[Federal Register Volume 60, Number 212 (Thursday, November 2, 1995)]
[Rules and Regulations]
[Pages 55774-55776]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-27225]




[[Page 55773]]

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Part III





Department of Transportation





_______________________________________________________________________



Federal Aviation Administration



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14 CFR Part 29



Airworthiness Standards; Rotocraft Engine Rotor Burst Protection; Final 
Rule

  Federal Register / Vol. 60, No. 212 / Thursday, November 2, 1995 / 
Rules and Regulations  

[[Page 55774]]


DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 29

[Docket No. 26037; Amendment No. 29-36]
RIN 2120-AB91


Airworthiness Standards: Rotorcraft Engine Rotor Burst Protection

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

-----------------------------------------------------------------------

SUMMARY: This final rule amends the airworthiness regulations to 
require that manufacturers of new design transport category rotorcraft 
minimize the adverse effects of a turbine engine rotor failure. Turbine 
engine rotor failures have occurred resulting in the release of high 
energy engine rotor fragments or other engine component fragments. 
These fragments have damaged critical rotorcraft structures, systems, 
controls, and adjacent engines, as well as caused serious or fatal 
injuries to passengers and crewmembers. This action is intended to 
minimize these hazards.

EFFECTIVE DATE: January 31, 1996.

FOR FURTHER INFORMATION CONTACT:
Mr. Ron Dalton, Federal Aviation Administration (FAA), Rotorcraft 
Directorate, Rotorcraft Standards Staff, Fort Worth, TX 76193-0110, 
telephone (817) 222-5127.

SUPPLEMENTARY INFORMATION:

Background

    A Notice of Proposed Rulemaking (NPRM) No. 89-29 was published in 
the Federal Register on October 17, 1989 (54 FR 42716), and the comment 
period was reopened by NPRM No. 89-29A, published in the Federal 
Register on January 14, 1993 (58 FR 4566). These NPRMs proposed to 
amend 14 CFR part 29 (part 29) to require designs that would minimize 
the hazards associated with the failures of turbine engine (engine) 
rotors in newly designed transport category rotorcraft. Since there has 
not been an adverse service history for normal category rotorcraft, 
similar changes to 14 CFR part 27 were not proposed. If an adverse 
service history for normal category rotorcraft should develop, similar 
changes to 14 CFR part 27 would be considered.

National Transportation Safety Board (NTSB) Recommendation

    This amendment responds to NTSB Safety Recommendation A-84-60 dated 
June 14, 1984. The NTSB recommends that the FAA review engine 
compartment design of all U.S. type certificated ``multiengined 
helicopters with regard to the probability that an uncontained engine 
failure will result in catastrophic damage to the drive train, 
electrical, and/or fuel and hydraulic system components.'' This rule 
responds directly to the recommendation.

Provisions of NPRM Nos. 89-29 and 89-29A

    NPRM No. 89-29 proposed changes to 14 CFR 29.901 and 29.903 
(Secs. 29.901 and 29.903) to increase the safety margin by requiring 
designs that minimize the hazards to transport category rotorcraft in 
the event of an engine rotor failure. The required designs may include 
items such as separation or duplication of critical components, engine 
location to reduce risk, or placement of critical components in benign 
locations. Containment provisions for one or more stages of the engine 
were not specifically proposed by that proposal; however, as stated in 
Notice No. 89-29A, containment provisions could be one of several 
effective means of compliance.
    NPRM No. 89-29A reopened the comment period and invited comments 
only on the issues of engine rotor containment and the use of advanced 
composite material. NPRM No. 89-29A also provided further clarification 
of the intent of the NPRM. Specifically, the FAA clarified that when 
evaluating an applicant's proposed method of compliance, the FAA would 
consider the available technology and the costs required to minimize 
the hazards from an engine rotor failure. The FAA also noted that 
engine rotor containment features have not been specifically required 
in airplane designs that comply with 14 CFR 23.903 and 25.903 
(Secs. 23.903 and 25.903). Likewise, containment features would not be 
specifically required in rotorcraft to minimize the hazards of an 
engine rotor failure. The guidance contained in Advisory Circular (AC) 
20-128, ``Design Considerations for Minimizing Hazards Caused by 
Uncontained Turbine Engine and Auxiliary Power Unit Rotor and Fan Blade 
Failures,'' is applicable to the requirements of Sec. 29.903 in the 
same way it now applies to Secs. 23.903 and 25.903 for airplanes. 
Furthermore, the guidance in AC-29-2A, ``Certification of Transport 
Category Rotorcraft,'' supplements that in AC 20-128.

