Weather Question
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Weather Question
OK, as SLF I am allowed to show my complete ignorance.....
...what does the 'cb' stand for when talking about weather that threatens the safety of the aircraft?
...what does the 'cb' stand for when talking about weather that threatens the safety of the aircraft?
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CB stands for Cumulonimbus cloud formations, which are very dangerous for all types of aviation from 747's to 152's!! The are associated with extreme weather conditions like hail, and extreme turbulence and winds. They also contain very strong updrafts and downdrafts. Thus they are not good for aircraft and commercial traffic uses the weather radar to navigate round them. The actually life span of the cloud formations can be quite short but they can extend from anything from 1500 feet to 30000 feet, so they get pretty big.
So basically they are not good news!!
Hope this helps
Tom
So basically they are not good news!!
Hope this helps
Tom
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DeepC
Just another bit of info for you - The Cumulo in Cumulo Nimbus means 'build up' and the Nimbus means 'rain bearing' - CB's tend to form when several active cells combine to form one large CB.
flappless
Just another bit of info for you - The Cumulo in Cumulo Nimbus means 'build up' and the Nimbus means 'rain bearing' - CB's tend to form when several active cells combine to form one large CB.
flappless
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CB
DeepC
A Cumulo Nimbus is to an acft what a reef is to a ship, that is to say, to be well avoided.
Apart from extreme turbulence capable of causing structural failure,turbulence at high altitude can cause "jet upset" (loss of control).
At lower altitudes, an encounter with hail in a Cb can cause damage to leading edges,engine nacelles & windscreens.
At ground level Cbs have caused T/O and LDG accidents due abrupt windchange & downdraft (microburst).
Rapid clear ice build up is another hazard in the vicinity of Cbs.
A Cb associated with a tornado or tornadic squall is the most dangerous.
Tomcs
30,000 ft is an average for Cb tops in temperate latitudes,in the tropics 50,000 ft is not uncommon.
In short fellas, a subject worth studying if you plan an aviation career.
Read up on some of the accident reports & devote some time to understanding acft wx radar as well.
A Cumulo Nimbus is to an acft what a reef is to a ship, that is to say, to be well avoided.
Apart from extreme turbulence capable of causing structural failure,turbulence at high altitude can cause "jet upset" (loss of control).
At lower altitudes, an encounter with hail in a Cb can cause damage to leading edges,engine nacelles & windscreens.
At ground level Cbs have caused T/O and LDG accidents due abrupt windchange & downdraft (microburst).
Rapid clear ice build up is another hazard in the vicinity of Cbs.
A Cb associated with a tornado or tornadic squall is the most dangerous.
Tomcs
30,000 ft is an average for Cb tops in temperate latitudes,in the tropics 50,000 ft is not uncommon.
In short fellas, a subject worth studying if you plan an aviation career.
Read up on some of the accident reports & devote some time to understanding acft wx radar as well.
Last edited by Capt. Crosswind; 2nd Jun 2002 at 04:38.
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Acft Wx Radar
LHR Director
I guess you've seen more than one acft blundering into a build up in the terminal area & complaining that ATC did not advise them of its presence.
The crew have switched the acft radar to standby & are relying on ATC to watch the weather.
What is not generally understood is that ATC Radar operates on
10cm ( L Band ) for range & the fact that a 10cm signal passes through precipitation with minimal reflection, as it must to track the traffic.
Acft wx radar operates on 3cm (X Band ) and gives much greater reflectivity
from precipitation.( I stand to be corrected but I think the radar reflectivity of a rain drop increases with the fourth power of the frequency )
In the terminal area acft wx radar should be set on max up tilt & a short range scale , for departure & arrival.
Unless ATC has a dedicated Wx radar facility they are not equipped to keep acft clear of wx.
I'll bet London to a house brick that the acft that have crashed on final or take off due a micro burst had the wx radar on STBY.
Note: There's a lot of good gen currently on Tech Log - see 'Storm scope v Wx Radar' & links thereon.
I guess you've seen more than one acft blundering into a build up in the terminal area & complaining that ATC did not advise them of its presence.
The crew have switched the acft radar to standby & are relying on ATC to watch the weather.
What is not generally understood is that ATC Radar operates on
10cm ( L Band ) for range & the fact that a 10cm signal passes through precipitation with minimal reflection, as it must to track the traffic.
Acft wx radar operates on 3cm (X Band ) and gives much greater reflectivity
from precipitation.( I stand to be corrected but I think the radar reflectivity of a rain drop increases with the fourth power of the frequency )
In the terminal area acft wx radar should be set on max up tilt & a short range scale , for departure & arrival.
Unless ATC has a dedicated Wx radar facility they are not equipped to keep acft clear of wx.
I'll bet London to a house brick that the acft that have crashed on final or take off due a micro burst had the wx radar on STBY.
Note: There's a lot of good gen currently on Tech Log - see 'Storm scope v Wx Radar' & links thereon.
Last edited by Capt. Crosswind; 6th Jun 2002 at 01:17.
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Don't remember where or in what context, other than that it was in this forum but someone posted a link not so long ago to a picture of an engine nacelle of an aircraft (I think a 737) which had sustained damage from hail after passing through CB clouds. The intake surround looked like the surface of a golf ball.
