Manufacturers of Part 25 transport aircraft weighing more than 75,000 pounds, including business jet OEMs, will be required to develop operational limitations for all future designs, under a far-ranging proposal aimed at eliminating “widespread fatigue damage” (WFD) as aircraft age.

Although business jet designs made after the effective date of the rule would be included, the proposal is part of the FAA’s long-running aging-aircraft program and is intended primarily to prevent WFD in older, high-time airliners, such as the 737, DC-9 and BAC 1-11.

Consequently, current Part 25 airplanes weighing more than 75,000 pounds mtow and not used in Part 121 or 129 operations–including Bombardier and Gulfstream business jets–are excluded from the operator requirements of the proposal. Only Part 121 U.S. and Part 129 foreign carriers would be required to develop a maintenance and inspection program to prevent WFD.

In any case, aircraft would be prohibited from operating beyond their established limit. However, the rule would provide a means for operators to extend the limit, after which the aircraft could no longer be operated in the U.S.

Proposed operational limits for some of the targeted airplanes are: 75,000 cycles for the 737; 85,000 cycles for the 1-11; and 100,000 cycles for the DC-9.

Comments on the proposal are due July 17. For further information, contact Walter Sippel, FAA, Transport Airplane Airframe/Cabin Safety Branch, Renton, Wash. Phone (425) 227-2774; fax (425) 227-1232.