3 miles mist - take off?

bflynn

bflynn

Final Approach
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Brian Flynn
Not flying today, but I was looking at weather this morning at the airport. The visibility is reported as 3 miles mist, winds calm. But is that 3 miles horizontal or vertical? At 3 miles, you should be able to clearly see down the runway, but if it is vertical, then the actual horizontal range could be much less. Take off or not?

I know from local observations and history that this is a common morning thing because the airport was built next to a swamp. It is not pervasive in the area and once at 100’, the visibility is greater than 10 miles with most stations near by reporting clear.
 
Depends on what other conditions are around. I’m usually rolling on at 3 and mist because at 100’ AGL it’s 10 and unlimited. Ours often calls ground fog as “mist”.
 
If they're reporting 3 miles and mist without any ceiling designation, what do you think it is, horizontal or vertical?
Come on, you know the answer to this.
 
bflynn said:
Not flying today, but I was looking at weather this morning at the airport. The visibility is reported as 3 miles mist, winds calm. But is that 3 miles horizontal or vertical? At 3 miles, you should be able to clearly see down the runway, but if it is vertical, then the actual horizontal range could be much less. Take off or not?

I know from local observations and history that this is a common morning thing because the airport was built next to a swamp. It is not pervasive in the area and once at 100’, the visibility is greater than 10 miles with most stations near by reporting clear.
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Horizontal. Vertical visibility is in Sky Condition, is called VV and reported in feet. Seldom more than few hundred feet. Like VV002
 
Depends on why and what else is around. if its localized conditions in a valley or something with blue skies overhead and all around, heck yes. Legal VFR. If 3 miles in mist is widespread, I'd think twice about it. Still might go, if my destination is clear and the mist (or whatever is causing the 3 mile visibility) is forecast to dissipate. Around here if the vis is 3 miles that means there's low clouds all around and marginal conditions. I usually try not to fly that.
 
Doesn't any vis less than 7 miles have to have some kind of condition denoting why the vis is reduced? In this case BR is reported from 7 miles to 5/8 of a mile, at that point it's reported as FG.
Many times as I copied the ATIS and heard something like 5 miles and BR, and looked out the window and there's nothing there to speak of. Mist, what mist, maybe some summer morning haze, but pretty much VFR.
 
I have taken of in those conditions and found that as soon as I was above the "mist' layer, the world was white below me. The mist reflected the bright sun, effectively rendering the mist opaque from above. From below, the blue sky was clearly visible.

The risk here is the inability to return to the runway you left, if troubles occur.

This also occurred to a friend at another airport, years ago, and he found that all the nearby airports were in the same condition, and landed his Luscombe on a convenient divided highway section that was free of "mist" as well as traffic, swung over onto the wide grass median, and waited for the mist to burn off.

This was many years ago, so the next part may not happen now. A State Trooper stopped to check on what had happened, he explained that he landed to conserve fuel in case the mist lasted too long. The Trooper promised to return at half hour intervals, and when he was ready to depart, the highway would be blocked while he departed. An hour and a half later, he departed with the assistance of the Trooper.

I have overflown several airports reporting "mist" that I could not see from above, and landed at one after requesting the runway light be turned on, bright. The lights were clearly visible, in spite of the sunlight reflection. The runway itself was clearly visible as soon as my wheels were on the ground, or sooner. Again, the thickness was no more than 10 or 15 feet, but from above, it resembled snow. The clerk at the FBO assured me there were no objects on the runway, as, at ground level, visibility was unobstructed beyond the runway ends.

How confident are you in your engine, and how far is it to a clear runway?
 
If you can take off, why couldn't you land? At 3 miles, you can see the runway, right, even if it's faded because of the mist?

Yes, my assumption was 3 miles horizontal visibility with an indistinct ceiling due to an inability to measure it. In this case, I know that other airports are reporting clear. This particular airport frequently gets early morning mist this time of year.
 
For me when that it on metar it’s helpful to look at close metars that have different altitude at field. We have a variety of elevation close to us airport wise.
 
