Dew point - isn't that the temperature at which water vapour condenses onto your roses early on a summer's morning? Why is it of interest to pilots? Are they all keen gardeners?Thanks for any info.Martin

I think that if the dew point and outside temp are close then carburator icing can occur sooner. When the speed of the air gets faster as it goes through the venturi of the carb, the air get colder. If dewpoint is close to air temp, then icing may occur in the carb. Thus card heat is applied.JimCYWG

Check this site out:http://www.pilotsweb.com/wx/w_sense.htm#temphttp://mywebpages.comcast.net/geofa/pages/rxp-pilot.jpg

Thanks for these two replies. I should have guessed there would be no simple answer!I have just got ActiveSky, so I am starting to take an interest in the weather. The web link looks excellent.Thanks againMartin

You know that dew point temp is the temp at which the atmosphere would be at 100% relative humudity right? Well, the main reason is that if the temp/dew was say 11/10 or even 10/10. Then the you only need the slightest reduction in tempreature for mist/fog and possibly an approach ban. If it is after anout 05:30 then the temp is gettering warmer. If it is after about 14:30 then the temp is likely to get cooler. Carb icing depends greatly on the OAT regardless of the dewpoint. By that I mean if the OAT is 5 deg C, then carb is relatively unlikely. If the OAT is 20 deg C, then it is very likely!Basically, it gives you the information you need to think ahead. Like the old avaition saying goes "Don't be where your brain didn't arrive five minutes before"

>You know that dew point temp is the temp at which the>atmosphere would be at 100% relative humudity right? >>Well, the main reason is that if the temp/dew was say 11/10 or>even 10/10. Then the you only need the slightest reduction in>tempreature for mist/fog and possibly an approach ban. If it>is after anout 05:30 then the temp is gettering warmer. If it>is after about 14:30 then the temp is likely to get cooler. >>Carb icing depends greatly on the OAT regardless of the>dewpoint. By that I mean if the OAT is 5 deg C, then carb is>relatively unlikely. If the OAT is 20 deg C, then it is very>likely!>>Basically, it gives you the information you need to think>ahead. >>Like the old avaition saying goes "Don't be where your brain>didn't arrive five minutes before"Carb icing can happen at temperatures well above freezing.

briefly, the dew point is the temperature at which, given the moisture content of the air, the air would be saturated and visible moisture will be present (rain, clouds, etc.). dew point/temperature spreads are used to predict rain, cloud bases, etc. If the dew points and temperature are close, expect challenging weather moisture-wise. vegetation doesn't warm as fast in the morning as some ground covers (driveways for example) and so when the air is moist and the dew point is close to the actual temp, dew collects on the colder surfaces of roses (the colder air just next to the rose surface having a slightly higher dewpoint than the air further away). Icing can occur at all temps, provided sufficient moisture is present and the process is only distantly related to to the dew point. At least that is how I remember things. I suspect some pilots are keen gardners though, but I've never met one :-)

Presumably, MSFS is incapable of modelling this?

That is exactly what I wrote, except more specific :)

Carb Ice: Not modelled.Dew Point: Indirectly via real weather METAR downloads.

> I suspect>some pilots are keen gardners though, but I've never met one>:-)> Could be true, after all, I do know a keen gardner who is also a pilot.

Here is a good chart from the FAA Publication on Winter Flying,http://www.faa.gov/ats/afss/newyork/ENROUTE.htm

>> the dew point is the temperature at which, given the moisture content of the air, the air would be saturated and visible moisture will be present (rain, clouds, etc.).This is mostly correct in that the air is indeed saturated, but not necessarily when visible moisture is present. A surface has to be present for the water vapor to collect and condense, similar to how rose petals were mentioned earlier. In regular air, condensation nuclei (solid particles suspended in the air like sea salt, combustion products, etc.) has to be present for condensation to occur. If the air is extremely clean, like at very high altitudes, the air may become "supersaturated" with the relative humidity exceeding 100%.C.T.R. Wilson invented an instrument called a cloud chamber in which clouds can be manually made. He discovered that in pure, clean air the relative humidity must reach 800% before water drops form.

I'am a gardener and a sim pilot. Home made pickels. I grow dill weed, cucumbers and garlic. Man, they are the best. There's always one and in this case, two. ejoiner, I like your attitude indicator.JimCYWG

When dew point and temperature are within 2 degrees of each other you get fog.