12360 Federal Register / Vol. 60, No. 43 / Monday, March 6, 1995 / Proposed Rules

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 33

[Docket No. 28107; Notice No. 95–3]

RIN 2120–AF57

Airworthiness Standards; Windmilling

and Rotor Locking Tests, and Vibration

and Vibration Tests

AGENCY: Federal Aviation

Administration, DOT.

ACTION: Notice of proposed rulemaking

(NPRM).

SUMMARY: The Federal Aviation

Administration (FAA) proposes to

change the windmilling and vibration

airworthiness standards for the issuance

of original and amended type

certificates for aircraft engines. This

proposal resulted from an effort to

harmonize the Federal Aviation

Regulations with European

requirements being drafted by the Joint

Aviation Authorities (JAA). The

proposed changes, if adopted, would

create one set of common requirements,

that would reduce the regulatory burden

on the aviation industry worldwide by

eliminating the need for applicants for

type certificates to comply with

different sets of standards when seeking

certifications from the FAA and JAA.

DATES: Comments must be submitted on

or before June 5, 1995.

ADDRESSES: Comments on this notice

should be mailed in triplicate to:

Federal Aviation Administration, Office

of the Chief Counsel, Attention: Rules

Docket (AGC–200), Docket No. 28107,

800 Independence Avenue, SW.,

Washington, DC 20591. Comments

delivered must be marked Docket No.

28107. Comments may be inspected in

Room 915G weekdays between 9:00 a.m.

and 5:00 p.m., except on Federal

holidays.

FOR FURTHER INFORMATION CONTACT: John

Golinski or Thomas Boudreau, 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

(617) 238–7119; fax (617) 238–7199.

SUPPLEMENTARY INFORMATION:

Comments Invited

Interested persons are invited to

submit written data, views, or

arguments on this proposed rule.

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 should identify

the regulatory docket number and

should be submitted in triplicate to the

Rules Docket address specified above.

all comments received on or before the

closing date for comments specified will

be considered by the Administrator

before taking action on this proposed

rulemaking. The proposals contained in

this notice may be changed in light of

comments received. All comments

received will be available, both before

and after the closing date for comments,

in the Rules Docket for examination by

interested persons. A report

summarizing each substantive public

contact with FAA personnel concerned

with this rulemaking will be filed in the

docket. Comments submitted in

response to this notice must include a

preaddressed, stamped postcard on

which the following statement is made:

‘‘Comments to Docket No. 28107.’’ The

postcard will be date stamped and

mailed to the commenter.

Availability of NPRM’s

Any person may obtain a copy of this

NPRM by submitting a request to the

Federal Aviation Administration, Office

of Public Affairs, Attention: Public

Inquiry Center, APA–200, 800

Independence Avenue, SW.,

Washington, DC 20591, or by calling

(202) 267–3484. Communications must

identify the notice 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

Part 33 of title 14 of the Code of

Federal Regulations (14 CFR part 33,

hereafter ‘‘part 33’’) prescribes

airworthiness standards for the issuance

of original and amended type

certificates for aircraft engines. Part E of

the Joint Aviation Requirements (JAR–E)

prescribes corresponding airworthiness

standards of the European Joint

Aviation Authorities (JAA). While part

33 and JAR–E are similar, they differ in

several respects. Non-uniform standards

impose a regulatory burden on

applicants seeking certification under

both sets of standards in the form of

additional costs and delays in the time

required for certification.

As part of its commitment to promote

harmonization of part 33 and JAR–E, the

FAA, with the cooperation of the JAA,

established the part 33/JAR–E

Authorities Engine Group to compare

part 33 and JAR–E. This group included

regulatory representatives from France,

Canada, Germany, the United Kingdom,

and the United States. The basis for the

comparison was part 33, as amended

through Amendment 11, and JAR–E, as

amended through Change 7. As its

initial effort, the study group focused on

gas turbine engines and concentrated on

JAR–E items that appeared to be more

stringent than part 33. The identified

differences were categorized into lists 1

and 2. List 1 included twenty items

where the differences appear to be

sufficiently significant to cause the JAA

to apply additional conditions to U.S.

manufacturers seeking JAA certification.

