Tower Weather Reporting

[BajtheJino]

One I couldn't understand: Called the airport in sight about 12 out, approach advised me RVR was down to 1200 so he was unable to issue the visual but the odd part was I could see the entire length of the runway...A small patch of fog had rolled up the hill and parked itself right over the Machine.
My question is, aren't the people in the tower "trained weather observers" and able to correct misc. info like what was happening? Weather all around the airport at the time was OVC 5,000, VIS 10+ with light showers in the area, valley fog.

[icephalt24]

Per the 7110.65 2-6-6

"When the prevailing visibility at the usual point of oberservation, or at the tower level, is less than 4 mores, tower personel shall take the prevailing visibility observations and apply the observations as follows

1. Use the lower of the two observations (tower or surface) for aircraft operations. "

Yeah, they're certificated weather observers, but thems the rules.

[surreal1221]

A lesson in prevailing and sector visbility may be in hand.

Yes, most tower FPC's are certified weather observers, but the odds of them actually doing any type of observing are pretty slim these days. Plus, the vantage point for a controller is much different than a surface based observer / automated sensor.

Also, what airport is this? The observation may be automated, and all towers do have the ability to augment / amend the observation before it is sent out. . .BUT. . .if there was a SFC based human observer monitoring the system he/she is the one who would augment / amend the observation.

[BajtheJino]

Yeah I knew most of that stuff already but the situation was the field was clear EXCEPT the small part of the airfield where the ASOS is-which is beside the edge of a steep hill, with a stream at the bottom that gets quite a bit of fog after a rain. The part I couldn't understand-1200RVR but they cleared me for the contact...Anywho...

[Stone Cold]

Originally Posted by BajtheJino

Yeah I knew most of that stuff already but the situation was the field was clear EXCEPT the small part of the airfield where the ASOS is-which is beside the edge of a steep hill, with a stream at the bottom that gets quite a bit of fog after a rain. The part I couldn't understand-1200RVR but they cleared me for the contact...Anywho...

So, you shot a contact approach with 1200RVR being reported? Not good. I remember chewing a few freight dawgs out about doing questionable stuff like that. Doesn't matter what you see, if it's below mins, it's below mins...especially for a contact approach.

I know, you're probably Part 91, but if the FAA gets a bug up their proverbial rear, it could be bad for you. Just FYI, not trying to be a prick or anything...just be careful, especially with the "paper friendly" FAA.

[SIUav8er]

thats interesting, especially if youre part 91. Flight visibility is just that...nothing on the ground can tell you what you see in flight. if i see the runway 12 miles out, id just cancel IFR and go visual.

[casey]

Originally Posted by BajtheJino

Yeah I knew most of that stuff already but the situation was the field was clear EXCEPT the small part of the airfield where the ASOS is-which is beside the edge of a steep hill, with a stream at the bottom that gets quite a bit of fog after a rain. The part I couldn't understand-1200RVR but they cleared me for the contact...Anywho...

RVR isnt measured at the ASOS station, its measured along the runway at one or both ends and possibly in the middle.

[Stone Cold]

Originally Posted by SIUav8er

thats interesting, especially if youre part 91. Flight visibility is just that...nothing on the ground can tell you what you see in flight. if i see the runway 12 miles out, id just cancel IFR and go visual.

I understand what you're saying, however, the FAA looks at it differently. If you cancelled and went VFR, you could get into some serious stuff with landing visually in an airport reporting 1200RVR (technically totally IFR, and below all mins except for specially trained crew). That's the way the FAA looks at it. I'd be surprised if the tower would even clear you to land VFR...

[surreal1221]

Originally Posted by casey

RVR isnt measured at the ASOS station, its measured along the runway at one or both ends and possibly in the middle.

With a transmissometer.

[exleardriver]

damn reply got erased. anyway, agree with stonecold...an rvr is 'gospel' as far as the faa is concerned, no matter what part you fly. part 91 may get away with a 'flight visibility' argument (and with good reason), but there's no 'video' to back up what you saw. an rvr report, however will have been noted for your arrival time. i teach not to mess with rvr's below min's no matter if you're part 91. if no rvr is available, and it's reported just under min. visibility, you may get away with it, but rvr is the lyncher.

[FlySmiley]

This is kind of related.. last night I was flying into an airport (part 135) reporting 2.5mi and 4900 few. Under our rules we can't cancel (even though I saw the airport nearly 30 miles away) since the airport has weather reporting etc.. I was cleared for an approach (tower was closed) and I just kept listening to the AWOS and when I got within 10 miles the vis went up to 3 miles and I just did the visual approach without any issues.

About 10 minutes later I was departing the same airport, and the wx was reporting 4mi and 4900 sct (VFR right?) but the sky was looking a bit different (lower) than when I landed, so I elected to pick up my clearance before departing rather than departing VFR and picking it up in the air. About 400' AGL I was in solid IMC conditions.

Moral of the story, follow the regs and use them to your advantage, but also trust your instincts and take automated wx observations with a grain of salt.

[BajtheJino]

Originally Posted by Stone Cold

So, you shot a contact approach with 1200RVR being reported? Not good. I remember chewing a few freight dawgs out about doing questionable stuff like that. Doesn't matter what you see, if it's below mins, it's below mins...especially for a contact approach.

I know, you're probably Part 91, but if the FAA gets a bug up their proverbial rear, it could be bad for you. Just FYI, not trying to be a prick or anything...just be careful, especially with the "paper friendly" FAA.

Thats just the thing, no where on the field, in the air or in the surrounding county was below mins. I had the field in site, tower had me in site but because of erroneous readings from a machine the whole field goes IFR i.e. unusable? That makes no sense. I wasn't the only operator doing the same thing. An ATR came in not five minutes behind me. Not that that makes it okay if its wrong...But I don't believe I did anything wrong.
And no, I'm not Pt. 91. And the FAA is not the big, bad wolf hiding behind the corner, they're just average people that couldn't hack it in the real world.