Aging Aircraft

June 1, 1999
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."

Section 44717 of 49 U.S.C. specifies that these inspections and reviews must be carried out as part of each aircraft's heavy maintenance check conducted "after the 14th year in which the aircraft has been in service." It also states that the air carrier must "demonstrate to the Administrator, as part of the inspection, that maintenance of the aircraft's age-sensitive parts and components has been adequate and timely enough to ensure the highest degree of safety." Section 44717 of 49 U.S.C. further states that the rule issued by the Administrator must require an air carrier to make its aircraft, as well as any records about the aircraft that the Administrator may require to carry out the review, available for inspection as necessary to comply with the rule. It also states that the Administrator must establish procedures to be followed for carrying out such an inspection.

On August 6, 1993, the FAA revised the airworthiness standards for small metallic airplanes to incorporate Amendment No. 23-45 (58 FR 42163) into 14 CFR Part 23. Those revisions provided an option to use damage-tolerance-based inspections and procedures as a means for achieving continued airworthiness of newly certificated normal, utility, acrobatic, and commuter category airplanes.

On Oct. 5, 1993, the FAA published Notice No. 93-14, "Aging Airplane Safety" (58 FR 51944). The proposals contained in that notice would have required operator certification of aging airplane maintenance actions and would have established a framework for the Administrator to impose operational limits on certain airplanes.

Other specific proposals related to operator certification of aging airplane maintenance actions were included in the notice. Those proposals included: (1) A definition of the terms "heavy maintenance check" (HMC) and "years in service;" (2) a requirement for certificate holders to establish an HMC interval for each airplane they operate; (3) a requirement for certificate holders to make a maintenance record at the start of each airplane's 15th year in service and at all subsequent HMCs to certify that the airplane met all maintenance program requirements; and (4) a requirement for certificate holders to notify the FAA at least 30 days before the start of an airplane's HMC (with the release of the latest rule, the 1993 the Aging Airplane Safety NPRM, Notice No. 93-14 (58 FR 51944, October 5, 1993) is withdrawn).

Finally, on February 9, 1996, the FAA revised part 23 by Amendment No. 23-48 (61 FR 5148) to require damage-tolerance-based inspections and procedures on all newly certificated commuter category airplanes. Other airplanes were not affected by the described rule changes and thus do not have prescribed damage-tolerance-based inspections and procedures.

These airplanes fall into four basic categories: (1) Airplanes with non-damage-tolerance-based SIPs, based solely on service history, as prescribed in AC No. 91-60, "The Continued Airworthiness of Older Airplanes;" (2) airplanes that were certificated with design- life limits on the entire airplane or on major components such as the wing, empennage, or fuselage; (3) airplanes that were designed to "fail-safe" criteria to comply with fatigue requirements; and (4) airplanes that were certificated with limited consideration being given to metal fatigue.

The latest proposal
As a result of requirements stipulated by Congress, the FAA proposes to prohibit the operation of certain airplanes in scheduled service unless the Administrator or the Administrator's designee has determined that maintenance of the aircraft's age-sensitive parts and components has been adequate and timely.

All airplanes operating under Part 121, all U.S.-registered multi-engine airplanes operating under Part 129, and all multiengine airplanes conducting scheduled operations under Part 135 would be affected. Air carriers would be required to make each airplane and certain records related to the maintenance of age-sensitive components of the airplane available to the Administrator. Also, each affected airplane would be prohibited from operating unless damage-tolerance-based inspections and procedures are included in the maintenance or inspection program used on each airplane in accordance with a specified schedule.

Damage-tolerance-based inspections and procedures would be required on all affected airplanes no later than December 20, 2010. The airplanes affected by this proposed rule transport a significant proportion of those passengers carried in scheduled passenger service and are the most prevalent airplanes operating in such service. This notice does not propose requirements for rotorcraft or single- engine airplanes, nor does it propose requirements for on-demand passenger- or cargo-carrying operations under 14 CFR Part 135. The scope of this proposal includes the preponderance of aircraft the Congress intended to cover under the AASA. In a future notice, the FAA will propose aging aircraft requirements necessary to cover the operation of all the other aircraft used by air carriers to provide air transportation.

Congress also instructed the Administrator to encourage governments of foreign countries and relevant international organizations to develop programs addressing aging aircraft concerns. Most foreign air carriers and foreign persons engaged in common-carriage operations have maintenance program requirements adopted by their governments. The FAA issues the airworthiness certificates for U.S.-registered airplanes. By including part 129 in this proposed rule, foreign air carriers and foreign persons operating U.S.-registered multiengine aircraft within or outside the United States would be required to include damage-tolerance-based inspections and procedures in their maintenance programs and be subject to aging aircraft records reviews and inspections.

This proposal would also revise current 14 CFR 183.33(a) to expand the authority of the Designated Airworthiness Representative (DAR). The DAR would be authorized to conduct the proposed records reviews and inspections on behalf of the Administrator.

The FAA intends to verify that each operator has records to show that they have accomplished all required maintenance tasks, as well as the damage-tolerance-based inspections and procedures that would be required by this proposal. The FAA would validate that these records are correct for each affected airplane during the records review and inspection required by this proposed rule. Section 44717 of 49 U.S.C. specifies that the records reviews and inspections be carried out as part of each aircraft's heavy maintenance check after the 14th year in service.

For airplanes that have already completed 14 years in service, the proposal would require the first records review and inspection within 3 to 5 years of the effective date of the rule. This proposal would generally require the first records review and inspection to be accomplished no later than 5 years after the 14th year in service. The FAA realizes that the first inspection required 5 years after the 14th year in service may not be consistent with current operator maintenance schedules. As a result, the records reviews and inspections carried out by the Administrator or the Administrator's designee may significantly affect these maintenance schedules because the reviews and inspections may not coincide with current maintenance schedules.

In formulating this proposal, the FAA considered options for setting repeat intervals. Among those considered were the heavy maintenance check interval, heavy maintenance visit interval, or the "letter check" (e.g., 'C', 'D', or 'E') interval or other equivalent check interval an operator may use.

This proposal would establish a new requirement for "total years in service." The FAA has determined that this new requirement is essential for the Administrator and the operator to determine the compliance time for the initial and repetitive inspections. To meet this requirement, the operator would retain records validating when the initial certificate of airworthiness was issued for each airplane. In addition, the FAA is aware that an airframe's flight cycles are not currently being collected by operators of small airplanes under part 135. This proposal would require that the operator make certain records and reports available to the FAA during the proposed aging airplane records review inspection.