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Flying at 1000 ft, would giving an airliner wing more girth but not length, allow the plane to fly more efficiently than it normally would at that height?

Yes, airliners fly best around 35,000 ft, but if it was restricted to fly at 1000 ft., what would be the best shape wing for it?

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    $\begingroup$ With that limit, better build it as a ground effect vehicle for intercontinental traffic across oceans. $\endgroup$ – Peter Kämpf Feb 22 at 7:21
  • $\begingroup$ Thermal efficiency reduces $\endgroup$ – Abdullah Feb 22 at 8:26
  • $\begingroup$ @PeterKämpf ...which could also lead us to the question: what is the minimal cruise altitude below which flying in ground effect is more efficient? $\endgroup$ – Gypaets Feb 22 at 9:26
  • $\begingroup$ @Gypaets: Yes, that is a very good question. I had once the task to do preliminary layout for a ground effect vehicle and used some optimization algorithm to do so. It resulted in a typical airliner, flying at 40 kft. I did not put in a height limit and the crossover point was at low altitude, but I cannot remember the exact figure. $\endgroup$ – Peter Kämpf Feb 22 at 18:43
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Silly comments aside, "fat" wings, ones with greater camber, were all the rage 100 years ago when designers found they could eliminate draggy external bracing by building cantilever wings. Hugo Junkers was one of these pioneers.

Wind tunnel testing also showed increased camber not only increased lifting efficiency, but also, combined with large, rounded leading edges, produced very benign stalling characteristics. One result of this research, the Fokker D.VII., so terrified opposing pilots that it was specifically banned after the end of the "Great War".

Heavily cambered wing design such as the Davis wing lived on until aircraft began pushing the limits of the "sound barrier". Aircraft fly higher to get more speed with the same amount of drag, and this works great until the wing approaches its critical Mach number. Above this, drag greatly increases, ending the reign of the "fat wing".

Modern "super critical" wings, literally "surf" the slower bottom airflow, leaving the top of the wing as flat as possible. This is what airliners use at 35,000 feet.

But at 1000 feet, where airspeed is limited to 250 knots, the "fat wing" makes a comeback by deploying slats and some flap. For a given wing area and Angle of Attack, the "thin wing" is only more efficient when Critical Mach Number is approached.

This is why many airliners have a never exceed speed for lower altitudes, and a Mach limit for higher altitudes.

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    $\begingroup$ Please - it's Fokker D.VII. $\endgroup$ – Peter Kämpf Feb 22 at 18:46

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