View Full Version : RVR towers
I saw the C17 landing at Lyneham and saw the RVR tower, painted in red and white checks as well. For those of you not familiar it stands for Runway Visual Range, and there are a seperate set of lights to the side of the runway lights and basically in low vis someone from thje towere will go out and count how many of these lights they can see. Up in the tower they can then work out what the visibilty is along the runway.
Sounds great but nine times out of ten the aircrew tend not to believe the figures. And it can actually be a job trying to tell the rvr lights apart from the runway lights.
Now that was how it was done in my day, as Lyneham still has an rvr tower Imguessding the system still operates like that. Can anyone enlighten me please?
Transmissometer's (http://en.wikipedia.org/wiki/Transmissometer) are used these days...
Some antiquated or to put it politely, underfnded airports/fields still rely on the poor firemen(& women) to go out and count the runway lights.
Only place I knew of that used the firemen was Leuchars, in my time at Marham we didnt have an rvr tower.
The Middle East airbase on which I worked in 1970 used a transmissometer. Never did find out who was responsible to clean the glass.....
Typically before commencing an instrument approach the reported met visibility (or RVR in this case) should be in excess of defined values. These values as measured by transmissometers (IRVR) relate to the Touchdown Zone, Mid Point and Stop End. So for a CAT1 ILS for example the values might be 550,150,150 CAT2 350,150,150 CAT3A 150.150.75. etc
The second and third readings (limits) in particular may be modified locally to meet requirements but broadly speaking would equate to low visbility take off minima. (rejected take off considerations) - It's worth noting that irrespective of reported RVR's pilots are still required to acquire prescribed visual cues prior to completing an approach. (maybe 4 lights for example)
Auto Landing is one thing.. visual cues for deceleration, stopping and vacating the runway should also be considered.
Most of you will have experienced the disorientating effects of "running into a fog bank" on the road - a similar effect may occur on landing where visibility is reduced after touchdown.
So for a CAT1 ILS a "human reported" RVR may be acceptable to commence an approach but pilots will still need to acquire the prescribed visual cues to continue it.
Visit the CAA website and search for CAP746 for more info on Met Observations at Aerodromes.
RVR Tower at Upper Heyford
A bit basic!!!!
Nasty horrible drafty little places, that leaked like buckets and were infested with flies....................Lac(w) bloggs, I have a job for you !
The old RVR towers at St Mawgan had been condemned and not used for years, before finally being torn down in 2008. St Mawgan had not had an RVR capability for quite a while as far as I know. Certainly no RVRs were reported since I returned in 2006.
Newquay airport has an IRVR. All high tech with readings taken from three sensors positioned along the edge of the runway, with the readings appearing on a small screen in front of the controllers, both in the VCR and Radar.
Wouldn't describe the Upper Heyford one as a "tower"
I have given this problem to the lady who was, certainly as far as Civil Aviation airfields was concerned, The Expert on RVR calibrations. We will see what we shall see! I ask your patience! Some of her responses may have to be sanitised!!!!!!!!!!!!!!!!!!!
Is that tower thing at Heyford an RVR tower? Im sure there was meant to be a certain height for them and it looks too short.
Sixteen foot according to a couple of web sites.
Cottesmore had them, it was a special membership of the squashed fly club only by invite ! At Shawbury it was removed bout 5 years ago as we were'nt allowed to use it.
The St Mawgan RVR towers were condemed not long before I got there ('98-'06), through a mixture of woodworm and bats, however the system was still in place and I was frequently asked to read the RVR from my vehicle, sometimes an ATC assistant did it from Rover. I seem to remember that the system became gradually dissused towards my time there, not sure why though.
It seemed to be used for when the weather was marginal, rather than good or very bad. The two sighting towers (one for each runway heading) and the the set of extra r/w lights were on one side of the runway only, both St Mawgan and St Athan had them north side of the r/w.
One thing I've never asked is how communication to the control tower was achieved, was it by radio?
