Airworthiness Standards; New Rotorcraft 30-Second/2-Minute One-Engine- Inoperative Power Ratings; Final Rule DEPARTMENT OF TRANSPORTATION

SUMMARY: This rule adopts new and revised airworthiness standards by

incorporating optional one-engine-inoperative (OEI) power ratings for

multiengine, turbine-powered rotorcraft. These amendments result from a

petition for rulemaking from Aerospace Industries Association of

America (AIA) and the recognition by both government and industry that

additional OEI power rating standards are needed. These amendments

enhance rotorcraft safety after an engine failure or precautionary

shutdown by providing higher OEI power, when necessary. These

amendments also assure that the drive system will maintain its

structural integrity and allow continued safe flight while operating at

the new OEI power ratings with the operable engine(s).

EFFECTIVE DATE: October 17, 1994.

FOR FURTHER INFORMATION CONTACT:

Mr. Scott Horn, Rotorcraft Standards Staff, FAA, Fort Worth, Texas

76193-0112, telephone number (817) 222-5125.

SUPPLEMENTARY INFORMATION:

Background

By letter dated September 20, 1984, the AIA petitioned for

rulemaking by requesting amendments to Parts 1, 27, 29, and 33 of the

Federal Aviation Regulations (FAR) to establish new 30-second, 2-

minute, and continuous OEI power ratings.

In the process of drafting the amendments, numerous meetings were

held with the industry groups and airworthiness authorities of other

countries in an attempt to identify and address all of the issues. As

set forth in the AIA's petition, only multiengine rotorcraft, with

turbine-powered engines, would be eligible for these new OEI power

ratings which would be applicable to the remaining engine(s) only after

an in-flight failure or precautionary engine shutdown. The rated 30-

second OEI power would be limited to periods of not more than 30

seconds at any one time and would enhance the OEI performance of the

rotorcraft during the transient phase of the takeoff and landing

maneuvers. The rated 2-minute OEI power would be limited to periods of

not more than 2 minutes at any one time and would achieve initial

stabilized climb of at least 100 feet per minute following takeoff or

balked landing flight with one engine inoperative. These ratings could

be used instead of the existing 2\1/2\-minute OEI power rating or

normal takeoff power.

The continuous OEI power rating and all aspects of its definition,

eligibility, qualification, and performance credit were adopted in

Amendments 1-34, 27-23, 29-26, and 33-12, Rotorcraft Regulatory Review

Program Amendment No. 3 (53 FR 34198, September 2, 1988).

This final rule is based on Notice of Proposed Rulemaking (NPRM)

No. 89-26 that was published in the Federal Register on September 22,

1989 (54 FR 39086). A corresponding NPRM, Notice No. 89-27, that

proposed changes to parts 1 and 33 for definitions and engines was also

published in the same issue of the Federal Register (54 FR 39080). In

addition, a joint public meeting was held on November 16, 1989, in

Forth Worth, Texas, to discuss both notices (54 FR 41986).

All interested persons have been given an opportunity to

participate in this rulemaking and due consideration has been given to

all matters presented. Some minor editorial changes have been made to

clarify the proposals. The changes are based on comments received and

further FAA review of the proposals. Except as indicated herein, the

proposals contained in the notice have been adopted without change.

Discussion of Comments

The commenters represented airframe manufacturers, airworthiness

authorities from other countries, rotorcraft owners and operators, and

private individuals. The commenters generally agree with the substance

of the proposal with certain recommended changes. The following

discussion addresses these recommendations and their disposition.

Sections 27.923 and 29.923 Rotor Drive System and Control Mechanism

Tests

The notice proposed changes to Secs. 27.923(e) and 29.923 (a) and

(b) that add the special tests to the rotor drive system endurance test

schedule, which are necessary to qualify the rotor drive system for the

new 30-second/2-minute OEI power ratings.

