The Arup S-4 (Model 104) is the last in a series of round-wing aircraft from C.L.

[2] The S-4 used a low aspect ratio, semi-circular planform wing with a conventional landing gear and a small rudder with attached elevator on the rear of the fuselage.

[3] The S-4 prototype flew extensively in promotional demonstrations.

The S-4 was emblazoned with Sears Roebuck and Company logos.

[4] A replica is on display in the atrium of South Bend Airport[7] Data from Janes, Popular AviationGeneral characteristics