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For some reason, I cannot find a relatively straightforward source online which discusses the relationship of wing aspect ratio and how it affects speeds of an aircraft.

Specifically, is there a decrease in efficiency to fly at a faster cruise speed as the aspect ratio of the aircraft's wing increases? Could an aircraft with a high aspect ratio - similar to those of gliders - travel at the same cruise speed as a jet?

Thanks in advance!

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  • $\begingroup$ Did you search for aspect ratio as suggests by the help center before asking $\endgroup$
    – Manu H
    Jun 6, 2020 at 7:06
  • $\begingroup$ this question Relation between drag and aspect ratio is highly related if not a dupe $\endgroup$
    – Manu H
    Jun 6, 2020 at 7:07
  • $\begingroup$ Are you looking for an explanation or just a link to an explanation? $\endgroup$
    – Guy Inchbald
    Jun 6, 2020 at 8:05
  • $\begingroup$ Yes - I read those other answers and searched before submitting. They don't specifically answer what I'm asking. I'm happy with either an explanation or a reference to one. $\endgroup$
    – sethkim
    Jun 6, 2020 at 18:07
  • $\begingroup$ You should highlight in your question why they don't address your problem as they are really similar to your one. $\endgroup$
    – Manu H
    Jun 6, 2020 at 20:53

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It's really the other way around, speed of the aircraft affects aspect ratio.

Hawks fold their wings to dive at high speeds, and have them straight out for lower speeds. At high speeds the main concern is drag. The less drag, the faster you can go. At lower speeds, the main concern is lift. Here a higher aspect wing is more efficient.

Why not use a smaller high aspect wing at higher speeds, and just vary the sweep?

This is done, but along with higher speed comes greater aerodynamic forces. This is one reason why modern fighters feature low aspect wings and deltas. These are simply much more able to withstand higher G forces.

The variable sweep wing concept was developed in the 1950s and 1960s, but generally carries a weight penalty. Variable camber is widely seen in airliners today. Some military aircraft, such as the B-1 bomber, use variable sweep to expand their useful flight envelope, giving them the ability to "get low and fast".

Cruise missiles, optimized for one speed only with little abrupt maneuvering, can be found with very simple high aspect swept wings, which offer an improvement in drag over a lower aspect wing, thereby increasing fuel efficiency and extending range

There is no direct relationship with speed and aspect ratio, indeed, high subsonic aircraft such as airliners, that strive for maximum efficiency, are seen with increasingly higher aspect ratios in recent years.

Structural strength is the main limitation which continues to challenge engineers today.

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  • $\begingroup$ Hi Robert - thanks for your response. You say that "there is no direct relationship with speed and aspect ratio, indeed, high subsonic aircraft such as airliners, that strive for maximum efficiency, are seen with increasingly higher aspect ratios in recent years." So if you were to theoretically double the aspect ratio of, say, a 737, and maintained the same cruise speed, you would only experience an increase in fuel efficiency (ignoring other effects such as a decrease in maneuverability)? $\endgroup$
    – sethkim
    Jun 6, 2020 at 18:10
  • $\begingroup$ Well, keeping the area the same, but reducing the aspect ratio would make a shorter, wider wing. much more drag from: higher angle of attack required for same lift and more drag from the trailing edge, but much stronger, able to withstand higher G forces. This is why the F-35 has its wing and the 737 has the higher aspect. Look at sailplanes! That is what you want as much as possible. The ones with jets are baby airliners without sweep, slats, flaps, and multiengines that develop later in life. $\endgroup$
    – Robert DiGiovanni
    Jun 6, 2020 at 19:36
  • $\begingroup$ You only lose efficiency when you have more wing than you need for a given weight, angle of attack, velocity, and air density as seen in the Lift Equation, which is why area is also included. $\endgroup$
    – Robert DiGiovanni
    Jun 6, 2020 at 19:42

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