Landing Minimums Question

[bozz66]

I'm confused over landing mins here in Midland, Tx.
I thought that for Part 135&121 that to be able to fly an IAP, you need at least the mins on that particular approach. Unless you go below mins inside the FAF, in which case you can continue the approach down to DH or MDA.

Well this is the Metar for Midland(KMAF):

METAR KMAF 271653Z 08005KT 1/8SM FG VV001 13/13 A3000 RMK AO2 SFC
VIS 1/4 SLP138 T01280128

It's been like this all day, yet listening to my scanner, I've heard a Southwest and a Cont. Express ride down the ILS 10.

The mins for the ILS 10 are RVR2400 for all Cats. here at KMAF.

Are their Operations Specs allowing them to do this with lower visibilties?

Thanks,
Mark

 

[flx757]

Did you hear the tower issue an RVR report? Typcially, RVR is not reported in the METAR. As you indicated, the minimums for the ILS 10 are RVR 2400. Therefore, if the tower reports an RVR of 2400 or greater, then they are legal for the approach.

 

[bozz66]

Thanks for the reply flx757.

No, I didn't hear the tower give out the RVR. Where I live, I can only hear the aircraft. I understand RVR is controlling when it comes to an approach. I thought since that RVR wasn't in the Metar, you could convert the visibilty to an RVR value. It just seems that 1/8mi visibilty would be well below 2400RVR. But like you said, the tower must have reported at least 2400RVR to these guys.

Got another question for ya,

If the RVR isn't in the METAR( which I originally thought it was ), where do 121 pilots ( or their dispatchers ) receive that info? My understanding is that they can't even depart when the destination is below mins.

Thanks,
Mark

 

[flx757]

Mark,

RVR, since it can change rapidly, is usually not reported in the METAR, though I have seen it occasionally. In the remarks section of the METAR you provided, it indicates that the observation was an automated observation and that the surface visibility was 1/4 SM. Where on the airport these observations were made is unknown (at least to me), but an RVR report is specific to the TDZ, midpoint, and rollout areas of that particular runway.

As far as departing under FAR 121 to a destination that is currently below landing minimums:

121.613 states that ....."no person may dispatch or release an aircraft for operations under IFR.....unless appropriate weather reports or forcasts, or any combination therof, indicate that the weather conditions will be at or above the authorized minimums at the expected time of arrival............

So, an aircraft may depart if the forecast indicates that the weather will be at or above landing minimums at the ETA. Of course, then there are considerations for the alternate airport(s).

 

[bozz66]

OK, I think I catch it now. Even if a Metar shows it below mins at your departure time, if a forcast shows it will be above mins, you're good to go.

Slowly fillin' in the gray areas!!!

It was kind of embarrassing this morning when I told my fiance that the airport was probably closed due to the WX and then turn the scanner on only to find out the airport is busier than it's been for a week



Thanks for the info,
Mark

 

[neflier]

A couple more points on this. As was stated, it is the TAFs that are controlling for dispatch. Depending on the ops manual, 121 can dispatch under exemption 3585, which will allow us to dispatch with the destination weather conditionally as low as 1/2 the published minimums. This is provided we have a second alternate listed, along with other restrictions.

Upon reaching the destination, the TDZ RVR is controlling. The tower vis may be 0, mid field and rollout RVR may be below landing mins, but with a good TDZ RVR, we can shoot the approach.

Clear as mud now?

 

[bigsky]

I havent seen your exact op specs however normally for exemption 3585- that only applies to the conditional language in the forecast(such as tempo, chance, prob) and the main body of the forecast has to be at or above mins.

 

[neflier]

I havent seen your exact op specs however normally for exemption 3585- that only applies to the conditional language in the forecast(such as tempo, chance, prob) and the main body of the forecast has to be at or above mins.

Uh, did you read my post?
"with the destination weather conditionally as low as 1/2 the published minimums"

Just trying to add more to this thread without painfully going into the details of 3585.

 

[doubtful]

from this page at the top you can click on the link and then find the rvr for many runways around the US.
http://rvr.fly.faa.gov/rvr/help.html

 

[cvsfly]

METARs are reported weather and may be automated in which case the RVR usually is not included. RVR will be reported in an ATIS if avail. I guess that prompted the new web site for RVR.