[Federal Register Volume 63, Number 58 (Thursday, March 26, 1998)]
[Rules and Regulations]
[Pages 14794-14801]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-7902]
[[Page 14793]]
_______________________________________________________________________
Part IV
Department of Transportation
_______________________________________________________________________
Federal Aviation Administration
_______________________________________________________________________
14 CFR Parts 23, 25 and 33
Airworthiness Standards; Rain and Hail Ingestion Standards; Final Rule
Federal Register / Vol. 63, No. 58 / Thursday, March 26, 1998 / Rules
and Regulations
[[Page 14794]]
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Parts 23, 25 and 33
[Docket No. 28652; Amendment Nos. 23-53, 25-95, and 33-19]
RIN 2120-AF75
Airworthiness Standards; Rain and Hail Ingestion Standards
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final rule.
-----------------------------------------------------------------------
SUMMARY: These amendments establish revisions to the Federal Aviation
Administration's certification standards for rain and hail ingestion
for aircraft turbine engines. These amendments address engine power-
loss and instability phenomena attributed to operation in extreme rain
or hail that are not adequately addressed by current requirements.
These amendments also generally harmonize these standards with rain and
hail ingestion standards being amended by the Joint Aviation
Authorities (JAA). These amendments establish nearly uniform standards
for engines certified in the United States under 14 CFR part 33 and in
the JAA countries under Joint Airworthiness Requirements-Engines (JAR-
E), thereby simplifying the certification of engine designs by the FAA
and the JAA.
EFFECTIVE DATE: April 30, 1998.
FOR FURTHER INFORMATION CONTACT: John Fisher, 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 01803-5229; telephone (781)
238-7149; fax (781) 238-7199.
SUPPLEMENTARY INFORMATION:
Availability of Final Rules
An electronic copy of this document may be downloaded, using a
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703-321-3339), the Federal Register's electronic bulletin board service
(20002-512-1661), or the FAA's Aviation Rulemaking Advisory Committee
Bulletin Board service (telephone 202-267-5948).
Internet users may reach the FAA's web page at http://www.faa.gov
or the Federal Register's web page at http://www.access.gpo.gov/
su__docs for access to recently published rulemaking documents.
Any person may obtain a copy of this final rule 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 amendment
number or document number of this final rule.
Persons interested in being placed on the mailing list for future
notices of proposed rulemaking and final rulemaking should request from
the above office a copy of Advisory Circular No. 11-2A, Notices of
Proposed Rulemaking Distribution System, that describes the application
procedure.
Small Entity Inquiries
The Small Business Regulatory Enforcement Fairness Act of 1996
(SBREFA) requires the FAA to report inquiries from small entities
concerning information on, and advice about, compliance with statutes
and regulations within the FAA's jurisdiction, including interpretation
and application of the law to specific sets of facts supplied by a
small entity.
If you are a small entity and have a question, contact your local
FAA official. If you do not know how to contact your local FAA
official, you may contact Charlene Brown, Program Analyst Staff, Office
of Rulemaking, ARM-27, Federal Aviation Administration, 800
Independence Avenue, SW, Washington, DC 20591, 1-888-551-1594. Internet
users can find additional information on SBREFA in the ``Quick Jump''
section of the FAA's web page at http://www.faa.gov and may send
electronic inquiries to the following internet address: 9-AWA-
[email protected].
Background
Statement of the Problem
There have been a number of multiple turbine engine power-loss and
instability events, forced landings, and accidents attributed to
operating airplanes in extreme rain or hail. Investigations have
revealed that ambient rain or hail concentrations can be amplified
significantly through the turbine engine core at high flight speeds and
low engine power conditions. Rain or hail through the turbine engine
core may degrade compressor stability, combustor flameout margin, and
fuel control run down margin. Ingestion of extreme quantities of rain
or hail through the engine core may ultimately produce a number of
engine anomalies, including surging, power loss, and engine flameout.
Industry Study
In 1987, the Aerospace Industries Association (AIA) initiated a
study of natural icing effects on high bypass ratio (HBR) turbofan
engines that concentrated primarily on the mechanical damage aspects of
icing encounters. It was discovered during that study that separate
power-loss and instability phenomena existed that were not related to
mechanical damage. Consequently, in 1988 another AIA study was
initiated to determine the magnitude of these threats and to recommend
changes to part 33, if appropriate. AIA, working with the Association
Europeenne des constructeurs de Materiel Aerospatial (AECMA), concluded
that a potential flight safety threat exists for turbine engines
installed on airplanes operating in extreme rain and hail. Further, the
study concluded that the current water and hail ingestion standards of
14 CFR part 33 do not adequately address this threat.
Engine Harmonization Effort
The FAA is committed to undertaking and supporting harmonization of
standards in part 33 with those in Joint Aviation Requirements-Engines
(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 arising from standards that need
harmonization, including the adoption of new standards when needed. All
parties agreed to work in partnership to address jointly the
harmonization task. This partnership was later expanded to include the
airworthiness authority of Canada, Transport Canada.