List 2 included requirements considered

to be equivalent to the corresponding

Federal Aviation Regulation (FAR) in

part 33 based on FAA policy and

practice.

In August 1989, at the request of the

Aerospace Industries Association (AIA)

and the Association Europeene Des

Constructeurs De Materiel Aerospatial

(AECMA), the FAA and JAA met in

Paris, France, with aerospace industry

representatives to initiate a process for

resolving List 1 comparison issues. At

an FAA/JAA management meeting in

June 1992, in Toronto, Canada, seven

part 33 engine ‘‘Harmonization’s Terms

of Reference’’ were introduced. Two of

these initiatives, windmilling and rotor

locking test requirements, and vibration

and vibration test requirements, were

contained in the FAA/JAA List 1 of

twenty items. They were the first engine

harmonization initiatives for which

consensus was reached by study groups

from domestic and international

industry and airworthiness authorities.

In December 1992, the FAA requested

the Aviation Rulemaking Advisory

Committee (ARAC) to further evaluate

the proposals (57 FR 58840). This task,

in turn, was assigned to the Propulsion

Harmonization Working Group of

ARAC. On June 18, 1993, the working

group reported to the ARAC, which

recommended to the FAA that the FAA

proceed with rulemaking. This NPRM

and a corresponding notice of proposed

amendment (NPA) to JAR–E reflect the

ARAC recommendations.

General Discussion of the Proposals

The proposals in the NPRM would

harmonize U.S. regulations with

existing and proposed requirements of

the European Joint Aviation Authorities,

codify current industry practices, and

clarify existing requirements.

Specifically, whey would (1) Clarify the

existing requirement that excessive

vibratory stresses may not be induced
Federal Register / Vol. 60, No. 43 / Monday, March 6, 1995 / Proposed Rules 12361

throughout the declared flight envelope

of the engine; (2) require that continued

windmilling following engine shutdown

must not create a hazard for the

airplane; (3) expand the scope of

vibration tests; (4) expand the

applicability of rotor locking tests; and

(5) clarify rotor locking and vibration

test requirements.

Windmilling and Rotor Locking Test

Requirements

Section 33.74 Windmilling

Parts 23 and 25 of title 14 of the CFR

prescribe the airworthiness standards

for airplanes. Sections 23.903(e)(2) and

25.903(c) in part, state that for turbine

engine installations, the means for

stopping the rotation of any engine need

be provided only where continued

rotation could jeopardize the safety of

the airplane. JAR–E presently provides

a safety objective for windmilling

without oil.

This proposal would add a new

section to state specific windmilling

requirements that are consistent with

the safety objectives of the airplane

requirements in §§ 23.903(e)(2) and

25.903(c), which address control of

engine rotation. The proposed new

requirements would ensure that

windmilling following engine shutdown

in flight would not create a hazard for

the airplane.

This proposal was developed and

agreed to by the ARAC Propulsion

Harmonization working group. The

proposed change contains language that

would be common to the language

proposed for JAR–E, thereby

establishing equivalency and creating

consistency between the two

regulations. In addition, because an

engine manufacturer must show

compliance to the proposed § 33.74

which has safety objectives consistent

with the corresponding airplane

requirements for windmilling engines

identified in §§ 23.903(e)(2) and

25.903(c), the engine manufacturer can

provide this information directly to the

airplane manufacturers to reduce the

amount of analysis performed by the

airplane manufacturers under

§§ 23.903(e)(2) and 25.903(c), which

could result in potential cost savings for

the airplane manufacturers.

