Talk:Ground effect (aerodynamics)

message: On August 28, Astra Space attempted to launch a test load to orbit.  One of five engines immediately failed reducing its unassisted lift-to-weight ratio below 1.00 for about 10 seconds before it burned off enough fuel to begin its ascent.
It is described in this YouTube video: https://www.youtube.com/watch?v=x2jU5W4ehPE
What is not mentioned in this video is how this rocket managed to avoid colliding with the ground for that first 10 seconds.  Unless you suspect that the engine was throttled to keep it in that low hover, it's ground effect.  And given the spectacular performance of the guidance system, it's safe to assume that it was not hovering by design.
This article should be updated to include this.  There are several ways of describing ground effect.  The one chosen in this article is "reduced drag".  For this rocket, the "assisted lift" explanation would be a better fit.
Scott Bowden (talk) 03:20, 30 August 2021 (UTC)
thread_title: Orbital Class Rocket remains in Ground Effect for about 10 seconds.

message: The explanation of the ground effect, specially what it says about vortices, is erroneus: "Wingtip vortices destroy massive amounts of the lift generated by the wing by increasing downwash behind the wing and therefore decreasing the aircraft's theoretical angle of attack". First off, vortices do not destroy lift by increasing downwash; downwash is inherent to lift: more downwash, more lift. The "theoretical angle of attack" is a misleading concept too. As far as I have read, and I understand, ground effect improves efficiency because the upwash (which is what the air flows like before the wing) is reduced, and because wingtip vortices are decreased. For some info visit: explanation for lift If you know about this it would be nice if you change it. I'd do it, but I prefer to wait until I know more. Keta 14:03, 16 October 2005 (UTC)
replies: text: I agree the current text is poorly worded. I think I see what the author is trying to say, but as it is it's inconsistent with other wikipedia articles that touch on this topic. If you can see a better way please go ahead and have a stab! Graham 06:41, 17 October 2005 (UTC)
replies: text: The subject is still not completly clear to be but aside from fixing the lift description so that it at least matches the one on the lift (force) page, shouldn't we divide ground effect into span dominated ground effect (reducing induced drag by cancling vortexes), and cord dominated ground effect (increasing lift)? that difference is causing a lot of confusion here. --Sukisuki 04:00, 30 October 2006 (UTC)
replies: text: I think the introduction could do with a revamp as well. I don't normally like to complain like this without just going ahead and fixing the article, but this is a subject I really don't know enough about to meddle with! But the phrase I find particularly convoluted is: "as it approaches within roughly twice the length of a wingspan's length". What nuances are we supposed to take from "approaches within roughly"? It'd be great if somebody who knows precisely what is being said there, could tidy it up a little. – Kieran T (talk) 15:16, 21 March 2007 (UTC)
replies: text: I echo Kieran T's comments (and his reason for not attempting an improvement!). There is also an apparent contradiction between this article's description of a helicopter hovering 'in ground effect' and the Vortex ring article's explanation of helicopters suffering a loss of lift due to recirculation of air. We need an expert to improve these articles! TraceyR 10:08, 22 March 2007 (UTC)
thread_title:  Bad effect explanation 

message: When I was in ground school, they taught me ground effect comes into play when the aircraft is about 1/4 of the wingspan
above ground.  This might be useful information to put in this article.  This was about airplanes, I do not know about
helicopters.
: Yes, ground effect depends critically on wingspan.  Here's one way to visualize it:  an everyday aircraft flying at high altitudes is a reaction engine which must perform work upon the oncoming air, flinging it downwards as a pair of down-moving vortices.  Helicopters do something similar.  A hovering rocket ship does the same, but the rocket supplies its own reaction mass exhaust, while an aircraft uses the surrounding air to generate the downward "exhaust stream."  This "reaction exhaust" process requires energy, uses extra fuel, and it causes lift-induced drag.   
: But if a wing had infinite span, or if the wingtips extended to the walls of a wind tunnel, in that case the wing resembles a venturi.  There are venturi-like pressure patterns, but there is no downward "exhaust". A venturi-wing is connected to a bound vortex and a starting vortex, but it does not create a stream of downward-moving air, so it neither experiences lift-induced drag, nor does it use fuel to perform work upon the air.  Simple?  No downward exhaust stream, so in theory no fuel needed for flight!   In practice, if an aircraft flys at an altitude much less than one wingspan, it acts like an infinite-span wing: it is lifted by the pressure pattern of its bound vortex and does not leave an "exhaust stream" of downward-deflected air.  But if the wing should fly higher, then this "ground effect mode" will vanish, and the aircraft will instead behave as a reaction engine which encounters still air and leaves a trail of downward-moving air.--Wjbeaty 04:31, 28 June 2006 (UTC)
thread_title:  WINGSPAN 

