[Federal Register Volume 64, Number 225 (Tuesday, November 23, 1999)]
[Rules and Regulations]
[Pages 65655-65656]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-30502]
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Rules and Regulations
Federal Register
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This section of the FEDERAL REGISTER contains regulatory documents
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Federal Register / Vol. 64, No. 225 / Tuesday, November 23, 1999 /
Rules and Regulations
[[Page 65655]]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 21
Applicability of 90-Day Rule for Intermixed Airplane Engines and/
or Nacelles
AGENCY: Federal Aviation Administration, DOT.
ACTION: Statement of policy.
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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
[[Page 65656]]
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. 99-30502 Filed 11-22-99; 8:45 am]
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