Flying with CB Activity
 

Flying has been somewhat curtailed recently due to either low cloud / mist / fog and now CB activity. I have always taken the view that CB activity in a TAF is a no no for light aircraft flying. Am I being too cautious? If there are few CB or sct CB would it be deemed safe to fly provided you steer clear of them? Or is the view that flying should be avoided if there is any CB activity around?

Try flying in Florida during the summer - CBs almost every day, they come and go within a couple of hours. Be aware of where they are and stay clear but it doesn't rule the day out for flying.

I tend to be wary of embedded CBs showing in the forecasts - it's not so bad if you can see them and navigate around them (for which I do the old 60 degree 2 minute dog leg).

So no hard and fast rules as it depends what kind of front is causing them too.

Isol, few, or CBs around a particular front all could indicate flying can be done.

Having said that, a building Cu (not CB) on one of my first solo navs once gave me a couple of severe jolts that made me give the big 'uns a bit more respect.

If you can see them, go around them. It's the embedded ones when you go IMC that will bite. No reason not to fly though.

That is one of those questions with no yes or no answer - it depends - and the dependance ultimately comes down to experience.

At one extreme well spaced CBs that are clearly visibile and avoidable are not going to present a problem.

Clearly, at the other extreme embedded CBs, without a stormscope are more than I am willing to take on.

Of course as is usually the case with the weather there is every variation in between.

There are a number of good books that deal with met for the VFR pilot which are well worth a read and include solid discussion about flying around CB activity and how to avoid the worst of the associated problems. I would certainly invest in one of the better ones before the summer season is properly underway!

I found out about embedded CBs once a few years back when (fortunately) flying with an instructor on a longish trip. It wasn't fun, but taught me a lot about icing, especially when the pitot heater failed :)

Has since made me very wary of days with CBs around and I think i err too much on the side of caution - have binned many a cross-country trip when they have been bubbling up. Another concern in the SE is that you often don't have much room for manoever due to controlled airspace. I do find though that CBs that seem to cover a massive area from the ground can look much more isolated once you're airborne....

Fuji - if you can recommend a specific book I'd be interested

You are too cautious.

It depends entirely on what other IMC there is about.

If there isn't any i.e. it is just CBs here and there, what you will have (UK/N European context, not Florida or Africa!) is some huge clouds, well scattered, with bases around 2000ft, very rarely lower than 1500ft (and rarely higher than 4000ft) and you can fly around them easily, or even under them if you want a 100-150kt car wash and get chucked around a fair bit. And the one you don't want to go under are obvious; the gap between the bottom of it and the ground is one solid column of water :)

So, VFR, not a problem, unless you get one close to departure or destination in which case you need to wait a bit. You don't want to be doing a landing anywhere near a CB (wind shear).

IFR is much worse, because you could be in IMC, and in any case under ATC control, and fly into an embedded one. I scrap any IFR flight where CBs are likely or forecast, unless the conditions as as in my VFR scenario above in which case visual avoidance is an option. There are problems with that though because of lack of online data on cloud tops especially with this kind of weather around.

In short, CBs are a non issue if you have lots of empty space to go to instead.

Skin Friction

Not to hand at the moment - I will PM you my favourite at the weekend.

Caution is a good thing where Cb's are concerned.

If you can see them, can fly around them, with plenty of room to get between them then that is ok. If you are IMC and can top them and / or have weather radar, that too is ok. Trying to fly in IMC with embeded Cb's around in Europe is Russian Roulet. In the USA ATC can give pretty good avoidance but over here it is non existant.

I think these are available to all, from AOPA ASF in the USA about thunderstorms and it gives some pretty good advice, although most is aimed at flying in the USA. Well worth a read....

http://www.aopa.org/asf/publications...WT.cg_n=aa_asf

http://www.aopa.org/asf/tstormCard.p...WT.cg_n=aa_asf

The main bugbears with weather diversions for CBs, heavy showers etc, is unplanned ( and unplannable) navigation changes, and resultant frequency changes etc, and controlled airspace incursion (possibly inadvertent, with all the knock-on repercussions of that)
In short, they can really cock up your whole day!

Well, yes, if you are going to fly in conditions that might actually require a change of route or even a change of destination, you want to be flying with a decent moving map GPS so you can see where you are at all times.

