Flying with CB Activity

[foxmoth]

or even under them if you want a 100-150kt car wash and get chucked around a fair bit.

I would be very careful flying under a CB, Airliners have been unable to cope with some. It is not necessarily when it is raining that you get the biggest problem, this usually happens as it starts raining heavily, that is when you get the biggest downdrafts - not to mention of course the chances of a lightening strike!

[IO540]

VFR: avoid visually, work out their track and cross behind them, not in front.

Why? The cloud moves with the wind, only. As far as the atmosphere is concerned, the cloud forms, builds up, and dies without moving along horizontally.

[172driver]

I would be very careful flying under a CB, Airliners have been unable to cope with some

Absolutely correct. You can easily get downdrafts which a small a/c simply cannot outclimb.

If at all possible, avoid CBs like the plague. And don't get fooled into thinking 'in Europe they are harmless'. They are not, and in some parts of Europe (Alps, Spanish Sierras) you can get stuff that rivals the US.

On a slightly different note, the argument about 'avoiding CBs might put you into CAS' is largely a UK problem. On the continent you generally get CAS penetration/transits very easily and ATC will usually be very accommodating if you explain why you need to do what you're doing. I've been cleared w/o any trouble through mil areas in France while slaloming through a squall line.

[rmac]

IO540

You make some very good points about limitations of MEA etc. I bet you are talking about the germanic types though

Down here in the centre, where there is a lot of CB a activity in the summer, arbitrary, non terrain related MEA can be negotiated. For example from Bratislava to Wiener Neustadt the SID takes you up to 7000ft and initially away from the destination for ten miles. I guess for separation from inbound traffic. If you don't file this, Eurocontrol will reject. However after departure I would normally ask for, and get, a level off at 3000ft and a short cut. Coming back the other way however, try getting anything out of the Austrians

If I come back from the Slovenian coast and the weather is iffy, I will take an extra 40 miles and dog leg through Hungary, to avoid the busy and less than flexible Vienna airspace.

[IO540]

I agree Rmac that one can discard the published MEAs "due weather" - I remember transiting Germany once at FL080 keeping just below the freezing level, IMC (and icing) all the way otherwise. They didn't like it but let us do it.

However I don't think this is a good IFR strategy, because down below the cloud you have severely limited options in bad weather. Clouds have a habit of lowering and before you know it you are back in the muck, and if CBs are forecast you are back in the risk of going into one. I'd rather be on top where one can see for tens of miles and be ahead of things.

[Wrong Stuff]

Originally Posted by IO540

VFR: avoid visually, work out their track and cross behind them, not in front.

Why? The cloud moves with the wind, only. As far as the atmosphere is concerned, the cloud forms, builds up, and dies without moving along horizontally.

Because of the relatively stronger higher level winds, any overhang or anvil will form downwind of the main body of the thunderstorm. Hail ejected from the upper levels of the thunderstorm and falling outside it in clear air will generally be from this overhang area.

[IO540]

OK, you are talking about really big CBs, with the anvil topping off at the inversion layer.

[SkyHawk-N]

OK, you are talking about really big CBs, with the anvil topping off at the inversion layer.

The anvil tops off at the tropopause. Try not to get infront of a large CB. You will probably find a strong gust front and roll clouds up to 15/20 miles ahead of it.

[DFC]

Why? The cloud moves with the wind, only. As far as the atmosphere is concerned, the cloud forms, builds up, and dies without moving along horizontally

Very true but most flights are planned to follow a ground track ( a line on the map).

If there is a CB ahead on your route and it is moving left to right over the ground then a change of track to the left will be more efficient (require less deviation from original track) that one to the right.

Never fly under a CB. The moment you decide that what you are looking at is a CB then the option to fly through or under it are gone.

If you can't go round then hold and wait for it to clear your track before proceeding.

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I would disagree that people who use visual navigation properly - i.e. map and ground will have problems. Provided that they can navigate and allow the appropriate margins.

The simple diversion techniques thaught at PPL level work very well. Can't decide if you were not taught them correctly or if you simply can't do them but in either case the problem is not with the technique.

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If in order to avoid a CB the only optionyou have is to enter (for example) the Heathrow Zone or an airway or any other controlled airspace then call and obtain a clearance - you can not be refused if it is your only safe option. i.e. the turn back option is not available. Even if you can not get the clearance and the only safe option is to enter controlled airspace then remember;

Aviate
Navigate
Communicate

Safety first, talk / write later.

Never fly through or under a CB.

Regards,

DFC

[rmac]

IO 540

You make some good points, however, if you refer back to my original post, I was recommending being in the IFR system under light IMC or VMC conditions where the CB's are visible, in order to secure sensible deviations without worrying about airspace infringements etc.

As you suggest if embedded then get on top if possible, but with the limitations that you earlier referred to i.e. possibility of running in to one on the way down.

I flew for four years in Singapore, initially was happy with on-board radar, after a few scares put in stormscope to help with identifying attenuation issues, eventually fitted water diviners and prayer mat too, just to be sure

[scooter boy]

Having CBs in the forecast just means be careful - you can still fly safely. The CB tops don't have to reach the stratosphere. They tops can can be from 10000 to 35000 (usually they are just above my svc ceiling!)

If they are not embedded then just keep your eyes open and fly around them giving them a wide berth.

If the CBs are embedded with tops below your svc ceiling then go over the top of them.

If they are isolated and the general cloud tops are below your svc ceiling then fly over the CuSc and avoid the CBs (you will see them sticking up - usually right along your route of flight and nowhere else!)

If they are widespread and embedded in a front or trough and represent a solid line that is not practical to route around then I would either plan a later departure or get as close as possible, land and let the weather pass over the top.

If they are very isolated and you have a stormscope / weather radar or preferably both then you can pick your way through but it can be rough and very icy in there.

I would recommend Richard L Collins book "Thunderstorms and Airplanes" - it dispels some of the myths about CBs.

SB

[mark147]

If the CBs are embedded with tops below your svc ceiling then go over the top of them.

Flying over the top can be a bad idea. If the CB is still developing, it can grow very rapidly (faster than you can climb). If its surface looks very crisp and well defined, only fly above it if you can stay well above or if your plane is fast enough to get of its way pretty quickly.

Lots of interesting stuff about CBs here:
http://www.ais.org.uk/aes/pubs/aip/p...4_P_081_en.PDF

Mark

[spitfires rule]

CB's

I would say if its isolated go flying but with frontal storms or embedded stay at home. Also never fly under a storm even if you can see through it and its best to deviate to the right of a storm because this way you will have a nice tailwind to help you get out of the storm area faster.
http://www.youtube.com/watch?v=Rx6mjyKuXdg