Section 33.92 Rotor Locking Tests

Section 33.92 currently specifies

engine test requirements for engines

installed on supersonic aircraft and also

specifies an endurance test for turbine

engine rotor stopping and locking

devices. This proposal would delete the

test requirements in § 33.92(a) and

clarify the endurance test for rotor

stopping and locking devices, that is

applicable to all turbine engines that

incorporate such a device. This

proposed requirement will also be

proposed in JAR–E, thereby

harmonizing with part 33 and

facilitating the harmonization of part 25

with JAR 25, by allowing deletion of

JAR 25.903(c)(1), which addresses

continued windmilling after loss of

engine oil.

The proposed deletion of current

§ 33.92(a) is based on the service

experience of the world’s only

supersonic commercial transport. The

British/French Concorde has

experienced a number of inflight engine

shutdowns at supersonic speeds since

1974. In each of these incidents, because

of the aerodynamic effect of drag and

loss of thrust, speed was rapidly

reduced to subsonic levels. Therefore,

requirements for conducting prolonged

engine windmilling tests at supersonic

speeds are unnecessary.

The proposal would move the

requirement that each engine

incorporating a rotor locking device be

shut down while operating at rated

maximum continuous thrust from

§ 33.92(b)(1) to proposed § 33.92.

Proposed revision § 33.92 would also

require that the means for stopping and

locking the rotor(s) must be operated as

specified in the engine operating

instructions.

The proposed revision to § 33.92

would clarify the endurance test

requirements currently identified in

§ 33.92(b) by establishing that following

rotor locking, the rotor(s) must be held

stationary for five minutes while being

subjected to the maximum torque that

could result from continued flight in

this condition. The harmonization

review has established that the current

requirement does not provide adequate

information on how to run the test.

Clarification is provided by the addition

of a five minute test to confirm the

durability of the system.

Vibration and Vibration Test

Requirements

Section 33.63 Vibration

Section 33.63 currently contains

vibration design and construction

standards for aircraft engines. This

proposal would clarify the existing text

by adding the term ‘‘declared flight

envelope’’ to ensure that excessive

vibration stresses are not induced at all

intended airborne and non-airborne

conditions of operation. This proposal

would harmonize the vibration

requirements.

Section 33.83 Vibration Test

Section 33.83 prescribes the testing

requirements that turbine engines must

undergo to establish the

aerodynamically induced system

vibration (flutter) as well as the

mechanically induced vibration

characteristics of components that could

induce failure. This proposal would

delete the existing text and replace it

with harmonized requirements. The

harmonized requirements address some

conditions that are currently being

addressed by analysis in § 33.75.

Section 33.83(a). This proposal would

replace the current text with new

harmonized text to clarify the existing

requirement that all components in each

engine that may be subject to

mechanically or aerodynamically

induced vibratory excitations must

undergo vibration surveys. These engine

surveys shall be based upon an

appropriate combination of experience,

analysis, and component test and

should address, as a minimum, blades,

vanes, rotor discs, spacers, and rotor

shafts. Substantive pre-certification

activity (tests and analyses) is necessary

for determining which engine

components require verification by the

engine certification process. The

proposal retains the current practice of

the FAA and JAA of limiting formal

certification test requirements to only

the final engine or major assembly rig

vibration test.

The proposal would replace the

phrase ‘‘at the maximum inlet distortion

limit’’ with ‘‘throughout the declared

flight envelope’’ to clarify that the

engine must be tested to cover all

intended airborne and non-airborne

conditions of operation. Using the term

‘‘declared flight envelope’’ better

describes the airworthiness objective of

this section. This change results in no

foreseen additional burden on

applicants because industry practice has

been to conduct vibration surveys

throughout the declared flight envelope.

This proposal would also move the

requirement specifying the range of

rotor speeds and power or thrust of the

vibration surveys from current § 33.83(a)

to proposed revised § 33.83(b).

