Originally Posted by
Winemaker
I may be stupid, but I don't see how the wing load is greater with the winglet. The load is aircraft weight and g loading; that hasn't changed. I can see stiffening the wing tip as the winglet is increasing the local loading, but the final load carried by the wing box is constant. The wing load profile will change, but not the total load.
There are two pairs of pickle forks on the 737, with the AD referring to cracks found in the rear pair (at STA 663.75).
It's possible that the presence/absence of winglets alters the lift distribution along the wing, and if that moves the C of P then it may well be that the proportion of the wing load carried respectively by the front/rear pickle forks changes, even if the total load remains constant.