Talk:Lift-to-drag ratio

message: Isn't "In zero wind conditions, L/D will equal altitude lost divided by distance traveled" backwards?
The article says that maximum range is at minimum drag???
Shouldn't this be minimum drag per unit distance?WolfKeeper 16:53, 24 August 2007 (UTC)
thread_title: Untitled

message: The explanation for induced drag in the article is wrong: lift is not defined as the force perpendicular to the wing (whatever reference line), but perpendicular to the free stream direction. Thus, induced drag cannot be explained as a consequence of the wing flying at an AOA, tilting the lift backwards. Actually, induced drag is zero for a two-dimensional wing or wing of infinite span. Induced drag is the result of the additional downwash induced by the tip vortices. This causes the wing to see a different averaged free stream which is angled downward.
Furthermore, best L/D occurs at minimum drag since this drag graph is calculated for constant lift (i.e. level flight). So it is wrong to say that at slower speed there is less lift.— Preceding unsigned comment added by JaRaMW (talk • contribs) 07:49, 31 May 2011 (UTC)
replies: text: Thanks for those valid observations.  I have made some changes.  See the diff. Dolphin (t) 12:11, 31 May 2011 (UTC)
thread_title:  induced drag, total drag 

message: It's right that these drop in supersonic flight; it is the result of wave drag due to lift, absent  when compressibility is not an issue. But I don't think the comparison of two different aircraft travelling at subsonic and supersonic speeds is helpful. In addition, the aerodynamics of a delta wing, even at low speeds is very different from straight or swept ones, as there are vortices not just at the tips but all along the leading edge.  Much better if we can get data for one aircraft, perhaps ideally with straight wings, in the two regimes. There is a plot of CD,0 for the T-38 at 0.2 < M < 1.4 in Anderson's Aircraft Performance and Design (it increases by a factor of about 3) but no CL.  Must be out there somewhere!TSRL (talk) 19:24, 27 October 2011 (UTC)
replies: text: The same book, page 136, also has drag polars at several Mach numbers for the F-15.  These are not ideally presented for extracting the maximum L/D but I get about 10.3 at M=0.2 and 4.3 at M=1.4, the difference being almost entirely due to the increase in CD.TSRL (talk) 19:14, 28 October 2011 (UTC)
thread_title:  Supersonic/hypersonic lift to drag ratios 

message: The lede contains a statement that Lift-to-drag ratios are usually found using a wind tunnel.  The cited source is NASA.  This statement is also found in Flight.  Its validity is presently under discussion at Talk:Flight#Lift-to-drag ratio. Dolphin (t) 08:02, 11 May 2012 (UTC)
replies: text: User:Writ Keeper has provided a Third Opinion on this matter.  See Talk:Flight#Lift-to-drag ratio.  I have altered the sentence so it now states: "Lift-to-drag ratios can be determined by flight test, by calculation or by testing in a wind tunnel." We must now turn our attention to provide ini-line citations that genuinely support this statement. To ensure we don't overlook it I have added "Fact" tag immediately after the sentence. Dolphin (t) 04:07, 15 May 2012 (UTC)
thread_title:  Wind tunnel 

message: eg.  - Rod57 (talk) 02:21, 7 December 2014 (UTC)
replies: text: Found it Template:Glide ratio examples - Rod57 (talk) 12:14, 9 December 2020 (UTC)
thread_title:  How do we edit the templates used in the Examples section 

message: A quick calculation shows the value of 7 for the C150 in cruise is too low, by at least 30 percent. No source is given. Can someone improve this entry? Thanks in advance.--Spray787 (talk) 01:36, 4 June 2015 (UTC)
thread_title:  L/D for the Cessna 150? 

