Aging Aircraft

New rules proposed

By Greg Napert

June 1999

Although the FAA and the industry has been dealing with aging aircraft regulation for years in the form of numerous ADs and inspection requirements, no rule has yet been passed which requires a specific "inspection program" for older aircraft.

The FAA attempted to propose such a rule in 1993, but the industry shot it down — pointing out many discrepancies and inadequacies with the proposal. The FAA then went back to the drawing board and now released a new NPRM with "damage tolerance" inspection requirements in it.

These inspection requirements have little impact on new air carrier equipment as manufacturers saw long ago the need to include these inspection programs with the new aircraft. So, in effect, the airlines have already been conducting damage tolerance inspections on their fleet. But for older aircraft without inspection programs, and for the majority of regional carriers, a new requirement to engineer inspection programs will be in place. Further, the FAA promises to apply these programs to "on demand" operators in the near future.

Because of the wide ranging effects that this rule will have on aircraft maintenance, AMT magazine brings you portions of the new proposed rule, which offers a historical perspective on aging aircraft, as well as a summary of what is being proposed. The following are selections from the NPRM:

Historical perspective
The continued airworthiness of aircraft structure is significantly affected by age-related fatigue damage. Evidence to date suggests that when all critical structure are included, damage-tolerance-based inspections and procedures provide the best approach to address aircraft fatigue. An underlying principle of damage tolerance is that the initiation and growth of structural fatigue damage can be anticipated with sufficient precision to allow damage-tolerance-based inspections and procedures to detect damage before it reaches a size that affects an airplane's airworthiness.

In 1978, the damage-tolerance concept was adopted for transport category airplanes as an amendment to 14 CFR 25.571 by Amendment No. 25-45 (43 FR 46238). That amended rule required damage-tolerance analysis as part of the type design of transport category airplanes for which application was received after October 5, 1978.

On May 6, 1981, the FAA published Advisory Circular (AC) 91-56, "Supplemental Structural Inspection Program for Large Transport Category Airplanes," guidance material based on the amended rule for existing designs. Using the guidance provided in AC 91-56, many manufacturers of large transport category airplanes (airplanes of more than 75,000 pounds) developed Supplemental Inspection Programs (SIPs) for their existing models.

Beginning in 1984, the FAA issued a series of airworthiness directives (ADs) requiring the operators of those airplanes to incorporate the SIPs into their maintenance programs. SIPs provide inspections and procedures that are based on damage-tolerance principles.

In October 1991, Congress enacted Title IV of Public Law 102-143, the "Aging Aircraft Safety Act of 1991" (AASA), to address aging aircraft concerns. The AASA was subsequently codified as section 447717 of Title 49, Unites States Code (49 U.S.C.). Section 44717 of 49 U.S.C. instructs the Administrator to "prescribe regulations that ensure the continuing airworthiness of aging aircraft."

That section also requires the Administrator to "make inspections, and review the maintenance and other records, of each aircraft an air carrier uses to provide air transportation." The records reviews and inspections would be those necessary to "enable the Administrator to decide whether the aircraft is in safe condition and maintained properly for operation in air transportation."