This partnership identified seven items which were considered the
most critical to the initial harmonization effort. New rain and hail
ingestion standards are an item on this list of seven items and,
therefore, represent a critical harmonization effort.
Aviation Rulemaking Advisory Committee Project
In December 1992, the FAA requested the Aviation Rulemaking
Advisory Committee (ARAC) to evaluate the need for new rain and hail
ingestion standards. This task, in turn, was 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 November 7,
1995, the TAEIG recommended to the FAA that it proceed with rulemaking
and associated advisory material even
[[Page 14795]]
though one manufacturer expressed reservations. The FAA published a
notice of proposed rulemaking on August 9, 1996 (61 FR 41688). This
rule and associated advisory material reflect the ARAC recommendations.
Discussion of Comments
All interested persons have been afforded an opportunity to
participate in this rulemaking, and due consideration has been given to
all comments received. The commenters represent domestic and foreign
industry, and foreign airworthiness authorities. Five commenters
provided the FAA with comments to the NPRM.
Four commenters expressed concern with the proposed wording for
Secs. 23.903 and 25.903. The commenters state that the proposal could
result in retroactive requirements imposed on certain engines already
type certificated. Three of the four commenters further state that this
part of the proposal represents a significant departure from the
proposal submitted to the FAA by ARAC.
The FAA agrees. It was not the intent of the FAA to retroactively
impose the new requirements on an engine design already type
certificated unless service history indicates that an unsafe condition
is present. The FAA has changed the wording for Secs. 23.903 and 25.903
back to that originally proposed by the ARAC.
All five commenters found a number of typographical errors and
suggested some editorial changes. One notable typographical error
appeared in the ``Disposition of Comments'' section of the preamble of
the proposal. When addressing a concern that the hail threat definition
was apparently rounded up to 10 g/m \3\, the value 8/3 g/m \3\ was
incorrect and should have been written as 8.7 g/m \3\.
The FAA also agrees to the other recommendations by the commenters
and the following grammatical corrections and changes to Sec. 33.78 and
Appendix B have been made to this rule:
Section 33.78(a)(1): ``Critical inlet fact area'' has been changed
to ``Critical inlet face area'' and the last sentence revised to read,
``the hailstones shall be ingested in a rapid sequence to simulate a
hailstone encounter and the number and size of the hailstones shall be
determined as follows:''.
Section 33.78(a)(1)(ii): The term ``one 20-inch'' has been changed
to ``one 2-inch''.
Section 33.78(a)(2): The following has been added to the beginning
of the paragraph, ``In addition to complying with paragraph (a)(1) of
this section and'', and a comma has been added immediately following
the phrase ``or loss of acceleration and deceleration capability''.
Section 33.78(b)(4): ``deceleration'' has been replaced with
``acceleration''.
Appendix B, Table B3: ``Contribution to total LWC (%)'' has been
changed to ``Contribution to total RWC (%)''.
Appendix B, Table B4: The term ``0.49'' has been changed to ``0-
4.9'', and ``hailstone'' has been replaced with ``hail'' in the title,
column heading, and footnote.
One commenter provided an additional clarifying statement with
respect to the hail threat level variations obtained from the Industry
Study. Given an extremely remote encounter probability and a typical
thirty second exposure to severe hail, the assessed hail threat level
varies from 8.7 g/m \3\ to 10.2 g/m \3\, depending upon the airspeed of
the aircraft traversing the hail shaft.
The FAA agrees with the commenter's additional explanation of the
assessed hail threat variation. However, the discussion of the Industry
Study in the proposal is technically correct.
One commenter states the need for advisory material to accompany
the rule to clarify various terms and criteria contained in the rule.
The FAA agrees. An extensive advisory circular (AC) was drafted
providing explanation of the various terms and criteria contained in
the rule. The FAA issued a notice of availability of proposed AC and
request for comments on September 5, 1996 (61 FR 46893). Further
information regarding this AC can be obtained by contacting the FAA at
the address specified under FOR FURTHER INFORMATION CONTACT:
One commenter suggested changes to the preamble discussion
regarding power loss and performance degradation. The commenter did not
suggest nor imply that any changes to the proposed rule were needed.
