Can TAF's visibility replace RVR?

[yunje]

Regarding TAF visibility and Appraoch WX minimum RVR.

When dispatch long distance flight (more than 2hour / In DISP PHASE)

- TAF Forecast visibility : 600m
- AIRPORT appraoch minimum : CAT 1 / VIS 800m (or RVR 550m)

Is it possible to dispatch in this case? (with one alternate airport)

TAF is below AIRPORT VIS minimum but above RVR

if you can help me with this, I’ll really appreciate it.
Best Regards!

[FlightDetent]

Fake TAF, real one would have RVR predictions for VIS below 2000. Or something like that.

Also, the question is impossible to answer until you state which regulatory framework you operate under.

Regards.

[imriozer]

Fake TAF, real one would have RVR predictions for VIS below 2000. Or something like that.

Also, the question is impossible to answer until you state which regulatory framework you operate under.

Regards.

never saw RVR in TAF

[KingAir1978]

RVR is always an observation, never a forecast. Therefore, it wouldn't be in a TAF.

Under EASA when vis drops below 800m, RVR is required. Since you CANNOT have the RVR, because it's not a forecast, but an observation, I would consider the wx below minima. It is permissible to dispatch in such a case, provided two alternates have been selected and fuel for the furthest is carried. Again, this is under EASA, other jurisdictions may have different rules.

[yunje]

Thank you for your reply.
but It is not Fake TAF.
actually the last year, RKSI/ICN TAF had been forecast VIS 600m.
At that time, our company discussed this matter for dispatch aircraft (CAPT qualification CAT1)
and I'm just curious about the others opinions
many thank you

[FlightDetent]

Thanks for correcting.

[sonicbum]

Regarding TAF visibility and Appraoch WX minimum RVR.

When dispatch long distance flight (more than 2hour / In DISP PHASE)

- TAF Forecast visibility : 600m
- AIRPORT appraoch minimum : CAT 1 / VIS 800m (or RVR 550m)

Is it possible to dispatch in this case? (with one alternate airport)

TAF is below AIRPORT VIS minimum but above RVR

if you can help me with this, I’ll really appreciate it.
Best Regards!


Hi,

the forecasted visibility is above the RVR required, so you can legally dispatch with 1 alternate.

[yunje]

RVR is always an observation, never a forecast. Therefore, it wouldn't be in a TAF.

Under EASA when vis drops below 800m, RVR is required. Since you CANNOT have the RVR, because it's not a forecast, but an observation, I would consider the wx below minima. It is permissible to dispatch in such a case, provided two alternates have been selected and fuel for the furthest is carried. Again, this is under EASA, other jurisdictions may have different rules.


Thank you for your reply.
I think so too
RVR is just observation value.
So if I want to dispatch this VIS 600m, I have to provide two alternate. (except short flight)

and If possible, can you tell me where I can see EASA regulation regarding this matter?

[yunje]

There are two opinions. (both my company colleagues and PPRuNe forums)

1. RVR is observation, not forecast.
so I have to compare TAF visibility 600m and appraoch minima's visibility 800m (not RVR 550m)
and It should be considered WX below minima

2. TAF visibility 600m is above appraoch minima's RVR 550m
so there is no problem, dispatch with 1 alternate

I'm not sure which is right.
It is not clear in my company regulation.
and I just wonder what ICAO/FAA/EASA ruels and others aviation workers opinion.

Thank you for many reply.
and please give us more other thinks.
many thks.

[Airmann]

The answer to this question will depend on national regulations and/or company regulations.

[Smokey Lomcevak]

I can’t add any more to the regulatory side of things, but is it not the case that if we assume a uniform distribution of cloud/mist/fog giving a met vis of 600m, we could reasonably expect an RVR measurement to give more than than 600m?

