Weather avoidance
 

Ok folks couple of general questions this time for me to get greater clarity on weather avoidance
1) at cruise levels when encountering CB cells en route is it better to deviate to the upwind side or the Downwind side of it?
2) are the tails of dissipating Cb's safe enough for penetration
3) At lower levels in terminal areas, my understanding is weather radar returns of green and yellow cells are indicative of rain. Though they are better avoided, in case of unavoidable situation I still can penetrate them and remain safe with some amount of chop expected. Am I right in this interpretation?

I have gone through a lot of literature on weather avoidance,however I find in practical flying, some captains are able to decipher and penetrate weather better than the over cautious approach the books adopt. Weather deviation and avoidance appears to be an area that I need to equip myself better, so any further inputs on practical weather avoidance would be appreciated.

One of the most intense TS I've witnessed recently only gave green returns at FL100. Weather avoidance is not an exact science. Always keep that in mind. You need a lot of experience to make sense of wx radar returns and even then there is a large amount of uncertainty. If in doubt, avoid.

Having said that, yes, the upwind side is usually smoother than the downwind side when avoiding a CB. If it is 'better' to deviate upwind, well, that depends on other factors. For instance do you really expect more than light turbulence 20 miles downwind of a CB? If not, then I would take the most direct route.

I'm not sure what you mean by tails, but if it is the green area extending say 30 miles downwind of some CB's, I would treat it with a lot of caution. Again, experience comes into play.

Again, you cannot just look at the color of the returns and declare it safe or unsafe. Sometimes red is just a heavy rain shower, sometimes green is an intense TS. Look at shape, vertical extent, the actual weather around you, etc. etc. etc.

There is a very nice publication by Honeywell somewhere on the net, I'm sure someone will link to it.

(by the way, I'm talking simple single cell CB's here)

Thank a ton PENKO. Thanks for your suggestions. As you rightly advised I have gone through Honeywell pdf fairly comprehensively. However as you said, weather avoidance is not an exact science. More often than not I find the skippers with several tons of hours of line flying able to predict and penetrate weather better than I do and I'm kinda anxious to master the trickery soon :)

I analyse the weather using manual tilt to analyze the top of the cloud and the vertical separation from the top. There are times when with the auto scan painting green,the manual scan reveals a clear picture till 4000-5000ft below and I decide to enter the patch, only to get jolted around. As you pointed out, I believe there's a lot of experience and general judgement coupled with bookish knowledge that goes a long way in making someone develop efficient weather avoidance skills.

In older radars with variable gain control consider going from AUTO gain to manual Max gain during high level cruise (recommended by one radar manufacturer). At max gain the radar will show a tiny echo which is very probably the tops of a CB which will not show in AUTO.

Treat all areas of CB's with caution.
Not only would I recommend as per previous poster to (if possible) navigate upwind, I would also advise to stay clear of the anvil, dissipated or not. The anvils or tails as you describe can have ice crystals in or under it, causing all sorts of problems to airframes, some even de-icing equipment cannot get rid off...

Folks,
I thoroughly agree with Centaurus's comments.

I have personally hosted (along with peers) a development engineer from one of the aircraft wx. radar manufacturers, he needed to personally see real weather because of complaints about that radar not "seeing" CBs.

He had a seriously new experience, 60,000+ tops were no longer a text book thing.

Hence max. manual gain at high level, "new" advice on use if tilt, and how to use manual gain and tilt at lower levels to distinguish heavy rain from Cb/TCu. All came from that trip. I hope it also aided software development for newer models.

As previously mentioned, this is one area where there is no substitute for experience, Bkdoss, it will come with time and only with time.

I am reminded of an occasion, many years ago, when an eminent and highly respected by all Training Captain, was approached by a relatively new F/O.

The conversation went something like (very oily pommy voice): "Captain XXXX, with your vast international experience, when would you consider it safe penetrate a Charlie Bravo??"
The answer was immediate, the accent thoroughly Australia: "Listen, son, I'll tell something for fxxxing nothing, if you never go into one, you are never going to have fxxxxing accident in one".

A very blunt exposition on the company policy on the matter. Stay well away, don't fly over (there is no safe height over), upwind if you can, downwind stay well out of any returns or what you can see visually. Some of the worst hail will come out of an anvil. Never discount what you can see out the window, correlate it with the radar picture, even at night. Especially at night.


And beware if the biggest trap of all, signal attenuation creating a suckers gap, that "thin line" is probably the edge of the biggest Ts you ever saw.