Comments to NPRM Nos. 89-29 and 89-29A

    Three commenters fully supported the proposals of NPRM No. 89-29. 
Three other commenters, including the Aerospace Industries Association 
(AIA), requested that the NPRM be withdrawn because they believed it 
strongly implied that the intent of the proposed rule was to require 
the designer to eliminate the hazards associated with the failure of an 
engine rotor through the use of containment devices made of advanced 
composite material. As discussed above, it was not the intent of NPRM 
No. 89-29 to require containment or the use of advanced composite 
materials; containment devices made of composite materials could be one 
means of compliance. Since this was unclear to the three commenters, 
several meetings with representatives of AIA were held. Subsequently, 
the FAA issued NPRM No. 89-29A, which reopened the comment period with 
a further explanation of the proposed amendments.
    Two comments were received in response to NPRM No. 89-29A. Neither 
commenter addressed the issues of engine rotor containment or the use 
of advanced composite material. As stated earlier in this document, 
request for comments on these issues was the reason for reopening the 
comment period for NPRM No. 89-29A.
    One commenter simply restated an opinion submitted in response to 
NPRM No. 89-29 that minimizing hazards resulting from engine rotor 
failures in helicopters is impractical. The other commenter disagreed 
with the proposed wording of Sec. 29.903. The commenter observed that 
the wording, ``Design procedures must be taken to minimize the hazards 
to the rotorcraft in the event of an engine rotor failure * * *,'' has 
been applied to fixed wing aircraft for some time with little or no 
success. The FAA disagrees that minimizing the hazards of engine rotor 
failure is impractical or that compliance with similar requirements for 
airplanes has not been successful. Based on a review of rotorcraft 
service history and engineering studies, the FAA concludes that the 
need for this amendment has been adequately demonstrated and shown to 
be practical for rotorcraft.
    The proposed change to Sec. 29.903 was inadvertently stated as 
revising paragraph (f). The correct cite should have been to paragraph 
Sec. 29.903(d). This error is corrected in this final rule. The FAA 
adopts the changes to Secs. 29.901 and 29.903 as proposed, except for 
the noted paragraph correction.

Regulatory Evaluation Summary

    Proposed changes to Federal regulations must undergo several 
economic analyses. First, Executive Order 12866 directs that each 
Federal 

[[Page 55775]]
agency shall propose or adopt a regulation only upon a reasoned 
determination that the benefit 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.

Costs

    On the basis of estimates from FAA and industry, incremental 
development and certification costs are estimated to be $33,600 per 
type certification project. Incremental manufacturing costs are 
estimated to be $560 for each single-engine rotorcraft and $1,120 for 
each twin-engine rotorcraft.
    In addition to increasing the acquisition costs of newly 
certificated rotorcraft, the rule could result in weight penalties. FAA 
and industry analyses suggest that this weight penalty could be as much 
as 6 pounds per engine. Each additional pound of weight increases fuel 
consumption for an average part 29 rotorcraft by approximately 0.0597 
gallons per flight hour. Assuming 527 flight hours per year for an 
average part 29 rotocraft, compliance with the rule will increase 
annual fuel consumption by about 31.46 gallons per pound of additional 
weight. Using a forecast jet fuel price of $1.78 per gallon, annual 
fuel costs could rise by about $56 per additional pound, or about $366 
per single engine transport rotorcraft, or $672 per twin-engine 
transport rotorcraft, respectively, per year.
    Assuming a production run of 15 years during which 10 aircraft are 
produced per year and assuming that each rotorcraft has an operating 
life of 15 years, the average costs of compliance are $5,824 for a 
single-engine rotorcraft and $11,425 for a twin-engine rotorcraft. 
Applying a discount rate of 7 percent, the average costs of compliance 
for single-engine and twin-engine rotorcraft are $2,271 and $4,326, 
respectively, at present value.

