Shooting Approach w/variable minimums

[calstar]

One night a while back while taxing out for takeoff I heard tower calling visibility to landing traffic "rvr 1000 variable 1200".

Our Cat II mins are 1200. Assuming you are outside the FAF are you legal to begin this approach?

 

[mar]

More information required

Assuming you're 121 (?) you need to dig into your OpSpecs Section C to get a better answer.

You'll find the TDZ RVR is required and controlling.
The midfield RVR is advisory.
And the rollout RVR is required.

Therefore, if the TDZ RVR is 1000 variable 1200 then, no, you're not legal to begin the approach. Go with the most conservative choice.

If the TDZ is 1200 and the midfield is INOP and the rollout is 1000 then you're good to go.

But if you're Part 91, then all of this doesn't matter and you're good to go with Zero Zero.

Post a follow up question if you need to.
Good luck.

 

[Donsa320]

One night a while back while taxing out for takeoff I heard tower calling visibility to landing traffic "rvr 1000 variable 1200".

Our Cat II mins are 1200. Assuming you are outside the FAF are you legal to begin this approach?

I'd fly the approach as far as the final approach segment and get one last RVR check there. If you have minmums, continue, if not, hold as close as you can if you have the fuel. The ILS outer marker is my first choice to hold. Once on the final approach segment I'd say you can take a look if the RVR was 1200 when you got there.

DC

 

[calstar]

Thanks for the feedback. Sorry for being vague.

We are 121. Our op specs state that Touchdown RVR is required and controlling and one other must be reporting. It can be reporting zero but one of the other two has to be reporting something.

Having said that, let's say you are being vectored for the Cat II ILS and you are advised that RVR is down to 1000 variable 1200.

With our Cat II mins of 1200 would you need RVR to be a solid 1200 or is variable to 1200 ok?

 

[mar]

Imagine trying to defend it in court

I'd go with the most conservative interpretation.

That is, TDZ is controlling, therefore you need a *solid* 1200.

One of the other two, as you noted just need to be operational.

1000v1200/1000/1000 is not good enough.

1200/1000/1000v1200 is ok.

Assumption: outside FAF.
Good luck.

 

[calstar]

Thanks for the posts.

I'll take the conservative approach and thus avoid "the carpet dance".

Thanks again.

 

[moving2vegas]

OK...so are observed measurements or reported the controlling factor? Example: ATIS reporting 1200 hard....tower observing 1000v1200. Personally when either one report below mins I go somewhere else, but you occasionally here tower saying this...usually right after the hand off.

 

[mar]

Hopefully you're landing near the TDZ

Only the TDZ RVR is controlling because, like, that's where you're gonna be landing.



If the tower offers his vis it's only for information. A lot of times there can be fog bank over a large airport with multiple runways and if you have the choice of an approach to a runway (with better vis) on the other side of the airport then (maybe) you should choose that one.

But don't base your decision of legality on what the tower is reporting.

 

[Global33]

tower observing 1000v1200

The tower cannot "observe" RVR readings. RVR is based on runway-specific transmissometer readouts only. However the tower can issue "tower visibility" reports, which usually involve the controller or weather guy looking at fixed objects at known distances from the tower. But that doesn't really help at an airport where RVR is used for the landing runway since the RVR is controlling for that runway and takes precedence over the tower vis.

 

[AngelKing]

The tower cannot "observe" RVR readings. RVR is based on runway-specific transmissometer readouts only. However the tower can issue "tower visibility" reports, which usually involve the controller or weather guy looking at fixed objects at known distances from the tower. But that doesn't really help at an airport where RVR is used for the landing runway since the RVR is controlling for that runway and takes precedence over the tower vis.

But the tower is looking at real time RVR readouts. The ATIS will always be behind since it has to be recorded.

AK