The FAA need not address those comments since they do not affect the
meaning of these regulations.
One commenter states that the criterion of no flameout contained in
Sec. 33.78(a)(2) and Sec. 33.78(b) was excessive. The commenter further
states that many engines are equipped with automatic re-ignition
systems that would ensure quick recovery from a flameout.
The FAA disagrees. Automatic re-ignition systems can facilitate
quick recovery from a flameout as a result of a momentary ingestion,
such as an ice shed. However, the rain and hail ingestion threats
addressed by the new standards are not momentary, and have been defined
for purposes of certification testing as 30 seconds duration for hail
and 3 minutes duration for rain. Once flameout occurs under these
conditions, it is unlikely that the engine will be capable of recovery
until the ingestion of rain or hail ceases, with or without an
automatic re-ignition system. Also, for actual encounters of severe
rain and hail, it is likely that the engine will continue to ingest
water, at lower concentrations, after exiting the area of severe rain
or hail. The effect of this ingested water is to lower the starting
capability of the engine. Therefore, if an airplane encounters severe
rain or hail with installed engines that are susceptible to flameout,
the airplane will be susceptible to an all engine out, forced landing.
For these reasons, demonstrating tolerance to flameout under conditions
of extreme rain and hail is a primary objective of the new standards.
One commenter states that the acceptance criteria for rain and hail
ingestion contained in Sec. 33.78(a)(2) and Sec. 33.78(b) appeared to
be more stringent than the acceptance for ice ingestion. The commenter
believes that the acceptance criteria for rain and hail ingestion
should be less stringent than for ice ingestion, since ice ingestion is
a more common occurrence than hail ingestion.
The FAA concurs with the commenter that the stringency of
acceptance criteria should be proportional to the occurrence rate of
the threat being assessed. However, the FAA disagrees with the
commenter's view that the acceptance criteria for rain and hail
ingestion are more stringent than for ice ingestion. Some amount of
sustained power or thrust loss is permitted following an ice ingestion
test. Also, the FAA would accept momentary but recoverable surges and
stalls encountered while testing to the new rain and hail ingestion
standards, but has not historically accepted momentary surges and
stalls following an ice ingestion test. Flameout, run down, continued
or non-recoverable surge or stall, and loss of acceleration and
deceleration are unacceptable conditions for rain, hail and ice
ingestion.
Finally, the FAA has made the following minor editorial changes to
better align this rule with recent changes to the JAA's requirements.
These changes do not affect the scope of the rule or change the intent
of these sections.
Section 33.78(a)(1): The phrase ``maximum true air speed'' replaces
the phrase ``maximum rough air speed'', and the phrase ``operating in
rough air'' is added following the words ``representative aircraft''.
[[Page 14796]]
Section 33.78(a)(1)(i) and (ii): The word ``area'' is changed to
read ``areas''.
Section 33.78(c): In the first sentence the phrase ``complying with
paragraph (a)(1) of this section'' is changed to read ``complying with
paragraphs (a)(1) and (a)(2) of this section.
Appendix B: The word ``hailstones'' is changed to read ``hail'' in
the introductory paragraph and also in Table B4.
After careful review of all the comments, the FAA has determined
that air safety and the public interest require the adoption of the
rule with the changes described.
Paperwork Reduction Act
In accordance with the Paperwork Reduction Act of 1995 (44 U.S.C.
3507(d), there are no information collection requirements associated
with this final rule.
Regulatory Evaluation Summary
Proposed changes to Federal regulations must undergo several
economic analyses. First, Executive Order 12866 directs that each
Federal agency shall propose or adopt a regulation only upon a reasoned
determination that the benefits of the intended regulation justify its
costs. Second, the Regulatory Flexibility Act of 1980 requires agencies
to analyze the economic effect of regulatory changes on small entities.
Third, the Office of Management and Budget directs agencies to assess
the effects of regulatory changes on international trade. In conducting
these analyses, the FAA has determined that this rule: (1) Will
generate benefits that justify its costs and is not a ``significant
regulatory action'' as defined in the Executive Order; (2) is not
significant as defined in DOT's Regulatory Policies and Procedures; (3)
will not have a significant impact on a substantial number of small
entities; and (4) will not constitute a barrier to international trade.
These analyses, available in the docket, are summarized below.
Incremental Costs
The proposed rule will permit a range of compliance options,
thereby enabling manufacturers to select cost-minimizing approaches.
