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February 12th, 2006, 22:52
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| Old Skool  Join Date: Jan 2006 Location: KLAS
Posts: 3,309
 |  Ground effect Okay so Im reading about ground effect in my ground school class. Does this happen all over the US or only in certain regions? Is it more frequent in valleys? Just curious if its a regional thing or simply a phenomenon. |
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February 12th, 2006, 23:07
| #2 | |
| Moderator  | Quote:
__________________ NJC or Bust.....CountDown Timer | |
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February 12th, 2006, 23:10
| #3 |
| Senior Member  Join Date: Jun 2003 Location: Indianapolis, IN
Posts: 902
| Are you talking about ground FOG or ground EFFECT? Ground effect happens whenever you're close enough to the surface. Ground fog most commonly occurs in low-lying areas on calm, cool nights. Big difference between the two!  Now lift, on the other hand, is only valid in the Northern hemisphere. Unless you have special Southern hemisphere compatible airfoils, you stall as soon as you cross the equator. It's a phenomenon that can really ruin your day!
__________________ .......__o .......\<, ....( )/ ( ) If it isn't fixed, it's broken. |
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February 13th, 2006, 08:12
| #4 | ||
| Old Skool  Join Date: May 2003 Location: Denver Colorado
Posts: 2,970
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February 13th, 2006, 08:36
| #5 |
| Old Skool  Join Date: Sep 2003
Posts: 1,853
| Ground fog is a fascinating occurrence. I rarely see it anymore because I largely fly into major airports in major cities...and it just doesn't have the chance to form due to the physical characteristics of the area. Areas with lots of concrete (big airports, cities, etc.) do not seem to fog in as much as areas with lots of fields around them. One such example is Chicago Midway airport...right smack in the middle of Chicago. Numerous outlying airports would all be socked in with fog...but MDW was always above minimums. I always attributed this to the fact that there was a sea of concrete around the place. Ground effect...I was taught in primary training...that the airplane was "floating on a cushion of air". We all know this is not true...but is caused by a reduction of induced drag as the downwash circulation of air is interrupted by contact with the runway. |
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February 13th, 2006, 10:56
| #6 |
| Junior Member  Join Date: Dec 2005
Posts: 160
| I think ground fog is more common on cloudless nights and early mornings since cloud droplets from clouds have the ability to radiate heat to the ground(after they condense). When there are no clouds at night, there is no heating of the ground so it cools to where fog forms again. |
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February 13th, 2006, 11:08
| #7 |
| Old Skool Join Date: Sep 2003
Posts: 1,853
| Yes, typically if there is a shallow layer of fog with clear skies above it will burn off very quickly. Typically the fog is extremely dense. If there is an overcast above the fog, or multiple layers of stratified clouds...the fog will be persistent throughout the day and may not "burn off"...however, the fog is typically less dense. |
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February 13th, 2006, 11:12
| #8 |
| Old Skool  Join Date: Mar 2004 Location: Ft. Lauderdale
Posts: 2,090
| That was a really funny question 
__________________ Don't call her a babe, ok? She is a Chechnyan prostitute, and you will address her as such! -ATHF Last edited by FlyingNole; February 13th, 2006 at 11:59. |
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February 13th, 2006, 12:22
| #9 |
| Old Skool Join Date: Jan 2006 Location: KLAS
Posts: 3,309
| I probably wont encounter too much fog here in Las Vegas but that ground effect thing scares the crap out of me. Does it happen very often? |
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February 13th, 2006, 12:35
| #10 | |
| Old Skool Join Date: May 2003 Location: Denver Colorado
Posts: 2,970
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February 13th, 2006, 13:02
| #11 |
| Senior Member Join Date: Jun 2003 Location: Indianapolis, IN
Posts: 902
| Now I'm confused, too! Based on the "is it regional and does it happen more in valleys" question, I assumed you were talking about fog. Why in the world would ground effect scare you? It a physical property that occurs whenever you're close enough to the ground and is just a part of flying a plane . . .
__________________ .......__o .......\<, ....( )/ ( ) If it isn't fixed, it's broken. |
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February 13th, 2006, 13:48
| #12 |
| Old Skool Join Date: Jan 2006 Location: KLAS
Posts: 3,309
| Well someone told me that it can cause the airplane to crash on take off because you might think you have enough speed for lift but your accually experiencing ground effect so when you lift too soon out of the pocket you drop like a rock. Im brand new at this only in week 3 of ground school. |
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February 13th, 2006, 14:08
| #13 | |
| Old Skool Join Date: May 2003 Location: Denver Colorado
Posts: 2,970
| Quote:
Don't worry about it. Ground effect is a natural phenomenon. When the wings are within about a wingspan from the ground, the proximity of the wings to the ground changes the airflow in a way that increase lift. Not quite accurate, but some people describe it as riding on a cushion of air. All that means is that the airplane can fly close to the ground at a slow airspeed than it can when higher. The phenomenon is not dependent on where you are geographically. Yes, a pilot who is not paying attention =could= fly out of ground effect during takeoff at too slow a speed. But the idea of learning to fly is to learn how to manage those things. The rotation speed you are being taught is high enough that you won't even notice ground effect on takeoff under normal circumstances. On takeoff, ground effect is actually helpful for certain things. You'll learn one of these when you learn about soft field takeoffs. One problem with taking off on a rough runway is that the airplane has a hard time accelerating to a proper takeoff speed. But, because of ground effect, you can safely get into the air at a slower speed , lower the nose and fly =in= ground effect until you are fast enough to climb out normally. In addition to soft/rough fields, variations of the technique are used by seaplane pilots and pilots flying at high mountain airports on very hot days. There is a lot of stuff in flying that is potentially hazardous. But understanding managing those risks is a big part of what flying (and the enjoyment of flying) is all about. Have fun! | |
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February 13th, 2006, 14:20
| #14 | |
| Senior Member  Join Date: Jul 2005 Location: The IND SOC / HFY
Posts: 619
| Quote:
If your flying the airplane in normal and legal conditions this won't happen. Ground effect is nothing to be scared of . Just know it's there and why. You'll understand it and it's effects more during your flight training. You'll use ground effect to your advantage during soft field tol's and such. The above quote is more likely to happen if you were way over gross weight in high density altitude conditions on a short runway, or somthing like that. Never put yourself in a position like that. Many have. | |
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February 13th, 2006, 14:45
| #15 |
| Old Skool Join Date: Jan 2006 Location: KLAS
Posts: 3,309
| Thanks guys, I read that section again and also found some illustrated figures showing how it works. Learning something new daily, I love it. |
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February 15th, 2006, 18:48
| #16 | |
| Old Skool  Join Date: Aug 2004 Location: CFI / CFII in PA
Posts: 2,661
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February 22nd, 2006, 11:52
| #17 |
| Junior Member Join Date: Feb 2006 Location: Madison, WI
Posts: 99
| Ground effect The wings do provide more lift and there is less induced drag as well in ground effect which is why the airplane will fly at the lower airspeeds. Don't worry though, I have had many students continue to pull upwards when practicing soft field takeoffs in ground effect. We leave ground effect with me saying 'drop the nose . . .. drop the nose . . . drop the nose!" but don't plumment back to earth. Now, I am not saying that it won't happen, but, in a high lift wing that most training airplanes have it is a little forgiving (hence the whole 'training' thing). Your flight instructor will show you the proper way to fly in and to leave ground effect. |
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