Of course it doesn’t always work like that in the real world - especially in the ranges of visibility we’re talking about here. It’s not unforeseeable that a rogue fog bank could envelope the TDZ RVR on such a day. But the chances of that happening on a day when one didn’t have the ability to carry extra fuel for another div and or holding without - say - offloading freight are pretty low, and one would still have their original alternate which must have met the more stringent requirements - from an EASA OPS pint of view. In that case - if you gotta go (to the alternate) then you gotta go...

[safetypee]

SL, the assumption that fog has a uniform distribution would be ill-founded.

Fog has many different structures, particularly variations between forming and dispersing.

Stratiform cloud-like 'onion layers' in compression (forming) with significant vertical variation in visibility in each layer. Alternatively 'pork-pie', mini cumulus with Horizontal variation in visibility and ambient light levels during dispersal.

A critical time for variable fog structure in wet fog is around Cat 2 RVRs, where a 'land' decision above DH can turnout to be poorly judged. Whereas Cat 3 RVRs are more likely to be a stable fog with little variability.

Then there is a range of visibility distributions associated with different particles; wet / dry cloud, snow - type or rate of snowfall, dust, smoke, etc.

RVR originated from extensive research into these areas and is a compromise between what can be measured accurately, and the pilots need for slant visual range - what might be seen at different heights.

[ShyTorque]

I agree, in practical terms, low viz is a highly unpredictable situation, even in the short term. Often even a METAR often goes out of date as soon as it’s published, let alone a forecast.

There’s often been times I’ve thought I’m glad not to have been a Met forecaster.

[OK4Wire]

Fake TAF or not, the same concept would apply if the destination had a non precision approach or similar.

Either way, in my region you could dispatch by factoring the visibility. If, for example, the destination had HIALS and it was night, the factor would be 2. So 600m becomes 1200m, thus above the minimum of 800m so you can launch.


edited to add that the 1200m is now what we call "equivalent RVR"

[yunje]

I can’t add any more to the regulatory side of things, but is it not the case that if we assume a uniform distribution of cloud/mist/fog giving a met vis of 600m, we could reasonably expect an RVR measurement to give more than than 600m?

Of course it doesn’t always work like that in the real world - especially in the ranges of visibility we’re talking about here. It’s not unforeseeable that a rogue fog bank could envelope the TDZ RVR on such a day. But the chances of that happening on a day when one didn’t have the ability to carry extra fuel for another div and or holding without - say - offloading freight are pretty low, and one would still have their original alternate which must have met the more stringent requirements - from an EASA OPS pint of view. In that case - if you gotta go (to the alternate) then you gotta go...

As 'safetypee' and 'ShyTorque' said,
Low VIS is a highly unpredictable situation.

In this case,
We have some regulation for Weather forecast destination airport

* When Below the weather minimum or weather information is not available.
1. More than 2 hours of flight time : NO DISPATCH
2. When flight time is less than 2 hours, If Current weather at the destination airport is above weather minimum : DISPATCH

So If METAR or AMOS's RVR is above WX minimum, We can dispatch less than 2 hours flight regardless of TAF

But More than 2 hours flight, I don't know which one to apply VIS 800m or RVR 550m.
Because No RVR is forecast for TAF.

[yunje]

Fake TAF or not, the same concept would apply if the destination had a non precision approach or similar.

Either way, in my region you could dispatch by factoring the visibility. If, for example, the destination had HIALS and it was night, the factor would be 2. So 600m becomes 1200m, thus above the minimum of 800m so you can launch.


edited to add that the 1200m is now what we call "equivalent RVR"


Thank you for your opinion.

We also have "equivalent RVR" table.

But There are special conditions for applying this regulation in our company.

* RVR Conversion Table Note
1. This table may not be used for takeoff minima determinations, CAT 2 or CAT 3, or if RVR is available and reported
2. This table may not be used for landing minima determinations on Flight Planning Stage.
3. Equivalent RVR = (Reported Prevailing Visibility) X Factor

anyway many thank you for your reply.

[exfocx]

Been back "home" (Oz) for some time now, but if my memory serves me right when in the M.E. we had a correction factor to go from Vis to RVR if only one was stated and you needed the other, factor was 1.5. When I was in HK I'm pretty sure that the company had a nominated destination VIS requirement, not given as an RVR.

