Flying over fog...
 

I should know this but I don't.

What distance of fog can a PPL legally overfly? I accept that the sensible side of this varies with height and that 1 mile of fog when at 3,000 feet is no issue compared to 5 miles at 500 feet.

I was met with a big white blanket today and teetered on the edge until sense kicked in and I abandoned.

Whilst driving where I had to go to instead, I wondered how much smaller that blanket would have been fro me to have decided to go for it.

I think had I been 10 years younger without wife and kids I would have gone for it. Having spent an hour stationary on the A34 I now wish I had!

Sorry if this has been asked before.

Never seen the UK CAA "in sight of surface" requirement defined.

according to vfr/vmc rules

Starting point for VFR is min flight vis 8km, min distance from cloud 1000ft vertically and 1500ft horizontally.

But:

Below FL100 Class D, E, F & G
Vis 5km, 1500m and 1000ft from cloud.

At or below 3000ft amsl Class D & E
Vis 5km, 1500m and 1000ft from cloud.
if 140knts or less Vis 5km, Clear or Cloud, in sight of surface.

At or below 3000ft amsl Class F & G
Vis 5km, Clear or Cloud, in sight of surface.

And isn't Fog a really Low level Cloud???

Not sure the above is relevant. Is surface fog a legal cloud, anyway?

It's also wrong, although I don't have the books handy; a UK PPL can fly down to 3000m vis and down to the ICAO VMC of 1500m if he has an IMCR or IR.

All the stuff about a specific distance clear of cloud is silly; nobody can remember the rules, nobody enforces it and the distance is impossible to estimate.

I think that the question was really aimed at getting some clarity on "in sight of the surface". This is not a limitation of the UK definition of VMC, so much of this thread is misplaced. Rather the concept is a PPL licence limitation removed if you hold either an IMC rating or IR.

So far as I am aware, there is no definition of "in sight of surface" contained within the usual reference sources.

To fulfil the spirit of law you might argue that the "surface" you can "see" should be sufficiently close and sufficiently large that you could glide down onto it without going IMC, should the need arise.

That definition is my own, make of it what you will.

2D

look at AIP ENR 6-1-4-1, it gives the table for ATS Airspace Classifications with VMC Minima for each Airspace. The question did not mention IMC just PPL and since most PPLs are not IMC qualified I just stated what was in the Trevor Thom Manual for Air Law.

One question, if there is fog and the conditions are below VMC minima can you fly with IMC rating or is it IFR and you have to file an IFR flight plan, then if conditions improve cancel the IFR plan and go to VFR? Also do you have to have a full IR rating to file and IFR Flight Plan? :hmm:

Cadaha

I think, in the nicest possible way, you may need to do a little more book work.

2d

Rule 5 (glide clear) for fog? Seems sensible, especially if you can see the extent of it...

Hmm.

The question that was asked was what was legal. I don't know of any legal requirement to be able to glide clear of fog. Rules about maintaining a given distance from cloud aren't relevant if you're sufficiently far above the fog or sufficiently low that the rules don't apply.

The only law I can think of that's relelvant is that you must be "in sight of the surface". And, from a legal point of view, surely that's all that's required - to be in sight of the surface? Doesn't matter what bit of surface it is, if you can see it, you're legal.

As is so often the case, though, what's legal and what's safe aren't necessarily the same. There's the ability to glide safely(but not if you're VFR in a twin without an IMC rating or IR). And there's the ability to navigate safely. And probably some other safety issues which aren't actually covered by the law but which are common sense.

FFF
----------------

In sight of the surface is the key.

Think slant angle. If you can see the surface then in most cases you can make that surface unless:

a) the surface is high ground beyond the fog
b) you're flying a winged brick :O

I've turned back more than once on encountering the local east coast haar

2d
Am doing:O

Great place for learning this forum is

I've binned my last copy of Loop but I sincerely hope they didn't write THAT !

If they did, I will light the BBQ with it without opening it :O

Regardless of the legalities, good airmanship would dictate that it is not a good idea to fly over fog in a SEP. What happens if you have an engine failure?

It's fantastic flying over fog. What is defined as the surface?

http://www.dubtrub.freeuk.com/LM032.jpg

Power towers?

http://www.dubtrub.freeuk.com/LM034.jpg

The hills in the background?

http://www.dubtrub.freeuk.com/LM036.jpg

Just loverley!!! Certain precautions need taking, but sometimes risks are worth taking, as long as one knows that a landing airfield within range is available.

And where does the "in sight of cloud, clear of the surface" rule become invoked?:rolleyes:

Fantastic pictures:ok:

Fantastic pics.

An engine failure over thick fog is no different to one on a dark overcast night in the middle of nowhere.

And nobody questions the latter one - in fact everyone is more than happy to take a grand off a PPL to teach them how to do it :O

Oh Yes They Do - on recent threads on the night rating there is certainly a camp (myself included) who prefer not to do it (with one engine) precisely because of the "is that black underneath me fields or cloud" question.

"It'll burn off"
 

Slightly off-topic, but besides the legality, fog, unlike the dark (which tends to start and end at predictable times), can be full of false promise. I planned a trip to La Rochelle with a friend. Checked the Met including the TAFs, starting foggy clearing by 9am. It WAS a foggy morning but on the drive to my airfield I see patches of blue sky with the sun peeping through and think "yes, it'll burn off".

I get to the airfield and although it looks a little hazy, we think we are within IMC rules and take off. Within less than a minute I have climbed above the blanket of fog and cannot see the ground at all. Those holes I saw from the car on the way to the airport have all gone. I am flying to La Rochelle, so continue with the belief that "it'll burn off" ('by 9'). The blanket continues across the channel, across Cherbourg, across Mont-St-Michel, across Rennes.

My friend (ex-army chopper pilot) and I are now adjusting our route to avoid towns and wondering what to do if a) the engine fails and b) we get to La Rochelle and the blanket of fog is still around. We radio La Rochelle and to our relief they have glorious sunshine.

The blanket of fog cleared about 30 miles north of La Rochelle after almost 3 hours flying. The flight over fog was beautiful and nerve-racking, and was also a good lesson in the unpredictable nature of fog clearing!

The return trip was one of the clearest flights I've experienced.

GTW

I agree. That's why I choose to not do night flights, unless I have to. The 100nm FAA PPL night x/c requirement is one unavoidable example of a long night flight.

The privilege is handy to get back in the early evening.

jayemm

The problem you describe is much more of a problem (and probably much more common) the other way round: low cloud hangs near the western French coast, anywhere along that super coastline from La Rochelle to San Sebastian. When present, it tends to be OVC006-008 and it can hang in there for days. When arriving, you can do a DIY descent offshore (through a hole in the cloud, of course :O ) but they will never let you depart VFR and if that doesn't make you want an IR, nothing will.

Sorry to hear about the hour on the A34, but yesterday above patches of fog was glorious, much like DubTrub's pics... but we didn't get anything like as close to the pylons!

The joy of flying aerobatics in the smooth air over Berkshire (which was CAVOK), with a silky layer of fog beyond the Chilterns close by made yesterday one of the very best days of the year for me... seeing just the tip of Didcot power station poking up through the fog and spouting it's steam was quite surreal!