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Light sport aircraft may have a max airspeed in level flight at MCP of 120kts. I have heard that there are some light sport aircraft that have had their wings clipped in order to have a lower cruise speed.

But why do they clip the wings to reduce the cruise speed? Wouldn't that require a higher speed as less lift is produced at the same speed with less wing area? Also, thinking about gliders having a big wing span and fighter jets having a short wing span I can not see why you would clip the wings? What am I missing?

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    $\begingroup$ Gliders have very long wings, but they also have a very narrow chord. Fighters have very short wings, but a (relatively) very wide chord. $\endgroup$
    – rbp
    Commented Dec 26, 2014 at 16:59
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    $\begingroup$ @rbp: read all about it $\endgroup$
    – Peter Kämpf
    Commented Dec 28, 2014 at 22:46

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You must have heard wrong. Clipping wings is done to reach higher maximum speed.

You mention light sport aircraft, so I assume they have propellers driven by piston engines. This means their power output is constant over speed and the thrust is inverse with speed. To calculate their optimum cruise speed, you can use the venerable Breguet equation which shows that the aircraft has to fly at its optimum L/D for maximum range. At this speed, induced drag equals zero-lift drag, and span helps to cut down the former. Clipping the wing will shift the optimum cruise speed up, not down.

With clipped wings the aircraft has less surface area, which will reduce zero-lift drag. This is the drag component which determines maximum speed. Induced drag at a given speed will go up, but it is insignificant at maximum speed, so the aircraft will be able to fly slightly faster.

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    $\begingroup$ Alright that's what I was thinking, just heard a experienced flight instructor say that so I didn't want to tell him that I thought he was wrong. $\endgroup$
    – Maverick283
    Commented Dec 24, 2014 at 11:38
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    $\begingroup$ @Maverick283: I respect flight instructors when it comes to practical knowledge, but I have long stopped believing them in questions of aircraft design. There is too much nonsense circulating, and most of it is easily disproven. Still, people keep repeating it. $\endgroup$
    – Peter Kämpf
    Commented Dec 25, 2014 at 11:17
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    $\begingroup$ It can also improve roll response and roll rate $\endgroup$
    – Jon Story
    Commented Dec 26, 2014 at 1:37
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    $\begingroup$ @JonStory: You are right, and much more can be said about the effects of clipped wings. This time I wanted to keep the answer short ;-) $\endgroup$
    – Peter Kämpf
    Commented Dec 27, 2014 at 10:19
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    $\begingroup$ Note that the Hughes H1 racer had two sets of wings: a short set for the high speed record flights, and a longer set for the transcontinental speed effort. Given that the power plant wasn't changed, the longer wings allowed for a more efficient high speed cruise, meaning fewer fuel stops, while the short wings were for maximum top speed in a short burst, where fuel consumption wasn't an issue (unless you let it run out of fuel during the attempt, as Hughes did). $\endgroup$
    – tj1000
    Commented Apr 8, 2018 at 15:46
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Keep in mind that less wing area means a higher stalling speed, which translates to more runway needed for TO & landing. Climb performance and max. altitude may also be reduced noticeably.

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Clipping the wings may help a plane meeting the max gross limit of the light sports, but there are also max stall and max cruise speed limitations, which would be adversely affected by clipping the wings, as Peter explains in his answer. A plane that already has very low stall and cruise speeds, but it pushing the max gross weight might be made to fit the light sport limits by clipping the wings. A J-3 perhaps?

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    $\begingroup$ Isn't official max limit simply imposed in the manual? Of course, it has a physical source, but just having larger wings and thus being able to lift more doesn't always mean it is allowed to lift more (and have greater MTOW); there may be many other constraints. Or are you talking about cutting the wings as a measure to save dry weight? $\endgroup$
    – Zeus
    Commented Jul 10, 2018 at 9:40

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