Lo Vis Procs LHR

[peeteechase]

I wonder if any LHR controllers would let me know what criteria are used for instituting Lo Vis Procs. Is it based on Pilot Reps or on the Met man?
No criticism intended of the guys on duty, but I operated into LHR last friday evening (20th Dec) and ended up holding for some 38 minutes. It didn't cause me any embarrassment because I had loaded extra fuel in anticipation. The weather was 2000m in Mist, Bkn/200 and Ovc/400 and Lo Vis Procs in force. The point is that most pilots would agree that in these conditions, a successful Cat One approach is pretty well guaranteed, we actually saw the lights at 300 ft aal. The LVP's had slowed the flow rate down considerably and caused unnecessary holding in my opinion. As a result a number of my passengers missed their onward longhaul connections.
My suggestion would be to base LVP's on pilot reports as well as the Met. It might well result in one or two aircraft having to go around on the odd occasion, but might save a lot of diversions, increased cost to the airlines and of course inconvenience to the travelling public.

ATB, PTC

[cossack]

In the UK LVPs are in force when:

The IRVR is less than 600m and/or
the cloud ceiling (BKN or OVC) is 200 feet or less.

There are differing categories of LVP for use by ATC and Airfield Operations, but to a pilot the term LVPs is all encompassing and any relevant info would be broadcast on the ATIS.

In the situation you describe, LVP "cloud" would have been in force. Inbound spacing would have been increased but not to the same extent had LVP "visibilty" been in force.

At Manchester in LVP cloud, all runway exits are available but in LVP vis. this is not the case.

A LHR ATCO will probably be able to tell you their specific requirements.

As for using pilot reports to base ATC procedures on, its a non-starter I'm afraid. We use the IRVR for the vis., a laser cloud base recorder for the cloud base (funnily enough!) and if thats all broke then the Met vis. and estimated cloud base from the trusty Met Observer.

Its all about protecting the ILS signal for following aircraft and that means slowing the traffic. You want to fly slower on approach too, so it all backs up. Landing rates may fall by 30-50% and delays go up.

Hope this starts to help a bit.

Merry Christmas

[ATCO Two]

The same LVP criteria as Manchester are applied at Heathrow, but there is no official differentiation between LVP "cloud" and LVP "visibility." The requirement is for the aircraft ahead to have cleared the Localiser Sensitive Area before the next aircraft has reached 1 nm from touchdown. Landing clearance should be given by 2 nm from touchdown and MUST be given by 1 nm from touchdown, or a go-around must be initiated. 6 nm spacing is recommended to achieve this.

In foggy conditions, cloud and visibility tend to fluctuate markedly, so I don't believe there is much to be gained by relying on pilots' reports which may be valid for extremely short periods. I suggest that if a pilot in the aircraft behind was relying on the pilot ahead reporting the weather conditions accurately, and if there was a catastrophe because of this, then those involved in the reporting extremely difficult position. At least transmissometer and meteorological reports can be tracked and recorded.

We are either in LVPs or not in LVPs, there is no middle ground. However, if the Air Controller observes that aircraft are vacating the LSA promptly, then the spacing requirements may be reduced accordingly. There is always a dialogue between Approach and the Tower under these circumstances. It is in everyone's interests to reduce the delays.

[cossack]

ATCO Two
We used to have the same landing clearance criteria in LVPs but due to an incident (at Birmingham I think) we now have to aim for landing clearance at 3 miles and must give it by 2 miles.

Have your criteria not been changed? If not why not? :confused:

[peeteechase]

Thanks for the quick replies guys,
The point about IRVR's and cloudbase is taken, but I can assure you that if it's 2000m and Bkn/200 then a Cat1 landing is practical in 99% of cases. If the base drops to 200ft why not ask landing aircraft the height they see the lights. I would think you would get a straight answer as most professional pilots would not wish to place anybody at risk. If the answer you get is 300ft then no problem. If it's 200ft then could be time to think about LVP's?
Anyway a Cat1 goaround is certainly not a catastrophic situation. My company requires the automatics to be used if visual contact is not anticipated by 1000 ft, this means an "all singing and dancing" fail active autopilot system which requires just a click of a switch to carry out a maximum energy goaround. We regularly practice these from very low level in the Simulator and on some occasions the wheels may even briefly, quite safely, contact the runway surface.
I know that your procedures are all about safety and I am fully in favour of that.
Over the other side of the pond at a (large fruit) city airport they seem to base their LVP's solely on whether aircraft are going around or not, I have had three goarounds there in my career (so far), two of which were on the same day when they said the weather had improved!
Keep up the good work guys
Happy Xmas, PTC

[terrain safe]

PTC I think you are missing the point of LVPs. They are not there to solely ensure that you can avoid an Overshoot, but to ensure that a landing ac does not not get incorrect readings on the approach and fly into the ground. That is solely for safety nothing else.

[Evil J]

peeteechase,

a go around may be no problem for you but at LHR its no picnic for the controllers involved I can assure you-especially in LVP's; if you don't believe me there is a very nasty airprox report (the airprox was nasty not the report-u know what I mean) from about 5 years ago(ATCO2 may be able to be more precise) from an a/c going around in fog-miss distance as I recall was in the order of 100ft no sighting.