Also, are not Vis and RVR different?

Edit: can see some have covered this.

https://www.universalweather.com/blog/aviation-weather-tips-visibility/3. Calculation of visibilityVisibility values are determined by both human observers and the Automated Surface Observing Systems (ASOS). The human observer determines visibility by identifying objects and landmarks at known distances throughout a 360 degree circle around the observation point. The greatest visibility observed over 50% or more of the 360 degree area is the prevailing visibility. If, however, there’s a sector of the 360 degree area that significantly differs from prevailing visibility, the observer may add a remark. ASOS measures and converts sensor-driven values to visibility values corresponding to what the human eye can see. Pilots must be mindful that nearly half the area around an airport may have lower conditions than the reported prevailing visibility.
5. RVR considerationsRVR is distance over which a pilot of an aircraft, on the centerline of a runway, can see delineated runway surface markings and centerline. RVR values are normally determined by the human eye or with an Instrumented Runway Visual range (IRVR) trasmissometer. RVR is important as it provides the main criteria used to determine category of visual aids operational at an airport as well as criteria/minima for instrument approaches.

[Don Coyote]

You may be considering when you have a legal TAF but a METAR below minimums as you are very unlikely to get RVR in a TAF. For planning purposes, you would use the TAF to determine dispatch requirements.

For EASA land CAT operations, the following would be applicable:

The table in GM1 CAT.OP.MPA.185 has useful guidance for applying TAF criteria to determine suitability of weather from a TAF. Once you have determined that the forecast is suitable (or not) then CAT.OP.MPA.185 would also require alternate weather of better than NPA RVR/VIS with ceiling at or above MDH for the most applicable runway as only CAT I is available at destination. Provided those conditions are met then you could dispatch with one alternate.

If the destination forecast is below limits, as per yunje’s example of RKSI/ICN TAF of 600m visibility (800m visibility required), then you would require two alternates with suitable weather forecasts as per CAT.OP.MPA.185.

Once you arrive at the destination then CAT.OP.MPA.305 becomes applicable. This requires that you cannot proceed below 1000 ft above the aerodrome if the reported RVR/VIS is less than the applicable minimum.

The conversion of reported met vis to RVR, detailed in AMC10 CAT.OP.MPA.110, would not be applicable at the planning stage.

[sonicbum]

You may be considering when you have a legal TAF but a METAR below minimums as you are very unlikely to get RVR in a TAF. For planning purposes, you would use the TAF to determine dispatch requirements.

For EASA land CAT operations, the following would be applicable:

The table in GM1 CAT.OP.MPA.185 has useful guidance for applying TAF criteria to determine suitability of weather from a TAF. Once you have determined that the forecast is suitable (or not) then CAT.OP.MPA.185 would also require alternate weather of better than NPA RVR/VIS with ceiling at or above MDH for the most applicable runway as only CAT I is available at destination. Provided those conditions are met then you could dispatch with one alternate.

If the destination forecast is below limits, as per yunje’s example of RKSI/ICN TAF of 600m visibility (800m visibility required), then you would require two alternates with suitable weather forecasts as per CAT.OP.MPA.185.

Once you arrive at the destination then CAT.OP.MPA.305 becomes applicable. This requires that you cannot proceed below 1000 ft above the aerodrome if the reported RVR/VIS is less than the applicable minimum.

The conversion of reported met vis to RVR, detailed in AMC10 CAT.OP.MPA.110, would not be applicable at the planning stage.

It’s not unlikely, it’s impossible to have RVR in a TAF as it is an actual measurement.
AMC10 CAT.OP.MPA.110 does not state that the CMV is not applicable at planning stage.

[Don Coyote]

AMC10 CAT.OP.MPA.110 does not state that the CMV is not applicable at planning stage.

