Aircraft certification: day rule applicability,
[Federal Register: November 23, 1999 (Volume 64, Number 225)]
[Rules and Regulations]
[Page 65655-65656]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr23no99-1]
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[[Page 65655]]
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
Applicability of 90-Day Rule for Intermixed Airplane Engines and/ or Nacelles
AGENCY: Federal Aviation Administration, DOT.
ACTION: Statement of policy.
SUMMARY: This document clarifies the continued applicability of the 90- day limit for certain changes in airplane type designs after the final compliance date requiring an all Stage 3 fleet in the contiguous United States. The Federal Aviation Administration (FAA) has received numerous inquiries regarding the use of the 90-day limit after December 31, 1999. This document provides guidance to operators that need to use that provision of the airplane type certification regulations, including the limits of its use.
FOR FURTHER INFORMATION CONTACT: Mr. Thomas Connor, Manager, Noise Division (AEE-100), Office of Environment and Energy, FAA, 800 Independence Avenue, SW., Washington, DC 20591; telephone (202) 267-8933, fax (202) 267-5594.
SUPPLEMENTARY INFORMATION:
Background
In 1980, the Air Transport Association of America (ATA) petitioned the FAA on behalf of its member operators for an exemption from 14 CFR 21.93(b), and for a corresponding rule change that would allow unlimited intermix of airplane engines and/or nacelles that do not conform to specified noise levels. On January 26, 1981, the FAA published a Notice of Proposed Rulemaking (NPRM) (46 FR 8347), proposing to amend the definition of ``acoustical change'' in the aircraft noise certification rules as it applies to turbojet engine- powered, large transport category airplanes. The NPRM proposed permitting the temporary installation and use (intermix) of airplane engines having different noise levels, provided that the affected airplane is brought back into conformance with an acoustically certificated configuration for that airplane type within 90 days of the initial change.
The final rule revising Sec. 21.93(b)(2)(iii) was published on January 7, 1982 (47 FR 756). The regulation provided relief to operators and manufacturers without resulting in a significant noise impact by allowing the unlimited intermix of engines and/or nacelles for maintenance purposes for up to a period of 90 days without triggering the acoustical change requirement of Sec. 21.93. The change did not affect any other applicable requirements for certification of type design or airworthiness, or for operating the affected airplanes.
The Stage 3 transition regulations contained in 14 CFR part 91 were promulgated in 1991 to implement the Airport Noise and Capacity Act of 1990. The law requires that after December 31, 1999, no person may operate to or from any airport in the contiguous United States any airplane with a maximum certificated weight of more than 75,000 pounds unless that airplane has been shown to comply with Stage 3 noise levels. The FAA issued a notice in the Federal Register (64 FR 51430, September 23, 1999) and has sent several letters to operators reminding them of the prohibition against the operation of Stage 2 airplanes after December 31, 1999.
Since the law places a ban on the operation of Stage 2 airplanes after December 31, 1999, several operators have inquired whether the relief provided in Sec. 21.93(b)(2)(iii) will continue to be available, or if the State 3 transition requirements eliminate that option for airplanes operated in the contiguous United States.
Essentially, Sec. 21.93(b)(2)(iii) allows an operator to operate a turbojet powered airplane with a mix of engines (for which compliance with the acoustical change provisions of 14 CFR part 36 have not been shown) for a period not to exceed 90 days. In a typical case, the operator of a multi-engine Stage 3 airplane would use this provision to install one Stage 2 engine while the Stage 3 engine is in repair. Another common situation occurs when a Stage 3 engine incurs a minor damage that changes its noise characteristics and can continue safe operation, but cannot be immediately repaired. Thus, the regulation refers to ``time-limited engine and/or nacelle changes.'' The rule allows the intermix without the configuration being considered an ``acoustical change'' that would otherwise invoke considerable certification requirements.
When the FAA changed the rule in 1981, it determined that these occasional changes would not have a substantial impact on overall airplane operating noise levels if the use was limited to 90 days. The first 90 days of such a configuration is not considered an acoustical change; over 90 days, an operator must demonstrate that the intermix meets the acoustical change provision of 14 CFR part 36, or it must bring the airplane into compliance with an acoustically certificated configuration for that airplane type.
The 1981 rule change also specifically noted that the 90-day allowance was intended for maintenance purposes (47 FR 758). Recently, the FAA has received information that some operators may be using this provision to maximize the size of their operating fleets--essentially, operators may not have a sufficient number of engines to maintain their entire fleets in Stage 3 configuration. To remedy the situation, operators may be trading out Stage 2 and Stage 3 engines every 90 days or so and ``invoking'' Sec. 21.93(b)(2)(iii) to maintain their status as having Stage 3 compliant aircraft. This situation came to the attention of the FAA when operators inquired whether they would be able to continue this practice after the December 31, 1999, compliance deadline.
The FAA stresses that the Sec. 21.93(b)(2)(iii) provision was designed to assist operators with unplanned engine damage or maintenance events. The rule was never intended to be used to demonstrate ``paper-only'' compliance with Stage 3 noise requirements on a continuing basis, either before or after the statutory final compliance date. While the FAA considered removing the 90-day allowance to prevent these ``musical engine'' activities, the agency also
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realized the value of the provision for its intended purposes and the substantial workload that would be generated for both the agency and the operators if the provision were removed.
Accordingly, the FAA has determined that the 90-day period allowed by Sec. 21.93(b)(2)(iii) will continue to be available after December 31, 1999. The affected operators are reminded that the 90-day period provision is only valid for maintenance purposes. Those airplanes using intermixed engines and/or nacelles will continue to be considered Stage 3 for compliance purposes as long as the reason for the configuration is maintenance-related. The FAA warns operators that the swapping of engines between airplanes will be closely monitored. If, for example, an engine is removed from a Stage 3 configured airplane, and replaced with an intermix engine operated under Sec. 21.93(b)(2)(iii), careful attention will be paid by the FAA to the status of the removed engine. If the removed engine is reinstalled on a different airplane, the FAA will monitor whether any required maintenance or repair was first accomplished, as stated by the agency when the rule was adopted.
If operators are found to be abusing Sec. 21.93(b)(2)(iii) in order to meet Stage 3 compliance requirements, operators will face enforcement action and the agency will consider removing the allowance or requiring prior approval for its use. A chronic lack of spare engines or a determination that an operator does not have sufficient engines available to operate a Stage 3 fleet at one time is not considered an acceptable reason for using Sec. 21.93(b)(2)(iii).
Operators may use Sec. 21.93(b)(2)(iii) to intermix engines only when maintenance must be performed on an engine and no conforming engine for the configuration is available. Engine removals that invoke Sec. 21.93(b)(2)(iii) will be carefully monitored by the FAA.
Issued in Washington, DC on November 17, 1999. James D. Erickson, Director of Environment and Energy.
[FR Doc. 99-30502Filed11-22-99; 8:45 am]
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