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Chris_CYWG

What is realistic visibility range for rain?

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I have pretty much given up using online wx in FS for various reasons. I now use the built-in wx generator in Fs9 with FSUIPC. I have the rain visibility range in FSUIPC set to 7 miles, but after landing in KBOS in a massive t-storm, I am wondering if this is realistic. I could just make out the VASI starting at 6 nm on approach. I suppose it depends on how low the cloud/mist curtain is. Yesterday at KDCA (in real life), we had a point where the rain vis was probably no more than 1 mile; it was appalling and I saw three aircraft in a row go-around, two of whom seemed hopelessly off course in such conditions!Anybody care to suggest a "standard" visibility range for rain in this sim?Thanks!JS


Jonathan Sacks

Dell XPS Gen 4, Pentium IV Northwood extreme 3.8Ghz, 3Ghz RAM, eVGA 7900 GTO,

12 GoFlight modules plus MCP-PRO AP and EFIS, GF pedestal, CH rudder pedals,

CH throttle quadrant, 42" LG LED, 24" DELL LCD, Windows XP, FS2004, FSUIPC 3.96

FS Autostart 1.1 (Build 11), FS Navigator 4.6, UT, FE, GE, REX, PMDG, Level-D, PSS, etc.

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Guest wildfire563

I can't really speak to this as I don't fly when it rains, and add to that I don't know anything about how FS interprets visibility range in the rain, but...Could you please restate your question a little more clearly. Visibility in rain is going to depend on a number of factors, so I don't quite understand what your "standard range" question means.Sometimes I can see for 20 miles in the rain, sometimes I can barely see past the hood of my car when I'm driving. More often than not, in my experience, disregarding limited visibility due to fog/clouds (for which the change in visibility will be independent of the change in visibility due to rain), you can usually see pretty far in the rain. It's only when it's really heavy that visibility becomes more limited, and around here, anyway (NE USA), it rarely rains really hard. Plus, I imagine FS must use some scale depending on how hard it is raining to adjust visibility. So at what point do you set the standard? Is the change in visibility due to fog/cloud level taken into account in the visibility level setting for rain? Wouldn't the fog/cloud level visibility change take care of itself independent of the amount of rain? What impacts my visibility most is how much water is on the windshield, but I don't think this has anything to do with your question.Thomas

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Depends on how hard its raining.. I've been cruising along in the Chieftain and its been raining so hard I have to go on the dials, if its a light rain I'd say 5-7 miles is normal forward vis, moderate rain 1-3 miles, heavy rain, might as well be IFR.Chris

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Guest allcott

If you do that in the sim (limit the vis to artificial levels) you can lose out on one of the real fun things in Real World flying - dodging the showers. To dodge them, first you have to see them. You can usually see showers 10-20 miles away in otherwise good conditions, 5-7 if there is also a lot of `clag`. And rain does NOT mean IFR, not automatically!Allcott

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Rain can occur in both stable and unstable air. In the former, visibilities are poor with a stratus cloud layer above, air is smooth. In unstable air, visibilities are better with cumulus clouds, possible thunderstorms and turbulence. Add to that the fact that rain can be -RA, RA, +RA; and you have many variables in visibility. What you could do is look at a weather map at weather.com or in the newspaper, see where the rain is forecast and go on-line and see what the METARs and TAFs are showing for visibility. That would give you some sort of range to work with perhaps.Bruce.


ASEL, Instrument.

KBJC, Colorado.

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Guest DNelson

>and I saw three aircraft in a row go-around, two of whom>seemed hopelessly off course in such conditions!>Given that DCA is limited to air carriers and professionally crewed bizjets, I really doubt that they were hopelessly off course. If they were using the rwy 19 localizer approach, the offset localizer on that runway could give that impression. If not, it was probably some other optical illusion.As others have said, visibility can vary greatly in rain showers. Out here in the low-humidity west, I've seen visibilities of 10 miles or more in light rain.

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> And rain does NOT mean IFR, not automatically!>>AllcottWhat I meant was if your in heavy rain and can't see you you're on the gauges so your pretty well IFR, even though your supposed to be VFR.... or as I call it VIFR = Visual IFR - I can see down but I can't see S**t forwards :)

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Hi JS -In real life the visibility is ususally affected by the difference between the temperature and dewpoint. The closer the temperatures ususally the lower visibility. That is what I use as a marker.When it is raining the intensity can drastically affect it by reducing visibility down to near zero in the heaviest precip. I would say that 6 miles in heavy rain is a little to high. Here is a good estimated scale:[table border=0' width='500' cellpadding='0' cellspacing='1' bgcolor='#bcbcbc][tr][td bgcolor=#dcdcdc]Intensity of Rain [/td][td bgcolor=#dcdcdc]Visibility Scale[/td][/tr][tr][td bgcolor=#ffffff]Drizzle (light rain)[/td][td bgcolor=#ffffff]8 to 10+ (Unless dewpoint is close to OAT)[/td][/tr][tr][td bgcolor=#ffffff]Light Rain: [/td][td bgcolor=#ffffff] 6 to 8[/td][/tr][tr][td bgcolor=#ffffff]Moderate Rain: [/td][td bgcolor=#ffffff] 4 to 6[/td][/tr][tr][td bgcolor=#ffffff]Heavy Rain: [/td][td bgcolor=#ffffff] 2 to 4[/td][/tr][tr][td bgcolor=#ffffff]Very Heavy Rain: [/td][td bgcolor=#ffffff]0 to 3[/td][/tr][/table]Another affect that I wish FS9 could do would be to compute for condensation. Sometimes the air gets so saturated that even lower clouds form just above the surface that makes it even lower. These are often isolated events, but they do occur and look very ominous. The way to approach this is to add an additional layer of clouds (set to few or scattered) just below the overcast base you set.I hope that doesn't sound long winded.


Reed Stough
Managing Partner
REX SIMULATIONS 

website:  www.rexsimulations.com
support: support@rexgamestudios.com

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Guest allcott

I'll just throw in a `wobbler` here and say that, as a GF6600GT user, I have just installed the new 81.33 drivers from www.guru3d.com and I think I'm seeing variations in light intensity and visibility I haven't seen before!More testing needed, and I won't get in front of the sim computer until this evening, but it might also mean that different cards and drivers might need different settings.Allcott

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