True, but given that it is reported met visibility it is unlikely to be of value for when you arrive two hours later in the example given by the OP. The only time it would possibly be applicable for planning minima, IAW CAT.OP.MPA.185, is when the reported met visibility is given to you before you depart and you will arrive in one hour or less.

[sonicbum]

True, but given that it is reported met visibility it is unlikely to be of value for when you arrive two hours later in the example given by the OP. The only time it would possibly be applicable for planning minima, IAW CAT.OP.MPA.185, is when the reported met visibility is given to you before you depart and you will arrive in one hour or less.

The OP is referring to a forecasted Vis, part of a TAF. This Visibility will be taken into account as we have no further details (TEMPO, BECMG, etc..) so we can assume it is the forecasted general visibility in the period covered by the TAF.
Worst case scenario Your CMV factor is 1.0, You’re above the required RVR of 550m.

[yunje]

Been back "home" (Oz) for some time now, but if my memory serves me right when in the M.E. we had a correction factor to go from Vis to RVR if only one was stated and you needed the other, factor was 1.5. When I was in HK I'm pretty sure that the company had a nominated destination VIS requirement, not given as an RVR.

Also, are not Vis and RVR different?

Edit: can see some have covered this.
3. Calculation of visibilityVisibility values are determined by both human observers and the Automated Surface Observing Systems (ASOS). The human observer determines visibility by identifying objects and landmarks at known distances throughout a 360 degree circle around the observation point. The greatest visibility observed over 50% or more of the 360 degree area is the prevailing visibility. If, however, there’s a sector of the 360 degree area that significantly differs from prevailing visibility, the observer may add a remark. ASOS measures and converts sensor-driven values to visibility values corresponding to what the human eye can see. Pilots must be mindful that nearly half the area around an airport may have lower conditions than the reported prevailing visibility.5. RVR considerationsRVR is distance over which a pilot of an aircraft, on the centerline of a runway, can see delineated runway surface markings and centerline. RVR values are normally determined by the human eye or with an Instrumented Runway Visual range (IRVR) trasmissometer. RVR is important as it provides the main criteria used to determine category of visual aids operational at an airport as well as criteria/minima for instrument approaches.


Thank you for your reply.

Comparing the definition of VIS with the definition of RVR, I can see sure that the two are different.

By the way, your said "home (Oz)" means, you were in AAR in korea?

Nice to meet you.

And thank you very much for your help.

[yunje]

You may be considering when you have a legal TAF but a METAR below minimums as you are very unlikely to get RVR in a TAF. For planning purposes, you would use the TAF to determine dispatch requirements.

For EASA land CAT operations, the following would be applicable:

The table in GM1 CAT.OP.MPA.185 has useful guidance for applying TAF criteria to determine suitability of weather from a TAF. Once you have determined that the forecast is suitable (or not) then CAT.OP.MPA.185 would also require alternate weather of better than NPA RVR/VIS with ceiling at or above MDH for the most applicable runway as only CAT I is available at destination. Provided those conditions are met then you could dispatch with one alternate.

If the destination forecast is below limits, as per yunje’s example of RKSI/ICN TAF of 600m visibility (800m visibility required), then you would require two alternates with suitable weather forecasts as per CAT.OP.MPA.185.

Once you arrive at the destination then CAT.OP.MPA.305 becomes applicable. This requires that you cannot proceed below 1000 ft above the aerodrome if the reported RVR/VIS is less than the applicable minimum.

The conversion of reported met vis to RVR, detailed in AMC10 CAT.OP.MPA.110, would not be applicable at the planning stage. Thank you for your reply.

Actually, I'm considering when I have a TAF with forecasted visibility 600m. (not METAR)
But when the airport weather minimum is 'VIS 800m or RVR 550m', I'm thinking about which one to compare with TAF.

I think, you want to said,
I have to compare 'TAF of 600m visibility' with 'airport minimum VIS 800m' (not RVR 550m)
and I need to have two alternates airport in this example.
(you said : If the destination forecast is below limits, as per yunje’s example of RKSI/ICN TAF of 600m visibility (800m visibility required)...)

