JulianUK
Topic Author
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Seeing Oncoming Clouds - Not On Weather Radar

Tue Sep 26, 2006 4:40 am

I was reading a recent report that stated a Virgin 747 suffered from severe turbulence because the pilots were monitoring the weather radar and nothing was shown and as they looked up they saw cloud ahead, entered a turn as soon as possible but still went through it and it caused severe turbulence.

How often does the weather radar fail to pick up things that you can see with your own eyes and how long have you got to react? At night it must be fairly impossible to see clouds not picked up?
 
Ralgha
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RE: Seeing Oncoming Clouds - Not On Weather Radar

Tue Sep 26, 2006 4:59 am

Airborne radar only picks up precipitation, so if that cloud isn't dropping precipitation, the radar, typically, won't show a thing.
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Bobster2
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RE: Seeing Oncoming Clouds - Not On Weather Radar

Tue Sep 26, 2006 7:28 am

Quoting JulianUK (Thread starter):
as they looked up they saw cloud ahead

My guess is that the turbulence woke them up from deep sleep, and they later agreed to make up a story about seeing the cloud at the last minute. How can you possibly not see a cloud? Gimme a break.  Smile
"I tell you this, no eternal reward will forgive us now for wasting the dawn." Jim Morrison
 
DashTrash
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RE: Seeing Oncoming Clouds - Not On Weather Radar

Tue Sep 26, 2006 7:43 am

It could happen. In areas of thunderstorm activity it can be easy to fixate on the radar and rely on it to keep you out of the bumps. You can forget to look out the window.

I once deviated around a thunderstorm and into a cloud that actually knocked a tach cable loose in the airplane. Some of the heaviest turbulence I've ever been through. That cloud would not have shown on the radar.
 
PhilSquares
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RE: Seeing Oncoming Clouds - Not On Weather Radar

Tue Sep 26, 2006 7:39 pm

Quoting Bobster2 (Reply 2):
My guess is that the turbulence woke them up from deep sleep, and they later agreed to make up a story about seeing the cloud at the last minute. How can you possibly not see a cloud? Gimme a break

Well Bobster, it can happen! Have you ever flown at night over the Indian Ocean? Or how about down over central Africa. Dark as hell.

Perhaps if you got out a little more and saw the world, you'd be less inclined to insult the pilots.

The weather radar is only designed to pick up precipation, no precip, no return. Sometimes if you adjust the gain manually you'll get a better return, but you have to know there's something out there.
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saab2000
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RE: Seeing Oncoming Clouds - Not On Weather Radar

Tue Sep 26, 2006 8:52 pm

Once when flying in Switzerland we flew into something which did not show up on radar. We were IMC at about FL180 over the mountains. Smooth as glass. Suddenly for about 30 seconds we had the most violent shaking I have ever had. Then it was over and smooth as glass. I wimpered to ATC what happened as we lost 300 feet on the altitude and we continued on.

Radar was on and we were IMC. Flew into something embedded.
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David L
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RE: Seeing Oncoming Clouds - Not On Weather Radar

Tue Sep 26, 2006 9:16 pm

Quoting PhilSquares (Reply 4):
Well Bobster, it can happen!

I'm sure he was joking. He can be pretty "evil"! It made me laugh but then he wasn't insulting me... this time.  biggrin 
 
JHSfan
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RE: Seeing Oncoming Clouds - Not On Weather Radar

Tue Sep 26, 2006 9:40 pm

Not being an expert on weather radars, I have heard that detecting very small water particles in the air will result in too many false alarms.
So most radars should be calibrated to neglect certain clouds. Clouds witout a huge amount of rain. Am I anywhere near the truth?

Just having red a little about the two NASA satellites CloudSat and Calipso, it seems that technology exists for more detailed info on clouds. But it may not be available for planes yet.

BTW: Returning to the VS 747 cockpit. Even with radar technology it's still a good idea to use your own eyes and the windows once in a while.

- JHSfan
Look at me, I´m riding high, I´m the airbornmaster of the sky...
 
saab2000
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RE: Seeing Oncoming Clouds - Not On Weather Radar

Tue Sep 26, 2006 9:58 pm

JHSfan,

Radars are not just 'static' pieces of equipment. Pilots can control the tilt of the radar, the 'gain' and the range.

By tilting the radar a pilot can tilt down to see the ground and then slowly tilt back up to see the clouds in front.

The 'gain' control adjusts the sensitivity of the radar return and I think this is what you are talking about. You can adjust the picture to disregard most smallish clouds. By playing with the 'gain' control a pilot can see the relative intensity of what is in front and hopefully make the right decision on what to avoid. I like the fly in normal 'gain' or 'gain +1' to display a bit more. But sometimes you have to turn it way down to see if a cell in front is really real.

And the range function is important too. When in the terminal airport area I use it in 20 or 40 mile range but while enroute usually 80 or 160 mile range. But beyond 160 it is more or less useless, at least in my airplane. The 160 mile range is good for telling me what I will see in 20 minutes, but I use the 80 mile range when flying around things.

I hope this helps. Other experienced pilots here will probably have different techniques.

I still can't imagine how pilots flew around thunderstorms before there was weather radar!!!
smrtrthnu
 
flymatt2bermud
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RE: Seeing Oncoming Clouds - Not On Weather Radar

Tue Sep 26, 2006 10:07 pm

This past Sunday on a flight from Napoli, Italy to New York we were level at 12,000 feet preparing for our initial approach. The winds were 74 knots at our altitude and there was a small line of clouds with tops not much more than FL200 or so. I turned on the seat belt sign and asked the flight attendant to buckle in as well. The line was about 4 miles wide and there was no precipitation, nothing on the lightning sensor in the line of building clouds that extended across the horizon for as far as we could see.

We were right at our turbulent air penetration speed when we entered the clouds, then about 30 seconds later it felt like all hell had broken loose. The turbulence violently shook the aircraft to the point we could not interpret the anything on the panel. It was difficult to reach for the Autothrottle disconnect, my arms were waving up and down in virtual weightlessness. The turbulence knocked all the glassware and dishes out of their holders. All items hung up were on the floor, though the bars remained intact. We were in it for about two minutes.

It's critical to keep your head up to potential dangers, had this line been embedded in clouds or had it been dark outside we would have had no warning.

I've turned on that seat belt sign 1,000 times before approaching darker more threatening looking clouds with barely a wisp of a bump. Sure glad we caught this one and the pax and crew were prepared. I think if anyone was not buckled in they may have been injured.
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward" Leonardo Da Vinci
 
JHSfan
Posts: 460
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RE: Seeing Oncoming Clouds - Not On Weather Radar

Sat Sep 30, 2006 8:11 pm

Quoting Saab2000 (Reply 8):

Thanks Saab2000, well explained!

Quoting Saab2000 (Reply 8):
I still can't imagine how pilots flew around thunderstorms before there was weather radar!!!

Hopefully someone has collected information on flying in the old days. I'm pretty sure that we electronic humans are not used to try to solve problems in simple ways.
Just like some pilots trust more in the electronics than in a mixture of electronic info and visual ditto. That could be a reason why the Virgin 747 went into severe turbulence, as JulianK's told us about.

Next to that turbulence also appears in not so cloudy conditions. Maybe a reason why some scientists work on anti turbulence systems.
I think that EU sponsors such a project with airbus involved. So far they con only detect turbulence a few seconds before the plane hits the violent air. So the radar info about turbulence goes directly to the electronics in the plane. It then automatically tries to compensate on the rudders.

Yours in calm air
JHSfan
Look at me, I´m riding high, I´m the airbornmaster of the sky...

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