One commenter, referring to Secs. 27.923(e)(2)(i) and

29.923(e)(3)(i), states that if the 5-minute takeoff power run to

qualify the drive system is conducted as part of the endurance run, and

the 30-second/2-minute OEI requirements are conducted on a bench test,

then the takeoff power 5-minute run will be conducted twice on the same

set of gears. The commenter proposes that the wording for the bench

testing requirements be changed to state ``* * * following

stabilization at takeoff power.'' The FAA does not intend to duplicate

the takeoff power 5-minute run and agrees that clarification is needed;

therefore, the recommended change has been incorporated.

Another commenter recommends doubling the test time in

Sec. 29.923(b)(3)(i) because the drive system, at the higher and

potentially more damaging 30-second/2-minute OEI power ratings, will be

substantiated by less endurance testing at these new powers. This

recommendation is beyond the scope of the notice. Further, the FAA

disagrees with the recommendation to double the test time for drive

system substantiation because the test time proposed for the new 30-

second/2-minute OEI power ratings is more severe than the current OEI

ratings, when considering expected usage. The test time was established

based upon the proportionate duration of load applications during these

test runs when compared with the expected service life of the rotor

drive system. In addition, the test time was also based upon the

statistical failure rate of turboshaft engines and three applications

of 30-second/2-minute OEI power during the expected life of the drive

system. The relationship between test time and anticipated OEI exposure

in service is more severe by a factor of 2.64 for the new OEI ratings.

Another commenter proposes removing the words `` * * * when engine

limitations either preclude repeated use of this power or would result

in premature engine removal * * *'' from Secs. 27.923(e)(2)(iii) and

29.923(b)(3)(iii). The FAA disagrees because the preferred method of

conducting the tests is on the rotorcraft where the entire drive system

is subjected to the OEI powers. Since the FAA recognizes that in some

cases it may not be possible to conduct these tests on the rotorcraft,

a bench test, which is representative of the aircraft, is included as

an acceptable alternative.

Another commenter proposes to clarify Secs. 27.923(e)(2)(iii) and

29.923(b)(3)(iii) by inserting the word ``vibration'' between the words

``the'' and ``frequency.'' The FAA agrees, and the change has been

made.

Other than some minor editorial changes, these amendments are

adopted as discussed.

Sections 27.1143 and 29.1143 Engine Controls

The notice proposed to include the requirement for automatic

control of the 30-second OEI power in Secs. 27.1143(e) and 29.1143(f).

One commenter suggests that Sec. 29.1143(f) is ambiguous in that it

does not adequately define the meaning of ``control.'' The FAA agrees

that additional clarification is necessary. The amendment now states

``* * * automatically activate and control the 30-second OEI power and

prevent * * *.'' Other than this clarification, the amendments are

adopted as proposed.

Sections 27.1305 and 29.1305 Powerplant Instruments

The notice proposed to include the requirements for a pilot alert

and a recording device when 30-second/2-minute OEI powers are used by

adding paragraphs (t) and (u) to Sec. 27.1305 and paragraphs (a) (24)

and (25) to Sec. 29.1305.

One commenter proposes to add the words ``* * * for use by ground

personnel * * *'' between the words ``provided'' and ``which'' in

Secs. 27.1305(u) and 29.1305(a)(25). The FAA agrees, and the change has

been made.

Another commenter states that because of the number of warnings

being introduced by Sec. 29.1305(a)(24), some guidance material is

needed. The FAA agrees and will address these concerns with forthcoming

advisory material.

A third commenter suggests adding the word ``automatically'' before

the word ``records'' in Sec. 29.1305(a)(25)(i). The FAA agrees, and the

amendments are adopted with the changes.

