ED Decision 2003/13/RM
There must be means to ensure that ground loads acting at the wing tips are adequately resisted. A limit load T = 40 daN must be assumed to act rearward at the point of contact of one wing-tip with the ground, in a direction parallel to the longitudinal axis of the sailplane, the yawing moment so generated must be balanced by side load R at the tail skid/wheel or nose skid/wheel (see Figure 4).
Figure 4 WING-TIP LANDING