[Federal Register Volume 63, Number 238 (Friday, December 11, 1998)]
[Proposed Rules]
[Pages 68636-68646]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-32734]



[[Page 68635]]

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Part V





Department of Transportation





_______________________________________________________________________



Federal Aviation Administration



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14 CFR Parts 23, 25 and 33



Airworthiness Standards; Bird Ingestion; Proposed Rule

  Federal Register / Vol. 63, No. 238 / Friday, December 11, 1998 / 
Proposed Rules  

[[Page 68636]]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Parts 23, 25 and 33

[Docket No. FAA-1998-4815; Notice No. 98-19]
RIN 2120-AF34


Airworthiness Standards; Bird Ingestion

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes to amend the FAA type certification 
standards for aircraft turbine engines with regard to bird ingestion. 
The proposed standards reflect recent analyses defining the actual bird 
threat encountered in service by turbine engines, and would harmonize 
the FAA bird ingestion standards with those being drafted by the Joint 
Aviation Authorities (JAA). The proposed changes would establish nearly 
uniform bird ingestion standards for aircraft turbine engines certified 
by the United States under FAA standards and by the JAA countries under 
JAA standards, thereby simplifying airworthiness approvals for import 
and export.

DATES: Comments to be submitted on or before March 11, 1999.

ADDRESSES: Comments on this document should be mailed, in triplicate 
to: Federal Aviation Administration, Office of the Chief Counsel, 
Attention: Rules Docket (AGC-200), Docket No. FAA-1998-4815, Room 915G, 
800 Independence Avenue, SW., Washington, DC 20591. Comments submitted 
must be marked: ``Docket No. FAA-1998-4815.'' Comments may also be sent 
electronically to the following internet address: 9-NPRM-
[email protected]. Comments may be examined in Room 915G on weekdays, 
except Federal holidays, between 8:30 a.m. and 5:00 p.m.

FOR FURTHER INFORMATION CONTACT: Marc Bouthillier, Engine and Propeller 
Standards Staff, ANE-110, Engine and Propeller Directorate, Aircraft 
Certification Service, FAA, New England Region, 12 New England 
Executive Park, Burlington, Massachusetts 01803-5299; telephone (781) 
238-7120; fax (781) 238-7199.

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed rule by submitting such written data, views, or arguments as 
they may desire. Comments relating to the environmental, energy, 
federalism, or economic impact that might result from adopting the 
proposals in this notice are also invited. Substantive comments should 
be accompanied by cost estimates. Comments must identify the regulatory 
docket number and be submitted in triplicate to the Rules Docket 
address specified above.
    All comments received, as well as report summarizing each 
substantive public contact with FAA personnel on this proposed 
rulemaking, will be filed in the docket. The docket is available for 
public inspection before and after the comment closing date.
    All comments received on or before the closing date will be 
considered by the Administrator before taking action on this proposed 
rulemaking. Late-filed comments will be considered to the extent 
practicable. The proposals contained in this notice may be changed in 
light of comments received.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this notice must include a pre-addressed, 
stamped postcard with those comments on which the following statement 
is made: ``Comments to Docket No. FAA-1998-4815.'' The postcard will be 
date stamped and mailed to the commenter.

Availability of NPRM's

    An electronic copy of this document may be downloaded using a modem 
and suitable communications software from the FAA regulations section 
of the Fedworld electronic bulletin board service (telephone: 703-321-
3339), the Federal Register's electronic bulletin board service 
(telephone: 202-512-1661), or the FAA's Aviation Rulemaking Advisory 
Committee Bulletin Board service (800)-322-2722 or (202)-267-5948.
    Internet users may reach the FAA's webpage at http://www.faa.gov/
avr/arm/nprm/nprm.htm or the Government Printing Office's webpage at 
http://www.access.gpo.gov/su__docs/aces/aces140.html for access to 
recently published rulemaking documents.
    Any person may obtain a copy of this NPRM by submitting a request 
to the Federal Aviation Administration, Office of Rulemaking, ARM-1, 
800 Independence Avenue, SW., Washington, DC 20591, or by calling (202) 
267-9680. Communications must identify the docket number of this NPRM.
    Persons interested in being placed on the mailing list for future 
NPRM's should request, from the above office, a copy of Advisory 
Circular No. 11-2A, Notice of Proposed Rulemaking Distribution System, 
which describes the application procedure.

Background

Statement of the Problem

    In 1976, the National Transportation Safety Board (NTSB), in 
response to an accident involving a wide-bodied aircraft that may have 
experienced multiple bird ingestion into the engines, issued Safety 
Recommendation A-76-64, recommending that the FAA, ``amend 14 CFR 33.77 
to increase the maximum number of birds in the various size categories 
required to be ingested into turbine engines with large inlets.'' 
Safety Recommendation A-76-64 also stated, ``these increased numbers 
and sizes should be consistent with the birds ingested during service 
experience of these engines.'' In response to the recommendation, the 
FAA sponsored an industry wide study of the types, sizes, and 
quantities of birds that had been ingested into aircraft turbine 
engines of all sizes, and the resulting affects on engine performance. 
Subsequently, the FAA requested that the Aerospace Industries 
Association (AIA) analyze the data, and report back to the FAA. Based 
on the AIA report, the FAA determined the actions to be taken, as well 
as the disposition of the NTSB safety recommendation A-76-64. The FAA 
concluded that the regulations contained in ( 33.77 should be modified 
to increase the severity of the bird ingestion testing requirements 
regarding large, high bypass ratio engines. In addition, the FAA found 
that it should update the design and testing requirements for all 
engine sizes to reflect the actual numbers and bird sizes being 
ingested. This effort was adopted as a part 33 and Joint Aviation 
Regulations for engines (JAR-E) harmonization project and was selected 
as an Aviation Rulemaking Advisory Committee (ARAC) project.

Industry Study

    The industry study consisted of FAA sponsored contracts which are 
summarized in FAA report number DOT/FAA/CT-84/13, dated September 1984. 
The AIA and the Association Europeenne Des Constructeurs De Material 
Aerospatial (AECMA), initially reviewed the historical bird threat and 
resulting impact to flight safety for a 20-year period through 1987. 
The data collected represented a cross-section of large, high bypass 
turbofan engines in service during that time period. After collection 
and review of the available data, an analysis was performed to 
characterize both the threat of bird

[[Page 68637]]

ingestion (sizes, quantities and occurrence rates) and consequences. 
The results of this initial data analysis were presented to the FAA in 
AIA reports dated October 17, 1986, and November 10, 1988. The results 
of the analysis were compared to the historical design standards and 
certification bases for the family of engines comprised in the 
database. As a result of that analysis, the industry study group 
identified bird encounter threats more severe than were addressed in 
either engine design practices of the time, or in part 33. 
Subsequently, additional data was collected and analyzed for small and 
medium sized turbine engines which were not represented within the 
initial database. This data is contained within FAA Technical Center 
reports dated December 1990, December 1991, and July 1992.
    In addition to the industry study and data analysis for large 
engines, industry also addressed the service experience of the small 
turbojet and turbofan engine designs. With the rapid expansion of the 
turbojet and turbofan engine powered business jet fleet in the late 
1960's and early 1970's, a significant number of multiple engine power 
loss accidents occurred due to flocking bird ingestion. Careful review 
of these turbojet and turbofan engine events showed that the flight 
crews had often flown through very large flocks of birds with ingestion 
of many birds in each engine which resulted in multiple engine 
flameouts.
    At the time, the FAA engaged in a discussion with engine 
manufacturers, and concluded that mechanical design changes alone would 
not alleviate the adverse affects of severe inlet blockage caused by 
massive flocking bird ingestions. The FAA and the manufacturers, then 
embarked upon a campaign to better inform the aviation community 
regarding bird hazards and necessary airport controls, and the accident 
rate due to bird ingestion decreased markedly. Additionally, the FAA 
amended part 33 effective October 31, 1974 (amendment 33-6), to require 
manufacturers to incorporate significant design improvements to address 
the typical flocking bird threat. The service experience of business 
jet engine designs that meet the standards of amendment of 33-6 
indicates that resistance to bird ingestion induced damage has greatly 
improved over earlier service history.