message: The opening sentence/paragraph needs to clearly define the cause and result of the ground effect. For someone with almost zero knowledge of aerodynamics, I got lost looking for it in the text - Jack (talk) 00:44, 11 August 2006 (UTC)
replies: text: That comment needs a confusing tag BonniePrinceCharlie 03:02, 14 December 2006 (UTC)
thread_title:  Confusing tag rational 

message: While the ground effects may have made his car faster than it otherwise would have been, given that his accident was caused more by a tragic misunderstanding about where he was going to pass the slower car, is the mention of his accident really relevant here? Angmering 06:58, 15 August 2006 (UTC)
thread_title: Gilles Villeneuve

message: THIS ARTICLE IS RUBBISH !!!!  87.64.195.155 20:41, 27 August 2006 (UTC)
replies: text: I updated the Principle of ground effect section because the old one was almost dangerous, yes, rubbish but Jaganath is correct; anyone can improve articles. (Without waiting 5 years for it to happen.)V7-sport (talk) 05:38, 30 June 2011 (UTC)
thread_title:  From a (Now retired) Pilot

message: "while the air which passes over the curved upper surface must move farther and faster to rejoin the air below at the trailing edge of the wing"
This is definitly wrong and a common misconception. There is no physical law that requires the air above to "hurry up" and rejoin with the air under the wing. It is true that the air above the wing moves faster, but it even reaches the trailing edge earlier than the air on the lower side. So there is no rejoining and this argument can't be used to explain lift! (See the article about lift). —The preceding unsigned comment was added by 81.223.147.216 (talk) 20:34, 10 December 2006 (UTC)
thread_title:  Common misconception 

message: Hi,
While looking into flight test data on an early fixed-wing VTOL aircraft Short SC.1, I came across a research memorandum which refers to the losses in vertical thrust due to what is referred to there as "ground effect". This seemed fine, since this is how I would have described it, so I added a link to the article ground effect. When I checked it, however, I discovered that this refers to a net gain in lift experienced by some conventional fixed-wing aircraft wing types when flying close to the ground, so I had to remove the link. 
There is a potential confusion here, which I would like to sort out.
*Is "vortex ring" specific to rotary wing aircraft?
*Is "vortex ring" perhaps the U.S. term, "ground effect" the British term for the same thing?
*I have also heard the loss of thrust effect described as "recirculation", but this appears to be more commonly used in the context of optimising effects within internal combustion engines.
Here is the reference: Discussion of ground effect w.r.t. the Short SC.1
I would still like to link the SC.1 article to a description of this effect. Is "Vortex ring" the right one? —The preceding unsigned comment was added by TraceyR (talk • contribs) 12:19, 14 January 2007 (UTC)
replies: text: SC1 and vortex ring are more similar to the helicopter ground effects, not the WIG / ekranoplan effects. One of the older Harrier history books has some good coverage on this (there's a tendency for a Pegasus to ingest its jet efflux, which limits hover time before overheating)  Andy Dingley (talk) 09:55, 22 September 2009 (UTC)
thread_title: Vortex ring / Ground effect in fixed-wing VTOL aircraft