Section 33.83(b). This proposal would

revise this paragraph to reorganize and

elaborate on existing requirements,

introduce terminology relevant to flutter

vibration, and achieve harmonization

where differences currently exist

between Part 33 and JAR–E. The

proposed paragraph (b) would require

the vibration tests to cover the ranges of

physical rotor speeds, corrected rotor

speeds, and engine power or thrust

corresponding to operations throughout
12362 Federal Register / Vol. 60, No. 43 / Monday, March 6, 1995 / Proposed Rules

the declared flight envelope from idling

speed up to 103 percent of the

maximum rotor speed permitted for

rating periods of 2 minutes or longer,

and up to 100 percent of all other rotor

speeds. The proposal would also add to

the revised paragraph (b) a requirement

that if there is any indication of a stress

peak arising at high physical or

corrected rotational speeds, the surveys

shall be extended. If it becomes

physically impossible to achieve these

extended rotor speeds, it would have to

be shown by analysis or other means

that no harmful vibration exists. Engine

manufacturing and build tolerances can

result in peak stresses occurring at

slightly different rotor speeds between

engines and engine parts (i.e., blades) of

the same type design. The speed

extension, therefore, is intended to

cover inherent engine-to-engine and

blade-to-blade variations in vibratory

response.

Section 33.83(c). The proposal would

revise the current paragraph (c) and

reword the existing text to harmonize

and clarify the existing requirement.

Current paragraph (c) requires that

during the vibration test, each accessory

drive and mounting attachment must be

loaded with the load imposed by each

accessory used only for aircraft service

up to the limit load specified by the

applicant for the engine drive or

attachment point. The proposal would

require that evaluations be made of the

effects on vibration characteristics of

operating with scheduled changes

(including tolerances) to variable vane

angles, compressor bleeds, accessory

loading, the most adverse inlet air flow

distortion pattern declared by the

manufacturer, and the most adverse

conditions in the exhaust duct(s).

Section 33.83(d) This proposal would

add a new paragraph (d) that would

require that the effects on vibration

characteristics of likely fault conditions

shall be evaluated by test, or analysis, or

by reference to previous experience and

be shown not to create a hazardous

condition. Since U.S. engine

manufacturers presently address and

evaluate the effects of vibration

characteristics through analysis in

accordance with the requirements of

§ 33.75, this proposal would harmonize

part 33 with JAR–E.

Section 33.83(e). This proposal would

add a new paragraph (e). The current

§ 33.83(b) requires that vibration

stresses of rotor and stator components

be less, by a margin acceptable to the

Administrator, than the endurance limit

of the material from which these parts

are made, adjusted for the most severe

operating conditions. This proposal

would slightly modify the text of the

requirement by incorporating the

standard industry practice of making

due allowance for variations in material

properties. Current industry practice is

based on the FAA interpretation of the

current requirement. The vibration

stresses associated with the vibration

characteristics determined under § 33.83

must be less than the endurance limits

of the materials concerned, after making

certain allowances. The suitability of

these stress margins would have to be

justified for each part and if it is

determined that certain operating

conditions, or ranges, need to be

limited, operating and installation

limitations would be established. The

proposed new paragraph (e) would

harmonize with existing JAR–E–650

provisions and conform with current

component vibration testing practices.

Section 33.83(f). Proposed new

paragraph (f) would require that

compliance with § 33.83 be

substantiated for each specific

installation configuration that can affect

the vibration characteristics of the

engine. The proposed language would

provide that if these vibrations cannot

be fully investigated during engine

certification, then the methods by which

they can be evaluated and compliance

shown shall be substantiated and

defined in the installation documents

required by § 33.5. The proposed

amendment would codify current

industry practice.

Paperwork Reduction Act

In accordance with the Paperwork

Reduction Act of 1990 (44 U.S.C. 3501

et seq.), an evaluation of the paperwork

burden of this proposal is not required

since there are no recordkeeping or

reporting requirements associated with

this proposed rule.