Benefits of Prevented Rotorcraft Damage and Loss

    The assessment of the hazards of uncontained turboshaft engine 
rotor bursts is based on data from the FAA, the Society of Automotive 
Engineers (SAE), and the National Transportation Safety Board (NTSB). 
For the period 1984 through 1989, in a sample representing 35.4 million 
flight hours and 44.3 million hours of engine operation, the FAA/SAE 
Committee on Uncontained Turbine Engine Rotor Events identified 68 
engine rotor separation events, which resulted in the escape of rotor 
fragments through the engine casing or the inlet structure. Thirty-
eight of those 68 events culminated in damage to rotorcraft structure 
or systems (other than the engine itself) or injuries to occupants. Of 
these, 17 events involved the release of turbine disk or spacer 
fragments which directly resulted in substantial damage to or loss of 
the aircraft. In the remaining 21 cases, damage and/or injuries were 
not directly attributed to the uncontained failure, but were ascribed 
to other causes. These 21 cases are excluded from the benefit 
calculations.
    Assuming 527 annual airborne hours for an average part 29 
rotorcraft, FAA estimates the annual average probabilities that a 
transport rotorcraft will be substantially damaged or destroyed as a 
direct result of an uncontained turbine rotor burst are 0.00012 and 
0.00066 for single- and twin-engine rotorcraft respectively.
    The benefits of prevented rotorcraft damage and loss are the 
avoided replacement and repair costs that would otherwise be incurred 
in the absence of compliance with this rule. In this analysis, average 
new unit costs of single- and twin-engine part 29 rotorcraft are 
estimated to be $3.200 million and $4.275 million respectively. 
Replacement cost is assumed to equal one-half the original new list 
price, and restoration cost is estimated to be 13 percent of 
replacement cost. The expected annual per-aircraft benefit of prevented 
rotorcraft damage and loss is the weighted sum of replacement and 
restoration costs where the weights are determined by the respective 
probabilities of aircraft damage or loss. The FAA/SAE data included 2 
single-engine rotorcraft destroyed, and 4 single-engine rotorcraft 
damaged, in 26.6 million flight hours; it also included 4 twin-engine 
rotorcraft destroyed, and 7 twin-engine rotorcraft damaged, in 8.8 
million flight hours. The FAA concludes that the annual average 
benefits of prevented rotorcraft damage are about $80 for single-engine 
rotorcraft and $628 for twin-engine rotorcraft.
    Under the same production run, operating life, and discount rate 
assumptions used to derive average costs, the FAA estimates the 
expected benefits of prevented aircraft damage/loss are $1,197 per 
single-engine rotorcraft and $9,413 per twin-engine rotorcraft, or $412 
and $3,243 at present value, respectively.

