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-   -   CAT I Minima with multiple RVRs (https://www.pprune.org/tech-log/552676-cat-i-minima-multiple-rvrs.html)

nick14 10th Dec 2014 15:40

CAT I Minima with multiple RVRs
 
CAT.OP.MPA.305 states that the threshold RVR is controlling, however if reported and relevant the midpoint is 125m and 75m for the stop end.

Is there anything else written anywhere to contradict the above as most people seem to think the T/O RVR needs to be applied? I can't see why legally but practically it makes sense.

jpboy 10th Dec 2014 16:03

Might need to clarify the scenario fella.

Cat I landing criteria is the min viz (or RVR if used) stipulated on the approach plate for the touchdown zone (usually 550m) then as you quote the mid pt and end if reported and relevant.. So minima is 550/125/75 unless your company is more restrictive.

If talking Cat I T/O then it's dependant on runway lighting and state minima which the company should then translate into something useable in your Part A or Flying Manual eg, Nil lighting= 500m (day only).

It's how we do it anyway (UK based).

barrichello72 10th Dec 2014 16:32

Relevant rvr
 
To add to what has been already said, relevant rvr refers to that portion of the rwy where the airplane is at a speed over 60kts. So if you are able to stop the airplane half way down the runway your stop end rvr does not affect you since you will be slower than 60kts.

B737900er 10th Dec 2014 17:47

You can't use 125m unless your operator has had the relevant training/ approval so it will most likely be 550/150/75.

The chances of the RVR being 550/150/75 would be very slim and would guess that its low level fog over the transmitters.

C_Star 10th Dec 2014 17:56

At my outfit the touchdown RVR is controlling but the mid/ (if reported/relevant) has to be i.a.w T/O minima - ie. 250 m with no CL, 125 with CL and 75m if rollout guidance is used.

IIRC it was clearly written in the old EU-OPS rules. However, in the new EASA PART-OPS I couldn't find a detailed chapter on minima... Has it been moved elsewhere (AMC, or other place:confused:)

Sir George Cayley 10th Dec 2014 19:59

If the vis is less than 550m it's not CAT I

nick14 10th Dec 2014 20:33

The rules quite clearly state that the minimum RVR is touchdown required as per the chart, and if reported and relevant 125/75. So as I read it, legally any operator could have that in their OMA regardless of their TO minimum approval because it complys with CAT.OP.MPA.305.

The reason I ask is the LTC on a line check wasn't sure as he was under the impression the RVR required for mid point and stop end was that required for TO. In this particular circumstance it was 450m. Reported was 550/400/350 hence the confusion whether it was a legal approach.

Skyjob 11th Dec 2014 00:34

"In this particular case" could refer to a runway with equipment downgrades, in which case the 125/75m cannot be applied, as different minimum requirements are published for downgraded equipment.

Just a thought.

Too Few Stripes 11th Dec 2014 08:15

The following is a direct copy/paste for EU ops. I don't have the EASA document to hand but imagine it's the same -

The touch-down zone RVR is always controlling. If reported and relevant, the mid point and stop end RVR are also controlling. The minimum RVR value for the mid-point is 125 m or the RVR required for the touch-down zone if less, and 75 m for the stop-end. For aeroplanes equipped with a roll-out guidance or control system, the minimum RVR value for the mid-point is 75 m.

The 125m for mid-point should not be confused with the minimum take-off minima which happens to be coincident with Cat C aircraft operated by airlines with special approval.

FE Hoppy 11th Dec 2014 10:31

Try looking in
AMC5 CAT.OP.MPA.110 Aerodrome operating minima


As has been said. If it's below 550(or the appropriate value for the approach based on DH and Class of lighting facility) then it's not CAT 1 anymore.

Only then does the multiple RVR bit apply.