This is the 31 tower, which is sited near the ILS Glidepth installation
This shows the placing of the 13 tower (bottom left below grasscutters), the other tower is on the same side of runway but out of shot beside the 31 threshold
St Mawgan had another visual visibilty system which was two powerful lights placed at two different points of the airfield, one was fixed to the B Centre at the 13 threshold and the other on a sub-station on the northern loop. I don't know exactly what readings they were meant to give or how the data was interpreted.
Does anyone know if other airfields had this system?
I seem to remember it was a "Hadley Box" that we used to talk to the VCR. Certainly that was the case at Brize when I was there, and I'm sure St Mawgan was the same. Although I do remember using the Storno at St Mawgan, probably when the hadley box was u/s. In my time, there was only one RVR tower on site, that being the Rwy 31 one adjacent to the GP building.
As for the light sited on the B1B building and also at Carnanton and 423 hangar (I think?) They were read by the Met office and Bill Flanders did have a hand held device to do this, but I just can't remember how it worked or what it was called. When I see him again I'll ask.
Great photo's there James.
Excellent photos MM!
The two lights are common to most airfields, basically theyre at known distances from the met office and met are able to use them to give a visibilty when the weather is foggy or misty. Must admit Ive never seen anywhere in the RAF with 2 RVR towers. And yes comms was hadley box or storno or whatever replaced storno.
In my time, there was only one RVR tower on site, that being the Rwy 31 one adjacent to the GP building.
Your memory is worse than mine Chris!
The 13 twr was there from when I started spotting in the early '80s to when I left at the end of '06, and that is shown photos. It was gone by late '07 though. Maybe you remember 31 as it was the dominant runway?
I assumed all airfields had two towers, to be able to check the runway in use.
Could St Mawgan have had two due to its weather (I have known sun at inland 31 while coastal 13 was in thick fog!), being in two pressure areas, or r/w length?
Paul, I did have some really good close up shots, but you guessed it...
Canberra thanks for clarifying the other vis lights, that sounds right.
At Mawgan we found a length of scaffold tube going right through the control tower external wall from the met office, I think we surmised that it might have been a viewing aid for one of these lights.
I'm fairly sure it wasn't there in 1983-86 but I could be wrong. Brize only had one in 1979.
I'm fairly sure it wasn't there in 1983-86.
Sorry Chris, I thought you were on the BCU into the 1990s!:oops:
Im fairly certain that RVR towers are normally only on one runway and that is the main instrument runway. The reason is very simple. When vis is poor the winds are often very light so the airfield will be on the main instrument runway, which in the RAF will be the only one equipped with ILS.
No prob James. I left St Mawgan in Sept 1990 having been on the civvy BCU with Baz for nearly two years. Prior to that I had been in air traffic, on and off, since 1983.
I still can't recall when the second (13 RVR) tower was erected though. Must have been during the above period sometime?? Perhaps St mawgan was unusual in having two?? I agree with canberra in that, RVR's were usually associated with the MIR, at least in my experience.
Nasty, drafty, fly ridden places at the best of times...............".LAC(W) Bloggs, I have a job for you....!" Wouldn't get away with it now though.....happy days.
Yes I've just spoken to the two controllers here, who have considerable experience amongst them and both have only known one RVR per a/f apart from St Mawgan and Brize Norton.
No real definitave answer is coming forward as to why, but I wonder with SM if Master Diversion Airfield status made it more nescesary, conbined with the sometimes odd weather patterens there, all important when Nimrods are operating 24hr SAR and sometimes having to approach from the coast side. BN might have been similar being 24hr.
The I3 twr must have been added before you left as the pic is dated '89, but it must have been there when you came back as we overlapped slightly, mind you the idea was out dated by then!
