CB / TS - during approch and landing
 

hi all

i am looking for advice on dealing with CB/TS Wx during the approch and landing phase of flight

i have tried the "net" but could not find anything useful (just theory of CB wx)

any advice and help much appreciated

fly safe

newcrew

Stay well away from them.

End of story!

What he said. Go to your alternate if necessary. Go to another alternative airport if the primary alternate is not available.

DFW and virtually everywhere in Tornado Alley - don't even
THINK about it! Either carry sufficient holding or bugger off
somewhere else.

i like that idea in theory but...

my understanding is that in some parts of the world (Africa and SE Asia) both the destination and alternate will be forcasting Sct CB (no prob or temp)

what now?

Hi,

You will have to avoid the weather using your weather radar and that's it. If there is too much of it, you may have to hold somewhere and decide to wait for improvement or divert, that means carry extra fuel. All approaches are different even with good weather so there is not a single working rule. Just use your knowledge and common sense and last but definitely not least your experience.

Cheers.

TEMP wx is also controlling for forecast destination/alternate wx, so make sure you plan appropriately. Once you get there, radar and eyeballs will be needed to keep yourself away from them. Make your divert decision early!

i guess the "problem" i have is that you may be diverting to a field which has the same (sct CB TSRA) forcast / actuals

therefore diverting from one bit of shi%^& WX to a alternate with the same!!!

not ideal to say the least...

Each operator will have their own guidance but generally it is 5-10nm horizontal separation down low and 20nm or more at altitude. On board radar is key for avoiding individual cells using the predictable and reliable precip and doppler shift returns to thread your way safely to your destination.

For terminal forecasts with 60% or greater thunderstorm coverage, additional fuel (generally 30-40 minutes) is uplifted to account for delays (ATC) or circuitous arrival paths.

Thinking that one can land in a TS is like an individual who shows up with a knife at gun fight. No good can come from it.

Remember the American Airlines MD 80 in Little Rock, AK?

That's why I said to PLAN APPROPRIATELY! If there are no distant alternatives available, and all the close alternates have the same forecast, then consider not taking off! Otherwise, look at the weather in the descent and divert to the distant alternative before you get low (You DID load the needed fuel, didn't you?).

Here's what happens :):

As Slasher says, adjust your 'extra' fuel for the weather.

It is often forgotten that the 'Div' fuel on your PLOG is from DA at destination. IF you make a sensible EARLY decision, either before TOD or soon after, you will have LOADS of fuel to reach even a far-away DIV and land with RESERVE, making INTRUDER'S logic the only sensible one if both DEST and planned DIV are rubbish.

I'm with newcrew. In my experience, it isn't the end of the story at all. If you take the tropics into consideration, there probably wouldn't be many viable airline routes in the wet season!

The way I see it, for an approach, you may well find the area covered with scattered CBs. If the airport is clear I don't see a problem with continuing the approach if you can remain clear of the weather and preferably upwind. Chances are the controller will be under a lot of pressure and you'll be vectored into the weather, so R/T traffic will be high with requests for deviations from track and late clearances can be expected. I have once heard the poor controller melt down too, obviously then you do what you have to to stay out of trouble.

I have often found CBs down the final approach track or crossing it. Quite often a change of runway is not possible or just plain refused. If faced with that you have to assess if you can parallel the track and/or get back on final before MSA and establish a stabilised approach, just be prepared to break off the approach as soon as you have doubts about achieving that and think well ahead of time in what direction you will break off to too!

Obviously the approach cannot be continued if there is TS in or around the airfield or anything where the required missed approach path will take you. Request an alternate missed approach early if necessary with consideration for how busy R/T is already.

Also, it is handy to have the confidence to be able to separate TCU from CB. TCU will be a bit bumpy but not problematic. It is also helpful to be able to differentiate radar rain returns from convective cells too. Innocent rain is flyable despite being painted red.

If you suspect that a hold maybe a good idea, try to request it early before the approach. Holding above MSA on final maybe an option too.

Keep a very sharp listen out for other traffic, keep each other informed of where the traffic is and what they are requesting, use the TCAS display with the above/below option if available.

During late final to landing, be alert for windshear, don't rely on reactive or predictive systems, but keep in mind the annunciated criteria for a windshear escape manoeuvre - its in the QRH. Obviously, with potentially challenging runway conditions a deep landing should probably be baulked.

With regards to fuel, clearly taking minimum flight plan fuel with the possibility of weather would be highly questionable. I'd probably be looking for an extra 30 mins plus, plus anything else that I usually take into consideration. Sometimes though, you have to make a decision to divert or commit, that decision needs to take into account your current position as you maybe holding away from the field significantly increasing track miles to the diversion field, so what you have entered in the FMC during preflight maybe misleading.

- but probably not - see previous post? People do forget. The Div fuel in the FMC is from DA at destination. Where you hold has little or no effect.

Sciolistes, firstly endorse your post there with much wisdom and common sense.


Going to put my hand up and plead ignorance here - how do you do that?

Cheers mate. So now I'll stick my head up. What I have seen is that convective cells paint a very distinctive picture with distinct edges and usually with clear and steep graduations from green to a red centre (usually offset). The cells can be conjoined but they are still clearly cells. Just rain from cu strat or what I presume are the remnants of CBs with no significant convection; this all looks like a nebulous mass with indistinct edges, sometimes green with indistinct splodges of yellow and red within or sometimes just a mass of nebulous red. For sure, you have to be careful using gain and tilt to ensure you are getting the fullest picture.

BOAC,
Point taken. All I can say is that I have unthinkingly come up with an divert time after reciting the prog and perf pages without thinking spatially. Likewise, I have picked the Capt up on it too. By extension I figured it is an easy and dumb mistake to make.

FFB - the only caveat I would place on 'assessing' rain as opposed to a CB is to, as SC rightly says, use the tilt carefully. Just when you think it is 'OK ' to go through that red/green 'splodge' because it is rain, beware, and think where that rain comes from. Known always (well, nearly always) to travel downwards, remember the old advice of being careful if you fly UNDER a CB.

Looking at the radar 'contour' is normally reliable as stated.

hi all

thanks for the reply's so far

what i was taught was never over / thru / under - your comments!

any minimim lateral avoidance if downwind of CB below 5000 agl?

fly safe

Clearly the "stay well away" strategy is optional in Cuba! Can anyone give an opinion on this landing? It looks nasty but at the same time there is little wind or turbulence.