dew point?

HI,

Where does a pilot use the dew-point? Why is the volmet transmiting
this info?

Thanks
frank

wrote:

Where does a pilot use the dew-point?

A close temperature/dewpoint spread (less than 5 degree Celsius difference
between the two) can indicate the presence or possibility of fog.

--
Peter

Thanks
joe

A close temperature/dewpoint spread (less than 5 degree Celsius difference
between the two) can indicate the presence or possibility of fog.

Also, knowing the temperature and dew point one can estimate the cloud
bases (using a standard lapse rate of 2 deg/1000 feet).

Jose
--
Money: what you need when you run out of brains.
for Email, make the obvious change in the address.

wrote:
HI,

Where does a pilot use the dew-point? Why is the volmet transmiting
this info?


A rule of thumb for the base of convection clouds
is 400 feet / degree C of temperature - dewpoint
difference.

--

Tauno Voipio
tauno voipio (at) iki fi

On Wed, 01 Mar 2006 18:22:11 GMT, Jose
wrote in : :

A close temperature/dewpoint spread (less than 5 degree Celsius difference
between the two) can indicate the presence or possibility of fog.

Also, knowing the temperature and dew point one can estimate the cloud
bases (using a standard lapse rate of 2 deg/1000 feet).

The Relative Humidity, of which due point and temperature are an
indicator, is useful in predicting induction system icing in
carbureted engines.


http://www.lycoming.textron.com/main...tionIcing.html
Every pilot who flies an aircraft powered by a carbureted engine
should be thoroughly educated about carburetor ice. They should
know that under moist conditions (a relative humidity of 50% to
60% is moist enough), carburetor ice can form with any outside air
temperature from 20o to 90oF. It is most likely in the 30o to 60oF
range. Temperatures in the carburetor can drop 60o to 70oF
(refrigerator effect) as a result of fuel vaporization and the
carburetor venturi effect. It also happens that carburetor ice
forms more readily when the engine is operated in the lower power
range. It will form while taxiing and this makes it very important
to check engine power before takeoff and to remove the ice if
necessary. Care should be taken to avoid dusty or dirty conditions
when utilizing carburetor heat on the ground.

Morgans wrote:

A close spread like stated above could also mean that carb ice will form
more easily.

Thanks, Jim.

Not having flown a carburetor-equipped aircraft since 1990 and considering
the fuel-injected BE35 I now own, I certainly overlooked the issue of carb
ice.



--
Peter

Morgans wrote:
A close temperature/dewpoint spread (less than 5 degree Celsius difference
between the two) can indicate the presence or possibility of fog.

A close spread like stated above could also mean that carb ice will form
more easily.


The same 2-3 degree difference between dewpoint and temperature may make the
difference in deciding to go or not. If it occurs as the sun is rising, going
is probably safe as the temperature is going to rise, widening the spread.
Conversely, if the sun is going down, it's a pretty good chance fog is going to
get you if you decide to fly.



--
Mortimer Schnerd, RN

VE

Live for one winter in Sacramento and you won't ask that question. Near
sunrise most pilot have ATIS continuously tuned monitoring the dew
point second by second. If the spread is right, the moment the first
bit of sun touches the earth the fog forms, sometimes going from CAVU
to 1/2 vis in just minutes.

-Robert

"Peter R." wrote in message
...
wrote:

Where does a pilot use the dew-point?

A close temperature/dewpoint spread (less than 5 degree Celsius difference
between the two) can indicate the presence or possibility of fog.

A close spread like stated above could also mean that carb ice will form
more easily.
--
Jim in NC