Just close your eyes and go! You can figure it out in the air.

Sent from my Pixel 2 XL using Tapatalk
 
3 miles vertical is almost 16,000 ft.. it must be horizontal, as the others posted
 
Depends on the bigger weather picture and forecast as well. Is the vis trending towards getting better, or worse? Usually I find in these conditions it is prevailing, meaning that as I move along it remains 3 miles or better around me. Usually ok. If there is a risk that it drops and I am staying local, I won't go personally.
 
I miss 'sky obscured' and stuff like that. I've tried to like it, but I still hate METAR compared to the old way
 
bflynn said:
I know from local observations and history that this is a common morning thing because the airport was built next to a swamp. It is not pervasive in the area and once at 100’, the visibility is greater than 10 miles with most stations near by reporting clear.
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If I was planning to depart VFR and knowing this I would go.
 
Three miles, a mile in front, a mile behind, and a mile above.
 
I flew in a reported three miles viz. I'll never do that VFR again.
 
Go to the airport, look, decide whether the visibility is good enough. Don't rely on a sensor that may have dust or bird poop on it to ruin a perfectly good flying day.
 
And just to allay any fears - I would file a flight plan.
 
Kenny Phillips said:
I flew in a reported three miles viz. I'll never do that VFR again.
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I've done 600 mile cross countries VFR where much of the route was 3 miles viz and 1500' ceilings. Would I have preferred CAVU and a 30 knot tailwind? Yep, but 3 and 1500 is OK.
 
After a thorough weather check in the area,I would have no problem going.
 
bflynn said:
If you can take off, why couldn't you land? At 3 miles, you can see the runway, right, even if it's faded because of the mist?

Yes, my assumption was 3 miles horizontal visibility with an indistinct ceiling due to an inability to measure it. In this case, I know that other airports are reporting clear. This particular airport frequently gets early morning mist this time of year.
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If you're in the mist you may very well be able to see the runway but once you're out in the sun the glare may obscure it. If it's thick enough you may be able to descend into it enough to where you can see it from a reasonable altitude, but if it's shallow you may not.

Here in the southeast it's quite often hazy in the summer, the visibility may be 3 to 5 miles, only if you're not looking towards the sun. If you are, visibility is closer to 1 mile.
 
my local airport often gets fog that rolls in off the ocean. There's times you can't see the tops of the trees within 2 miles of the ocean, but its a clear day just on the outside of it. I've seen people take off in non-IFR aircraft and disappear into the fog as they climb then turn west to get out of it. Not really a big deal if you know the area well. Non-towered airport, no instrument approaches. I haven't done it as I'm a little more cautious.
 
Yeah, there's a difference in a place with terrain or obstacles and a lot of places. We've done mile and clear of clouds in uncontrolled airspace across the flats of the midwest airport hopping from field to field. At other times 3 miles is too little visibility.

Note the VFR visibility minimums are only there for avoiding other aircraft. You can be effectively in instrument conditions above the VFR minimums.
 
And we just had a fella go flying in mist. He T-boned a grey municipal water tower. Punched a big dent into the tower to boot.
 
Kenny Phillips said:
I flew in a reported three miles viz. I'll never do that VFR again.
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Standby for the wrath of veteran Los Angeles Area flyers. Tower weather observers reporting 2 1/2 as 3 was SOP back in the big car pre california smog rule days. My eyes are watering just thinking about it
 
i dont think anyone can answer for you OP, i guess its dependent on your comfort level. i have flown in 3 viz VFR as well as during IFR training, i prefer to stay on the ground than worry about hitting a tower. 3 reported viz and Haze is a completely diff beast and i aint doing that without IR. but again i am wimpy pilot and i like it that way
 
Mist in the area is ground fog. With other stations reporting clear and after having seen it from higher ground driving to the airport, I’d be inclined to take off at 3 miles or greater, but only because I know the area, including where to look for fields if forced to land straight ahead. More cautious if it isn’t familiar territory.
 
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