The aircraft structure is a damage tolerant structure, so damage would be detectable after a hard landing, and there are hard landing inspections to be done in the areas known to be subject to possible damage. If these areas are OK, the structure can be cleared.
Landing gear on the other hand are safe life items (not damage tolerant), so in case of loading beyond the limit load the parts need to be NDT'd and checked for plastic deformation and residual stresses. Residual stresses cause stress corrosion cracking (most landing gear structural members are 300M UHTS Steel), and localised fatigue cracking.
Last edited by Plastique; 13th Dec 2003 at 00:21.