Who'd have thought wooden boxes could be so interesting, hello any one there, er heellooo...:lol:
The device that was used by Met Office staff to view a Visibility Light was called a Gold Visibility Meter. At airfields there were often two Vis Lights. These were very high quality incandescent bulbs of a known candle power. The Vis Meter (invented by Ernest Gold Ė a famous Met Man) consisted of a graduated glass slide ranging from completely clear to completely black. Each Observer routinely calibrates themselves on nights of very good visibility. This is done by drawing the slide across the viewing field until the Vis Light is just extinguished. On a night of poor vis the point at which the light then extinguishes gives an indication of the opacity (hydrometeors or lithometeors) of the atmosphere between the observer and the Vis Light. The length of scaffolding pole through the Met Office wall was to enable readings to be taken without going outside. Mostly was in use on RAF airfields where it gave an equivalent daylight visibility at night. RVR was invented after the Vanguard (G-APEE) crash at Heathrow in 1965. RVR gives an actual pilotís equivalent visibility from as near the point where the pilotís eyes would be Ė which is not the same as the meteorological visibility. RVR was (is?) very labour intensive. There have been a number of attempts to automate visibility measurements. I donít know what system they use nowadays, but some of the early systems were a bit Heath-Robinson!! I can give a potted history (off-forum) if anybody is interested.
I would think that the reason that St Mawgan and Brize Norton had an RVR tower at each end of the main instrument runways, was because these runways had an ILS at each end. Brize certainly does, I'm not sure about St Mawgan but I would have thought it did. Most RAF stations only had one ILS, and therefore one RVR tower.
Runway visual range is only required when making an approach in poor visibility, and pilots need to know the runway visibilty at the touch down end of the runway. In order to make an approach in poor visibilty pilots need to make what is now known as a precision approach. This is typically an ILS approach. Therefore RVR is normally only required when making an ILS approach. If there is no ILS installed for a particular runway there is no need for the RVR.
I hope that makes sense.
I would think that the reason that St Mawgan and Brize Norton had an RVR tower at each end of the main instrument runways, was because these runways had an ILS at each end. Brize certainly does, I'm not sure about St Mawgan but I would have thought it did.
This was mentioned when I spoke to the chaps this morning, but as far as I can remember when St Mawgan was RAF it had ILS to 31 only, I've certainly only ever seen the one set of GS & Loc aerials.
EGDGZTCW should be able to confirm that though.
Also is it possible to have had ILS facing out to sea, thinking of middle and outer markers here?
Also is it possible to have had ILS facing out to sea, thinking of middle and outer markers here?
I believe if there's a co-located DME such an installation is OK
Just confirmed Mawgan had ILS to 31 only (should have remembered from Ryanair hassles!).
I can't help thinking it had two RVRs due to 24hr and MDA status.
RVR readings may also be required to satisfy take off criteria (in case of rejected take off), and generally when it's 'foggy' the winds are light so aircraft often elect to depart on a preferred runway or one with "better" readings.
Thats correct MM, RAF St Mawgan only ever had one ILS right until the end, that being Rwy 31 or Rwy 30 as it became in August 06. But it did have two RVR towers as previously discussed, never the less. So ILS didn't always mean an RVR, or the other way around, at least not then anyway. Brize only had one RVR tower, that being on Rwy 26 in 1979/80 but not sure about an ILS on Rwy 08 back then, but def not an RVR tower on Rwy 08. I left BZN in 1980, I'm sure things have changed since then.
Resmoroh - Thanks for the explanation. The SMetO did show me the glass slide but I never got to see it used in anger. It was years before I even noticed the tube in the corner of his office !!
Newquay (St Mawgan as was) now has an ILS at both ends with corresponding (I)RVR's. All done on DME, I believe middle markers and outer markers are a thing of the past, not sure though.
Thats correct MM, RAF St Mawgan only ever had one ILS right until the end, that being Rwy 31 or Rwy 30 as it became in August 06. But it did have two RVR towers as previously discussed
Thanks Chris, I am assuerd that Brize did have two RVRs and an ILS for both headings, but this could well have been after you left in '80.
BTW I was amazed when we all saw that tube on that last visit, did you know about it before that? Those met guys liked to keep there antics to themselves!
Now, what is DME again?!
Is it worth opening this thread up to all airfield weather related installations, or is there already one?
Yes you can have an ILS out to sea, Leuchars ILS is on 27 no outer marker though!!!
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