After various Boeing types with various vintage of Wx. radars and various operators I found the amount of info on Wx. radar usage pitifully minimal. When ever I tried to illicit more info from the tech guys or the training dept. it was unsuccessful. I asked the new upgrades what their command course suggested. Pitifully minimal. "Stay away etc. etc." What I wanted to know was how to use this bit of kit to its best. I knew lots of theory, but we were very much on our own.
I remember once, at night, over the ocean, B767, on HF spotting some returns ahead. We were at FL330. Lots of tilting and sin & co-sin calculations with much thumb sucking. I asked for FL370, which was near our limit, but not so far above optimum to suggest a problem. It took a long time to receive clearance and by then, I do confess, we'd slipped a coupe of miles off the NAT track upwind. During the climb, about FL360 the ROC stopped. It then started to descend at 200fpm while still at climb power and climb attitude. MCT and .02 less Mach broke us out of this snarling quick sand, but at night IMC it was not comfortable. I suspect it was the down flow around the sides of a CB as we cleared its top. So even the upwind side needs respect.
I admit I never did manage to find out all there was to know about the Wx radar installations. Certainly, no manufacturer's handbook was ever issued. FCTM & Flight manuals were pitifully minimal. Company ground schools were non-existent. It reminds me of the continuous discussion we have on here about flying skills and understanding the a/c envelope. Many companies say it is not necessary because SOP's keep you so far from the edge so that is all you need to know. Keep away from the edge and stay within the SOP nest. Same with weather radar: see a yellow or red and don't go near it. They have minimum bypass distances and minimum overfly heights. They warn of the first return perhaps being the small shark hiding the return of the Great White lurking in the shadows behind. And don't fly between 2 close cells. And that's about it. Use of tilt & gain was bypassed.
The biggest problem I had was assessing the returns <10,000. The ground took over. If I used reduced gain you can be suckered into believing what you want; that it's clear. ATC in USA were great. One day going into Orlando ATC took us out over the Gulf so our arrival was coordinated with departures routings around the weather. We didn't ask for it, we were told where to go because they could see and anticipate the problem. Brilliant. In EU I've often refused HDG's at low-level to an ILS because of Wx radar returns, but ATC said they could not see any problem. I was getting ground reflections. You reduce gain and it might go away, but can you trust it. You tilt it up and you aim at the CB above.
Other occasions in EU, when I asked for routing advice from ATC, the reply was they had Wx. switched off because of overload clutter, were relying only on transponder returns, and our onboard was probably better than theirs.

Good luck and keep it safe.

Thanks for the wonderful insight guys.

As you guys rightly elucidated it makes sense to stay clear of any strong returns. What I'm trying to decipher going ahead is, supposed I'm pushed in to a corner with a connected CB system running into 40 to 50 either side, would I be able to judiciously decide on the path of least damage, where only turbulence is expected but I stay out of harm's way. I'm sure the insights I gain from this thread would further hone my weather avoidance skills.

I recently had this experience of having to choose to fly between two close cells with a 5nm green patch between the anvil of one cell and the head of other or deviate 50-60 miles off track. I being the PF in the sector decided to penetrate and the enterprising captain let me go in after securing the cabin. Fortunately it was nothing more than a rough ride. But going by your experiences, I'm tempted to believe that I should have chosen the safer option of deviating.

RAT5. Just a point to ponder. At cruise altitudes with a flat rated engine, I thought MCT doesn't give additional thrust over and above what's available with CLB thrust. Don't know about the 767 though. Either ways the incident you narrated is actually scary. The important take away is upwind side deserves respect too. Thanks

What about Honeywell's RDR-4000 ?

I can't like this radar, seriously !

It looks just perfect on theory, but it is a pain in the arse to deviate around weather with this. Please, please, don't come and tell me to read it's manual, I've done that several times, I've also watched the video produced by the manufacturer available on youtube.

My complain is: this radar only gets really accurate with less than 40nm ! If you have some nasty weather ahead, that means you'll have to deviate much more than what you would have to with some older models.

Going manual, playing with gain, I've tried everything. Nowadays, my police is: fly straight to the weather and when about 30nm to the encounter decide what's the best way out (even if it means going 70+degs off route).

This is a ND picture I took a few days ago
http://i.imgur.com/LPopz8P.jpg?1

We were at FL380...

I feel like a fool, deviating from weather weeeeeeeeeelll below :ugh:

B737, Personally I'd prefer to have the Honeywell rdr 4000 than to have Rockwell Collins model on my side when trying to avoid weather. Having used both I find Honeywell beating Rockwell hands down. The latest Honeywell rdr 4000 mod on the Airbus gives you weather pic at any Flight Level as demanded by a rotor switch. Honeywell too suffers from the the problem of getting accurate only at 40nm as you said, but Rockwell fares even worse. In some situations what appears as a small patch keeps growing as you enter it and lasts for eternity.

That's really sad to read Bkdoss...

I never had the chance to fly an acft equipped with a Collins version of a multiscan radar, but I was hoping they had developed a better product.

The RDR-4B is a far, far better radar. But that's only my humble opinion !

* As a matter of info, as we approached the weather depicted in the image above, we took the same path of the guys ahead of us. We switched to manual and set the scan level to something like FL300, where we still had some green returns... Guess what ? Not even a light chop as we went thru ! *

All the best !

:ok:

I have the same issue with the Honeywell. It invents weather where there isn’t any and doesn’t show the obvious.

Was deviating further and further off track going through China recently due to a line of red returns. Noticed other aircraft flying through the middle of it with no comment plus ATC were getting twitchy due military airspace. Got all the crew sat down, put the speed in the middle then flew through it. In the centre of the red on the radar, I could clearly see the ground... Nothing there at all!