Aviation Rulemaking Advisory Committee (ARAC) Project

    The FAA is committed to undertaking and supporting the 
harmonization of part 33 with JAR-E. In August 1989, as a result of 
that commitment, the FAA Engine and Propeller Directorate participated 
in a meeting with the Joint Aviation Authorities (JAA), AIA, and AECMA. 
The purpose of the meeting was to establish a philosophy, guidelines, 
and a working relationship regarding the resolution of issues 
identified as needing to be harmonized, including some where new 
standards are needed. All parties agreed to work in a partnership to 
jointly address the harmonization effort task. This partnership was 
later expanded to include the airworthiness authority of Canada, 
Transport Canada.
    This partnership identified seven items as the most critical to the 
initial harmonization effort. The proposed bird ingestion standards 
represent one item on the list of seven, and, therefore, represent a 
critical harmonization effort.
    The bird ingestion standards proposal was selected as an ARAC 
project, and assigned to the Engine Harmonization Working Group (EHWG) 
of the Transport Airplane and Engine Issues Group (TAEIG) on December 
11, 1992 (57 FR 58840). On April 9, 1997, the TAEIG recommended that 
the FAA proceed with the proposed rulemaking and associated advisory 
material even though one working group member disagreed with the 
proposal. This proposed NPRM reflects the ARAC recommendations on that 
rulemaking.
    The basis for the development of this proposed rule is to (1) 
minimize the threat to aircraft from the historical bird threat to one 
or more engines; and (2) substantiate that the engine design provides 
at least a 1E-8 per aircraft cycle freedom from risk of a hazardous 
consequence to the aircraft due to the bird ingestion threat. For all 
bird ingestion threats, a hazardous consequence occurs when the 
resulting damage to the engine results in an unsafe condition specified 
in Sec. 33.75; and in the specific case of small and medium birds, 
where insufficient power is retained to provide engine run-on 
capability to ensure a safe landing.
    Medium bird ingestion criteria for small engines was established 
consistent with corresponding criteria for medium and large engines, 
which is freedom from multi-engine power loss events at a rate of 1E-8 
per aircraft cycle. These criteria are based on the assumption that 
current standards for airport certification will be maintained, that 
the historical environment will not worsen, and that airport operators 
and pilots will maintain at least their current awareness of the bird 
ingestion threat.
    The development of this proposal recognizes that each engine design 
must address the bird ingestion threat, without regard to the ingestion 
capability of previous designs as described in the service history 
database. Unless the proposal addresses the actual in-service bird 
ingestion threat, there can be no assurance that future designs would 
continue to exhibit acceptable capability.
    The results of this data analysis are summarized as follows:
    1. Dual engine power loss events with hazardous consequences 
(flocking birds of all sizes) have occurred at the rate of 3.2E-7 
occurrences per aircraft cycle for large high-bypass ratio engines. 
This finding reflects service data for the 20-year period through 1987.
    2. Multiple engine ingestion of flocking birds up to 2.5 lbs. has 
occurred at the rate of 1E-6 occurrences per aircraft cycle for large 
high-bypass ratio engines.
    3. Single engine power loss events due to ingestion of birds 
smaller than the current Sec. 33.77 standard has occurred at a rate of 
1E-6 or greater per aircraft cycle for all large high-bypass ratio 
engines.
    4. Single engine ingestion of a large bird (4-8 lb. based on inlet 
area) has occurred at a rate up to 3.1E-6 occurrences per aircraft 
cycle.
    5. Dual engine ingestion of flocking birds up to 1.5 lbs. has 
occurred at a rate of 1E-8 occurrences per aircraft cycle for small 
engines.
    6. Bird ingestion service difficulty issues relating to engine 
models not type certificated to the proposed requirements, can safely 
be addressed by continued airworthiness control programs.
    This proposal recognizes the need to design a conservative test, 
while at the same time being representative of in-service combinations 
of critical ingestion parameters. Since testing for all possible 
combinations of events is impractical, a degree of conservatism was 
called for in a single test demonstration. That conservatism was 
incorporated into the proposed tests by selecting bird sizes or 
quantities, or both, among the most severe encountered within the 1E-8 
service history, as well as requiring critical test parameters to be at 
worse case combination (speeds and aim points). It is therefore 
reasonable to accept a satisfactory test outcome which is conservative 
with respect to the various combinations of critical test parameters, 
and their demonstrated rate of occurrence in service.
    An example of parametric rule consideration during regulatory tests 
is the question of multiple bird impacts to the same rotor blade. The 
likelihood of multiple impacts on one blade is dependent on the number 
of birds, the

[[Page 68638]]

number of blades, and the exposed frontal area. The aircraft and engine 
manufacturers have stated that it is not always possible to achieve a 
uniform distribution of birds across the complete face of the engine in 
a single engine test. This situation could result in multiple birds 
striking the same blade, and may be viewed as unrepresentative and 
overly conservative based on probabilities appropriate to a random 
ingestion (averaged over a multiple ingestion event).
    With respect to the flocking bird threat, this proposal considers 
the potential affects on the engine associated with the size and number 
of birds, and operating conditions of pertinent aircraft. For smaller 
flocking birds (0.5 to 1.5 lb.), greater quantities of birds may be 
ingested when compared to quantities associated with larger size 
flocking birds. The proposed tests would require the applicant to 
consider both the affects of bird size on the impact loading of the 
engine components, as well as the quantity ingested with potential 
multiple target locations being struck on the face of the engine. 
Additionally, the applicant would have to consider the potential 
affects of the ingestion and the resultant damage to the front face of 
the engine, as they affect the engine core and engine's run-on 
capability.
    Analysis of the service record of engines with an inlet surface 
area larger than 2,000 square-inches over a 20-year period has led to 
the conclusion that some additional certification standards are 
required. The proposed standards are intended to reduce the risk of a 
dual engine power loss from current in-service rates. The improvement 
goal is approximately 1E-8 or better per aircraft departure. The data 
analysis has identified specific flocking bird threats up to 
approximately 8 lb. size (Canada goose). Therefore, it is the intent of 
this proposed rule to strengthen the engine airworthiness requirements 
by increasing the medium bird ingestion requirements from 1.5 to 2.5 
lb. birds (representing the herring gull threat) and, by increasing the 
single large bird ingestion requirements, to address bird threats from 
4 to 8 lb. (Canada goose). (The term ``1E-8'' is a standard scientific 
notation.)
    The FAA recognizes that flocking birds larger than those specified 
in this proposed rule may be encountered. While available engine 
technology alone may not provide mitigation of this risk to 
approximately 1E-8 or better per aircraft departure, mitigation of this 
threat may be provided by compliance with the more severe requirements 
of this proposal. In addition, the introduction of aircraft that can be 
operated with up to a 50-percent power loss from each engine (large, 
twin engine, transport aircraft) and improved airport bird control 
methods and awareness will further address this very large bird threat. 
The data summary supporting this conclusion for medium to large high 
bypass engines (70 to 100 inch inlet diameter except as noted) is as 
follows:

Multiple engine ingestions of birds greater than 1.0 lb. = 2.1E-6*
Multiple engine ingestions of birds greater than 1.5 lb. = 1.4E-6*
Multiple engine ingestions of birds greater than 2.5 lb. = 1.4E-7**
Multiple engine ingestions of birds greater than 4.0 lb. = 8.8E-8**
Multiple engine ingestions of birds greater than 2.5 lb. = 9.5E-8***

    *Data collection period 1970-1987
    **Data collection period 1970-1995
    ***Data collection period 1970-1995 for 60 to 100 inch diameter 
inlets

    The data also suggests that the number of birds likely to be 
ingested into all engines during a flock encounter was inversely 
proportional to the size of birds. These data were examined on an 
exceedence basis, and show that 95-percent of the time no more than the 
following quantities of birds would be ingested into all engines on an 
aircraft during a flock encounter. As an example, the following 
quantities of birds ingested for engines in the 6,000 square-inch class 
are as follows:

------------------------------------------------------------------------
                                                                 Number
                        Weight of bird                         of  birds
------------------------------------------------------------------------
1.0-1.5......................................................          3
1.5-2.5......................................................          3
2.5+.........................................................          2
------------------------------------------------------------------------