Approaches that maximize the use of analytical methods will most likely
be the least expensive means to demonstrate compliance, while
approaches that rely primarily on engine testing in a simulated rain
and hail environment will likely be the most costly. Incremental
certification cost estimates supplied by industry varied depending on
engine model and the testing method used.
FAA conservatively estimates that incremental certification costs
for an airplane turbine engine design will be approximately $627,000--
this includes $300,000 in additional engineering hours, and $327,000
for the prorated share of the cost of a test facility.
Based on statements from industry, the FAA expects that, once Rain/
Hail centrifuging and engine cycle models are established, compliance
will be accomplished through design modifications that will have little
impact on manufacturing costs. Such design features may affect: (1) fan
blade/propeller, (2) spinner/nose cone, (3) bypass splitter, (4) engine
bleeds, (5) accessory loads, (6) variable stator scheduling, and (7)
fuel control. Similarly, the FAA expects that the rule will have a
negligible effect on operating costs.
Expected Benefits
Rain or hail related in-flight engine shutdowns are rare
occurrences. This is due, in large part, to the high quality of
meteorological data available to ground controllers and pilots, and to
well established weather avoidance procedures. However, while such
events are infrequent, they pose a serious hazard because they
typically occur during a critical phase of flight where recovery is
difficult or impossible.
An examination of the FAA accident/incident database system and
National Transportation Safety Board (NTSB) records revealed two
accidents that were the result of inflight engine shutdown or rundowns
caused by excessive water ingestion. In each case, the aircraft was in
the descent phase of flight. These accidents form the basis of the
expected benefits of the subject rule. However, what follows should be
considered a conservative estimate of the rule's potential benefits for
three reasons.
First, the rule should have the effect of increasing turbine engine
water ingestion tolerance regardless of the source of water Accident/
incident records show that many events (not included in the benefits
estimates that follow) were caused by other forms of water such as snow
and graupel. It is possible that some of these cases would have
benefited from the subject rule.
Second, several other incidents, while not resulting in a crash,
nevertheless had catastrophic potential. This potential could be
exacerbated by the development of more efficient turbofan powerplants
which have permitted large aircraft designs incorporating fewer
engines. An industry study identified seven events (not recorded in
either the FAA or NTSB databases) in which rain and/or hail affected
two or more engines and resulted in an inflight shutdown of at least
one engine.
Third, heavy rain and hail are often accompanied by severe
turbulence and windshear. While recovery from a water induced engine
shutdown is frequently successful, the ability to maintain engine power
during an encounter with an unexpected downdraft could be crucial to
avoiding a crash.
The available accident and aircraft usage data suggest the
categories that are used to classify the benefits of the subject rule.
These classifications are: (1) Large air carrier aircraft (operated by
major and national air carriers), and (2) other air carrier aircraft
(operated by large regional, medium regional, commuter, and other small
certificated air carriers). An examination of accident records for the
20-year period 1975-1994 indicates that, in the absence of the subject
rule, the probability of a hull loss due to a water induced loss of
engine power is 0.0094 per million departures for large air carriers,
and 0.0249 per million departures for other air carriers.
The calculation of the rule's benefits, then, depends on the degree
to which the rule can reduce this risk. According to industry
representatives, compliance with the revised water ingestion standards
will reduce the rate of engine power loss events by two orders of
magnitude. This analysis assumes that the rule's effect on the accident
rate will be proportionately equal to the rule's effect on the event
rate.
Using projections from the FAA Aviation Forecast, this analysis
assumes that the average large air carrier airplane has 168 seats and a
load factor of 61%. The average regional air carrier airplane is
assumed to have 30 seats and a load factor of 51%. The estimated
distribution of fatal, serious, and minor injuries is based on the
actual distribution of casualties in the accidents cited above. On the
basis of these assumptions, FAA estimates the annual benefits of
prevented casualties per airplane will be $3,360 for large air carriers
and $618 for other air carriers.
Benefits and Costs Analysis
The benefits and costs of the rule are compared for two
representative engine certifications: (1) An engine designed for
operation on a large jet transport (corresponding to the ``large air
carrier'' category described earlier), and (2) an engine designed for
operation on a regional transport (corresponding to the ``other air
carrier'' category).
For each certification, the following assumptions apply: (1) 50
engines are produced per year for 10 years (500 total
[[Page 14797]]
engines produced per certification), (2) incremental certification
costs are incurred in the year 2000, (3) engine production begins in
the year 2002, (4) the first engines enter service in the year 2003,
(5) each engine is retired after 10 years, (6) the discount rate is 7%.
