New Standards Proposed for Composite Helo Parts
Last month the FAA published a proposed NPRM covering new airworthiness standards for composite structures on normal-category rotorcraft under FAR Parts 27 and 29.
A proposed new section in the regulations establishes guidelines for damage tolerance and fatigue testing of these structures. Applicants would need to demonstrate that components that are “principal structural elements” (PSEs) of the rotorcraft would not suffer catastrophic failure under static and fatigue loads throughout the rotorcraft’s operational life or prescribed inspection intervals by performing damage tolerance evaluations of the strength of the parts, detail design points and fabrication techniques. Parts covered under the NPRM include PSEs of the airframe as well as main and tail rotor drive systems, main and tail rotor blades and hubs, rotor controls, fixed and movable control surfaces, engine and transmission mountings, landing gear, and “fabrication techniques deemed critical by the FAA.” The FAA stated that it does not expect the new NPRM to increase operator costs because “inspection time for a composite part will be the same as or less than for a metallic part inspection.” However, the agency requests “comments regarding this assumption.” The comment period closes April 6.