Sections 27.1521 and 29.1521 Powerplant Limitations

The notice proposed to add paragraphs (j) and (k) to Sec. 27.1521

and paragraphs (i) and (j) to Sec. 29.1521 to include the 30-second/2-

minute OEI power limitations, along with rotorcraft applicability and

the conditions for their use. One commenter supports this proposal if

the amendments to Parts 1 and 33 ensure mandatory maintenance of the

engine following use of the 30-second OEI power rating. In addition,

the commenter further states that the transmission and gearbox should

not be subject to mandatory maintenance. The testing requirements

proposed in Secs. 27.923 and 29.923 for the 30-second/2-minute OEI

power ratings will minimize the need for mandatory maintenance of the

transmission and gearbox following application of the 30-second/2-

minute OEI power in service. The amendments, which concern the airframe

requirements, are adopted without change.

Sections 27.1549 and 29.1549 Powerplant Instruments

The notice proposed to revise Secs. 27.1549(e) and 29.1549(e) by

defining the instrument markings associated with the 30-second/2-minute

OEI power ratings. One commenter supports the proposal and suggests

that some guidance material is needed. The FAA agrees, and guidance

material will be developed. These amendments are adopted as proposed.

Section 29.67 Climb: One Engine Inoperative

The notice proposed to revise paragraph (a)(1)(i) to specify that

for rotorcraft certificated for the 30-second/2-minute OEI power, only

2-minute OEI power may be used to comply with the 100-foot-per-minute

rate of climb required by this section.

One commenter supports the proposal. Another comment concerns

paragraphs (a)(2) and (b), which are not changed by this rulemaking. It

is noted that OEI climb performance required by the current rules can

be determined by using either 30-minute or continuous OEI power. There

are no restrictions on which long duration OEI power rating may be used

with the short duration 30-second/2-minute OEI power ratings. OEI climb

performance will be based upon the highest long duration OEI power for

which certification is requested.

The amendment is adopted without change.

Additional Discussion

Training

Although outside the scope of this rulemaking, the FAA has

recognized the need for additional training for flight crewmembers in

the correct procedures and use of these new OEI power ratings. A

commenter notes that the use of these new ratings could result in

serious damage to the operating engine and that additional training

must be available to satisfy the operational and airworthiness needs.

The FAA agrees, and these training procedures will be considered by

operations specialists during the certification process.

Power Assurance

A commenter notes that power assurance requirements, as given in

Secs. 27.45(f) and 29.45(f), will be affected by these amendments and

recommends the issuance of guidance material. The FAA recognizes the

importance of the power assurance requirement for approval and use of

these new OEI power ratings, and appropriate guidance material will be

developed.

Limiting Height-Speed Envelope

One commenter asks whether the 30-second power is the ``greatest

power for which certification is requested'' as currently contained in

Secs. 27.79(b)(2) and 29.79(b)(1). For these amendments, 30-second

power is the greatest power for which certification could be

accomplished.

Airworthiness Limitations Section

One commenter addressed the need for changes to Appendix A33.4,

Airworthiness Limitations Section. Since this comment addresses part

33, it will be handled in the rulemaking effort underway addressing

that part.

Regulatory Evaluation Summary

Regulatory Evaluation

This section summarizes the full regulatory evaluation prepared by

the FAA that provides more detailed estimates of the economic

consequences of this regulatory action. This summary and the full

evaluation quantify, to the extent practicable, estimated costs to the

private sector, consumers, and Federal, State and local governments, as

well as anticipated benefits.

Executive Order 12866 dated September 30, 1993, directs Federal

agencies to promulgate new regulations and maintain current regulations

only if they are required by law, are necessary to interpret the law,

or are made necessary by a ``compelling public need.'' The order also

requires that agencies assess all costs and benefits of available

regulatory alternatives and select the alternative that maximizes the

net benefits and imposes the least burden on society.