message: It is not polar coordinates, so why is it called a polar plot? 
2600:1700:4CA1:3C80:2536:CFC6:40D7:3026 (talk) 23:02, 22 August 2020 (UTC)
replies: text: At Drag polar#The drag polar you will find the following explanation: "If, in a wind tunnel or whirling arm system an aerodynamic surface is held at a fixed angle of attack and both the magnitude and direction of the resulting force measured, they can be plotted using polar coordinates. When this measurement is repeated at different angles of attack the drag polar is obtained. Lift and drag data was gathered in this way in the 1880s by Otto Lilienthal and around 1910 by Gustav Eiffel, though not presented in terms of the more recent coefficients. Eiffel was the first to use the name drag polar." Dolphin (t) 08:36, 23 August 2020 (UTC)
thread_title:  Why called polar? 

message: I was looking for the L/D for flat rectangular plates at various AoA, but nothing here or at Lift (force). - Rod57 (talk) 11:22, 9 December 2020 (UTC)
replies: text: Fig 5 of Effects of aspect ratio and inclination angle on aerodynamic loads of a flat plate Shaderman et al. has Cd & Cl plots for AoA > 30 degrees, and the L/D at 30 degrees inclination seems to be about 1.5. - Rod57 (talk) 11:39, 9 December 2020 (UTC)

text: Maximum Lift/Drag Ratio of Flat Plates with Bluntness and Skin Friction at Hypersonic Speeds has formula for hypersonic plates - Rod57 (talk) 12:19, 9 December 2020 (UTC)

text: Flat plate lift (and LDR) can be bimodal as a function of inclination eg as in fig 10 of  - Rod57 (talk) 12:29, 9 December 2020 (UTC)
thread_title:  What can we say about the L/D for flat rectangular plates 

message: I have come here because it has been raised on the Project talk page (thank you for that, ). The best way ahead here is to remain calm, respect the WP:CIVIL pillar of our editing community, and pick off the issues of disagreement one at a time. No more "You started it, you invaded Poland!" type personal rhetoric. Just the salient points in making this encyclopedia better.
So, to take the lead image of the Wright flyer. I agree with the IP editor that the caption does not make clear the link between AoA and l/d. Nor should it; if AoA is to be used as a discussion point, that should be done in the main text and not in an image caption. Nor should the lead image attempt to depict such a secondary relationship. The fact that it has been here a long time is irrelevant, it needs to either go lower down near the associated discussion, or be deleted. I propose that for now it should be moved down to the section on drag (that section is no better in technical clarity than the current image caption, but this one change is enough for a first discussion).
— Cheers, Steelpillow (Talk) 20:35, 2 January 2022 (UTC)
replies: text: Thanks, Steelpillow. I do think the Wright pic should be removed completely, as we agree the main thing it illustrates is AoA: where it is already used. 95.91.246.145 (talk) 21:37, 2 January 2022 (UTC)
thread_title: Composite image of the Wright flyer

message: This image is also the subject of controversy:
My own view is that it does not support the section it is currently in, viz. Examples of L/D ratios, because it shows lift-minus-weight vs drag and not lift alone vs drag. Also, the presence or otherwise of dynamic (acceleration) effects is not clear. Nor can I see any other section it is more suited to. Therefore it should be deleted. What do others think? — Cheers, Steelpillow (Talk) 18:39, 4 January 2022 (UTC)
replies: text: The Wright Flyer is listed in the examples (8.3:1). The caption could be changed for your formulation "lift-minus-weight vs drag". The picture seems stabilised, with no dynamic acceleration, photography wasn't instantaneous in 1902.--Marc Lacoste (talk) 19:20, 4 January 2022 (UTC)
thread_title: Remaining image of a Wright glider

message: Participate if you want. 95.91.246.145 (talk) 08:19, 5 January 2022 (UTC)
replies: text: Thank you for letting us know. — Cheers, Steelpillow (Talk) 11:02, 5 January 2022 (UTC)
thread_title: There is a related discussion at [https://en.wikipedia.org/wiki/Wikipedia:Administrators%27_noticeboard/Incidents#Edit_war_and_personal_attacks_from_an_IP_editor_in_Lift-to-drag_ratio noticeboard]