    Considering the desire to evaluate multiple critical target 
locations on the face of the engine, this proposal selects a size of 
flocking bird that corresponds to a bird quantity of two or more birds. 
However, the FAA recognizes that there would be a residual risk of 
encounter of potentially larger bird sizes than specified in this 
proposed rule, and possibly greater quantities of birds than specified 
in this proposed rule. This proposal, however significantly increases 
the severity of the certification demonstration and provides a 
reduction in risk of a dual engine power loss due to flocking bird 
ingestion of any size and quantity.
    In considering single large bird threats for sizes greater than 
that demonstrated under the medium flocking bird threat to multiple 
engines, the data analysis attempted to quantify exposure rates for 
birds weighing 4 lbs. and up as a function of inlet throat area. Data 
from a series of FAA Technical Center reports published between 1990 
and 1992 were used, in addition to the original AIA studies.
    The data showed that small and medium engine sizes up to an inlet 
throat area of 2,100 square-inches had a relatively constant threat 
from birds greater than 4 lbs. at approximately 5E-7 ingestions per 
aircraft departure. Reports from the manufacturers also showed that 
this size of engine was more likely to ingest only portions of large 
birds, due to the much higher probability that an ingested bird may not 
enter the inlet on the engine centerline and, therefore, would strike 
the inlet structure and be dismembered before reaching the engine rotor 
blades. This conclusion is further substantiated by the absence of 
reports of unsafe engine shutdown due to single large birds greater 
than 4 lbs. for engines in this size range.
    For engines with inlets larger than 2,100 square-inches, the rate 
of exposure to single large birds tracked roughly with increasing inlet 
size. The exposure rate for birds larger than 4 lbs. for the large 
population of engines with inlet surface areas in the 2,100 to 6,000 
square-inch range was 1.5E-6 ingestions per aircraft departure. Review 
of the revenue service data however showed that medium and large 
turbofans exposed to single large birds above 4 lbs. have demonstrated 
safe shutdown characteristics as defined under Sec. 33.75 even with 
bird sizes up to 15 lbs. The rate of unsafe shutdown occurrences in 
accordance with Sec. 33.75 criteria was approximately one event per 120 
occurrences. This unsafe shutdown rate was attributed to the blade-out 
containment test requirements of Sec. 33.94 constituting a more severe 
test relative to safe shutdown criteria for almost all engines.
    The intent of this proposed rule is to establish the single large 
bird size as a function of inlet surface area greater than 2,100 
square-inches at a level where the exposure to birds beyond that 
specified in this proposed rule would be in the range of 1E-6 to 1E-7 
ingestions per aircraft departure. This coupled with the prior service 
history record of satisfactory shutdown experience when exposed to very 
large birds, provides a potential improvement for hazardous 
consequences to continued safe flight into the extremely remote range 
of probability, i.e., 1E-7 to 1E-9.
    This proposed rule conservatively establishes the single, large 
bird requirement for engines with inlet surface areas in the 2,100 to 
6,000

[[Page 68639]]

square-inch range at 6 lbs. where the average exposure to larger birds 
was 8E-7 ingestions per aircraft departure. For engines with inlet 
surface areas greater than 6,000 square-inches, the requirement was 
increased to 8 lbs. to maintain an equivalent margin of safety.
    The selection of the 200-knot ingestion speed for the large bird 
test was based on consideration of impact loading on the engine front 
stage blading. It was determined that for most current turbine engine 
designs, conducting the test at 250-knots (maximum allowed airspeed 
below 10,000-feet altitude) would likely result in a relatively low 
blade impact vector, which results in less than maximum bird impact 
forces on the blade(s). Coupled with the specified bird mass variations 
with engine inlet size, the proposed rule would fix the ingestion speed 
at 200-knots, and would require applicants to perform an analysis to 
determine the critical spanwise target location for a particular engine 
application.
    Large turbofan engines certified to the medium bird requirements of 
Sec. 33.77, amendment 33-6, which requires bird velocities of 250-
knots, sustained in-service blade fractures and loss of power for 
ingested bird weights less than those demonstrated for certification 
test. Second generation turbofan engines certified under Sec. 33.77, 
amendment 33-10, used bird velocities which were equivalent to 
V2 (takeoff safety speed) for the application aircraft (160 
to 180-knots for the large transports). While the in-service record was 
significantly improved, these second generation engines were still 
experiencing blade fractures and power loss for bird weights less than 
the certification standard.
    Engine ingestion parameters contributing to more than 50-percent 
power loss events were evaluated by AIA and AECMA. The most critical of 
the parameters evaluated which affected power loss were found to be 
bird weight, bird velocity, aiming point, and engine power setting. 
Each of these critical ingestion parameters have been evaluated in the 
proposed rule to determine the most severe conditions under which the 
medium bird test should be conducted.
    The velocity to be used for the medium bird test was first 
established as the most critical velocity between V1 
(takeoff decision speed) and 250-knots indicated airspeed (KIAS) in 
order to cover the full range of takeoff and initial climb conditions 
that were considered to be potentially hazardous to the aircraft. In 
recognition of commuter and small business jet applications, the 
criterion was modified to reflect the fact that 250 KIAS was above the 
normal takeoff and climb speeds for this class of aircraft. A 
compromise criterion was chosen which required the medium bird 
ingestion velocity to be the most critical velocity between 
V1 and the velocity reached at 1,500-feet above ground level 
(AGL).
    Bird strike data for rotorcraft are not as comprehensive as that 
available for fixed wing aircraft, probably for a variety of reasons 
associated with reporting standards, forward speed, low altitude 
operations, and the extensive use of inlet protection or inherent 
installation shielding on rotorcraft. The following helicopter bird 
ingestion data was reviewed in support of this proposal: (France) 
Direction Generale de L'Aviation Civile (DGAC), 1983 through 1990; 
(United Kingdom) Civil Aviation Authority (CAA), 1976 through 1987, and 
1989 through 1990; (U.S.A.) FAA, 1985 through 1990; (Canada) Transport 
Canada, 1981 through 1989; and International Civil Aviation 
Organization (ICAO), 1981 through 1989. The review showed reports of 
more than 600 bird strike events, but only four events were reported as 
engine ingestions, and none were multiple events. Many of the 600 
events involved flocks of small birds making engine ingestion very 
probable. Since there are no reports of significant power loss or 
mechanical damage it can be assumed that these ingestions had no affect 
on the engine.
    The FAA did not find any records of hazardous events or service 
difficulties associated with engine bird ingestion in multi-engine 
rotorcraft operation. To require a rotorcraft engine to demonstrate 
medium bird ingestion capability will impose an unnecessary burden upon 
the design while producing no measurable safety benefit. The FAA, 
therefore, proposes that engines intended for use in multi-engine 
rotorcraft need not show compliance with the medium bird ingestion 
requirements of this proposed rule.
    With respect to the actual test day conditions when demonstrations 
are made, this proposal considers the variability of engine performance 
as a function of changing ambient conditions. For example, substantial 
variations in engine rotor speed may take place between test 
demonstrations performed on cold days versus testing on hot days. These 
variations in rotor speed could in turn lead to variations in resulting 
damage, engine power, and operating characteristics. Even with no 
variation in blade damage, significant variations in power or other 
characteristics could be expected for conditions considerably different 
than for the test demonstration. Therefore, the FAA proposes to allow 
the actual test day ambient conditions and engine pretest conditions to 
vary, permitting equal flexibility among applicants and avoid conduct 
of engine tests in unrepresentative conditions which could lead to 
cycle mismatches. However, each applicant must account for these 
potential variations by extrapolation to other conditions specified in 
the type design. From the standpoint of power and operating 
characteristics, the applicant must show that the engine condition 
following bird ingestion can be extrapolated to that specified in the 
type design. Therefore, the FAA determined that the sea level, hot day, 
corner point represents a worst case set of ambient conditions for 
which to substantiate bird ingestion capability for both single large 
and flocking birds. From the standpoint of potential limit exceedences, 
the applicant must consider the worst performing production engine that 
is allowed by the type design.
    The current rules consider the possibility of imminent failure 
following a bird ingestion encounter producing damage. Considering this 
possibility, the proposed rule recognizes the need to provide a 
positive margin to demonstrate run-on capability and the ability for an 
engine to safely function throughout a conservative time for an 
emergency return to the airport of departure immediately following a 
bird ingestion event. This scenario includes a recognition that the 
most critical encounters typically occur during heavy weight takeoffs 
and may require dumping of fuel before returning to land. During this 
period, it may be necessary to operate damaged engines throughout their 
operating cycle, including a need to make a go-around due to debris or 
equipment on the runway. This proposed rule would require the applicant 
to demonstrate the engine's ability to operate satisfactorily during 
such circumstances. However, this proposal also recognizes that it is 
not possible to extend this demonstration to include all possible 
conditions occurring throughout a flight, particularly should the pilot 
decide to continue the flight to its originally intended destination. 
Lastly, considering the probable nature of bird ingestions, compliance 
with Sec. 33.75 does not allow for circumstances which could lead to a 
hazardous failure as defined under that section. Therefore, seemingly 
normal operation of multiple damaged engines will not likely result in 
the failure of multiple engines within

