Present weather conditions ( rain.) has tempted me to recount a shared flight I had with a fellow syndicate IMC rated pilot, on a trip from Sleap to Elstree.
He flew our C172 there, in very good VMC, following his magenta line, as they do..!


I had the return trip, but bumped into a wall of rain clouds around Clee Hill. So my tactic was to descend to 550ft agl to remain in VMC. However it got worse, and maybe below legal VMC conditions. So I handed control to my friend, who seemed to be worried about Minimum Safety Altitude, and he decided we needed to climb to 2100ft, where the rain was even worse with zero visibility. No sooner than we had climbed, we broke out of the back side of the rain-cloud into cavok again.


I think this just shows the different strategies of VFR and IFR flight.
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That was the right choice your friend did. If you're being pushed down to 500 AGL and you're not capable of climbing into the clouds, it's a good time to divert and turn back to where you came from. But for the love of God don't get trapped under a closing gap between clouds and terrain!

Just shows different levels of capability we have on the forum.


I fly helicopters. On days with low cloud I have the bug on the Radar Alt set at 600ft. If the "boing" triggers, I turn around, or find a way around, or put it in a field to wait for the cloud height to improve.


Personally, I won't continue if cloud forces me that low (and I have no IFR option anyway on single-engine un-stabilized helicopters). I don't consider myself to be good enough (I don't have military low-level training) to fly safely in those conditions.


Hats-off to those that do have the skill

This has happened to me a few times when pushing conditions.

Certified light aeroplane response - climb into cloud.

Microlight response - land in a field next to a pub.

Both are entirely legitimate, depending upon steed and circumstance.

Not allowing yourself an option of course, is where legitimacy of action breaks down.

The single engine helicopter pilot's actions are pretty obvious. Field. Pub !

G

Could somebody please post a picture of real marginal weather conditions to compare it to the perfect VMC of the first post?

I think "marginal" varies with pilot and aircraft

Perhaps a decent rule of thumb is that when you struggle to see the ground over the nose of the aircraft in level flight it's getting "marginal". Frankly, I find that trying to do navigation by chart and features is pretty difficult when you can't see in front. At 2000' in yer average spam can, you can't see nearer than a couple of miles in front so when the ground starts to disappear from the forward view you're still legal, but whether it's sensible is quite another matter.

Let's not deceive ourselves here. The legal limits for VFR are - in the UK - IMHO really low. When the visibility drops towards the legal minimum, the last thing you need to be worrying about is the legality of the flight. If you're only trained for VMC you need to think fast to achieve a safe outcome.

Minute 5 in this video, I'd say this is marginal VMC:

https://www.youtube.com/watch?v=UCzvEZOR7t0

Haze is reported in METARs/TAFs....(HZ)....but, like mist (BR), it should only be reported when visibility is 5km or less.

They say later in the vid that visibility is around 5 miles - 5x UK legal minimum.

You mean 5 times the minimum of 1.5 km for special VFR?
Special VFR only applies within a Control Zone and is subject to ATC clearance.

Anyway, minimum visibility is 5 km below 10000 feet. If they were reporting 5 statute miles, which is 8 km, it's 1.6 times the minimum. BTW, 8 km is the minimum above 10000 feet.

This comes to show how low the legal minima are. 8 km visibility is not much at all, certainly a big stressor for the VFR pilot if he's flying in unfamiliar territory.

I still consider a widespread visibility of 8 km as marginal for VFR flight.

I agree. If any of the metars or forecasts relevant to your flight are less than 10km then your average vfr only pilot needs to think carefully about what they are about to do.
Cloudbase too is often treated casually. Less than 2000'? Think carefully about the met situation. What is going to happen next?

Nope. I mean 5x the legal minimum of 1.5km flying in class G, in the UK and under 140kt.

In my world marginal visual flight rules MVFR do have a definition.

See what at 5 Km? A white house against dark moorland, or a cloud against the grey haze background?
I'm not happy in haze unless it's unlikely to contain cloud at my level. Cloud base of 2000' or less doesn't bother me IF the air below is crystal clear, with a few rain showers easily avoidable. Cloud forming at my minimum cruise altitude is definite turn-back/divert.

I've happily flown air experience flights in a microlight (55kt) in 4,000m haze but overcast at about 2,000ft hence no sun effect so it was uniform all round. All depends what speed you are doing.

That minimum is not the "standard" minimum but one that applies under special conditions. It should not be used as a reference...

Flying VFR with a vis of 1.5 km is asking for big trouble regardless of how legal it is.

https://i.imgur.com/6Bqguvi.png

In my opinion, one "shall" not attempt VFR flight with vis less than 5 km and/or ceiling less than 1500 feet. This is the "absolute" minimum. A 50 hour PPL should definitely not fly when just barely legal, your mileage may vary...

Crystal clear air and few showers means instability, TCUs and CBs. You may be happily flying under the overcast and suddenly enter the convective updraft/downdraft of a nasty CB right over you. You don't want to be in that situation at a low altitude.

Not saying what you do is wrong or whatever, just that you should know what you're doing. If that's the case, no complaints (would like to fly with you in that situation to learn how you do it because I wouldn't dare to be honest).

For me it's "embedded CBs" in the forecast - if they're forecast I don't take off.

1.5km is standard inasmuch as it is legal in the UK. The original question was about the legality of flight and the possibility of loss of licence. The fact is, it is legal to fly VFR with visibility down to just less than a mile.

I am not advocating VFR flight in poor visibility and I agree with you that flying VFR down to legal minima is asking for trouble. I'm sure most of us would want to be back in the cafe when we can no longer see the ground over the nose of the aeroplane.