The quick back-of-a-fag-packet diversion calculation done in the PPL doesn't really work when doing it for real under pressure, especially if trying to avoid CAS.

Dead reckoning is OK if everything goes to plan but if you have to divert from halfway between two waypoints and do some random weather avoidance, the plan falls apart fast.

CBs in the USA tend to be more of a problem than those encountered in the UK, although I agree you have to be careful while flying around any CB.
The ones in the USA develop to a much bigger beast and the danger of extreme turbulance, updrafts, downdrafts and shear are that much greater (not forgetting the hail, rain and lightning!). Flying around them can be difficult due to their size, it's best to land and seek shelter until they have well and truly passed by. You don't often see anvil heads over the UK but in the US they are a regular occurence.

Dennis Newton's Severe Weather Flying is a must-read, though it's more focused on IFR needs.

The ones in the USA develop to a much bigger beast and the danger of extreme turbulance, updrafts, downdrafts and shear are that much greater (not forgetting the hail, rain and lightning!

Not to forget tornados.

I've seen one, not a reassuring sight :{

If CB's are about on a light IMC or VFR day, consider filing IFR even if you intend to remain in VMC as much as possible. Once you are in the system then CAS busts and navigation worries for deviations become much less of an issue.

I came back to Europe from Singapore two years ago and last summer was amazed by the level of CB activity down here in the centre. Not quite Singapore levels but heading towards it on some days.

This week we have already had a fair bit of convective activity and it is still only early May. To be honest this years annual I had storm scope fitted to back up the picture from the weather radar after a few hairy days last year.

I would concur with most of what has been said here, other than to remind you that on a good convective day, (late spring/mid summer, high humidity, light winds), CBs/Cu's develop very quickly and can do so behind you blocking off your point of return.

Be well prepared to divert and sit it out and, until you have the skills to navigate away from any poor weather, never ever go near or underneath a CB.

Oddly enough, I would argue that one both ways.

It's true that if on an IFR/airways flight plan, flying under ATC control, controlled airspace becomes irrelevant, so you can ask ATC for a "20-left due weather" etc and they will (usually) let you. Even national frontiers, within Europe anyway, become irrelevant, although ATC can get very grumpy if your diversion means they have to make a phone call to the other country's unit...

However, European airways routing levels (MEAs normally FL070+) normally place you initially in IMC, so the strategy is to fly VMC on top where it's nice, sunny and smooth. But you have to get there somehow, and back down again at the other end, and the IMC section cannot be avoided, and if that IMC has embedded CBs then you are in big trouble.

However, if you can do a flight under VFR in Class G (by far the most common UK private flying context) then you can avoid IMC at your leisure, and ensure that you can always see what you are flying into.

I had a very good one last year south of the Alps, where a specific IFR flight would have taken me into solid IMC with embedded CBs, big thunderstorms actually looking at the sferics data for the region, and due to the SID distance would have doubled the flight distance. Whereas a VFR flight at ~ 3000ft was in perfect VMC and smooth.

Filing "low level IFR" (below the airways i.e. not on a Eurocontrol flight plan) in the UK, which an IMC Rated pilot can do, doesn't help at all since the flight plan doesn't go anywhere of relevance. ATC units either file such flight plans as VFR (in which case nobody looks at it unless looking for the wreckage) or they file them correctly (via Eurocontrol) which usually fails because of the problems in filing IFR flight plans OCAS. And it still doesn't help because the pilot doesn't get the implied enroute IFR clearance which airways pilots get.

But yes, accurate means of navigation is a must because one must not bust airspace while flying a diversion. It also raises an issue with notams; if you bust some summer airshow...

Hi

Another great book is Weather flying by Robert Buck. Seems to be regarded as on of the classics on the subject. Currently available in some london highstreet bookshops.

And I agree, CB are not a problem if you can see and avoid, we would be grounded 6 months of the year in Africa otherwise!

Best

Crash

IFR: embedded? don't fly without WX radar.
VFR: avoid visually, work out their track and cross behind them, not in front.

Even if US CBs are more "developped" than UK ones, any CB (even junior-CB) are dangerous for light aircraft.

As someone who flew a lot where thare are also nasty, rocky, pointy things (a.k.a The Alps), I learned that deviation or circumnavigation is not always possible. Get any single CB in the Geneva area, and you can hardly fly in and out. And if I had to choose between CB and rock... well I don't.