Is this right?

Anyway, thank you again.

[FlightDetent]

In your original example, the VIS was greater than the RVR planning minima.

The agreement hereabove is, it is legal to dispatch. Correct? Multiplication factors not required.

[oggers]

- TAF Forecast visibility : 600m
- AIRPORT appraoch minimum : CAT 1 / VIS 800m (or RVR 550m)

Is it possible to dispatch in this case? (with one alternate airport)

It is not clear in my company regulation.
and I just wonder what ICAO/FAA/EASA ruels and others aviation workers opinion.

KingAir1978 was basically correct early in the thread.

In Europe, if the wx is below minima at destination two alternates are required (in general that is, not necessarily applicable to all operators). In the USA dispatch would be permitted with one alternate.

ICAO Annex 6 Pt 1 states that 2 alternates are required if the weather forecast is below minimums at destination. Not necessarily implemented in each country. EASA requires 2 alternates. The FAA is 1 alternate unless the weather at the alternate is "marginal" when two are required. EASA reference is CAT.OP.MPA.185. FAA reference is 14CFR 121.619 and 621.

Soncibum says:

Worst case scenario Your CMV factor is 1.0, You’re above the required RVR of 550m.

Maybe, but in Europe it is not permitted to convert the met visibility to RVR when the RVR minimum is less than 800m according to CAT.OP.MPA.110 AMC10. The implications of this rule could be discussed at length but as far as answering the OP is concerned it is a moot point because in his company:

* RVR Conversion Table Note
2. This table may not be used for landing minima determinations on Flight Planning Stage.

Furthermore...

- AIRPORT appraoch minimum : CAT 1 / VIS 800m (or RVR 550m)...
...[if] TAF visibility 600m is above appraoch minima's RVR 550m
so there is no problem, dispatch with 1 alternate

...these two things imply to me that the OP needs 2 alternates for dispatch because the forecast visibility is below the quoted Cat 1 vis of 800m and it is not permitted to convert it to equivalent RVR for the purposes of dispatch planning.

[FlightDetent]

oggers thanks for assembling the pieces back together.

It transpires then, that any LVP CAT II/III alternate cannot be planned for, unless their forecasted VIS is 800 or more. EASA land.

​​

[sonicbum]

Soncibum says:



Maybe, but in Europe it is not permitted to convert the met visibility to RVR when the RVR minimum is less than 800m according to CAT.OP.MPA.110 AMC10. The implications of this rule could be discussed at length but as far as answering the OP is concerned it is a moot point because in his company:



Furthermore...



...these two things imply to me that the OP needs 2 alternates for dispatch because the forecast visibility is below the quoted Cat 1 vis of 800m and it is not permitted to convert it to equivalent RVR for the purposes of dispatch planning.

oggers,

(a) A conversion from meteorological visibility to RVR/CMV should not be used:
(1) when reported RVR is available;
(2) for calculating take-off minima; and
(3) for any RVR minima less than 800 m.

point 3) in intended after a conversion i.e. with a Vis of 400 m and a conversion factor of 2.0 you would get a CMV of 800m, but with, let's say a min RVR of 550 you could not do the conversion with a Visibility of, let's say 300m.

[KingAir1978]

oggers,

(a) A conversion from meteorological visibility to RVR/CMV should not be used:
(1) when reported RVR is available;
(2) for calculating take-off minima; and
(3) for any RVR minima less than 800 m.

point 3) in intended after a conversion i.e. with a Vis of 400 m and a conversion factor of 2.0 you would get a CMV of 800m, but with, let's say a min RVR of 550 you could not do the conversion with a Visibility of, let's say 300m.
SonicBum (nice nickname!), In EASA land when you're at the planning stage, you cannot apply the conversion, because of point (3), when you're in flight and the visibility drops below 800m and you want to shoot an ILS approach, RVR should be provided. Therefore point (1) prohibits you from doing the conversion.