[[Page 68640]]

the same flight. For these reasons, there is no requirement within this 
proposed rule to further consider imminent failure after bird 
ingestion.
    The EHWG also considered differences between part 33 and JAR-E with 
respect to the maximum emergency rating. The EHWG reached a consensus 
that there is no need to consider emergency ratings if it can be shown 
that the relative frequency of a bird ingestion event when using an 
emergency engine rating is less than 1E-8. Since part 33 does not 
define emergency ratings for turbofan engines, and the EHWG did not 
recommend that the FAA add that language, this proposal would not 
result in harmonizing part 33 with JAR-E in this regard.
    Critical ingestion parameter tolerances were reviewed, and 
supporting arguments were made to justify the reasonableness of using a 
plus or minus 10-percent tolerance for variations within the test 
parameters. The application of this tolerance was discussed in the 
context of setting the engine speed and thrust parameters to test day 
takeoff conditions as described within this proposed rule. In contrast, 
the bird weight is controlled to ``no less than'' the weight specified 
within this proposed rule. The expectations of achieving the bird aim 
points and impact speed within plus or minus 10-percent or its 
equivalent regarding aim point was compared against the general 
collective test experience. A sensitivity analysis was conducted to 
evaluate the expected affect on thrust or power, should there be first 
stage blade damage, for variations in the following test parameters up 
to 10-percent: engine speed, bird speed, and target location. In 
general, these tolerances resulted in damage variations which produced 
approximately a 5-percent affect on thrust or power.
    The EHWG determined that the current requirements of Sec. 33.75 and 
JAR-E510 are not exactly the same, and, therefore, are not fully 
harmonized. The requirement of Sec. 33.75 is restated in the proposed 
Sec. 33.76 compliance criteria for the proposed medium and large bird 
ingestion tests. The bird ingestion requirements proposed by the JAA 
(Notice of Proposed Amendment (NPA-E-20)) includes a reference to JAR-E 
510 for compliance criteria. However, the JAA compliance criteria is 
not the same as contained in this proposed rule. The FAA recognizes 
that full harmonization of Sec. 33.75 and JAR-E 510 is still desirable, 
and will address this issue in future propulsion harmonization 
activities.

Disposition of Minority Position (as Stated in the NPA for the JAR on 
This Subject)

    The JAA has expressed disagreement with a portion of this proposal, 
and is quoted as follows:

    The JAA expressed a dissenting opinion by requiring the new 
rules to include consideration of the threat which is created by 
flocking birds larger than 2.5 lb. The JAA proposed, in the draft 
new rules, the imposition of an additional requirement for each 
engine having an inlet area of 2100 square-inches or more. The 
applicant would be required to establish that when the fan assembly 
of such an engine is subjected to the ingestion of a single bird 
weighing at least 4 lb., under the same ingestion conditions as 
prescribed for the 6 lb. or 8 lb. bird ingestion test, the fan 
assembly retains sufficient integrity to demonstrate a total 
imbalance level less than 12 percent of the imbalance level 
corresponding to the loss of one complete fan blade airfoil.

The JAA Rationale

    The stated aims of the draft new rules include reducing the risk 
of a dual engine power loss, the improvement goal being 
approximately 1E-8 or better per aircraft departure, and 
substantiation of that goal. The preamble also states that ``unless 
the rule addresses the actual in-service bird threat, there can be 
no assurance that future designs would continue to exhibit 
acceptable capability''. Allowing fan blades to be shown, during 
certification, as being less capable to withstand some sizes of 
birds than current in-service designs is not compatible with those 
stated aims.
    The draft new rules (without the addition proposed by JAA) 
retain the same acceptance criteria for single large bird ingestion 
standard as in the existing rules. Extensive damage leading either 
to an immediate shutdown or necessitating a shutdown after 15 
seconds is permitted, the only limit to the severity of the damage 
to the fan being safe containment, safe loads and no fire. However, 
in practice there are very good reasons for the manufacturers to 
establish that, with respect to containment, loads, fire, etc., the 
damage is not more severe than occurs with a full fan blade release. 
That practice is recognized in the draft new rules by a provision 
for waiving a full engine test demonstration of compliance with the 
large bird ingestion standard if it can be demonstrated that 
compliance with the requirements for containment of a full fan blade 
is a more severe demonstration.
    Thus, because the minimum design allowed by the draft new rules 
is actually set primarily by the blade containment requirements, the 
large bird is allowed to cause extensive damage equivalent to that 
which results from the release of one entire fan blade. The increase 
of the weight of the large bird in the draft new rules, from 4 lb. 
to 6 lb. or 8 lb., will not improve the safety level if engines are 
designed to the minimum allowed by those new rules because it is a 
lower minimum that was demonstrated during certification of many, 
possibly most, of the current in-service engines. Further, it does 
not automatically follow that designing for a ``safe'' shutdown with 
a 6 lb. or 8 lb. bird results in a higher safety level than 
designing for a ``safe'' shutdown with a 4 lb. bird.
    The certification tests on most of the types of large engines 
currently in service demonstrated that the 4 lb. bird certification 
ingestion test did not result in extensive damage to their fan 
blades. Therefore, the service experience which is the basis for the 
aims of the draft new rules is derived mainly from engines which 
were better during certification than required by the existing rules 
and better than can be allowed under the draft new rules without the 
JAA proposed addition.
    The draft new rules require the large engines to retain a run-on 
and a 75 percent thrust capability when subjected to a multiple 2.5 
lb. bird ingestion test but, as mentioned previously, the 6 lb. or 8 
lb. bird ingestion is allowed to result in such extensive fan damage 
as to necessitate an immediate shutdown. In this case no information 
would then be available on the behavior of the fan in the event of a 
4 lb. bird ingestion because the draft new rules do not address 
either medium (flocking) birds heavier than 2.5 lb. or large birds 
lighter than 6 lb. or 8 lb. The ingestion of a 4 lb. bird could, 
with some fan designs, also result in an immediate unavoidable 
engine shutdown.
    There is already an example of a new engine which complies with 
the draft new rules for 2.5 lb. and 8 lb. bird ingestion's but the 8 
lb. bird was shown to cause extensive damage commensurate with an 
immediate unavoidable shutdown. It would not have been possible, 
from only that damage, to make any reasonable assessment of what 
damage would have resulted from a 4 lb. large bird certification 
test. Economic pressure could lead to an increased use of fan blades 
which are designed to the minimum allowed by the draft new rules 
because it provides an opportunity to reduce the weight of the fan 
blades, disc and containment ring.
    Allowing new fan designs to be less capable than current in-
service designs to withstand the ingestion of a 4 lb. bird would not 
be a concern if the multi-engine ingestion threat did not include 
birds weighing up to, and more than, 4 lb. However, the service 
experience supporting the draft new rules shows that the multiple 
engine ingestion rate for birds larger than 2.5 lb. is greater than 
1E-7. With current in-service engines these events have resulted in 
a marginally acceptable risk of multi-engine shutdown. If no 
certification data is available to show that new designs are equal 
to, or better than, current designs at withstanding those birds, it 
must be assumed that such encounters will result in unavoidable 
multi-engine shutdowns at a rate of roughly 1E-7 which is in excess 
of the declared aim of 1E-8. The JAA proposed additional requirement 
is intended to provide such certification data.
    All parties involved in the development of the draft new rules 
recognize that flocking birds larger than 2.5 lb. may be encountered 
and the JAA does not disagree totally with the position that 
mitigation of this risk to 1E-8 or better per airplane departure 
cannot be

[[Page 68641]]

economically provided entirely by available engine technology. 
However, the JAA believes that future engine fan technology must not 
be allowed to be less capable at mitigating that risk than current 
in-service engines.
    Consequently the JAA concluded that the draft new rules are not 
achieving the stated aims by an amount that is more than necessary 
and not ensuring an achievable retention or improvement to the 
safety level by not ensuring that new fan designs are equal to, or 
better than, current designs at retaining their integrity when 
subjected to the ingestion of a 4 lb. bird under the conditions 
applicable to large bird ingestion requirements. The additional 4 
lb. bird consideration proposed by JAA is intended to do no more 
than to provide some assurance of parity with current in-service fan 
designs, it is not intended to ensure a full run-on capability after 
the ingestion of a 4 lb. bird.

