View Full Version : Unusual MET scenario
A few days ago a very low, thick layer of clouds blocked the threshold of runway 25.
JUST the threshold.
All the rest was CAVOK, and we easily made a visual approach on the opposite runway.
The Metar reported a visibility of a few hundred meters, but actually, besides a very little portion of the runway end, it was CAVOK.
My question: LEGALLY SPEAKING, is it OK to land when the official report gives you a visibility BELOW minima under these circumstances? (once again, 9/10 of the rwy fully cavok).
Jetstream Rider
2nd Jun 2005, 10:06
With the introduction of "prevailing visibility" I think the report on the ATIS or from the ground should reflect the fact that most ot the airfield was clear, (although the METAR will not as far as I know).
I can't remember what the law says here, I think it is "the visbility must be..." rather than "the reported visibility must be...".
I have a feeling that in France it is the reported visibility. In the UK it is the actual visibility. In other words if it came to defending yourself you could be in trouble in France, but off the hook here.
Pegasus77
2nd Jun 2005, 10:36
LEGALLY speaking, we only need sufficient visibility on the FAR-field-length, meaning that on a 10000 metre runway, only the first 2 kilometres or so (depends on your required landing distance) must be ok, the rest can be densely fogged.
Therefore in said scenario I would have asked for RVR's along the runway.
There is always a danger in landing if you see the runway from above, but the given visibility is incredibly low. From above, the fog-layer could be only 30ft thick and appear non-existent, then when the nosegear hits the runway, suddenly you try looking through 12000ft of fog.
P77
bookworm
2nd Jun 2005, 11:22
is it OK to land when the official report gives you a visibility BELOW minima
Do you really have visibility minima? Aren't they RVR minima? If the latter, then RVR is runway-specific.
With 'visibilty minima', you cannot 'factor' met vis as it is not a 'minimum' RVR. PRN is one place where this has caused me a problem.
Pegasus77
2nd Jun 2005, 15:13
What is the official report?
The METAR? The ATIS? Or the TWR just before touchdown?
Or could your own estimate be official enough? (like for a LOVIS departure, where you can count the amount of visible CL-lights and thus decide how big the 1st RVR really is compared to the one broadcast on the ATIS)
P77
LEM - it would help if you could give us:-
The minima for each runway - are they VISIBILITY or RVR based?
The reported visibilty (RVR?) for both runways.
(PS was it PRN?)
It can happen that the met office or tower is sitting in a fog bank while the real airfield basks in warm sunshine!:D Happened to me in BCN once with sea fog around the tower. 10k+on all runways except 02.
You're right Gentleman, RVR is controlling but visibility is not, so even if the tower reports a very poor visibility (no RVR available), you can start the approach and decide wether to land or not.
The ATC being "african style" in that place (southern Italy) and the met report buried in a long blah blah, I then got a bit confused about the legal aspect...
This is really a case where you ask yourself "Why the hell I had this stupid doubt??" :O
Maybe I need a vacation, after more than one year without a single day of leave :ugh:
Sorry for the waste of time.
I believe if RVR is not available, you have to convert reported visibility into RVR, using the conversion factor as stated in JAR-OPS for the prevailing conditions (night/day. full approach lights or not).
Then the approach ban would apply, so getting past the outer marker/equivalent point is the tricky bit, after that...if you have your required visual cues, land!
Can I start a visual approach if RVR is 300 meters? I don't know, will ATC even clear me for a visual approach? Probably not!
Regards,
Ziggy