Section 33.23 - Engine mounting attachments and structure(a) The maximum allowable limit and ultimate loads for engine mounting attachments and related engine structure must be specified.(b) The engine mounting attachments and related engine structure must be able to withstand- (1) The specified limit loads without permanent deformation; and(2) The specified ultimate loads without failure, but may exhibit permanent deformation.Amdt. 33-10, 49 FR 6851, Feb. 23, 1984