[FlightDetent]

For reference only, EASA starting point is CAT.OP.MPA.185 Planning minima for IFR flights — aeroplanes. Then it follows to CAT.OP.MPA.110.

If, A conversion from meteorological visibility to RVR/CMV should not be used .... for any RVR minima less than 800 m. [AMC 10 (a)(3)]
and by definition any TAF will only have VIS
then anywhere CAT I is required, RVR 550 must be disregarded and VIS 800 used.

That's different from sonic's suggestion. Thoughts?
point 3) in intended after a conversion i.e. with a Vis of 400 m and a conversion factor of 2.0 you would get a CMV of 800m, but with, let's say a min RVR of 550 you could not do the conversion with a Visibility of, let's say 300m. this leaves me perplexed.

[sonicbum]

SonicBum (nice nickname!), In EASA land when you're at the planning stage, you cannot apply the conversion, because of point (3), when you're in flight and the visibility drops below 800m and you want to shoot an ILS approach, RVR is required. Therefore point (1) prohibits you from doing the conversion.

Hi King,

guess I have spent too much time in the SIM and not enough on the line in the past couple of years.
Here is an answer I gave to a similar question a couple of years ago.

Yes, the RVR is controlling.


At dispatch You will only have the forecasted visibility issued by the TAF. In Your example a RVR reading is available at destination so You are not allowed to use the conversion of reported meteorological visibility to RVR, hence if forecast vis +/- 1 hour is less than the required one for the approach You are considered below minima and need 2 suitable alternates to dispatch (EASA land).

in THIS (https://www.pprune.org/tech-log/610170-rvr-visibility-ils-charts.html) thread.

[Stanley Eevil]

For reference only, EASA starting point is CAT.OP.MPA.185 Planning minima for IFR flights — aeroplanes. Then it follows to CAT.OP.MPA.110.

If, A conversion from meteorological visibility to RVR/CMV should not be used .... for any RVR minima less than 800 m. [AMC 10 (a)(3)]
and by definition any TAF will only have VIS
then anywhere CAT I is required, RVR 550 must be disregarded and VIS 800 used.

That's different from sonic's suggestion. Thoughts?
this leaves me perplexed.
The conversion factors for CMV, I believe, are 1.5 for daytime operations and 2.0 for night time operations assuming full lighting/facilities etc.
Let`s assume a CAT1 ILS at dest`n with a minimum published RVR requirement of 550m.
The way I interpret the 800 m limitation is that notwithstanding our 550 m RVR requirement we can`t `play` with an RVR below 800 m when conducting the conversion back to an equivalent met visibility.
Therefore at night: 800/2 = 400 and so the min forecast visibility in the TAF at ETA +/-1 hr is 400 m in order to dispatch with just 1 dest`n alternate.
For a daytime approach 800/1.5 = 533.3, so effectively the min met vis in the TAF at ETA +/-1 hr is 550 m (although in a TAF they forecast in 100 m increments so I guess you`d be looking for a minimum forecast vis of 600 m).
Anyway, it`s purely an opinion (and probably wrong!)
Any thoughts?

[KingAir1978]

The conversion factors for CMV, I believe, are 1.5 for daytime operations and 2.0 for night time operations assuming full lighting/facilities etc.
Let`s assume a CAT1 ILS at dest`n with a minimum published RVR requirement of 550m.
The way I interpret the 800 m limitation is that notwithstanding our 550 m RVR requirement we can`t `play` with an RVR below 800 m when conducting the conversion back to an equivalent met visibility.
Therefore at night: 800/2 = 400 and so the min forecast visibility in the TAF at ETA +/-1 hr is 400 m in order to dispatch with just 1 dest`n alternate.
For a daytime approach 800/1.5 = 533.3, so effectively the min met vis in the TAF at ETA +/-1 hr is 550 m (although in a TAF they forecast in 100 m increments so I guess you`d be looking for a minimum forecast vis of 600 m).
Anyway, it`s purely an opinion (and probably wrong!)
Any thoughts?

