14 C.F.R. § 23.2235
Structural strength
The structure must support:
(a) Limit loads without—
(1) Interference with the safe operation of the airplane; and
(2) Detrimental permanent deformation.
(b) Ultimate loads.
The structure must support:
(a) Limit loads without—
(1) Interference with the safe operation of the airplane; and
(2) Detrimental permanent deformation.
(b) Ultimate loads.