[HEATHROW DIRECTOR]

<<if you don't believe me there is a very nasty airprox report (the airprox was nasty not the report-u know what I mean) from about 5 years ago(ATCO2 may be able to be more precise) from an a/c going around in fog-miss distance as I recall was in the order of 100ft no sighting.>>

I am sure that a good many ATCOs could relate plenty of tales of aeroplanes going around well below 100 ft - absolutely nothing to it. I've seen planes go around after they've actually touched the runway in LVPs - saw it on the ASMI, gave it the usual "landed at 38, vacate right on the greens" and the guy said "We're going around"... No incident.. nothing. Low go-arounds are one thing; airproxes are another and there is no reason to suppose that LVP go-arounds will end in airproxes if crews and ATC get things right. Given a bad foggy morning at Heathrow you could get a dozen or more go-arounds.

What always amazed me about LVPs was exactly what depended on the measurement of cloudbase. Maybe things have changed since I was a met observer, but in those days a lot of it was eyeball because the cloudbase measuring light was fixed in one vertical direction so if there was lower cloud elsewhere one had to guess it. I hope it's more accurate nowadays because one hell of a lot depends on it. Not long before I retired we had 100ft cloud base at Heathrow and one pilot said he needed 110 ft!!!! Now how on earth can one measure that?

[West Coast]

HD
Not quite sure what he meant, but he could have been speaking of a DH based off the radar altimeter. The RAs I have worked with are capable of displaying height in 10ft increments from 2500-3000 on down. He was not overly clear though. When we do cat II approaches, we base DH off the RA and not the baro.

[HEATHROW DIRECTOR]

Evil J wrote: "a go around may be no problem for you but at LHR its no picnic for the controllers involved I can assure you-especially in LVP's"

I meant to comment on this too.. I don't know if Evil J works at Heathrow but I'd like to assure crews that go-arounds in any wx conditions are no big deal for ATC. The handling of the go-around and other traffic is quite straightforward and should present no problems. OK, the next one or two departures may be delayed by a minute or so and one or two inbounds might have to go the extra mile or two downwind but it's really no problem.

[Spitoon]

Just to confirm what HD says, go-arounds are something that every controller should plan for from each and any approach.

It may be nothing more than keeping a hole available for an aircraft to go - in many cases the crew will get non-standard instructions on the go-around because following the standard missed approach procedure would bring the aircraft into conflict with other traffic. This is no problem for ATC (and hopefully wouldn't be for crews). Granted in the London area this may be difficult to achieve but it's good ATC practice in my book.

[peeteechase]

Oh dear, I wish I hadn't mentioned goarounds.
Just to clarify to the uninitiated (and possibly the gutter press) goarounds are normally, safe and acceptable manoeuvres that regularly occur in flying operations and are practised on simulator checks. Promulgated goaround procedures are specifically designed to avoid conflict with other traffic eg. takeoffs from the same or a parallel runway. Goarounds can and are, modified by the ATC controller on the day in order to further enhance that separation. Most press reports of landing aircraft coming close to aircraft taking off are total alarmist bullshine!
Now to the serious stuff:

The whole purpose of this thread was to point out that:
1. LVP's can on occasion be uneccessarily conservative (and were last week on one of my flights in my opinion)
2. LVP's at a busy airport cause delays and may cause diversions
3. If the RVR stays within reasonable limits and does not constitute an approach ban then I would suggest the best judge of whether LVP's are necessary or appropriate is the Met observer **in conjunction** with pilot reports.

I have made successful Cat 1 approaches in 600m Ovc/100, so the cloudbase is not the full answer. When visibility/cloudbase deteriorates it usually does so slowly; so guys, why not ask the people who are in the best position to judge the conditions? These days few of us are civil servants and we have to run a safe(no.1) and profitable(no.2) operation n'est ce pas?
Have a Happy New year, PTC

[HEATHROW DIRECTOR]

PT.. I don't think any ATCO would disagree. I've spent a good part of my life putting 6-8 miles between a/c for no good reason other than the fact that the cloud determined that I should. But.. ATC doesn't make the rules; they simply apply them.

Being older than God I've usually got an appropriate story so here's one.. When LVPs first came in I was the Tower controller at Heathrow one bright sunny summer day; visibility 93 million miles, etc. The automatic RVR indicator in the Tower suddenly gave a touchdown reading of about 50m.. we quickly rang the engineering people and they said as far as they could tell the instrumented RVR system was full serviceable.. As required by my instructions I therefore read the RVR to a Trident.. he asked me to confirm that it was a true reading and when I confirmed that the equipment was working OK he said he was bound to go-around.. and did. He knew it was lunacy - and said so; I knew it was lunacy - and said so.... but rules is rules!

At the other end of the scale within the last 12 months a pilot asked ATC NOT to read him the RVR on final approach if it dropped below his minima. I know who I'd rather fly with..

[Scott Voigt]

Retired Heathrow Director <G>....

Guess that is one of the differences between here and where you are... We would have just called the RVR out of service and kept moving aircraft <G>....

regards

[Line up and go]

Remember when the firemen counted the edge lights from the fire vehicle at the side of the runway! I'm afraid I do.
At Aldergrove last century only Rwy 17/35 available at night, a we bit foggy and a Herald ( Aaaah) trying to land. He needed ( I think) 1100m RVR.
Runway was just reopened after resurfacing. Firemen call number of edge lights seen and this is transposed into RVR and passed to pilot.
Visibility improves... 14 Lights seen...RVR 900m....
Visibilty improves...14 lights seen.....RVR 900m...
Met Vis 2000m.......14 lights seen....RVR 900m...
etc.
Luckily pilot had discretion to use factorised Met Vis and landed.

You may have guessed by now, runway had a hump in it and when resurfaced the edge lights were correspondingly lower than previously....you can work out the rest!

[Spitoon]

Line up, I though that was why the look up tables had to be recalibrated after any work that may affect the lights.