Additionally, the order requires agencies to submit a list of all

rules, except those specifically exempted by the Office of Information

and Regulatory Affairs (OIRA) because they respond to emergency

situations or other narrowly defined exigencies, to determine if the

rules constitute ``significant regulatory action.'' ``Significant

regulatory action'' means an action that is likely to result in a rule

that may (1) have an annual effect on the economy of $100 million or

more or adversely affect in a material way the economy, a sector of the

economy, productivity, competition, jobs, the environment, public

health or safety, or state, local, or tribal governments or

communities; (2) create a serious inconsistency or otherwise interfere

with an action taken or planned by another agency; (3) materially alter

the budgetary impact of entitlements, grants, user fees, or loan

programs or the rights and obligations of recipients thereof; or (4)

raise novel legal or policy issues arising out of legal mandates, the

President's priorities, or the principles set forth in the Executive

Order. ``Significant regulatory action'' is submitted to centralized

regulatory review by OIRA.

OIRA and the FAA have determined that this rule is not ``a

significant regulatory action.'' However, a cost-benefit analysis,

including evaluation of cost-reducing alternatives to this rule has

been prepared. This analysis also contains the regulatory flexibility

determination required by the Regulatory Flexibility Act and a Trade

Impact Assessment. If more detailed economic information is desired,

the reader may refer to the full evaluation contained in the docket.

Economic Evaluation

The use of the new optional rating structure will provide

significant benefits to operators of Category A helicopters. Category A

helicopters are multiengine, can withstand any single engine becoming

inoperative, and can continue safe flight or landing within a

demonstrated field size. In addition to increased payloads, the

amendments will enable rotorcraft operators to operate from

significantly smaller heliports with the same degree of safety because

of the decrease in the minimum required rejected takeoff distance for

Category A operations. The rejected takeoff distance is the distance

from the start of the takeoff to the stopping point after landing. The

current regulation puts operators using shorter fields at a

disadvantage because of the inability to satisfy Category A operational

requirements. This increased operational flexibility should enable them

to fly Category A operations and possibly use more efficient and

profitable route structures (where larger fields are not available).

The rule establishes OEI ratings for periods of shorter duration

than previously allowed and will provide an additional optional

capability to manufacturers. The testing costs associated with

obtaining these ratings should be viewed as the price of an additional

capability and will be evaluated by the individual rotorcraft

manufacturers based on market potential. The principal operational

benefit of these new optional ratings is the ability to carry higher

payloads from existing fields or to takeoff from smaller fields with

current payloads. The AIA estimates that the use of the new rating

structure for a given Category A mission could result in an increase in

productivity of 48 percent for a 37,000-pound design gross weight (DGW)

helicopter, and up to 125 percent for a 7,500-pound DGW helicopter if

operators who fly only Category A missions choose to take full

advantage of the increase in payload that will be permitted. The AIA

further notes that the public will also benefit from these changes

because the availability of viable, short-field performance should

encourage the development of downtown heliports, thereby enhancing

convenience.

For a manufacturer considering a new design, the issue of whether

to design a helicopter to accommodate engines capable of satisfying the

new OEI rating scheme (use of the new ratings will affect helicopter

performance standards as well as the structural and drive system

requirements) will be influenced by the following factors:

The availability of appropriately sized engines (larger

helicopters designed for Category A use will be able to use a smaller

engine).

The OEI capability of competitive products.

The operator mission requirements.

The cost (for increased testing and increased engine

performance) of obtaining the new OEI capability compared to the

benefit derived from the increase in payload or flexibility of route

structures afforded by this capability.

The availability of the new OEI capability could provide

substantial benefits to rotorcraft manufacturers and operators.

However, such benefits are difficult to quantify because the number of

products certificated to this standard cannot be estimated. In

addition, the specific increase in dispatch payload cannot be estimated

because it will depend on the specific rotorcraft design in relation to

the engines that will be available. These optional ratings should

enhance the ability of operators who are limited by current regulations

to Category B operations, because of the small size fields they use to

fly more Category A operations, which should improve their

profitability. The extent of these benefits cannot be predicted since

they will depend, to a large degree, on the mix of Category A and B

operations that are chosen. The FAA has not been able to quantify these

potential benefits either on a per-unit or industry-wide scale due to

the changes in rotorcraft design and performance that these optional

ratings could promote and the large number of highly variable factors

that would influence the magnitude of the overall benefits. The FAA

concludes that the optional OEI ratings will not have a negative impact

on manufacturers or operators. Since these ratings are optional,

manufacturers will provide this capability only if the additional costs

can be recovered in the market place.