Much prefer the older tech. radars. Maybe with a software update it would work better but I just don’t trust it as much. ITCZ would be a nightmare.

Had good experiences with the Rockwell Collins radar (WXR-2100) on the 737NG, worked beautifully in most situations, over reported a bit below FL150 though. Playing with gain is not a bad idea in any case.

On the A320 the same radar doesn't work as well though, especially on the earlier installations. Some needed a permanent gain offset (+4/+8) to show a good picture of the weather. On newer MSNs it works quite a lot better though, but still not as nice as on the 737.

Surprisingly on neither aircraft have i witnessed the 40NM behavior though, first time i read about it here. Gonna have an eye on that next time i have to work my way around weather.

Bk,
Then go further.
One "old story", B707 days and a Marconi doppler navigator that only accommodated 100 L or R, and your truly as a really junior S/O in the RHS, and a very senior management Captain dozing in the LHS. We were getting close to 100 off track --- I rouses him and "sought advice" ---- the answer was: zero the counter and don't forget that you are already 100 miles off" and went back to sleep.

I have seen some horribly damaged aircraft, that didn't go far enough around the returns, including a B747-200 that had to do an autoland into Hong Kong, the windscreens were so thoroughly smashed, and the nose cone, leading edges and engine cowls didn't look to bright, either.
We both departed Bangkok for Honkers within minutes of each other, as my F/O and I sat in the sunlight, we watched the Jumbo disappear into the 'orrible black mass, remarks were passed across the cockpit at to the likely outcome.

Fortunate we had enough holding fuel at Hong Kong, that we were able to wait out the emergency.

Not wanting to incur a few minutes delay en-route delayed the said Jumbo for about three weeks in VHHH. Not to discount the PR damage from 300 or so very frightened passengers.

Don't ever think there is a "safe height" over the top, many pilots do not understand the prevalence of a lightening discharge to the stratosphere, quite apart from the fact that a rising TCu/TS will outclimb any civil jet.

That's a good advice that I take home from this thread today. Better to be safe than sorry. Some captains adopt the daredevil approach and that might have rubbed off onto me. Somewhere down the line, I started believing that I'm not worth my salt if the captain chooses an optimal deviation compared to me. So I started to shrink my margins. In hindsight, that might not be the best approach. Have to accept the fact that experience can never be substituted.

Thanks B737SFP. Just for my better understanding, wouldn't your planned route be the safer one to fly through, looking at the weather radar picture ?

Denti... Yeah exactly. The older MSN's have the issue of adjusting GAIN to +4 / CAL on every climb and descent. The later ones have the option of leaving it at CAL gain all the way through.

Weather avoidance
 

The best literature available is 'Weather Flying' by Robert N. Buck and the audio visual presentation available in CD form from Sport's Pilot shop by Archie Trammell.

Regarding overflight of CB's, our manuals state a minimum overflight altitude. I'm not advocating overflight of CB's but to say 'never overfly a CB' is of course the other extreme. If a CB tops out at FL270, it will probably not even show on your radar at FL390.

Again, experience will dictate what is wise in this regard. Has there ever been a recorded upward lightning strike, from the top of the clouds?

Another piece of advice: scan all the way down during the descent. You will not be the first crew to successfully avoid the big cells left and right during descent only to fly directly towards the smaller and undetected lower cell in front.

I find this statement a bit disturbing in light of your original questions. I find it hard to believe someone is actually flying around this type of weather with the lack of understanding suggested by your questions.

1) All else equal, upwind is by far the best course! If the storm is spewing hail, it can go much farther aided by the wind.

2) NO! How do you know how far 'dissipated' it is? You cannot see any hail that may remain. Use the tail as an indicator of the real wind in the vicinity, and stay at least 20 miles away if downwind.

3) There is no single answer. You have to be aware of the weather above. If the returns are at the bottom of a CB, you do NOT want to go in. If they are rain coming from stratus clouds, you can usually go into the rain, but it may be heavy. If towering Cu, but no lightning, you'll have to further assess the rate of development, local temperature, and what's going on around it.

Penko,
The question then is, is it really a Cb. The answer depends on the latitude, there are some hard little bastards to be found in north Atlantic cold fronts --- but the comment about vertical discharges still holds true.

And it is always better to not be struck by lightening --- when there is damage, it can be very expensive. For example, around here, multiple strikes on a Dash8 --- not only airframe repairs, but a double engine change as discharges had run through both engines.

Personally, I found about vertical (up) discharges by getting in the way of one.

Damage was extensive, one HF transmitter antenna reduced to a black mess, both HF receiver antenna likewise, several skin patches required, one engine changed on RTB.

Given the recommended miss distances from a Cb, it is a bit hard to be 30nm over the top.

There are several very interesting research papers about discharge to the stratosphere (I got that wrong in the my original post) sorry I can't give you an immediate link, but google is your friend.

LeadSled, thanks for the information, I will keep it in the back of my mind :ok: