Talk:Aspect ratio (aeronautics)

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Removed from Aspect Ratio[edit]

In aviation, the aspect ratio of aircraft tapered wings is found by dividing the square of the wing span {b} by the total wing area (S):

AR = b2/S

If the wing has a constant chord, the aspect ratio is the result of dividing the wingspan (b) by the value of the chord (c):

AR = b/c

Similarly, if the value of the mean geometric chord is known, the aspect ratio is the result of dividing the wingspan by the value of the mean geometric chord:

AR = b/cmean

(Material is posted for review or incorporation and may be deleted after period of review.) Stephen Charles Thompson (talk) 07:40, 5 July 2008 (UTC)

(other)[edit]

Should there be an entire paragraph devoted to the flight patterns of migratory birds? A sentence or two should suffice.

I removed the paragraph (and the associated external reference) since it was also almost totally wrong. I don't see V-formation flying in migratory birds as too relevant to aspect ratio. 58.96.71.120 22:10, 2 December 2007 (UTC)


I removed this section, added by an anon contributor:

Drag: an aircraft wing works by employing lift. Lift is created by causing the air to take a longer path across the top of the wing. This creates lower pressure above the wings than below the wings, moving the aircraft upwards. The longer the winds, the more drag is created by the wings, slowing down the aircraft. However, in low aspect-ratio wings, the air simply travels from under the wing to above the wing along the sides. This causes turbulence, which slows the plain down more than the drag did. The XF5U fighter used an inovative method to solve this problem.

This is wrong in so many ways. First the explanation of lift is false. See lift (force). Second, while a bigger wing will produce more drag than a smaller one in absolute terms, it's the L/D RATIO that matters. Higher aspect ratios always have better L/D ratios, therefore citing drag as a disadvantage is wrong. Third, the explanation of turbulence is couched in wooly language without any scientific rigour, and fails to get to the heart of the matter, which in any case is covered admirably elsewhere - notably at induced drag. Fourth, there are some bizarre spelling mistakes. Fifth, the XF5U may or may not be relevant but this passage doesn't even begin to explain why. The anon contributor would do well to read up on the full extent of the aerodynamics coverage on WP (which is extensive) before adding ad-hoc and badly thought-through passages like this one. Sorry to sound so harsh but I also refer you to my views about anon contributors in general. Graham 03:46, 30 August 2005 (UTC)