Also, in order to compare incremental engine costs with expected
benefits (which are expressed in terms of the reduction in the aircraft
accident rate) this analysis assumes that each aircraft has two
engines.
Under the assumptions enumerated above, total lifecycle benefits
for a representative engine designed for operation on a large airplane
equal approximately $9.3 million or $3.5 million at present value (1997
dollars). Total lifecycle benefits for a representative engine designed
for operation on a regional airplane equal to approximately $1.8
million or $0.7 million at present value.
This analysis postulates that incremental certification costs for
both representative engine designs are the same. As discussed above,
incremental costs are approximately $627,000 or $512,000 at present
value.
FAA finds that the rule would be cost-beneficial. Under very
conservative production, service life, and incremental engine
certification cost assumption, the expected discounted benefits of
prevented casualties and aircraft damage will exceed costs by a ratio
ranging from 6.9 to 1 for large air carriers to 1.3 to 1 for other air
carriers.
Harmonization Benefits
In addition to the benefits of increased safety, the rule
harmonizes with JAR requirements, thus reducing costs associated with
certificating aircraft turbine engines to differing airworthiness
standards.
Regulatory Flexibility Determination
The Regulatory Flexibility Act of 1980 establishes ``as a principle
of regulatory issuance that agencies shall endeavor, consistent with
the objective of the rule 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 principal, the Act requires agencies to solicit and
consider flexible regulatory proposal and to explain the rational for
their actions. The Act covers a wide range of small entities, including
small businesses, non-for-profit organizations and small governmental
jurisdictions.
Agencies must perform an analysis to determine whether a 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
a regulatory flexibility analysis (RFA).
However, if after an 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 1980 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 the proposal
and determined that it would not have a significant economic impact on
a substantial number of small entities. That determination was
published in the Federal Register on August 9, 1996 as part of the
Notice of Proposed Rulemaking. No comments were received regarding the
economic analysis of the rule. No substantial changes were made in the
final rule from the proposed rule, and estimated costs were not
significantly modified. Accordingly, pursuant to the Regulatory
Flexibility Act, 5 U.S.C. 605(b), the Federal Aviation Administration
certifies that this rule will not have a significant economic impact on
a substantial number of small entities.
International Trade Impact Assessment
The rule will have little or no effect on trade for either U.S.
firms marketing turbine engines in foreign markets or foreign firms
marketing turbine engines in the U.S. Generally, this rule harmonizes
FAA requirements with existing and proposed JAA requirements.
Federalism Implication
The regulations will not have substantial direct effects 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. Therefore, in accordance with Executive
Order 12612, it is determined that this rule will not have sufficient
federalism implications to warrant the preparation of a Federalism
Assessment.
Unfunded Mandates Reform Act
Title II of the Unfunded Mandates Reform Act of 1995 (The Act),
enacted as Public L. 104-4 on March 22, 1995, requires each federal
agency, to the extent permitted by law, to prepare a written assessment
of the effects of any federal mandate in a proposed or final agency
rule that may result in the expenditure by state, local, and tribal
governments, in the aggregate, or by the private sector, of $100
million or more (adjusted annually for inflation) in any one year.
Section 204(A) of The Act, 2 U.S.C. 1534(A), requires the federal
agency to develop an effective process to permit timely input by
elected officers (or their designees) of state, local, and tribal
governments on a proposed ``significant intergovernmental mandate''. A
``significant intergovernmental mandate'' under The Act is any
provision in a federal agency regulation that will impose an
enforceable duty upon state, local, and tribal governments, in the
aggregate, of $100 million (adjusted annually for inflation) in any one
year. Section 203 of The Act, 2 U.S.C. 1533, which supplements section
204(A), provides that before establishing any regulatory requirements
that might significantly or uniquely affect small governments, the
agency shall have developed a plan that, among other things, provides
for notice to potentially affected small governments, if any, and for a
meaningful and timely opportunity to provide input in the development
of regulatory proposals.
The FAA determines that this rule does not contain a significant
intergovernmental or private sector mandate as defined by the act.
List of Subjects in 14 CFR Parts 23, 25 and 33
Air transportation, Aircraft, Aviation safety, Safety.
Adoption of the Amendments
In consideration of the foregoing, the Federal Aviation
Administration amends 14 CFR parts 23, 25, and 33 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 23.901 is amended by revising paragraph (d)(2) to read
as follows:
Sec. 23.901 Installation.