I'm not really sure what you're trying to say, Stanley.
EASA:

First of all it is possible to convert visibility to CMV/RVR, I don't think you can reverse it and convert a required RVR to visibility that should be present.

The conversion factor -in case of HI approach lights/runway lights- 1,5 day and 2.0 night.

The conversion cannot be used for:

Take off
For calculating a required RVR less than 800 m (i.e. 550 meters for a standard ILS)
When RVR is available.

Secondly, when the VIS drops below 800 m YOU SHOULD PROVIDED with RVR information.

[FlightDetent]

Although it is a full circle from the OP's question, here's a familiar sample case. EASA rules.

Your destination WS is ok, however company preferred alternate is not looking great. TAF LIMC (MXP) V2kt 2000 BR NSC 3/1 Q1003 TEMPO 14-18 0600 FG BECMG 20-24 220/5 6000

A well equipped major hub with dual runways, CATIIIB and given the forecast it still is a respectable choice. BTW destination is CAVOK, and a non-preferred alternate is 8000 m VIS half way between DEST and LIMC.

Alternate planning minima is one grade more restrictive than what's available, i.e. for Milano CAT I ILS R550 / VIS 800.

As much as we agreed the paragraphs we're looking at do not allow conversion of TAF 600 VIS to 900 CMV, because the target minimum is R550 (less than 800) ...
... when you ran the above scenario through the flight planning system, the answer is ACCEPTABLE.

Where's the catch? :E

[Stanley Eevil]

I'm not really sure what you're trying to say, Stanley.
EASA:

First of all it is possible to convert visibility to CMV/RVR, I don't think you can reverse it and convert a required RVR to visibility that should be present.

The conversion factor -in case of HI approach lights/runway lights- 1,5 day and 2.0 night.

The conversion cannot be used for:

Take off
For calculating a required RVR less than 800 m (i.e. 550 meters for a standard ILS)
When RVR is available.

Secondly, when the VIS drops below 800 m YOU HAVE TO BE PROVIDED with RVR information.

Would this mean then that if you arrive at destination, (which, let`s assume, has a published minimum CAT1 RVR of 550 m), that if the met vis on the ATIS is 700 m, but the RVR system is inoperative, that you can`t make an approach - even though the `RVR` (if it was available) is HIGHLY LIKELY to be over 1000 m?

Or, what about a single pilot CAT1, who with his `limited` available ac equipment/avionics, is forced to use a modified min EASA RVR of exactly 800 m. He would, surely, be legal because he now CAN use a CMV conversion: [700 met vis x 1.5 (day)] = 1050 m CMV!! = LEGAL!!

So, is the obvious solution for the A320 CAT1 two-pilot operation to knock out the co-pilot, fly a manual/raw approach, and become a `single pilot operation` ?

Just out of interest, I can`t see any reference to a min met visibility of 800 m for a CAT1 approach in EASA; I assume it is mentioned in ICAO?
EASA CAT1 Definition:
‘Category I (CAT I) approach operation’ means a precision instrument approach and landing using an instrument landing system (ILS), microwave landing system (MLS), GLS (ground-based augmented global navigation satellite system (GNSS/GBAS) landing system), precision approach radar (PAR) or GNSS using a satellite-based augmentation system (SBAS) with a decision height (DH) not lower than 200 ft and with a runway visual range (RVR) not less than 550 m for aeroplanes and 500 m for helicopters;

[sonicbum]

Although it is a full circle from the OP's question, here's a familiar sample case. EASA rules.

Your destination WS is ok, however company preferred alternate is not looking great. TAF LIMC (MXP) V2kt 2000 BR NSC 3/1 Q1003 TEMPO 14-18 0600 FG BECMG 20-24 220/5 6000

A well equipped major hub with dual runways, CATIIIB and given the forecast it still is a respectable choice. BTW destination is CAVOK, and a non-preferred alternate is 8000 m VIS half way between DEST and LIMC.

Alternate planning minima is one grade more restrictive than what's available, i.e. for Milano CAT I ILS R550 / VIS 800.