I was the anon user who added that paragraph. All information there was based on the History Channel program Secret Allied Aircraft of World War II, which aired 8/29/05, at 5:00pm EST. The importance of the overall lowering of drag, while raising the ratio is important because the XF5U utalized this principle along with propellers at the edge of its wings to allow for the lowest drag ratio possible. I am by no means a scientist, and understand very little about aircraft, aerodynamics, drag, or life (apparently). I direct the person that removed by paragraph to the "Bernoulli's principle" section of the lift article he linked to. That was what I was trying to state in my definition of lift.
In my opinion, the increase in overall drag created by low aspect ratio wings, and how this is properly utilized by the XF5U should be included somewhere in the article. However, since I will invariably explain it wrong, it would be appreciated if someone else would explain it correctly and simply. Thank you. Gogf 22:14, 30 August 2005 (UTC)
Hi. First, please don't take anything here personally - we are only concerned that the articles are well-written and correct. The explanation of lift that you mention is not Bernoulli's Principle, but a bastardised (and unfortunately popular) form of it. This is covered at lift (force) under the section headed "common explanation of lift is false". I think you are getting confused about what is meant by "high" and "low" aspect ratios (possibly) - the article wasn't all that clear on this so I added a sentence to make it clear. The XF5U has exceptionally LOW aspect ratio wings, but in the context of this article is something of a red herring, or maybe the exception that proves the rule. The reason the XF5U has low drag DESPITE its aspect ratio is that the rotating vortices from the propellors actively cancel the wingtip vortices shed by the wing (the propellers rotate anti-clockwise on the left side, and clockwise on the right side, as viewed from the front - you can visualise this as causing the air that would normally spill around the wingtip to be held in place by the rotating airstream coming off the propellors). However, this in no way challenges the general rule about aspect ratio - in fact it helps prove it by demonstrating that the drag is caused by these tip vortices. You had listed "drag" as a disadvantage along with other disadvantages of a high aspect ratio wing, but the truth is the exact opposite - low drag is the key ADVANTAGE of high aspect ratios. Some mention of the XF5U might add something here, but needs to be carefully worded so that it doesn't create confusion. Graham 23:34, 30 August 2005 (UTC)
Thanks for the explanation Graham :). I'm still confused as to whether the higher the aspect ratio the higher the drag (yet lower the L/D ratio). I did not take it personally, and honestly took your response as proof of how great Wikipedia is. When I first started reading Wikipedia, I was skeptical at least, as anyone can edit the information. However, my explanation, which was by no means a crazy fact, but more of a misconception, but it was quickly corrected. It's people like you that make me trust Wikipedia. I'll be sure to make sure I have my facts right before editing an article next time. Also, thanks for showing me how to properly format a discussion page. Gogf 20:40, 31 August 2005 (UTC)
Hey, no worries... Higher aspect ratio -> higher drag? Well, that could be true, in the limited sense that form drag is proportional to the frontal area of the wing, and a high aspect ratio wing will have a larger frontal area compared to a low aspect ratio wing of the same overall surface area. However this is only the parasitic or form drag of the wing, but for performance we need to take both this and induced drag into account. Induced drag falls with airspeed, while parasitic drag rises with airspeed. Add them together and you end up with a U-shaped drag curve which shows a minimum value at some airspeed. Ideally the aircraft will be set up to fly close to this airspeed most of the time, giving the best performance in the cruise. Changing the aspect ratio of the wing will move this minimum drag point to a different airspeed, so we can use aspect ratio as a design tool to place this point where we want it, though of course there will be lots of other design factors too. A high aspect ratio wing will have a lower amount of induced drag (for a given amount of lift), but possibly more form drag - but as it's the lift/drag ratio that's really important, the absolute figure for drag doesn't matter so much as long as the wing is doing its job for us, and in general terms a high aspect ratio will give us a more efficient wing. It's just that efficiency isn't everything - gliders need to be as efficient as possible as they are unpowered - hence they have "no compromise" ultra-high aspect ratio wings. When we have an engine though, we can overcome a lot of the inefficiencies just by using more power, allowing us to compromise the wing design to more practical ends. Graham 23:54, 31 August 2005 (UTC)

Hi, I changed the stability disadvantage of high AR wings to the more specific "pitch stability". Ever tried to turn a high AR aircraft? they feel really heavy and are sluggish, they are super-stable in the roll axis so to say low AR wings are generally more stable is a bit misleading (esp. considering how 'twitchy' low AR fighters are). I should've really said something about how the pitch stabilty is also affected by the tail (mainly in its distance from the quarter chord) but that would be complicating the matter further. Maybe there should be a link to longitudinal stability? I'm swamped with other work at the mo but I may fix it later. Also, on the topic of drag, high AR reduces *induced* drag as compared to a lower AR wing of the same lift coeff. Its been a long time since I was a 2nd year aerospace engineering student, but I do remember something about the AR being on the bottom of the fraction in drag, so increasing it would lower induced drag, note though that as the speed increases the induced drag will diminish but the profile drag will increase. So for the argument of what is better for drag, high AR or low AR, it depends entirely on what speed you're wanting to fly at! There is a famous graph of drag vs. airspeed, showing a minimum where the two drags are equal. In general though, the slower you fly, the higher you want your AR, and vice versa. However I believe it is not in the scope of this particular article to discuss drag. Shaun 19:11 20 April 2006 (BST)

Re-work of article[edit]

Since April 2009 I have been re-working this article, primarily to incorporate references and in-line citations, and to refine the math. Please peruse my re-work at User:Dolphin51/Sandbox. Before I paste it into the article, I am interested in any comments. Please post comments at User talk:Dolphin51/Sandbox.

Part of the existing article begins There are several reasons why all aircraft do not have high aspect wings. I have been unable to find any in-line citations to support this claim. I would be grateful if others can identify suitable citations for this part of the article. Dolphin51 (talk) 03:45, 15 October 2009 (UTC)

Eight days have passed without objection or comment, so I have pasted the content of my sandbox into the article. Dolphin51 (talk) 03:41, 23 October 2009 (UTC)