    The FAA disagrees. The JAA position statement contains two major 
concerns: (1) That flocking birds larger than 2.5 lb. are a significant 
enough threat to require an evaluation for run-on capability; and (2) 
that this proposed rule may allow a lesser capable engine than those 
certified to the current rule with respect to medium flocking and 
single large bird ingestion.
    With respect to JAA's first major concern, the FAA believes this 
proposed rule adequately addresses the flocking bird threat within the 
stated goal of this proposed rulemaking. That improvement goal is to 
reduce the risk of a dual engine power or thrust loss greater than 50-
percent from current in-service rates to approximately 1E-8 or better 
per aircraft departure.
    The worldwide bird ingestion threat database used for the medium 
and large engine portion of this proposed rulemaking includes 
substantial data from 1970 through 1995 and encompasses approximately 
85-million aircraft flights. The database includes data for engine 
models with fan inlet diameters from 60 to 100 inches. This database 
shows the rate of multi-engine ingestions of birds larger than 2.5 lb. 
to be approximately 1E-7 per aircraft departure. The probability of a 
dual engine shutdown is predicted to be approximately 1E-8 per aircraft 
departure. This probability is based on the observed multi-engine 
ingestion rate and demonstrated rate of engine shutdown for ingestion 
of birds in this size range. These rates and probabilities are for 
engines certified to the current 1.5 lb. medium flocking and 4 lb. 
single large bird standards, which are less severe than this proposed 
rule.
    The JAA position statement notes that the dual engine power loss 
and shutdown rate is marginally acceptable today. This proposed rule 
requires 2.5 lb. medium flocking birds and 6 to 8 lb. large single 
birds, depending on inlet size, both of which are more severe 
demonstrations, and which the FAA believes can only improve the overall 
worldwide fleet bird ingestion capability. This conclusion is also 
supported by the additional run-on evaluation requirements for the 
proposed medium bird test. Therefore, the FAA disagrees that additional 
run-on evaluation requirements for flocking birds larger than 2.5 lb. 
is necessary.
    With respect to the JAA's second major concern for ingestion of 
medium flocking birds, the current marginally acceptable dual engine 
power loss rate relates primarily to engines certified to a 1.5 lb. 
bird ingestion requirement with 5 minutes of run-on. This proposed rule 
is for a 2.5 lb. bird with a 20 minute run-on evaluation requirement. 
This proposed rule represents a more severe design and test requirement 
than for engines certified to the current rule and should yield a more 
capable engine, not a less capable one. This requirement is supported 
by a test that is run to worst case conditions of fan speed, target 
location, number of birds, and new run-on evaluation requirements. The 
original review of historical data used in the development of this 
proposed rule showed that ingestion of single large birds greater than 
2.5 lb. resulted in a significant engine power loss about 50-percent of 
the time, which was mostly due to mechanical damage to the fan. It is 
difficult to see how these earlier certified engines could have a 
greater ingestion capability than that demonstrated by a minimum engine 
that passes both the proposed 2.5 lb. medium flocking run-on and 6 to 8 
lb. single large bird safe shutdown tests.
    With respect to single large bird ingestion, the current marginally 
acceptable dual engine power loss rate relates primarily to engines 
certified to a 4 lb. single large bird safe shutdown requirement. With 
identical test criteria, an engine passing the proposed test will be at 
least as capable of a large bird safe shutdown as a current engine. 
Engine models that are tested using the proposed certification 
standards would have greater axial loads and greater local stresses on 
the impacted blades than for the 4 lb. requirement. Therefore, the 
blades must have greater capability with respect to a safe shutdown 
criteria. The FAA does not believe the proposed large bird ingestion 
criteria allows sufficient latitude such that an engine can pass the 
proposed 6 to 8 lb. test but not the current 4 lb. test. The proposal 
does not alter the current objective of a safe shutdown after a large 
bird ingestion.
    The JAA also states that economic pressures could reduce the margin 
above the stated compliance criteria that engines may be designed for, 
and therefore result in less costly and less capable new designs of 
reduced margin when compared to engines currently in service. The FAA 
does not believe it is necessary to consider the margin above the 
certification standard with which any particular engine model 
demonstrates compliance, and that discussion of economic pressure has 
no place in objective evaluations of safety. The purpose of this 
proposed rule is to establish minimum certification requirements below 
which it is considered unsafe. Every engine meeting these proposed 
minimum requirements will be considered safe; either the regulatory 
criteria is appropriate, or it is not. Margin is not an issue when 
discussing properly chosen criteria. The FAA considers this proposed 
criteria as appropriate and, therefore, demonstrated margin above that 
criteria is not necessary. With respect to engines certified to the 
current 4 lb. single large bird ingestion safe shutdown test standard, 
some fan designs have exhibited blade fragmentation during the test 
while others have not. It is incorrect, however, to infer continued 
run-on capability simply from lack of fan blade fragmentation during 
the 15-second ``hands-off'' period of the large bird ingestion test. 
Secondary damage and operability affects of continued high power 
operation with mechanical or aerodynamic unbalance, or both, would have 
to be taken into consideration.
    It is also true that currently certified designs which have 
experienced fan blade fragmentation in large bird ingestion tests have 
accumulated well over 50-million hours in revenue service with a 
satisfactory bird ingestion record. The fact that these engines 
continue to operate and produce greater than 50-percent thrust in a 
significant percentage of revenue service large bird ingestion events, 
may well be attributable more to the combination of ingestion 
conditions being less severe than the certification test, rather than 
to the robustness of the fan design. The FAA expects this same mixed 
result will continue to occur in the single large bird ingestion 
certification test. In addition, such mixed results relative to fan 
blade fragmentation are not significant relative to this proposed 
rulemaking's intent of improving the world fleet rate of dual engine 
power loss.
    The FAA disagrees with the JAA statement that this proposed rule 
has a lower design minimum than the current rule. The FAA believes that 
this

[[Page 68642]]

proposed rule significantly increases the certification standards for 
medium and large bird ingestion by increased severity of bird size, 
run-on, and target location. The test criteria of the current rule is 
less severe than that specified under this proposed rule, therefore, it 
cannot be described as providing a ``greater margin'' when compared to 
a marginally compliant engine under this proposed rule. Furthermore, no 
evidence has been offered to demonstrate that engines certified under 
the current rule would always have a margin for run-on following the 
ingestion of a 4 lb. flocking bird. Thus, the arguments of current 
versus proposed criteria are considered subjective and unproven as 
indicators of future performance in service.
    Consequently, for the reasons stated above, the FAA has concluded 
that evaluation of run-on capability for birds or ingestions larger 
than 2.5 lb. is not necessary to meet this proposed rulemaking 
objective, and therefore the JAA proposal does not need to be 
incorporated into this proposed rule.

General Discussion of the Proposals

Sections 23.903(a)(2) and 25.903(a)(2)

    The proposal revises parts 23 and 25 requirements associated with 
foreign object ingestion into turbine engines to be consistent with the 
proposed part 33 requirements.

Section 33.76

    The proposed new (Sec. 33.76 would contain the new bird ingestion 
requirements. This proposal was developed by the engine harmonization 
working group, and contains substantial common language that will be 
reflected both in part 33 and JAR-E. Also, the proposed new section 
adopts the approximate metric equivalents for certain test parameters 
to further commonality between part 33 and JAR-E.