The FAA maintains that, after an engine failure under the revised

regulations for limited-use ratings, safety will be at least equivalent

to operational safety under the previous regulations. This condition is

supported by the fact that these 30-second and 2-minute OEI ratings are

``limited use/mandatory inspection ratings.'' Following one mission

cycle of rating use, specific requirements for inspection will have to

be met to verify continued airworthiness of the engine. Under current

regulations, there is no requirement for an inspection following an OEI

power application. Any rotorcraft parts found to be unsuitable for

further use must be replaced after application of these ratings. As a

result of new test and analysis requirements, a high level of safety

will be maintained.

Regulatory Flexibility Determination

The Regulatory Flexibility Act of 1980 (RFA) was enacted by

Congress to ensure that small entities are not unnecessarily and

disproportionately burdened by government regulations. The RFA requires

agencies to review rules that may have ``a significant economic impact

on a substantial number of small entities.'' The FAA's criteria for a

small aircraft manufacturer is one employing fewer than 75 employees. A

substantial number is a number that is not fewer than 11 and is more

than one-third of the small entities subject to the rule. A significant

impact is one having an annual cost of more than $14,900 (1987 dollars)

per manufacturer.

A review of domestic helicopter manufacturing companies indicates

that there are fewer than eleven small helicopter manufacturers.

Therefore, the amendments to Parts 27 and 29 will not affect a

substantial number of small entities.

Trade Impact Analysis

The rule changes will have little or no impact on trade for both

U.S. firms doing business in foreign countries and foreign firms doing

business in the United States. In the U.S. market, foreign

manufacturers will have the option of designing engines and helicopters

capable of satisfying the new OEI ratings and, therefore, will not be

at a competitive disadvantage with U.S. manufacturers. Because of the

large U.S. market, foreign manufacturers are likely to certificate

their rotorcraft to U.S. rules, which will limit any competitive

advantage U.S. manufacturers might gain in foreign markets.

Federalism Implications

The regulations adopted herein 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 final

rule does not have sufficient federalism implications to warrant the

preparation of a Federalism Assessment.

Conclusion

For the reasons discussed in the preamble, and based on the

findings in the Regulatory Flexibility Determination and the Trade

Impact Analysis, the FAA has determined that this regulation is not a

significant regulatory action under Executive Order 12866. In addition,

the FAA certifies that these amendments do not have a significant

economic impact, positive or negative, on a substantial number of small

entities under the criteria of the Regulatory Flexibility Act. These

amendments are considered nonsignificant under DOT Regulatory Policies

and Procedures (44 CFR 11034; February 26, 1979). A regulatory

evaluation of the amendments, including a Regulatory Flexibility

Determination and Trade Impact Analysis, 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 Parts 27 and 29

Air transportation, Aircraft, Aviation safety, Rotorcraft, Safety.

Adoption of the Amendments

Accordingly, Parts 27 and 29 of the Federal Aviation Regulations

(14 CFR Parts 27 and 29) are amended as follows:

PART 27--AIRWORTHINESS STANDARDS: NORMAL CATEGORY ROTORCRAFT

1. The authority citation for Part 27 continues to read as follows:

Authority: 49 U.S.C. 1344, 1354(a), 1355, 1421, 1423, 1425,

1428, 1429, and 1430; 49 U.S.C. 106(g).

2. Section 27.923 is amended by revising paragraph (e) to read as

follows:

Sec. 27.923 Rotor drive system and control mechanism tests.

* * * * *

(e) A 10-hour part of the test prescribed in paragraph (b) of this

section must be run at not less than takeoff torque and the maximum

speed for use with takeoff torque. The main and auxiliary rotor

controls must be in the normal position for vertical ascent.