* * * * *
(d) * * *
(2) Ensure that the capability of the installed engine to withstand
the ingestion of rain, hail, ice, and birds into the engine inlet is
not less than the
[[Page 14798]]
capability established for the engine itself under Sec. 23.903(a)(2).
* * * * *
3. Section 23.903 is amended by revising paragraph (a)(2) to read
as follows:
Sec. 23.903 Engines.
(a) * * *
(2) Each turbine engine must either--
(i) Comply with Secs. 33.77 and 33.78 of this chapter in effect on
April 30, 1998; or as subsequently amended; or
(ii) Comply with Sec. 33.77 of this chapter in effect on October
31, 1974, or as subsequently amended prior to April 30, 1998, and must
have a foreign object ingestion service history that has not resulted
in any unsafe condition; or
(iii) Be shown to have a foreign object ingestion service history
in similar installation locations which has not resulted in any unsafe
condition.
Note: Sec. 33.77 of this chapter in effect on October 31, 1974,
was published in 14 CFR parts 1 to 59, Revised as of January 1,
1975. See 39 FR 35467, October 1, 1974.
* * * * *
PART 25--AIRWORTHINESS STANDARDS; TRANSPORT CATEGORY AIRPLANES
4. The authority citation for part 25 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701-44702, 44704.
5. Section 25.903 is amended by revising paragraph (a)(2) to read
as follows:
Sec. 25.903 Engines.
(a) * * *
(2) Each turbine engine must either--
(i) Comply with Secs. 33.77 and 33.78 of this chapter in effect on
April 30, 1998 or as subsequently amended; or
(ii) Comply with Sec. 33.77 of this chapter in effect on October
31, 1974, or as subsequently amended prior to April 30, 1998, and must
have a foreign object ingestion service history that has not resulted
in any unsafe condition; or
(iii) Be shown to have a foreign object ingestion service history
in similar installation locations which has not resulted in any unsafe
condition.
Note: Sec. 33.77 of this chapter in effect on October 31, 1974,
was published in 14 CFR parts 1 to 59, Revised as of January 1,
1975. See 39 FR 35467, October 1, 1974.
* * * * *
PART 33--AIRWORTHINESS STANDARDS: AIRCRAFT ENGINES
6. The authority citation for part 33 continues to read as follows:
Authority: 49 U.S.C. 106(g) 40113, 44701-44702, 44704.
7. Section 33.77 is amended by revising paragraphs (c) and (e) to
read as follows:
Sec. 33.77 Foreign object ingestion.
* * * * *
(c) Ingestion of ice under the conditions prescribed in paragraph
(e) of this section, may not cause a sustained power or thrust loss or
require the engine to be shut down.
* * * * *
(e) Compliance with paragraphs (a), (b), and (c) of this section
must be shown by engine test under the following ingestion conditions:
----------------------------------------------------------------------------------------------------------------
Speed of foreign
Foregin object Test quantity object Engine operation Ingestion
----------------------------------------------------------------------------------------------------------------
Birds:
3-ounce size............. One for each 50 Liftoff speed of Takeoff.................... In rapid
square inches typical sequence to
of inlet area, aircraft. simulate a
or fraction flock encounter
thereof, up to and aimed at
a maximum of 16 selected
birds. Three- critical areas.
ounce bird
ingestion not
required if a
1\1/2\-pound
bird will pass
the inlet guide
vanes into the
rotor blades.
1\1/2\-pound size........ One for the Initial climb Takeoff.................... In rapid
first 300 speed of sequence to
square inches typical simulate a
of inlet area, aircraft. flock encounter
if it can enter at selected
the inlet, plus critical areas.
one for each
additional 600
square inches
of inlet area,
or fraction,
thereof up to a
maximum of 8
birds.
4-pound size............. One, if it can Maximum climb Maximum cruise............. Aimed at
enter the inlet. speed of critical area.
typical
aircraft, if
the engine has
inlet guide
vanes.
Liftoff speed of Takeoff.................... Aimed at
typical critical area.
aircraft, if
the engine does
not have inlet
guide vanes.
Ice:
Maximum accumulation on a Sucked in....... ................ Maximum cruise............. To simulate a
typical inlet cowl and continuous
engine face resulting maximum icing
from a 2-minute delay in encounter at 25
actuating anti-icing deg. F.
system, or a slab of ice
which is comparable in
weight or thickness for
that size engine..
----------------------------------------------------------------------------------------------------------------
Note: The term ``inlet area'' as used in this section means the engine inlet projected area at the front face
of the engine. It includes the projected area of any spinner or bullet nose that is provided.