Section 33.77

    The proposed revisions to (Sec. 33.77 would remove the bird 
ingestion standards now specified in (Sec. 33.77(a) and (Sec. 33.77(b). 
Paragraphs (a) and (b) would be held in reserve. Paragraphs (d) and (e) 
would be revised to eliminate any reference to paragraphs (a) and (b). 
The table in paragraph (e) would be revised to remove bird ingestion 
standards.

Paperwork Reduction Act

    As there are no requirements for information collection associated 
with this proposed rule, no analysis of paperwork requirements is 
required under the Paperwork Reduction Act of 1995 (44 U.S.C. 3501 et 
seq.).

Regulatory Evaluation Summary

    Four principal requirements pertain to the economic impacts of 
changes to the Federal regulations. First, Executive Order 12866 
directs Federal agencies to promulgate new regulations or modify 
existing regulations after consideration of the expected benefits to 
society and the expected costs. The order also requires federal 
agencies to assess whether a proposed rule is considered a 
``significant regulatory action.'' Second, the Regulatory Flexibility 
Act of 1980 requires agencies to analyze the economic impact of 
regulatory changes on small entities. Third, the Office of Management 
and Budget directs agencies to assess the effect of regulatory changes 
on international trade. Finally, Public Law 104-4 requires federal 
agencies to assess the impact of any federal mandates on state, local, 
tribal governments, and the private sector.
    In conducting these analyses, the FAA has determined that this 
proposed rule would generate cost-savings that would exceed any costs, 
and is not ``significant'' as defined under section 3 (f) of Executive 
Order 12866 and DOT policies and procedures (44 FR 11034, February 26, 
1979). In addition, under the Regulatory Flexibility Determination, the 
FAA certifies that this proposal would not have a significant impact on 
a substantial number of small entities. Furthermore, this proposal 
would not impose restraints on international trade. Finally, the FAA 
has determined that the proposal would not impose a federal mandate on 
state, local, or tribal governments, or the private sector of $100 
million per year. These analyses, available in the docket, are 
summarized below.

Cost and Benefits

    The FAA estimates that the proposed rule would add $250,000 to 
$500,000 to each new engine model's certification costs, depending on 
engine inlet area. These costs would be incurred primarily in two 
areas. First, additional analysis required to verify the affects of a 
large bird impact on the front of the engine could necessitate a 
component test costing $250,000. Second, the proposed rule would 
require additional analysis or testing on the full fan assembly for 
engines with inlet areas greater than 2,092 square-inches. Such testing 
would cost an additional approximately $250,000 for those engines.
    In addition, the revised bird test weights could necessitate 
strengthening fan components, thereby affecting fan performance. The 
FAA estimates that reduced fan efficiency would result in a 0.2-percent 
increase in fuel consumption. On average, this would increase annual 
fuel costs by $4,770 per airplane.
    Benefits associated with the proposed rule include: (1) benefits 
from averted fatalities and injuries, (2) benefits from averted 
property damage (primarily hull losses), and (3) benefits associated 
with reduced maintenance and repair costs. Based on historical accident 
information, the FAA estimates that the expected annual per-airplane 
benefit from averted airplane damage or loss is approximately $657. The 
expected annual per-airplane benefit from averted fatalities and 
injuries is $654 and $75, respectively.
    The estimated value of maintenance/repair savings associated with 
the proposed rule is based on an analysis of the relationship between 
bird ingestion weight and the probability of damage. The FAA estimates 
that, on average, the proposed rule would save operators approximately 
$4,654 per airplane per year.
    To compare the costs and benefits of the proposed rule, the 
evaluation considers a hypothetical representative engine 
certification. The engines are assumed to be installed on a notional 
twin-engine jet transport with a seating capacity of 161 (the average 
seating capacity of jet transports in commercial service in 1996). In 
addition, this analysis assumes that: (1) the discount rate is 7-
percent, (2) incremental engine certification costs equal $250,000 in 
year 0 and $250,000 in year 1, (3) production of engines commences in 
year 2, (4) engines are installed in aircraft and enter service 
beginning in year 3, (5) each engine has a 15-year service life, and 
(6) 24 engines are produced per year for 10 years so that there are 240 
total engines and 120 airplanes per certification. Under these 
assumptions, the expected discounted benefits of the proposed rule 
would exceed discounted costs by a factor of 1.11 ($4,333,000 to 
$3,906,000).

International Trade Impact Analysis

    The proposed rule would have little or no affect on international 
trade for either U.S. firms marketing turbine engines in foreign 
markets or foreign firms marketing turbine engines in the U.S.

Regulatory Flexibility Determination

    The Regulatory Flexibility Act of 1980 establishes ``as a principle 
of regulatory issuance that agencies shall endeavor, consistent with 
the objectives of the rule

[[Page 68643]]

and of applicable statutes, to fit regulatory and informational 
requirements to the scale of the businesses, organizations, and 
governmental jurisdictions subject to regulation.'' To achieve that 
principle, the Act requires agencies to solicit and consider flexible 
regulatory proposals and to explain the rationale for their actions. 
The Act covers a wide range of small entities, including small 
businesses, not-for-profit organizations, and small governmental 
jurisdictions.
    Agencies must perform a preliminary analysis of all proposed rules 
to determine whether the rule will have a significant economic impact 
on a substantial number of small entities; if the determination is that 
it will, the agency must prepare an initial regulatory flexibility 
analysis (RFA).
    However, if after a preliminary analysis for a proposed or final 
rule, an agency determines that a rule is not expected to have a 
significant economic impact on a substantial number of small entities, 
Section 605(b) of the Act provides that the head of the agency may so 
certify. The certification must include a statement providing the 
factual basis for this determination, and the reasoning should be 
clear.
    The FAA conducted the required preliminary analysis of this 
proposal and determined that it will not have a significant economic 
impact on a substantial number of small entities. The following 
statement summarizes the basis for this determination. The proposed 
rule would apply only to newly designed turbine aircraft engines 
certificated in the future. Each new engine certification could affect 
two types of small entities.
    First, the manufacturer would be required to perform additional 
analysis or testing to demonstrate that the proposed new bird ingestion 
requirements are met. There are currently nine turbine aircraft engine 
manufacturers with headquarters in the U.S. (this count includes 
subsidiaries of foreign entities and consortiums of domestic and/or 
foreign entities). Information available to the FAA at this time 
indicates that only one of these--a U.S. manufacturer of small turbine 
engines--has less than 1,500 employees and, therefore, qualifies as a 
small business under guidelines issued by the Small Business 
Administration.
    It is difficult to estimate total costs to this single manufacturer 
because these costs are a function of the number of engines 
certificated. The manufacturer is not expected to conduct bird 
ingestion testing in the foreseeable future. In view of this 
uncertainty, this analysis focuses on per engine costs for both 
manufacturers and operators. The proposed rule is estimated to add 
about $250,000 for a small engine type as currently manufactured by the 
single small entity (these are one time costs per certification). The 
FAA estimates that the proposed rule would impose no manufacturing 
costs. In light of the fact that there is only one known small business 
manufacturing turbine aircraft engines, and that manufacturer is not 
expected to be affected by the proposed rule in the foreseeable future, 
this analysis will assume that manufacturing costs imposed by this 
proposed rule will be passed on to operators who purchase the new 
engines and analyze these costs on small operators.
    Aircraft operators would incur slightly higher engine prices, plus 
pay increased operating or fuel costs due to the small decrease in 
engine efficiency described in the full regulatory evaluation. 
According to FAA data, there are about 3,000 air carriers having less 
than 1,500 employees--approximately 100 air carriers operating under 
part 121 (or both part 121 and part 135), and 2,900 air carriers 
operating under part 135.
    Assuming conservatively that: (1) All incremental certification 
costs are passed on to the buyer/operator, (2) the manufacturer 
recovers incremental certification costs by applying a uniform price 
increase to 240 engines produced during a 10-year production run, and 
(3) that the discount rate is 7-percent; then the FAA estimates that 
average engine prices will increase by approximately $3,070 per larger 
engine and $1,587 per smaller engine. When these costs are amortized 
over the 15-year life of an engine (again, assuming a 7-percent 
discount rate), the incremental annualized cost per engine is 
approximately $315 and $163 for larger and smaller engines, 
respectively. Therefore, assuming a typical airplane has two engines, 
the incremental annualized cost for a large airplane is approximately 
$630 and the incremental annualized cost for a smaller airplane is 
approximately $326.
    For larger engines, the rule will also increase annual airplane 
operating costs as a result of the proposed medium bird ingestion 
requirements (these requirements would have a negligible affect on 
smaller engines). On average, annual operating costs per large 
airplane, therefore, would increase by approximately $4,770. However, 
the reduction in average annualized maintenance costs associated with 
the more damage resistant engines that would be developed as a result 
of this proposed rule would almost completely offset incremental 
operating costs. These reduced maintenance costs are described more 
fully in the full regulatory evaluation.
    Total annualized costs for operators of larger and smaller 
airplanes would therefore be approximately $630 and $326 per airplane, 
respectively. Consequently, the FAA makes an initial certification that 
the proposed rule would not have a significant economic impact on a 
substantial number of small entities.