(1) For multiengine rotorcraft for which the use of 2\1/2\ minute

OEI power is requested, 12 runs during the 10-hour test must be

conducted as follows:

(i) Each run must consist of at least one period of 2\1/2\ minutes

with takeoff torque and the maximum speed for use with takeoff torque

on all engines.

(ii) Each run must consist of at least one period for each engine

in sequence, during which that engine simulates a power failure and the

remaining engines are run at 2\1/2\ minute OEI torque and the maximum

speed for use with 2\1/2\ minute OEI torque for 2\1/2\ minutes.

(2) For multiengine turbine-powered rotorcraft for which the use of

30-second and 2-minute OEI power is requested, 10 runs must be

conducted as follows:

(i) Immediately following a takeoff run of at least 5 minutes, each

power source must simulate a failure, in turn, and apply the maximum

torque and the maximum speed for use with 30-second OEI power to the

remaining affected drive system power inputs for not less than 30

seconds, followed by application of the maximum torque and the maximum

speed for use with 2-minute OEI power for not less than 2 minutes. At

least one run sequence must be conducted from a simulated ``flight

idle'' condition. When conducted on a bench test, the test sequence

must be conducted following stabilization at takeoff power.

(ii) For the purpose of this paragraph, an affected power input

includes all parts of the rotor drive system which can be adversely

affected by the application of higher or asymmetric torque and speed

prescribed by the test.

(iii) This test may be conducted on a representative bench test

facility when engine limitations either preclude repeated use of this

power or would result in premature engine removal during the test. The

loads, the vibration frequency, and the methods of application to the

affected rotor drive system components must be representative of

rotorcraft conditions. Test components must be those used to show

compliance with the remainder of this section.

* * * * *

3. Section 27.1143 is amended by adding paragraph (e) to read as

follows:

Sec. 27.1143 Engine controls.

* * * * *

(e) For rotorcraft to be certificated for a 30-second OEI power

rating, a means must be provided to automatically activate and control

the 30-second OEI power and prevent any engine from exceeding the

installed engine limits associated with the 30-second OEI power rating

approved for the rotorcraft.

4. Section 27.1305 is amended by adding paragraphs (t) and (u) to

read as follows:

Sec. 27.1305 Powerplant instruments.

* * * * *

(t) For rotorcraft for which a 30-second/2-minute OEI power rating

is requested, a means must be provided to alert the pilot when the

engine is at the 30-second and the 2-minute OEI power levels, when the

event begins, and when the time interval expires.

(u) For each turbine engine utilizing 30-second/2-minute OEI power,

a device or system must be provided for use by ground personnel which--

(1) Automatically records each usage and duration of power at the

30-second and 2-minute OEI levels;

(2) Permits retrieval of the recorded data;

(3) Can be reset only by ground maintenance personnel; and

(4) Has a means to verify proper operation of the system or device.

5. Section 27.1521 is amended by adding paragraphs (j) and (k) to

read as follows:

Sec. 27.1521 Powerplant limitations.

* * * * *

(j) Rated 30-second OEI power operation. Rated 30-second OEI power

is permitted only on multiengine, turbine-powered rotorcraft, also

certificated for the use of rated 2-minute OEI power, and can only be

used for continued operation of the remaining engine(s) after a failure

or precautionary shutdown of an engine. It must be shown that following

application of 30-second OEI power, any damage will be readily

detectable by the applicable inspections and other related procedures

furnished in accordance with Section A27.4 of Appendix A of this part

and Section A33.4 of Appendix A of part 33. The use of 30-second OEI

power must be limited to not more than 30 seconds for any period in

which that power is used, and by--

(1) The maximum rotational speed, which may not be greater than--

(i) The maximum value determined by the rotor design; or

(ii) The maximum value demonstrated during the type tests;

(2) The maximum allowable gas temperature; and

(3) The maximum allowable torque.