Preliminary Regulatory Evaluation,

Initial Regulatory Flexibility

Determination, and Trade Impact

Assessment

Proposed changes to Federal

regulations must undergo several

economic analysis. First, Executive

Order 12866 directs that each Federal

agency 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 effect of

regulatory changes on international

trade. In conducting these analyses, the

FAA has determined that this rule (1)

Would generate benefits outweighing its

costs; (2) is not a ‘‘significant regulatory

action’’ as defined in the Executive

Order; (3) is not ‘‘significant’’ as defined

in DOT’s policies and procedures; (4)

would not have a significant impact on

a substantial number of small entities;

and (5) would not constitute a barrier to

international trade. These analyses,

available in the docket, are summarized

below.

Regulatory Evaluation Summary

Of the several proposals, only one

might result in additional cost. The FAA

has identified the requirements in

proposed § 33.83(b) as the only one that

could require minor additional engine

testing and engineering analysis,

resulting in negligible compliance costs.

The reference to experience, analysis,

and component tests in proposed

§ 33.83(a) should not impose additional

costs since it incorporates current

industry practice. The revised engine

windmilling requirements of proposed

new § 33.74 and the proposed

amendments to § 33.92(a) could

potentially result in cost savings to

engine and transport airplane

manufacturers. The FAA solicits

comments from interested persons on

the costs of the proposed rule.

The primary benefits of the proposed

rule would be harmonization of

airworthiness standards with the

European Joint Aviation Requirements

and clarification of existing standards.

The resulting increased uniformity of

standards would simplify airworthiness

approval for import and export purposes

and would avoid some of the costs that

can result when manufacturers seek

type certification under both sets of

standards. While not readily

quantifiable, the cost economies of

harmonization would far exceed the

minor incremental costs of the proposed

rule.

Regulatory Flexibility Determinations

The Regulatory Flexibility Act of 1980

(RFA) was enacted by Congress to

ensure that small entities are not

unnecessarily or disproportionately

burdened by Federal regulations. The

RFA requires a Regulatory Flexibility

Analysis if a proposed rule would have

a significant economic impact, either

detrimental or beneficial, on a

substantial number of small entities.

Based on thresholds in implementing

FAA Order 2100. 14A, Regulatory

Flexibility Criteria and Guidance, the

FAA has determined that the proposed

rule would not have a significant

economic impact on a substantial

number of small entities.
Federal Register / Vol. 60, No. 43 / Monday, March 6, 1995 / Proposed Rules 12363

International Trade Impact Assessment

The proposed rule would not

constitute a barrier to international

trade, including the export of U.S.

aircraft engines to foreign countries and

the import of foreign aircraft engines

into the United States. Instead, the

proposed standards would harmonize

with existing and proposed standards of

foreign authorities, thereby lessening

restraints on trade.

Federalism Implications

The regulations proposed herein

would 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

proposal would not have sufficient

federalism implications to warrant the

preparation of a Federalism Assessment.

Conclusion

For the reasons discussed above,

including the findings in the Regulatory

Evaluation and the International Trade

Impact Assessment, the FAA has

determined that this proposed

regulation is not significant under

Executive Order 12866. In addition, the

FAA certifies that this proposal, if

adopted, will not have a significant

economic impact, positive or negative,

on a substantial number of small entities

under the criteria of the Regulatory

Flexibility Act. This proposal is not

considered significant under DOT

Regulatory Policies and Procedures (44

FR 11034, February 26, 1979). An initial

regulatory evaluation of the proposal,

including a Regulatory Flexibility

Determination and International Trade

Impact Assessment, has been placed in

the docket. A copy may be obtained by

contacting the person identified under

FOR FURTHER INFORMATION CONTACT.

List of Subjects in 14 CFR Part 33

Aircraft, Aviation safety.

The Proposed Amendment

In consideration of the foregoing, the

Federal Aviation Administration

proposes to amend 14 CFR part 33 as

follows:

PART 33—AIRWORTHINESS

STANDARDS: AIRCRAFT ENGINES

1. The authority citation for part 33

continues to read as follows:

Authority: 49 U.S.C. 1344, 1354(a), 1355,

1421, 1423, 1424, 1425; 49 U.S.C. 106(g).