Federalism Implications

    The regulations proposed herein would not have substantial direct 
affects on the States, on the relationship between the national 
government and the States, or on the distribution of power and 
responsibilities among the various levels of government; and would not 
impose substantial direct compliance costs on States or local 
governments. Therefore, in accordance with Executive Order 12612, it is 
determined that this proposal would not have sufficient federalism 
implications to require consultation with representatives of affected 
States and local governments.
    In addition, the regulations proposed herein would not 
significantly or uniquely affect the communities of the Indian tribal 
governments and would not impose substantial direct compliance costs on 
such communities. Therefore, in accordance with Executive Order 13084, 
it is determined that this proposal would not require consultation with 
representatives of affected Indian tribal governments.

Environmental Assessment

    FAA Order 1050.1D defines FAA actions that may be categorically 
excluded from preparation of a National Environmental Policy Act (NEPA) 
environmental assessment (EA) or environmental impact statement (EIS). 
In accordance with FAA Order 1050.1D, appendix 4, paragraph 4(j), 
regulations, standards, and exemptions (excluding those, which if 
implemented may cause a significant impact on the human environment) 
qualify for a categorical exclusion. The FAA has determined that this 
rule qualifies for a categorical exclusion because no significant 
impacts to the environment are expected to result from its finalization 
or implementation. In accordance with FAA Order 1050.1D, paragraph 32, 
the FAA has determined that there are no extraordinary circumstances 
warranting preparation of an environmental assessment for this proposed 
rule.

[[Page 68644]]

List of Subjects in 14 CFR Parts 23, 25 and 33

    Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

    In consideration of the foregoing, the Federal Aviation 
Administration proposes to amend parts 23, 25 and 33 of Title 14, Code 
of Federal Regulations as follows:

PART 23--AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND 
COMMUTER CATEGORY AIRPLANES

    1. The authority citation for part 23 continues to read as follows:

    Authority: 49 U.S.C. 106(g), 40113, 44701, 44702, 44704.

    2. Section 23.903 is amended by revising paragraph (a)(2) to read 
as follows:


Sec. 23.903  Engines.

    (a) * * *
    (2) Each turbine engine and its installation must comply with one 
of the following:
    (i) Sections 33.76, 33.77 and 33.78 of this chapter in effect on 
(effective date of final rule), or as subsequently amended; or
    (ii) Sections 33.77 and 33.78 of this chapter in effect on April 
30, 1998, or as subsequently amended before (effective date of final 
rule); or
    (iii) Section 33.77 of this chapter in effect on October 31, 1974, 
or as subsequently amended before April 30, 1998, unless that engine's 
foreign object ingestion service history has resulted in an unsafe 
condition; or
    (iv) Be shown to have a foreign object ingestion service history in 
similar installation locations which has not resulted in any unsafe 
condition.
* * * * *

PART 25--AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES

    3. The authority citation for part 25 continues to read as follows:

    Authority: 49 U.S.C. 106(g), 40113, 44701, 44702, 44704.

    4. Section 25.903 is amended by revising paragraph (a)(2) to read 
as follows:


Sec. 25.903  Engines.

    (a) * * *
    (2) Each turbine engine must comply with one of the following:
    (i) Sections 33.76, 33.77 and 33.78 of this chapter in effect on 
(effective date of final rule), or as subsequently amended; or
    (ii) Sections 33.77 and 33.78 of this chapter in effect on April 
30, 1998, or as subsequently amended before (effective date of final 
rule); or
    (iii) Comply with Sec. 33.77 of this chapter in effect on October 
31, 1974, or as subsequently amended prior to April 30, 1998, unless 
that engine's foreign object ingestion service history has resulted in 
an unsafe condition; or
    (iv) Be shown to have a foreign object ingestion service history in 
similar installation locations which has not resulted in any unsafe 
condition.
* * * * *

PART 33--AIRWORTHINESS STANDARDS: AIRCRAFT ENGINES

    5. The authority citation for part 33 continues to read as follows:

    Authority: 49 U.S.C. 106(g), 40113, 44701, 44702, 44704.

    6. Section 33.76 is added to read as follows:


Sec. 33.76  Bird ingestion.

    (a) General. Compliance with paragraphs (b) and (c) of this section 
shall be in accordance with the following:
    (1) All ingestion tests shall be conducted with the engine 
stabilized at no less than 100-percent takeoff power or thrust for test 
day ambient conditions prior to the ingestion. In addition, the 
demonstration of compliance must account for engine operation at sea 
level takeoff conditions on the hottest day that a minimum engine can 
achieve maximum rated takeoff thrust or power.
    (2) The engine inlet area as used in this section to determine the 
bird quantity and weights will be established by the applicant and 
identified as a limitation on the inlet throat area in the installation 
instructions required under Sec. 33.5.
    (3) The impact to the front of the engine from the single large 
bird and the single largest medium bird which can enter the inlet must 
be evaluated. It must be shown that the associated components when 
struck under the conditions prescribed in paragraphs (b) or (c) of this 
section, as applicable, will not affect the engine to the extent that 
it cannot comply with the requirements of paragraphs (b)(3) and (c )(6) 
of this section.
    (4) For an engine that incorporates an inlet protection device, 
compliance with this section shall be established with the device 
functioning. The engine approval will be endorsed to show that 
compliance with the requirements has been established with the device 
functioning.
    (5) Objects that are accepted by the Administrator may be 
substituted for birds when conducting the bird ingestion tests required 
by paragraphs (b) and (c) of this section.
    (6) If compliance with the requirements of this section is not 
established, the engine type certification documentation will show that 
the engine shall be limited to aircraft installations in which it is 
shown that a bird cannot strike the engine, or be ingested into the 
engine, or adversely restrict airflow into the engine.
    (b) Large birds. Compliance with the large bird ingestion 
requirements shall be in accordance with the following:
    (1) The large bird ingestion test shall be conducted using one bird 
of a weight determined from Table 1 aimed at the most critical exposed 
location on the first stage rotor blades and ingested at a bird speed 
of 200 knots for engines to be installed on airplanes, or the maximum 
airspeed for normal rotorcraft flight operations for engines to be 
installed on rotorcraft.
    (2) Power lever movement is not permitted within 15 seconds 
following ingestion of the large bird.
    (3) Ingestion of a single large bird tested under the conditions 
prescribed in this section may not cause the engine to:
    (i) Catch fire;
    (ii) Release hazardous fragments through the engine casing;
    (iii) Generate loads greater than those ultimate loads specified 
under Sec. 33.23(a); or
    (iv) Lose the ability to be shut down.
    (4) Compliance with the large bird ingestion test requirements of 
this paragraph may be waived if it can be demonstrated that the 
containment requirements of Sec. 33.94(a) constitute a more severe 
demonstration than the requirements of this paragraph.

