require LVP's to be in operation in order to carry out a CAT II/III approach.

So, with cloud broken at 200' and rvr 550m, and CAT II ils protection procedures in force (but no lvp's in force), our SOP's preclude us from carrying out a CAT II approach.

As I mentioned, I know this is SOP for at least several airlines.

Are these SOP's inadequate?

Or, are procedures for protection of cat II/III ils integrity, low vis procedures, even with 'high' visibility?

[Sir George Cayley]

200' cloud ceiling and 550m vis at the limit of CAT l

Therefor that's the approach you should be making. Why do a CAT ll APP op in CAT l conditions.

CAT 1 is in the UK consideres as low vis and therefore should be covered in the Aerodrome Manual and ATC MATS Pt 2.

For a CAT ll approach the localiser sensitive area (LSA) has to be safeguarded out to 150m (I think) though 137 is allowed in UK.

When flying a CAT ll app are you using A/P? What D/H do you use. And, where is this airport?

Sir George Cayley

[Wonder Boy]

Hi Sir George.

A cloud base is rarely a completely uniform flat layer. I've found from experience, when doing cat I approaches with a base at 200' one can sometimes fail to see any of the approach lighting system at minimums due to the fact that you may reach minimums in a section of cloud that has a downward bulge. Why raise the possibility having to carry out a missed approach by doing a cat I in such conditions when cat II facilities are there and ready to be used?

Do you know what the Aerodrome Manual and ATC MATS Pt2 have to say with respect to whether or not procedures for protection of cat II/III ils are defined as LVP's? I'm going to see if I can get access to those documents.

Yes, A/P is used and the airport is in Ireland. I'd rather not say what airport but I'll say the cat II DH IS 122 radio....... Although I'm not sure why you ask about these factors given the nature of my query?

Thanks.

[Henry VIII]

Checked on Jeppesen General Flight Supplement Booklet, ch. Regulation, JAA AOM, pagg. 601 and following.

Actually LVP in force are required for LowVis TO only. No requirements neither for CAT II nor CAT III.

Looks strange to me, but seems legal. Thankfully many company SOPs require LVPs in force below CAT I.

[Wonder Boy]

Thanks Henry, I'll check it out.

I think lvp's are mandatory with conditions below 200' cloud base and rvr 550m (i.e. the bottom line for cat I).

However, with conditions at these cat I limits, ATC report 'cat II approaches available and protection in place'. Despite the fact that we would like to avail of the cat II, we cannot because ATC will not enforce lvp's (because from their perspective they are not necessary), even though lvp's are required for such an approach as per SOP's.

[The Tramp]

Is there a list of CAT III capable airports? Easy had their own at the front of the Jepps.

[ComJam]

From a purely technical point of view, as long as the CAT II/III protection (of both Localiser and Glideslope) is in place there should be no reason not to accept and CAT II/III approach regardless of the LVP state.

Probably being stupid here but....if LVP's don't need to be in force for landings in such conditions, why are they required for Take-offs?

Cheers

[Henry VIII]

Is there a list of CAT III capable airports?As far as i know jepp can produce a tailored list according company requirements in various format. At an extra cost.if LVP's don't need to be in force for landings in such conditions, why are they required for Take-offs?
May be to protect against runway incursion.

[411A]

From a purely technical point of view, as long as the CAT II/III protection (of both Localiser and Glideslope) is in place there should be no reason not to accept and CAT II/III approach regardless of the LVP state.



Technically correct, however some airlines (not certainly all, however) require LVP in place.
if LVP's don't need to be in force for landings in such conditions, why are they required for Take-offs?



The short answer is, they aren't, at some airports....especially outside Europe/UK.
Some takeoff minima are quite restrictive, however, again depending on the specific airport and regulatory authority.

[ali1]

My understanding is that aerodromes in the uk must have lvp's in force when cloud base is below 200' and vis is less than 600m. Correct????

[windowjob]

Not quite correct, Cloud CEILING below 200ft and vis less than 600m.
But just because the wx has got to this doesn't mean that LVP's are automatically in force - only when the Airfield is Safeguarded (gates locked, contractors cleared, barriers at vulnerable points out), all vehicles are accounted for i.e free ranging stopped and vehicles left the maouvering area, the standby generators running and powering the essential stuff (so that if it fails there's an instant switch over to mains as opposed to the delay in running up if it were the other way round, the ILS confirmed as Cat2/3, the correct spacing in place to allow LVP's to take place, traffic no closer to the Runway than Cat3 holds, pilots informed - only then can LVP's start. You may be given RVR/Cloud and told Safegurding not completed yet and LVP's not yet in force, which may take 20mins or so if all goes well. You have the choice of making an approach or waiting for protection.

[Spitoon]

The procedures implemented to support all weather ops vary hugely across the world. In the UK and many other parts of Europe the view is generally taken that declaring 'LVPs in force' tells pilots that it's safe to make a Cat II/III appraoch (assuming such procedures are published). But the procedures applied at the airport do far more than protect the ILS sensitive areas.

The actual procedures will often vary depending on the visibility on the ground or from the tower. Essentially, as the ground visibility falls more and more restrictions on ground activities are permitted, the intention being to prevent a variety of hazards to aircraft operations.

For example, one of the first things that usually happens is that contractors (i.e. those less familar with the airport or airside procedures) working on the manoeuvring area will be withdrawn - largely to stop them getting lost and going onto the runway.

When the visibility from the tower is limited restrictions are put in place to overcome the fact that the controller cannot see where the aircraft are. When the visibility gets so bad that the pilots are unlikely to be able follow instructions to follow the ABC A320 or whatever, further restrictions are put in place.

In the old days there were some fairly draconian restrictions that were implemented as soon as the weather reached certain criteria. This was not very flexible and often invoked unjustified limitations - I can recall days when there was some cloud (BKN I think) at around 200ft and 50 KM visibility below it.....and contractors had to stop work, almost no vehicles were allowed on taxiways, and so on.

Nowdays LVPs can be tailored to the operations at the airport and only protect whatever needs to be protected for safe ops in the prevailing conditions. But the principle that 'LVPs in force' means that the ILS is protected for Cat II/III ops remains.

It's not a perfect situation. There have been some incidents where misunderstandings about what is protected or what type of operation is permitted in LVPs. The one which sticks in my mind - or, at least, vestiges of it stick in my mind - is a Speedbird B737 (or maybe a B757) at Manchester which suffered a substantial uncommanded roll at 200ft or so during a Cat II approach because the ILS sensitive area was not protected.

As for LVPs for departure, that just means that measures to protect the runway from incursions and other things deemed necessary for movements on the ground are in place. For similar reasons you'll find LVPs at airports with only Cat I approaches or, somestimes, no precision approach at all.

[Dan Winterland]

Yes it is legal, strange as it may seem. One of our destinations is on a very flat area close to the coast. It can have a ceiling of under 200', but very good vis and they frequently don't use LVP with CAT II being used. My company was bought by a bigger one not long ago, and their SOPs which we now use state that LVPs must be in force to fly a CAT II. It hasn't happened yet, but I suspect the policy will change with the first diversion!