(k) Rated 2-minute OEI power operation. Rated 2-minute OEI power is

permitted only on multiengine, turbine-powered rotorcraft, also

certificated for the use of rated 30-second OEI power, and can only be

used for continued operation of the remaining engine(s) after a failure

or precautionary shutdown of an engine. It must be shown that following

application of 2-minute OEI power, any damage will be readily

detectable by the applicable inspections and other related procedures

furnished in accordance with Section A27.4 of Appendix A of this part

and Section A33.4 of Appendix A of part 33. The use of 2-minute OEI

power must be limited to not more than 2 minutes for any period in

which that power is used, and by--

(1) The maximum rotational speed, which may not be greater than--

(i) The maximum value determined by the rotor design; or

(ii) The maximum value demonstrated during the type tests;

(2) The maximum allowable gas temperature; and

(3) The maximum allowable torque.

6. Section 27.1549 is amended by revising paragraph (e) to read as

follows:

Sec. 27.1549 Powerplant instruments.

* * * * *

(e) Each OEI limit or approved operating range must be marked to be

clearly differentiated from the markings of paragraphs (a) through (d)

of this section except that no marking is normally required for the 30-

second OEI limit.

PART 29--AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT

7. The authority citation for Part 29 continues to read as follows:

Authority: 49 U.S.C. 1344, 1354(a), 1355, 1421, 1423, 1424,

1425, 1428, 1429, and 1430; 49 U.S.C. 106(g).

8. Section 29.67 is amended by revising paragraph (a)(1)(i) to read

as follows:

Sec. 29.67 Climb: one engine inoperative.

(a) * * *

(1) * * *

(i) The critical engine inoperative and the remaining engines

within approved operating limitations, except that for rotorcraft for

which the use of 30-second/2-minute OEI power is requested, only the 2-

minute OEI power may be used in showing compliance with this paragraph;

* * * * *

9. Section 29.923 is amended by revising paragraphs (a)

introductory text and (b)(1); and by adding paragraph (b)(3) to read as

follows:

Sec. 29.923 Rotor drive system and control mechanism tests.

(a) Endurance tests, general. Each rotor drive system and rotor

control mechanism must be tested, as prescribed in paragraphs (b)

through (n) of this section, for at least 200 hours plus the time

required to meet the requirements of paragraphs (b)(2), (b)(3), and (k)

of this section. These tests must be conducted as follows:

* * * * *

(b) * * *

(1) Except as prescribed in paragraphs (b)(2) and (b)(3) of this

section, the takeoff torque run must consist of 1 hour of alternate

runs of 5 minutes at takeoff torque and the maximum speed for use with

takeoff torque, and 5 minutes at as low an engine idle speed as

practicable. The engine must be declutched from the rotor drive system,

and the rotor brake, if furnished and so intended, must be applied

during the first minute of the idle run. During the remaining 4 minutes

of the idle run, the clutch must be engaged so that the engine drives

the rotors at the minimum practical r.p.m. The engine and the rotor

drive system must be accelerated at the maximum rate. When declutching

the engine, it must be decelerated rapidly enough to allow the

operation of the overrunning clutch.

* * * * *

(3) For multiengine, turbine-powered rotorcraft for which the use

of 30-second/2-minute OEI power is requested, the takeoff run must be

conducted as prescribed in paragraph (b)(1) of this section except for

the following:

(i) Immediately following any one 5-minute power-on run required by

paragraph (b)(1) of this section, each power source must simulate a

failure, in turn, and apply the maximum torque and the maximum speed

for use with 30-second OEI power to the remaining affected drive system

power inputs for not less than 30 seconds, followed by application of

the maximum torque and the maximum speed for use with 2-minute OEI

power for not less than 2 minutes. At least one run sequence must be

conducted from a simulated ``flight idle'' condition. When conducted on

a bench test, the test sequence must be conducted following

stabilization at takeoff power.

(ii) For the purpose of this paragraph, an affected power input

includes all parts of the rotor drive system which can be adversely

affected by the application of higher or asymmetric torque and speed

prescribed by the test.

