RVR measurement
 

When RVR is measured by an obsever, can anyone tell me what height above the runway it is supposed to be done? I seem to remember from my CPL met days that it was about 12 feet but can't be sure.

Gday Fella, it probably depends on the temperature but if the airfield doesn't have automatic equipment (like Melbourne) and it is Winter, then it is normally done from the sitting position in the front seat of the 4x4 that the observer is sitting in.

Sorry I couldn't be more help than that!

5 metres above ground is the figure in my old MO Observers Handbook.

According to CAP168 the observers eye height should be 5m above the runway surface

Thanks everyone......Keg having watched them do it at SYD during the past week, I was concerned with the method used i.e. front seat of a 4WD.
I remembered approximately the method used in Europe in the old days and have also seen it done in AKL in the last year or so.
So one has to ask how accurate these SYD readings were? I have my doubts!

Are there any ATC people who can help?

Years ago, the fire service would count lights from the cab of the fire truck. (3 m above ground)

The met people should be using 5 m. A 4 wd assessment is not really valid.

Better still electronic measurement.

... at LST in the fogginess of darkest winter night ... I recall a useful alternative .. ... the crew would line up ... count lights ... one (on the left) .. two (on the right) and so forth ... seemed to work pretty well ..

Canadian practice (AIP RAC 9.20 et sequ) dictates using the term RVR when visibility measured electronically with some form of automatic sensor. Runway lights set at levels 1-3 for 'normal' reporting. If settings of 4 or 5 are used then ATC will give RVR and light setting used.

If Mk I eyeball used then the term is "Ground visibility". How ATC measure this is a closely guarded secret, but may involve runway lights <img src="smile.gif" border="0">

Rgds
CB

[ 06 January 2002: Message edited by: Code Blue ]</p>

In the UK the term IRVR (Instrumented Runway Visual Range) refers to electronic measurement. The 'Human Observer' method gives RVR, although in either case normally passed on the R/T as "RVR".
The Official Met. visibility is assessed by a qualified 'Met. Observer', who will either be a Met. Office employee, or more usually these days, at Civil Airports, a member of the ATC staff who has obtained the appropriate training and qualification.

I remember at EGSS in the mid 80's that the RVR collection process was very much the human observer method. Basically, there was a shed on stilts on the eastern side of the runway. In this shed was a heater, a telephone and a decode sheet. Every 30 mins the tower would phone up and you would count how many opposite side runway edge lights you could see - "x" many= 400m "y" many = 450m and so on, not very scientific, and a damn lonely job punctuated only by the discrete pile of "adult" reading material (ahem!!) that got the poor unfortunate through a foggy night shift!! <img src="smile.gif" border="0"> <img src="smile.gif" border="0"> <img src="smile.gif" border="0"> :) :) :)