                Table 1.--Large Bird Weight Requirements
------------------------------------------------------------------------
    Engine inlet area (A) square-meters
              (square-inches)                   Bird weight kg. (lb.)
------------------------------------------------------------------------
1.35 (2,092)>A............................  1.85 (4.07) minimum, unless
                                             a smaller bird is
                                             determined to be a more
                                             severe demonstration.
1.35 (2,092)A<3.90 (6,045).....  2.75 (6.05).
3.90 (6,045)A..................  3.65 (8.03).
------------------------------------------------------------------------

    (c) Small and medium birds. Compliance with the small and medium

[[Page 68645]]

bird ingestion requirements shall be in accordance with the following:
    (1) Analysis or component test, or both, acceptable to the 
Administrator, shall be conducted to determine the critical ingestion 
parameters affecting power loss and damage. Critical ingestion 
parameters shall include, but are not limited to, the affects of bird 
speed, critical target location, and first stage rotor speed. The 
critical bird ingestion speed should reflect the most critical 
condition within the range of airspeeds used for normal flight 
operations up to 1,500 feet above ground level, but not less than 
V1 minimum for airplanes.
    (2) Medium bird engine tests shall be conducted so as to simulate a 
flock encounter, and will use the bird weights and quantities specified 
in Table 2. When only one bird is specified, that bird will be aimed at 
the engine core primary flow path; the other critical locations on the 
engine face area must be addressed, as necessary, by appropriate tests 
or analysis, or both. When two or more birds are specified in Table 2, 
the largest of those birds must be aimed at the engine core primary 
flow path, and a second bird must be aimed at the most critical exposed 
location on the first stage rotor blades. Any remaining birds must be 
evenly distributed over the engine face area.
    (3) In addition, except for rotorcraft engines, it must also be 
substantiated by appropriate tests or analysis or both, that when the 
full fan assembly is subjected to the ingestion of the quantity and 
weights of birds from Table 3, aimed at the fan assembly's most 
critical location outboard of the primary core flowpath, and in 
accordance with the applicable test conditions of this paragraph, that 
the engine can comply with the acceptance criteria of this paragraph.
    (4) A small bird ingestion test is not required if the prescribed 
number of medium birds pass into the engine rotor blades during the 
medium bird test.
    (5) Small bird ingestion tests shall be conducted so as to simulate 
a flock encounter using one 85 gram (0.187 lb.) bird for each 0.032 
square-meter (49.6 square-inches) of inlet area, or fraction thereof, 
up to a maximum of 16 birds. The birds will be aimed so as to account 
for any critical exposed locations on the first stage rotor blades, 
with any remaining birds evenly distributed over the engine face area.
    (6) Ingestion of small and medium birds tested under the conditions 
prescribed in this paragraph may not cause any of the following:
    (i) More than a sustained 25-percent power or thrust loss;
    (ii) The engine to be shut down during the required run-on 
demonstration prescribed in paragraphs (c)(7) or (c)(8) of this 
section;
    (iii) The conditions defined in paragraph (b)(3) of this section.
    (iv) Unacceptable deterioration of engine handling characteristics.
    (7) Except for rotorcraft engines, the following test schedule 
shall be used:
    (i) Ingestion so as to simulate a flock encounter, with 
approximately 1 second elapsed time from the moment of the first bird 
ingestion to the last.
    (ii) Followed by 2 minutes without power lever movement after the 
ingestion.
    (iii) Followed by 3 minutes at 75 percent of the test condition.
    (iv) Followed by 6 minutes at 60 percent of the test condition.
    (v) Followed by 6 minutes at 40 percent of the test condition.
    (vi) Followed by 1 minute at approach idle.
    (vii) Followed by 2 minutes at 75 percent of the test condition.
    (viii) Followed by stabilizing at idle and engine shut down. The 
durations specified are times at the defined conditions with the power 
lever being moved between each condition in less than 10 seconds.
    (8) For rotorcraft engines, the following test schedule shall be 
used:
    (i) Ingestion so as to simulate a flock encounter within 
approximately 1 second elapsed time between the first ingestion and the 
last.
    (ii) Followed by 3 minutes at 75 percent of the test condition.
    (iii) Followed by 90 seconds at descent flight idle.
    (iv) Followed by 30 seconds at 75 percent of the test condition.
    (v) Followed by stabilizing at idle and engine shut down. The 
duration specified are times at the defined conditions with the power 
being changed between each condition in less than 10 seconds.
    (9) Engines intended for use in multi-engine rotorcraft are not 
required to comply with the medium bird ingestion portion of this 
section, providing that the appropriate type certificate documentation 
is so endorsed.
    (10) If any engine operating limit(s) is exceeded during the 
initial 2 minutes without power lever movement, as provided by 
paragraph (c)(7)(ii) of this section, then it shall be established that 
the limit exceedence will not result in an unsafe condition.

                         Table 2.--Medium Flocking Bird Weight and Quantity Requirements
----------------------------------------------------------------------------------------------------------------
 Engine inlet area (A) square-meters
           (square-inches)                            Bird quantity                    Bird weight kg. (lb.)
----------------------------------------------------------------------------------------------------------------
0.05 (77.5)> A.......................  None......................................  .............................
.05 (77.5) A < 0.10 (155).  1.........................................  0.35 (0.77).
0.10 (155) A < 0.20 (310).  1.........................................  0.45 (0.99).
0.20 (310) A < 0.40 (620).  2.........................................  0.45 (0.99).
0.40 (620) A < 0.60 (930).  2.........................................  0.70 (1.54).
0.60 (930) A < 1.00         3.........................................  0.70 (1.54).
 (1,550).
1.00 (1,550) A < 1.35       4.........................................  0.70 (1.54).
 (2,092).
1.35 (2,092) A < 1.70       1.........................................  1.15 (2.53).
 (2,635).
                                       Plus 3....................................  0.70 (1.54).
1.70 (2,635) A < 2.10       1.........................................  1.15 (2.53).
 (3,255).
                                       Plus 4....................................  0.70 (1.54).
2.10 (3,255) A < 2.50       1.........................................  1.15 (2.53).
 (3,875).
                                       Plus 5....................................  0.70 (1.54).
2.50 (3,875) A < 3.90       1.........................................  1.15 (2.53)
 (6045).
                                       Plus 6....................................  0.70 (1.54).
3.90 (6045) A < (6975)....  3.........................................  1.15 (2.53)
4.50 (6975) A.............  4.........................................  1.15 (2.53).
----------------------------------------------------------------------------------------------------------------


[[Page 68646]]


                                    Table 3.--Additional Integrity Assessment
----------------------------------------------------------------------------------------------------------------
 Engine inlet area (A) square-meters
           (square-inches)                            Bird quantity                    Bird weight kg. (lb.)
----------------------------------------------------------------------------------------------------------------
1.35 (2,092)> A......................  None......................................  .............................
1.35 (2,092) A 2.90         1.........................................  1.15 (2.53).
 (4,495).
2.90 (4,495) A < 3.90       2.........................................  1.15 (2.53).
 (6,045).
3.90 (6,045) A............  1.........................................  1.15 (2.53).
                                       Plus 6....................................  0.70 (1.54).
----------------------------------------------------------------------------------------------------------------

    7. Section 33.77 is amended by removing and reserving paragraphs 
(a) and (b) and by revising paragraphs (d)(3) and (e) to read as 
follows:


Sec. 33.77  Foreign object ingestion.

* * * * *
    (d) * * *
    (3) The foreign object, or objects, stopped by the protective 
device will not obstruct the flow of induction air into the engine with 
a resultant sustained reduction in power or thrust greater than those 
values required by paragraph (c) of this section.
    (e) Compliance with paragraph (c) of this section must be shown by 
engine test under the following ingestion conditions:

----------------------------------------------------------------------------------------------------------------
 Foreign object      Test quantity    Speed of foreign object         Engine operation             Ingestion
----------------------------------------------------------------------------------------------------------------
Ice.............  Maximum             Sucked in..............  Maximum cruise...............  To simulate a
                   accumulation on a                                                           continuous
                   typical inlet                                                               maximum icing
                   cowl and engine                                                             encounter at 25
                   face resulting                                                              degrees
                   from a 2-minute                                                             Fahrenheit.
                   delay in
                   actuating anti-
                   icing system, or
                   a slab of ice
                   which is
                   comparable in
                   weight or
                   thickness for
                   that size engine.
----------------------------------------------------------------------------------------------------------------

    Issued in Washington, DC, on December 2, 1998.
Elizabeth Erickson,
Director, Aircraft Certification Service.
[FR Doc. 98-32734 Filed 12-10-98; 8:45 am]
BILLING CODE 4910-13-P