Skyjob 11th Dec 2014 11:42

125/75 can only be used if crew can determine things like centreline lighting etc.
Downgraded equipment such as removal of centreline lights can reduce this capability.
Think about it, if you can land and require 1200m as nil approach lights, no centreline lights, no touchdown zone lights (BHX 15 at present for instance due WIP) then on rollout you need guidance of some form. FD's don't contribute on the rollout, and without lights on the centreline and at night centre line barely visibly... RVR's are increased for a good reason, not just during approach.
Granted however, only TDZ RVR is required for a Cat 1 approach.

JeroenC 11th Dec 2014 15:43

CAT I Minima with multiple RVRs
 
Our manuals used to state TO RVR was needed but that got changed (corrected?) a while ago.

Topper80 11th Dec 2014 20:38

Hi,
IMHO there is no relation between landing RVR and TO RVR !! Are just same numbers eg 125, but not related....
Do you have any other reference?? Also from old ops.....

LNIDA 11th Dec 2014 21:11

Sir George Cayley
 
Not quite so simple to say if its below 550 RVR its not CAT1

We now have OTS & LTS approaches (other than standard & lower than standard)

Good old Jersey R26 is a case in point the CAT 1 is 550m but it also has LTS CAT1 with a minima of 450m RVR the DA is unchanged.

R08 CAT 1 is 1000m RVR but just 600m on the LTS CAT 1

Not for the faint hearted given the runway length......

nick14 11th Dec 2014 23:23

The category of the approach is irrelevant. The regulation in question as I stated above is from the Air Operations regulation effective 28/10/2014.

My issue comes out of RVRs issued for all thirds of a Runway for an approach. Touchdown is above that required for the approach. The other two are below take off but above the 125m / 75m as required by CAT.OP.MPA.305.

After a bit of research our OMA gives the above minima so I guess that answers my question.

The regulation also allows any operator to stipulate a minima for the approach of 125/75 regardless of the takeoff minima approval.

nick14 11th Dec 2014 23:46

737900ER,

I don't under stand how you are part applying the TO restrictions for an operator who doesn't have 125m approval but still allowing the 75m. The regulation doesn't provide any exceptions to the rule, the Minimum for the approach is 125/75. Operators are of course going to apply their own restrictions above the minima as they see fit.

Citation2 13th Dec 2014 15:17

The first thing is to define the required RVR for CAT1 by regulation , and does multiple RVR apply to CAT 1? regardless of OM-A or company specific requirements , The minimums for a CAT 1 approach in terms of multiple RVR seems to be quite ambiguous.
Let's say you are not LVP qualified , no LTS qualified , just flying a cessna 172 , IFR equipped , coming to land to an airport with 550/125/75 , are you allowed to shoot the approach by regulation?

ItsMeFromEarth 13th Dec 2014 16:32


just flying a cessna 172
for public transport :confused:

nick14 13th Dec 2014 19:40

Citation,

That's my main problem. I am aware that the majority of airports that have only CAT I provide a touchdown RVR only however there are a number of airports that give all thirds (Riga for example).

Unless there is any other contradicting regulation then CAT.OP.MPA.305 seems to allow anyone to commence/continue the approach with 550/125/75.

peekay4 13th Dec 2014 23:16


Let's say you are not LVP qualified , no LTS qualified , just flying a cessna 172 , IFR equipped , coming to land to an airport with 550/125/75 , are you allowed to shoot the approach by regulation?
Yes you may shoot the approach, because in a 172 you will be less than 60 kts before the mid-point of a multi-RVR runway, so the mid- and stop-end RVRs are not "relevant" to you.

If your landing performance indicates you will cross the mid-point at > 60 kts, then the mid-point RVR is relevant, and must at least be 125m if reported (since this is lower than the CAT I touchdown RVR requirement of 550m).

Remember, relevant means over 60 kts at that portion of the runway.

(The rules differ by country... e.g., in the FAA world only the touchdown RVR is controlling for CAT I. The mid- and stop-end RVRs are always advisory for CAT I).


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