(iii) This test may be conducted on a representative bench test

facility when engine limitations either preclude repeated use of this

power or would result in premature engine removals during the test. The

loads, the vibration frequency, and the methods of application to the

affected rotor drive system components must be representative of

rotorcraft conditions. Test components must be those used to show

compliance with the remainder of this section.

* * * * *

10. Section 29.1143 is amended by adding paragraph (f) to read as

follows:

Sec. 29.1143 Engine controls.

* * * * *

(f) For rotorcraft to be certificated for a 30-second OEI power

rating, a means must be provided to automatically activate and control

the 30-second OEI power and prevent any engine from exceeding the

installed engine limits associated with the 30-second OEI power rating

approved for the rotorcraft.

11. Section 29.1305 is amended by adding paragraphs (a)(24) and

(25) to read as follows:

Sec. 29.1305 Powerplant instruments.

* * * * *

(a) * * *

(24) For rotorcraft for which a 30-second/2-minute OEI power rating

is requested, a means must be provided to alert the pilot when the

engine is at the 30-second and 2-minute OEI power levels, when the

event begins, and when the time interval expires.

(25) For each turbine engine utilizing 30-second/2-minute OEI

power, a device or system must be provided for use by ground personnel

which--

(i) Automatically records each usage and duration of power at the

30-second and 2-minute OEI levels;

(ii) Permits retrieval of the recorded data;

(iii) Can be reset only by ground maintenance personnel; and

(iv) Has a means to verify proper operation of the system or

device.

* * * * *

12. Section 29.1521 is amended by adding paragraphs (i) and (j) to

read as follows:

Sec. 29.1521 Powerplant limitations.

* * * * *

(i) Rated 30-second OEI power operation. Rated 30-second OEI power

is permitted only on multiengine, turbine-powered rotorcraft, also

certificated for the use of rated 2-minute OEI power, and can only be

used for continued operation of the remaining engine(s) after a failure

or precautionary shutdown of an engine. It must be shown that following

application of 30-second OEI power, any damage will be readily

detectable by the applicable inspections and other related procedures

furnished in accordance with Section A29.4 of Appendix A of this part

and Section A33.4 of Appendix A of part 33. The use of 30-second OEI

power must be limited to not more than 30 seconds for any period in

which that power is used, and by--

(1) The maximum rotational speed which may not be greater than--

(i) The maximum value determined by the rotor design; or

(ii) The maximum value demonstrated during the type tests;

(2) The maximum allowable gas temperature; and

(3) The maximum allowable torque.

(j) Rated 2-minute OEI power operation. Rated 2-minute OEI power is

permitted only on multiengine, turbine-powered rotorcraft, also

certificated for the use of rated 30-second OEI power, and can only be

used for continued operation of the remaining engine(s) after a failure

or precautionary shutdown of an engine. It must be shown that following

application of 2-minute OEI power, any damage will be readily

detectable by the applicable inspections and other related procedures

furnished in accordance with Section A29.4 of Appendix a of this part

and Section A33.4 of Appendix A of part 33. The use of 2-minute OEI

power must be limited to not more than 2 minutes for any period in

which that power is used, and by--

(1) The maximum rotational speed, which may not be greater than--

(i) The maximum value determined by the rotor design; or

(ii) The maximum value demonstrated during the type tests;

(2) The maximum allowable gas temperature; and

(3) The maximum allowable torque.

13. Section 29.1549 is amended by revising paragraph (e) to read as

follows:

Sec. 29.1549 Powerplant instruments.

* * * * *

(e) Each OEI limit or approved operating range must be marked to be

clearly differentiated from the markings of paragraphs (a) through (d)

of this section except that no marking is normally required for the 30-

second OEI limit.

Issued in Washington, D.C., on September 9, 1994.

David R. Hinson,

Administrator.

[FR Doc. 94-22970 Filed 9-15-94; 8:45 am]

BILLING CODE 4910-13-M