VIBAL, what is it?

[clmax]

I was recently asked if I knew what VIBAL meant, found on some French Jepp plates. As I didn't know I thought it a good idea to find out. I did search PPRune but only found a reference to it a few years ago without a definitive answer.

Here's what I found out: RVR readings are taken using a transmissometer (machine), and VIBAL (visibilité balise) is a RVR/visibility reading taken by a person.

As too how Pilots can use it legally is another thing. Any ideas?

[Bus14]

Thanks clmax, another piece of trivia for me to stow away in my head.

Before the IRVR machines were installed at my base (UK, not France), the RVR was observed visually. The fire crews were deployed to the side of the runway and counted the visible runway edge lights. This was reported to the tower, mutliplied by the distance between the lights, and passed on to the pilots. All legal in UK, if somewhat old fashioned.

[blackmail]

vibal

hello everyone,

VIBAL = (french) & means : " VIsualisation BALises " = human observation of rvr along the rwy by counting the rwy lights(balises) visible when no electronic rvr is available.

kind regards,
bm

[NorthRider]

Dangers of VIBAL

True story

An fireman was sent out to "count the lights" to establish vis when no measuring equippement was available. Even though the airport was covered in thick fog he reported he could see so an so many lights. Visibility was reported as 9999. Turns out the guy was new to the airport and had counted ALL the lights he could see.

[Spitoon]

Here's what I found out: RVR readings are taken using a transmissometer (machine), and VIBAL (visibilité balise) is a RVR/visibility reading taken by a person.

As too how Pilots can use it legally is another thing. Any ideas?

RVR is RVR, regardless of how it is assessed. Commonly it is measured by transmissometer and you will often hear this referred to as IRVR, standing for Instrumented Runway Visual Range. The other common method is to count the lights, often referred to as Human Observer RVR or HO RVR. Both are standard methods (there are others) and assessments from whichever method is in use will be passed to pilots as THE RVR for a runway. I've never come across a pilot that needed to know the method of assessment - or cared, come to that.

By the by, IRVR isn't completely straightforward nowadays. IRVR used only to be assessed by transmissometers - for the last 10 or 15 years forward scatter meters have been in operational use. Again, as a pilot you'll probably not know if such a system is in use, you'll just be passed an RVR value.

HO RVR is acceptable for Cat I operations but, if I recall correctly, for Cat II/III operations RVR must be assessed by instrumented means.

If you really want to know more ICAO Doc 9328 Manual of Runway Visual Range Observing and Reporting Practices will probably keep you rivetted.

[luddite]

A veritable font of knowledge! A few airlines ago (silly industry) I must have driven everyone mad asking what on earth this VIBAL thing was. Many, many blank faces later I decided it couldn't be that important and gave up wondering - now I am enlightened. Thank you PPRuNe!