2. Section 33.63 is revised to read as

follows:

§ 33.63 Vibration.

Each engine must be designed and

constructed to function throughout its

declared flight envelope and operating

range of rotational speeds and power/

thrust, without inducing excessive

stress in any engine part because of

vibration and without imparting

excessive vibration forces to the aircraft

structure.

3. A new section 33.74 is added to

read as follows:

§ 33.74 Windmilling.

If the engine continues to windmill

after it is shut down for any reason

while in flight, continued windmilling

of that engine must not result in damage

that could create a hazard to aircraft

representing a typical installation

during the maximum period of flight

likely to occur with that engine

inoperative.

4. Section 33.83 is revised to read as

follows:

§ 33.83 Vibration test.

(a) Each engine must undergo

vibration surveys to establish that the

vibration characteristics of those

components that may be subject to

mechanically or aerodynamically

induced vibratory excitations are

acceptable throughout the declared

flight envelope. The engine surveys

shall be based upon an appropriate

combination of experience, analysis,

and component test and shall address,

as a minimum, blades, vanes, rotor

discs, spacers, and rotor shafts.

(b) The surveys shall cover the ranges

of power or thrust, and both the

physical and corrected rotational speeds

for each rotor system, corresponding to

operations throughout the range of

ambient conditions in the declared

flight envelope, from the minimum rotor

speed up to 103 percent of the

maximum rotor speed permitted for

rating periods of two minutes or longer,

and up to 100 percent of all other

permitted rotor speeds, including those

that are overspeeds. If there is any

indication of a stress peak arising at

high physical or corrected rotational

speeds, the surveys shall be extended in

order to quantify the phenomenon and

to ensure compliance with the

requirements of § 33.63.

(c) Evaluations shall be made of the

effects on vibration characteristics of

operating with scheduled changes

(including tolerances) to variable vane

angles, compressor bleeds, accessory

loading, the most adverse inlet air flow

distortion pattern declared by the

manufacturer, and the most adverse

conditions in the exhaust duct(s).

(d) The effects of likely fault

conditions (such as, but not limited to,

out-of balance, local blockage or

enlargement of stator vane passages, fuel

nozzle blockage, incorrectly scheduled

compressor variables, etc.) on vibration

characteristics, shall be evaluated by

test or analysis, or by reference to

previous experience and shall be shown

not to create a hazardous condition.

(e) The vibration stresses associated

with the vibration characteristics

determined under this section must be

less than the endurance limits of the

materials concerned, after making due

allowance for operating conditions and

permitted variations in properties of the

materials. The suitability of these stress

margins must be justified for each part

evaluated. If it is determined that

certain operating conditions, or ranges,

need to be limited, operating and

installation limitations shall be

established.

(f) Compliance with this section shall

be substantiated for each specific

installation configuration that can affect

the vibration characteristics of the

engine. If these vibration effects cannot

be fully investigated during engine

certification, the methods by which they

can be evaluated and methods by which

compliance can be shown shall be

substantiated and defined in the

installation documents required by

§ 33.5.

5. Section 33.92 is revised to read as

follows:

§ 33.92 Rotor locking tests.

If windmilling is prevented by a

means to lock the rotor(s), the engine

must be subjected to a test that includes

25 operations of this means under the

following conditions:

(a) The engine must be shut down

from rated maximum continuous thrust

or power, and

(b) The means for stopping and

locking the rotor(s) must be operated as

specified in the engine operating

instructions while being subjected to the

maximum torque that could result from

continued flight in this condition; and

(c) Following rotor locking, the

rotor(s) must be held stationary under

these conditions for five minutes for

each of the 25 operations.

Issued in Washington, DC, on February 22,

1995.

Daniel P. Salvano,

Acting Director of Aircraft Certification

Service.

[FR Doc. 95–5419 Filed 3–3–95; 8:45 am]

BILLING CODE 4910–13–M