Lowest recorded RVR

Can be as bad as zero, often due to fog rather than low clouds, but then it may have a significant vertical gradient. I’ve seen ground covered with a layer of fog that looked like whipped cream, but only up to my chest or so, with clear air above it.

If I recall right I did have a measured RVR of 50m at ZRH at some point during the last 20 years. I think the sensors won’t record anything less than that.

Met Vis I’ve seen less than 10 m at some point, in as so far that I walked out of the door of the obs station and could not see the end of the terrace. I walked ca 3 more steps and when turning around saw nothing at all. Pretty funny feeling, thankfully not in an open space but in a limited area, so by walking straight I eventually found the door back.

I recall an accident where a plane landed CAT IIIb and ended up stuck on the runway as the cockpit could not see the ground. They sent out a car to look for him, which ended up crashing into the nose gear. The driver was severely injured. Brings back the point why CAT IIIc ops is pretty senseless, as taxiing with 0 vis is impossible.

Fog is quite intense at some airports, mainly because they have been built on drained swamps. ZRH is one of those, MUC another. Often enough, swamps are the only flat piece of real estate around, so that is why some airports are on areas which are prone to fog just by their very location.

arj1 wrote:

I know that RVR 75m is min for LVTO

Not sure for what aircraft, or what type of ops, but on my last commercial ride, the 320 series, LVTO minima was RVR125m. IIRC the slant distance was also taken into consideration to derive these numbers.
These were the conditions:
Subject to the approval of the Authority, and provided the requirements in paragraphs (A) to (E) below have been satisfied, an operator may reduce the take-off minima to 125 m RVR (Category A, B and C aeroplanes) or 150 m RVR (Category D aeroplanes) when:
(A) low visibility procedures are in force;
(B) high intensity runway centreline lights spaced 15 m or less and high intensity edge lights spaced 60 m or less are in operation;
(C) flight crew members have satisfactorily completed training in a Flight Simulator;
(D) a 90 m visual segment is available from the cockpit at the start of the take-off run; and
(E) the required RVR value has been achieved for all of the relevant RVR reporting points

(ii) Subject to the approval of the Authority, an operator of an aeroplane using either:
(A) an approved lateral guidance system; or,
(B) an approved HUD/HUDLS for take-off may reduce the take-off minima to an RVR less than 125 m (Category A, B and C aeroplanes) or 150 m (Category D aeroplanes) but not lower than 75 m provided runway protection and facilities equivalent to Category III landing operations are available.

I remember only once having had to wait close to an hour to take off, on the CATIII hold of 35R at LIMC, until the 100m RVR improved…

IIRC FAA Part91 allows a 0/0 take off.

Not legally in EASA-land, as of a rule change some years ago

I’ve done a departure in something like 100m and it is quite spooky. The same picture the whole time until you rotate and then instant zero vis. I did a video but can’t post it