RVR or Met Vis (Takeoff minima)

[PitotTube]

This is a photo of the takeoff minima. Is this RVR or Met vis? Anyone have a clue? Where can I find info about this.
http://img338.imageshack.us/img338/6295/img1399f.jpg

cheers

[Nightrider]

Every publisher of these manuals has also a binder with the content "General".
In this you will find a section which explicitly describes everything they use on their charts; usually nicely sorted, i.e. Abbreviations or Symbols, there is also a section which shows a picture like yours with all details explained.

[eckhard]

As far as I'm aware, it's either.

In other words, if the airport has an RVR system, then you use the reported RVR. If not, you use the met vis.

Unlike for an approach, you can't factor the met vis to get an RVR for take-off (under EU rules).

As your example states that 'LVP must be in force', it sort of implies that there will be an RVR system in place (but not definitely).

Which airport are you talking about?

Eck

[PitotTube]

The publisher of this chart is Jeppesen, and when I read the "general content" binder it says that it will "specify what it is".. but in this case??? Nothing is specified on any other page neither??

- The airport is Stockholm Skavsta airport ESKN/NYO

[chevvron]

The figures shown on the chart conform to the RVR for departures from a runway with high intensity edge lights and centreline markings; there should also be yellow caution zone edge lights at the stop end.
As far as I'm aware, if you have approved LVPs, you must have a means of determining RVR as part of the LVPs, but I recognise I could be wrong there.

[spring222]

It has to be RVR...
For lower visibility takeoff..LVTO..it is always RVR

Visibility is a general visibility or sector visibility whereas RVR is related to Runway visual Range which governs the LVTO..and it is same for landing as well always RVR.

Minimas are based on RVR.

If you open the next question posted by Big bad d regarding the EU ops link and go through the manual you would see that all the minimas mentioned states RVR

[Spitoon]

Although it is unusual, it is possible for only met vis to be available at an aerodrome which supports LVOs. The most likely situation where this might occur is an aerodrome that has no instrument approaches but sufficient lighting/markings to permit departures in poor visibility.

[eckhard]

I agree with Spitoon, but would add that even at an airfield with ILS it is possible to not have RVR transmissometers. Oxford, UK (EGTK) is an example.

Oxford has an ILS approach to RWY 19 but no RVR system. The minima are 460 (200) ft and 750m. As there are no transmissometers, the quoted 750m must be a meteorological visibility (met vis). Of course, this met vis may be factored under EU-OPS rules, depending on day/night, etc.

The take-off minimum is 250m, as the runway has centreline markings and edge lights. Again, this has to be a met vis, although in this case factoring is not allowed.

At Skavsta, there is an RVR system on RWY 08/26 and the take-off minimum is again 250m as there are centreline markings and edge lights. Interestingly, the same take-off minimum is applicable for RWY 16/34 (as shown in the attached photo) even though this runway has no RVR system.

The ILS minima are 330 (200)ft and 550m and again this would be an RVR. If the RVR system failed, the met vis would be used instead.

LVPs can be invoked at 'big' airports, where ground radar and stop bars, etc will control the ground movement of traffic. At 'simpler' airports (no disrespect), LVPs can still be in force, provided that the airport operator "takes all reasonable steps to ensure either that the aircraft in question is the only traffic on the manoeuvring area at the time of take-off or landing or has another system in place to ensure that the runway is clear of other trafffic...." (or I believe words to that effect).

Anyway, to return to the original question, I reckon that the quoted visibilty at any airport for take-off or landing can be RVR or met vis. After all, if the RVR system should fail, what are you going to do? Divert? No, use the met vis.

Eck

[Spitoon]

For Cat I approaches a 'human observer' RVR can be measured. This is typically done by someone counting the number of edge lights that are visible from a particular place near the runway threshold. To do this the lights normally need to be 'calibrated' periodically - that is, the number of lights visible need to be converted into a RVR value. In the UK the CAA do this (certainly used to anyway) but it's costly and as soon as most airports go Cat II/III they get transmissometers and drop the human observer option.

I suspect that if Oxford reports RVR it will be based on human observer measurements. Indeed, I would guess that the majority of Cat I (only) airports that report RVR use the human observer method.

[eckhard]

Good point Spitoon, I hadn't thought of that.