§23.21 Proof of compliance.

(a) Each requirement of this subpart must be met at each appropriate combination of weight and center of gravity within the range of loading conditions for which certification is requested. This must be shown-- (1) By tests upon an airplane of the type for which certification is requested, or by calculations based on, and equal in accuracy to, the results of testing; and (2) By systematic investigation of each probable combination of weight and center of gravity, if compliance cannot be reasonably inferred from combinations investigated. (b) The following general tolerances are allowed during flight testing. However, greater tolerances may be allowed in particular tests: ItemTolerance Weight------------------------------------------------------+5%, -10% Critical items affected by weight------------------+5%, -1% C.G.----------------------------------------------------------�7% total travel.