Lvp's and CATII/III approaches
 

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. (An Irish aerodrome)

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.

Is this correct? I ask this because my company's SOP's require that lvp's are in place before CATII/III approaches are carried out. However, when cloud is broken 200' and rvr greater than 550m ATC will offer CATII approaches but will not enforce lvp's (because from their perspective they are not necessary).

The reason we want to do cat II rather than cat I approaches in these conditions is because the cloud base is rarely a uniform layer and sometimes you can arrive at minimums in a section of cloud with a downward bulge. It is better to land off a cat II than go-around off a cat I in this situation.

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. Are the company SOP's inadequate?

I appreciate clarification.

Low visibility procedures - RVR (touchdown) is less than 800m and/or ceiling is at or less than 200 ft.

Wonder Boy,

There are minimum legislative requirements determining when LVP's will be introduced, particularly visibility falling to 1500m (CAT I) or below and cloud ceiling of 200' or less. Obviously for CAT II or III approaches the vis minima are more restrictive (800m or lower) but the cloud ceiling minima are more difficult to stipulate as a lot of the time different minima could apply to different aircrew flying the same approach depending on crew qualifications and airborne/ground equipment available.

Also, there are different methods of implementation (and different names for the various methods!) at different airfields, and will be detailed in that airfield's ATC instructions or MATS II. However, each method will have to have been fully audited and approved by the relevant regulator before it can be used.

I think what you are referring to here may be an airfield where the runway and vehicle holding points are far enough from the runway centreline that they provide the equivalent of CAT II/III protection in all weather conditions, and the vehicle holding/access points have some method of positive control that enables their use in poor or marginal conditions without a requirement for them to be physically blocked off (i.e the use of traffic lights that are switchable from the tower, for example).
Provided that all of the relevant holding points and airfield access points are visible from the tower and the controller can therefore maintain positive control of the manoeuvring area, thereby protecting the ILS sensitive and critical areas, then there is no reason why CAT II ops cannot proceed without the actual declaration of LVP's. Obviously there will have to be some form of airfield procedures enforced to ensure the required safeguarding, but that does not necessarily equate to full LVP's.

An airfield at which I previously worked got around the problem to which you refer by having various stages of LVP's depending on the conditions which prevailed or were forecast. With reference specifically to the scenario you mentioned, where the cloud ceiling fell to 200' or below (either at the 'field or affecting the approach) but the visibility remained good below cloud, the procedures adopted were known as "LVP Cloud", and provided the required safeguarding for the approach aids without having the airfield surface traffic grind to a halt unnecessarily! It meant that it was (almost) business as usual on the ground, while the airborne crews were satisfied that they had the minimum equipment protection in place to guarantee a safe approach.

EastCoaster,
Thanks for the reply. It clears things up alot. From your information, it would seem to me that there is a slight discrepancy in perspective when I compare company SOP's to airfield procedures.

If the airfield in question described CATII protection as 'LVP cloud' when offering CATII approaches with 'broken 200', rvr 550m', we would be able to carry out the approach.

This is because our SOP simply states 'LVP's must be in place before a CATII/III approach is commenced'. I think this SOP is too restrictive/inflexible given that there are different definitions applied to methods implemented at different airfields (i.e. whether CATII protection is LVP cloud or not in the conditions described).

No problem WB, glad to have been of assistance.

I should clarify though, before anybody picks up on this thread and misunderstands what I was getting at, the condition "LVP Cloud" described a specific state of operations on the ground only, applying to the airfield manouevring area, and as such was completely transparent to aircraft making an approach to land.
The ATIS was broadcasting "ATC Low Visibility Procedures in force", and the aircrews were therefore completely unaware of any difference in operating procedures from the more traditional "full" LVPs. The system was designed to provide full ILS signal protection, while at the same time allowing airfield surface ops to continue while it was still practical to do so.

A very canny piece of planning on the part of the SATCO who came up with the idea I think. Well done to that man :ok:

Hope this helps.