Just thought of a scenario that can't stop thinking of. I think I know the answer but thought I would throw it out into the public and see what others think.

I was being "nerdy" this morning looking at MSP. They were CATI all morning but had a program and ground stop and then this METAR came out:

KMSP 231544Z 04015G19KT 1/2SM R30L/1800V2000FT SN FZFG BKN003 OVC010 M02/M04 A2974 RMK AO2 P0001



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Per the jepp, minimums for ILS30L is RVR18, which we have. My question that arose is, what if you got a variable report of R30L/1500V1800FT. Can we still shot the approach? Keep in mind this scenario is only based on what the METAR/ATIS says, not the updated RVR reports from rvr.fly.faa.gov and/or tower.

I'm thinking we can't based on R30L/1500V1800FT alone but if tower indicates the TDZ RVR is 1800FT, we can still continue obviously.

I know its a once in a million question but I can easily see this as a prime interview question you know

Thanks!

 

I am going to say tower trumps the METAR in the case of a fresh or current RVR statement, so if they say its actually 1800FT RVR then the approach is a go. I would want to verify what the RVR is while on the approach one more time to be really sure and for CYA purposes to make sure it is on tape.

 

We use to have some that would play this game with the winds. ATIS calling winds out of limits and a flight would sit down at the hold short for the runway and ask tower for a wind report about every 30 seconds until they got the answer they wanted and then shoot of ito the wild blue yonder.
In this case - as Cub said - the report from the tower (real time) outweighed the recorded report (ATIS)
- as a note - others would then come up and request that tower update the current ATIS with either the new winds or, more than likely, a problem with the new visibility.

USMCFLYR

 

You'll see that on METAR reports from time to time. They are trying to convey that the RVR is different than the prevailing, and that it is variable. It could be changing often, or it could be that they are saying that the touchdown and mid are different. When on approach, you will never hear that the RVR is variable. They will just read you what it says for touchdown, mid, and rollout. It may be changing often, so you may need to ask again, or stop asking once you hear what you want to. Also, never ask for a RVR report if you are already inside the FAF.

 

Thanks.... I knew the towers TDZ RVR report (MID if TDZ is OTS) trumps what the ATIS/METAR says. Just one of those "gotcha's" that would make the perfect interview question, hence the reason I asked

All the reports are only applicable to CATII/III and takeoff minimums right? I'm thinking too much and its causing me to forget what I know

Thanks

 

A variable RVR is the high and low of the last 10 minutes. You don't care what happened ten minutes ago. All that matters is what the RVR is when you join the final segment of the approach.

For a CAT 1 approach, TDZ is controlling. CAT 2, TDZ is controlling, rollout is required. CAT 3 to 600 feet, TD and MID are controlling, RO is required. Below 600 feet all three are controlling

 

I have a follow up to the original question. Suppose the flight was planned at :40 minutes. Can you be dispatched per 121, CAT I, if the RVR is variable between 1500V2000?

 

See I knew that but thinking of this weird question threw my head for a loop. I didn't know about the below 600' thing, guess its similar to CL & HIRL runway lighting for 500' takeoff minimums yeah?

I'm almost positive you can't solely use a METAR to dispatch but in theory you could use 3585 if you have the exemption.

 

121.599 says to be familiar with reported and forecast weather conditions. 3585 only provides for the remarks sections of a TAF. I had this happen to me a few years back. I opted to wait until dispatch could either find a better METAR or until the weather got better just to CYMOA.

I'm just wondering if I was being too conservative or if it was actually legal.

 

It would depend on what the TAF says. Current conditions are never an absolute no-go, it all depends on forecast at ETA.