As much as we agreed the paragraphs we're looking at do not allow conversion of TAF 600 VIS to 900 CMV, because the target minimum is R550 (less than 800) ...
... when you ran the above scenario through the flight planning system, the answer is ACCEPTABLE.

Where's the catch? :E

Hi FD,

in your example, the forecasted visibility is greater than the required RVR for CAT I, hence LIDO (example of what we use in my company) will accept it and will not mark it as "U".
Regarding the conversion, you can convert 600 m of visibility. What the rule says is that you can't convert in order to find RVRs lower than 800 m. If I have a general visibility of 400 m and a conversion factor of 2.0 I will find a CMV of 800m, I'm ok. On the other hand, if I have a conversion factor of 1.5 with the same visibility (daytime, HIRLS) I will find 600 m, less than 800 m , so not allowed.
Let me know your thoughts.

[sonicbum]

Would this mean then that if you arrive at destination, (which, let`s assume, has a published minimum CAT1 RVR of 550 m), that if the met vis on the ATIS is 700 m, but the RVR system is inoperative, that you can`t make an approach - even though the `RVR` (if it was available) is HIGHLY LIKELY to be over 1000 m?

No, You can by using the CMV table.

[Stanley Eevil]

No, You can by using the CMV table.
KingAir1978 would disagree with you I believe?

[sonicbum]

Secondly, when the VIS drops below 800 m YOU HAVE TO BE PROVIDED with RVR information.

ICAO :

4.6.3 Runway visual range

Note: Guidance on the subject of runway visual range is contained in the ICAO Manual of Runway Visual Range Observing and Reporting Practices (Doc 9328).

4.6.3.1 Runway visual range as defined in 1 above shall be assessed on all runways intended for Category II and III instrument approach and landing operations.

4.6.3.2 [Recommendation] Runway visual range as defined in 1 above should be assessed on all runways intended for use during periods of reduced visibility, including:

(a) Precision approach runways intended for Category I instrument approach and landing operations; and
(b) Runways used for take-off and having high-intensity edge lights and/or centre line lights.

Note: Precision approach runways are defined in ICAO Annex 14, Volume I, Chapter 1, under “Instrument runway”.

4.6.3.3 The runway visual range, assessed in accordance with 4.6.3.1 and 4.6.3.2 above, shall be reported in metres throughout periods when either the visibility or the runway visual range is less than 1 500 m.

4.6.3.4 Runway visual range assessments shall be representative of:
(a) The touchdown zone of the runway intended for non-precision or Category I instrument approach and landing operations; 19
(b) The touchdown zone and the mid-point of the runway intended for Category II instrument approach and landing operations; and
(c) The touchdown zone, the mid-point and stop-end of the runway intended for Category III instrument approach and landing operations.

[Stanley Eevil]

Hi FD,

in your example, the forecasted visibility is greater than the required RVR for CAT I, hence LIDO (example of what we use in my company) will accept it and will not mark it as "U".
Regarding the conversion, you can convert 600 m of visibility. What the rule says is that you can't convert in order to find RVRs lower than 800 m. If I have a general visibility of 400 m and a conversion factor of 2.0 I will find a CMV of 800m, I'm ok. On the other hand, if I have a conversion factor of 1.5 with the same visibility (daytime, HIRLS) I will find 600 m, less than 800 m , so not allowed.
Let me know your thoughts.
This is EXACTLY in accordance with my own interpretation of the rules for CMV as I posted earlier.

[KingAir1978]

No, You can by using the CMV table.
KingAir1978 would disagree with you I believe?
No I typed something from memory that wasn't entirely correct. Below 800m LVP should come in force, and you SHOULD be provided with RVR. I've amended my previous post.

With regards to single pilot ops... I'm not too knowledgeable about that, because it's been more than 15 years ago that I've operated single pilot. I seem to recall that you need a working autopilot or HUD if the vis/rvr falls below a certain level, but I'll leave that for others to answer.