[[Page 14799]]
8. Section 33.78 is added to part 33, to read as follows:
Sec. 33.78 Rain and hail ingestion.
(a) All engines. (1) The ingestion of large hailstones (0.8 to 0.9
specific gravity) at the maximum true air speed, up to 15,000 feet
(4,500 meters), associated with a representative aircraft operating in
rough air, with the engine at maximum continuous power, may not cause
unacceptable mechanical damage or unacceptable power or thrust loss
after the ingestion, or require the engine to be shut down. One-half
the number of hailstones shall be aimed randomly over the inlet face
area and the other half aimed at the critical inlet face area. The
hailstones shall be ingested in a rapid sequence to simulate a
hailstone encounter and the number and size of the hailstones shall be
determined as follows:
(i) One 1-inch (25 millimeters) diameter hailstone for engines with
inlet areas of not more than 100 square inches (0.0645 square meters).
(ii) One 1-inch (25 millimeters) diameter and one 2-inch (50
millimeters) diameter hailstone for each 150 square inches (0.0968
square meters) of inlet area, or fraction thereof, for engines with
inlet areas of more than 100 square inches (0.0645 square meters).
(2) In addition to complying with paragraph (a)(1) of this section
and except as provided in paragraph (b) of this section, it must be
shown that each engine is capable of acceptable operation throughout
its specified operating envelope when subjected to sudden encounters
with the certification standard concentrations of rain and hail, as
defined in appendix B to this part. Acceptable engine operation
precludes flameout, run down, continued or non-recoverable surge or
stall, or loss of acceleration and deceleration capability, during any
three minute continuous period in rain and during any 30 second
continuous period in hail. It must also be shown after the ingestion
that there is no unacceptable mechanical damage, unacceptable power or
thrust loss, or other adverse engine anomalies.
(b) Engines for rotorcraft. As an alternative to the requirements
specified in paragraph (a)(2) of this section, for rotorcraft turbine
engines only, it must be shown that each engine is capable of
acceptable operation during and after the ingestion of rain with an
overall ratio of water droplet flow to airflow, by weight, with a
uniform distribution at the inlet plane, of at least four percent.
Acceptable engine operation precludes flameout, run down, continued or
non-recoverable surge or stall, or loss of acceleration and
deceleration capability. It must also be shown after the ingestion that
there is no unacceptable mechanical damage, unacceptable power loss, or
other adverse engine anomalies. The rain ingestion must occur under the
following static ground level conditions:
(1) A normal stabilization period at take-off power without rain
ingestion, followed immediately by the suddenly commencing ingestion of
rain for three minutes at takeoff power, then
(2) Continuation of the rain ingestion during subsequent rapid
deceleration to minimum idle, then
(3) Continuation of the rain ingestion during three minutes at
minimum idle power to be certified for flight operation, then
(4) Continuation of the rain ingestion during subsequent rapid
acceleration to takeoff power.
(c) Engines for supersonic airplanes. In addition to complying with
paragraphs (a)(1) and (a)(2) of this section, a separate test for
supersonic airplane engines only, shall be conducted with three
hailstones ingested at supersonic cruise velocity. These hailstones
shall be aimed at the engine's critical face area, and their ingestion
must not cause unacceptable mechanical damage or unacceptable power or
thrust loss after the ingestion or require the engine to be shut down.
The size of these hailstones shall be determined from the linear
variation in diameter from 1-inch (25 millimeters) at 35,000 feet
(10,500 meters) to \1/4\-inch (6 millimeters) at 60,000 feet (18,000
meters) using the diameter corresponding to the lowest expected
supersonic cruise altitude. Alternatively, three larger hailstones may
be ingested at subsonic velocities such that the kinetic energy of
these larger hailstones is equivalent to the applicable supersonic
ingestion conditions.
(d) For an engine that incorporates or requires the use of a
protection device, demonstration of the rain and hail ingestion
capabilities of the engine, as required in paragraphs (a), (b), and (c)
of this section, may be waived wholly or in part by the Administrator
if the applicant shows that:
(1) The subject rain and hail constituents are of a size that will
not pass through the protection device;
(2) The protection device will withstand the impact of the subject
rain and hail constituents; and
(3) The subject of rain and hail constituents, stopped by the
protection device, will not obstruct the flow of induction air into the
engine, resulting in damage, power or thrust loss, or other adverse
engine anomalies in excess of what would be accepted in paragraphs (a),
(b), and (c) of this section.