message: I've observed pigeons "hovering" long distances over the ground with no wing-flaps, and often wondered how exactly they were doing that... I guess this must explain it. (Unsigned comment)
REPLY: You'll note that the "ground effect" occurs mostly within the wingspan of the flying object. Thus, a pigeon hovering "a long distance" above the ground is unlikely to be experiencing ground effect. I suggest what you are seeing is them taking advantage of the wind, which increases in energy as you gain altitude (ever been on top of a good sized building?). While a pigeon, or hawk, or albatross may appear to be hovering relative to the ground, because of the wind, it is the same as if they were flying at a fixed speed through the air, thus lift is generated without need for flapping wings to generate forward velocity. Make sense? Gliders can "hover" the same way in a high enough wind; indeed, if it is very strong, both gliders and birds can appear to be flying BACKWARDS in relation to the ground. This is the important distinction in aeronautics between airspeed and speed over ground. They are rarely the same thing..45Colt 01:47, 18 August 2014 (UTC)
replies: text: I think you misunderstood his wording: he said "'hovering' long distances over the ground", not "'hovering' at a long distance above the ground". In other words, he was watching pigeons "float" just above the ground, covering a long distance before finally touching down. This would count as ground effect at work. --Colin Douglas Howell (talk) 09:52, 25 January 2019 (UTC)
replies: text: I've observed hawks (c. 3lbs.) carrying prey of c. 1.5 lbs, flying  3-5 ft. off the ground for 1-200 ft. until close (20 ft?) to a perchable tree, at which point they climb and slow down to perching speed (~ 0 mph!). Are they taking advantage of ground effects in choosing this flight profile? DCDuring (talk) 00:26, 5 October 2022 (UTC)
thread_title:  Pigeons 

message: Wasn't there a ground-effect vehicle featured in Metal Gear Solid: Snake Eater? Perhaps an In Fiction category could be added to facilitate this reference. —The preceding unsigned comment was added by Justin Herbert (talk • contribs) 03:20, 31 January 2007 (UTC)
thread_title:  Metal Gear Solid Reference 

message: I have literally dozens of books on aircraft, flying, pilotage etc. that all say "ground effect". Googling "ground effect aircraft" turns up lots of hits both with an without WIG mentions. I believe this article has been moved to the wrong title, only the moreso because it's been capitalized. I will accept a compromise position of "ground effects in aircraft". Maury 20:46, 2 February 2007 (UTC)
replies: text: Wholly agree. -Ravedave (Adopt a State) 22:26, 2 February 2007 (UTC)

text: Sounds good, especially in the plural TraceyR 23:17, 2 February 2007 (UTC)

text: Yes, i wouldn't object. It was me that moved the article, i really just wanted to disambiguate the effects in cars, i chose Wing In Ground becuase this was the section title, bold in the intro, etc. "ground effects in aircraft" sounds good to me, but i'll leave it to those who know more about aircraft.Spute 14:19, 4 February 2007 (UTC)
replies: text: Ok guys, moved successfully (I'll do some link checking). Thanks for the quick replies! Maury 21:53, 5 February 2007 (UTC)

text: Could you all take a sec or two and check for links? There's a lot of them! Maury 22:04, 5 February 2007 (UTC)
replies: text: I know, i changed them all last week!Spute 20:07, 6 February 2007 (UTC)

text: Oh boy, I forgot entirely about the S. I did it this way because it's the same as cars, which also lacks the S. Definitely NOT worth another move! Good edits BTW. Maury 23:43, 6 February 2007 (UTC)
replies: text: The article is still lacking any real discussion of other ground effects and continues to use the term when "wing in ground" effect is meant. Perhaps defining the abbreviation "WiG effect" and using it in the article where appropriate would remove the confusion (and start a new trend?). TraceyR 23:37, 1 March 2007 (UTC)
thread_title:  Whoa, bad article name 

message: Ok, throwing this out there in the article to see what comes back. I'll try to add some vector diagrams later.
Cheers MickycOZ 10:27, 27 February 2007 (UTC)
thread_title:  Rotary Wing Stuff 

message: I gather at one point the article was entitled "Wing In Ground Effect", and there was some complaint over this. I don't see why this should have entailed removing any use of the term from the article at all. Shouldn't it mention somewhere that ground effects are "also known as the 'wing in ground effect' due to its relation to the wingspan of the aircraft"? I know there are certain articles that link to this page with the term "wing in ground effect", because I recall clicking it out of curiosity once upon a time..45Colt 01:53, 18 August 2014 (UTC)
thread_title:  Wing In Ground 

message: The article begins “In fixed-wing aircraft...”, but it later talks about helicopters' rotors and has even an animation involving a helicopter. Which is the best way to fix this? Goochelaar (talk) 18:29, 27 December 2015 (UTC)
replies: text: They're really two quite different effects (a third if we include VTOL aircraft like the Harrier). These could be separate articles. They certainly need clearly separate sections. Andy Dingley (talk) 20:08, 27 December 2015 (UTC)
thread_title:  Just fixed or also rotary wings? 

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