Where are splices prohibited in a wooden wing spar?

The prohibition of splices under wing attach fittings in a wooden wing spar is important for maintaining structural integrity and safety. Wing attach fittings are critical points in the wing structure where the wing is connected to the fuselage or other support structures. Any imperfections or weak points in this area could lead to catastrophic failure during flight, especially considering the stresses placed on wings during various flight conditions.

Splices can create potential weak points in the spar, and when they are located under the wing attach fittings, they can compromise the load distribution and strength at one of the most critical junctures. It's essential for these areas to have uninterrupted, continuous wood grain to ensure that the load transfer can occur uniformly, thus preventing potential points of failure.

In contrast, splices may be more acceptable in areas like the leading edge, the trailing edge, or the center span, where they may not face the same magnitude of direct shear and tension forces as where the fittings are located. Nevertheless, even in these areas, care must be taken to follow specific guidelines regarding splice quality and placement to ensure the overall strength and safety of the wing structure.