9. Appendix B is added to part 33, to read as follows:
Appendix B to Part 33--Certification Standard Atmospheric
Concentrations of Rain and Hail
Figure B1, Table B1, Table B2, Table B3, and Table B4 specify
the atmospheric concentrations and size distributions of rain and
hail for establishing certification, in accordance with the
requirements of Sec. 33.78(a)(2). In conducting tests, normally by
spraying liquid water to simulate rain conditions and by delivering
hail fabricated from ice to simulate hail conditions, the use of
water droplets and hail having shapes, sizes and distributions of
sizes other than those defined in this appendix B, or the use of a
single size or shape for each water droplet or hail, can be
accepted, provided that applicant shows that the substitution does
not reduce the severity of the test.
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Table B1.--Certification Standard Atmospheric Rain Concentrations
------------------------------------------------------------------------
Rain
water
content
(RWC)
Altitude (feet) (grams
water/
meter \3\
air)
------------------------------------------------------------------------
0............................................................ 20.0
20,000....................................................... 20.0
26,300....................................................... 15.2
32,700....................................................... 10.8
39,300....................................................... 7.7
46,000....................................................... 5.2
------------------------------------------------------------------------
RWC values at other altitudes may be determined by linear interpolation.
Note: Source of data--Results of the Aerospace Industries Association
(AIA) Propulsion Committee Study, Project PC 338-1, June 1990.
Table B2.--Certification Standard Atmospheric Hail Concentrations
------------------------------------------------------------------------
Hail
water
content
(HWC)
Altitude (feet) (grams
water/
meter \3\
air)
------------------------------------------------------------------------
0............................................................ 6.0
7,300........................................................ 8.9
8,500........................................................ 9.4
10,000....................................................... 9.9
12,000....................................................... 10.0
15,000....................................................... 10.0
16,000....................................................... 8.9
17,700....................................................... 7.8
19,300....................................................... 6.6
21,500....................................................... 5.6
24,300....................................................... 4.4
29,000....................................................... 3.3
46,000....................................................... 0.2
------------------------------------------------------------------------
HWC values at other altitudes may be determined by linear interpolation.
The hail threat below 7,300 feet and above 29,000 feet is based on
linearly extrapolated data.
Note: Source of data--Results of the Aerospace Industries Association
(AIA Propulsion Committee (PC) Study, Project PC 338-1, June 1990.
Table B3.--Certification Standard Atmospheric Rain Droplet Size
Distribution
------------------------------------------------------------------------
Contribution
Rain droplet diameter (mm) total RWC
(%)
------------------------------------------------------------------------
0-0.49.................................................... 0
0.50-0.99................................................. 2.25
1.00-1.49................................................. 8.75
1.50-1.99................................................. 16.25
2.00-2.49................................................. 19.00
2.50-2.99................................................. 17.75
3.00-3.49................................................. 13.50
3.50-3.99................................................. 9.50
4.00-4.49................................................. 6.00
4.50-4.99................................................. 3.00
5.00-5.49................................................. 2.00
5.50-5.99................................................. 1.25
6.00-6.49................................................. 0.50
6.50-7.00................................................. 0.25
-------------
Total................................................. 100.00
------------------------------------------------------------------------
Median diameter of rain droplets in 2.66 mm
Note: Source of data--Results of the Aerospace Industries Association
(AIA Propulsion Committee (PC) Study, Project PC 338-1, June 1990.
Table B4.--Certification Standard Atmospheric Hail Size Distribution
------------------------------------------------------------------------
Contribution
Hail diameter (mm) total HWC
(%)
------------------------------------------------------------------------
0-4.9..................................................... 0
5.0-9.9................................................... 17.00
10.0-14.9................................................. 25.00
15.0-19.9................................................. 22.50
20.0-24.9................................................. 16.00
25.0-29.9................................................. 9.75
30.0-34.9................................................. 4.75
35.0-39.9................................................. 2.50
40.0-44.9................................................. 1.50
[[Page 14801]]
45.0-49.9................................................. 0.75
50.0-55.0................................................. 0.25
-------------
Total................................................. 100.00
------------------------------------------------------------------------
Median diameter of hail is 16 mm
Note: Source of data--Results of the Aerospace Industries Association
(AIA Propulsion Committee (PC) Study, Project PC 338-1, June 1990.
Issued in Washington, DC, on March 20, 1998.
Jane F. Garvey,
Administrator.
[FR Doc. 98-7902 Filed 3-25-98; 8:45 am]
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