Benefits of Prevented Injuries and Fatalities

    Using data from the FAA and the NTSB, the FAA identified five 
fatalities and eight injuries resulting from the uncontained events 
documented by the FAA/SAE Committee. Two of the fatalities occurred as 
the result of a failed autorotation landing involving a single-engine 
category B rotorcraft. In this case, the rotor burst did not directly 
cause the failed landing and, therefore, the fatalities were excluded 
from this analysis. The remaining three fatalities and three of the 
injuries occurred in twin-engine rotorcraft. Five of the injuries 
occurred in single-engine rotorcraft. Based on the available casualty 
history, the FAA concludes that in 8.8 million twin-engine part 29 
rotorcraft flight hours, the rule could prevent 3 fatalities, 1 serious 
injury, and 2 minor injuries. The FAA also concludes that in 26.6 
million single-engine part 29 rotorcraft flight hours, the rule could 
prevent 2 serious injuries and 3 minor injuries.
    Assuming 527 annual flight hours for a typical part 29 rotorcraft, 
and based on costs of $2.5 million, $640,000 and $5,000 per each 
fatality, serious injury, and minor injury, respectively, the average 
annual benefits derived from avoiding fatalities and injuries are about 
$488 per twin-engine transport rotorcraft and $26 per single-engine 
rotorcraft.
    Using the production run, operating life, discount rate, and other 
assumptions listed above, the FAA estimates that the benefits of 
avoided injuries and fatalities are $385 per single-engine rotorcraft, 
and $7,321 per twin-engine rotorcraft, or $133 and $2,523 at present 
value, respectively.

Cost-Benefit Summary

    With respect to twin-engine rotorcraft, the benefits of avoided 
aircraft damage and avoided fatalities and injuries are expected to 
exceed the estimated development, certification, manufacturing and 
operating costs of the rule by a margin of roughly 1.3 to 1 ($5,766 to 
$4,326 in present value terms).

[[Page 55776]]

    The benefits for single-engine rotorcraft, however, are less clear. 
Because part 29 rotorcraft type-certificate applications for single 
engine rotorcraft are unlikely, FAA's economic analysis of single-
engine types concludes that the rule will be cost-beneficial only if 
design and manufacturing costs are modest. It should be noted that the 
analysis of the benefits of prevented injuries and fatalities, 
summarized above, does not assume that a fatality from operation of a 
single-engine part 29 rotorcraft would be prevented; therefore, the 
prevention of one fatality that would have occurred but for compliance 
with this rule, would make benefits clearly exceed costs.

International Trade Impact Statement

    The rule will have little or no effect on trade for either U.S. 
firms marketing rotorcraft in foreign markets or foreign firms 
marketing rotorcraft in the U.S. Each applicant for a new type 
certificate for a transport category rotorcraft, whether the applicant 
be U.S. or foreign, will be required to show compliance with this rule. 
The rule harmonizes with proposed European Joint Aviation Requirements.

Regulatory Flexibility Determination

    The Regulatory Flexibility Act (RFA) of 1980 was enacted by 
Congress to ensure that small entities are not unnecessarily or 
disproportionately burdened by Government regulations. The RFA requires 
a Regulatory Flexibility Analysis if a rule is expected to have a 
``significant economic impact on a substantial number of small 
entities.''
    Based on the standards and thresholds specified in implementing FAA 
Order 2100.14A, Regulatory Flexibility Criteria and Guidance, the FAA 
has determined that the rule will not have a significant impact on a 
substantial number of small entities, because there are no ``small 
entity'' rotorcraft manufacturers, as defined in the order.

Federalism Implications

    The regulations 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 regulation will not have 
sufficient federalism implications to warrant the preparation of a 
Federalism Assessment.

Conclusion

    For the reasons discussed above, and based on the findings in the 
Regulatory Flexibility Determination and the International 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 this regulation will not have a significant 
economic impact, positive or negative, on a substantial number of small 
entities under the criteria of the RFA. This regulation is not 
considered to be significant under DOT Order Regulatory Policies and 
Procedures (44 FR 11034; February 26, 1979). A final regulatory 
evaluation of the regulation, including a final Regulatory Flexibility 
Determination and International 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 Part 29

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

The Amendment

    Accordingly, the FAA amends part 29 of the Federal Aviation 
Regulations (14 CFR part 29) as follows:

PART 29--AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT

    1. The authority citation for part 29 is revised to read as 
follows:

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

    2. Section 29.901 is amended by revising paragraph (c) to read as 
follows:


Sec. 29.901  Installation.

* * * * *
    (c) For each powerplant and auxiliary power unit installation, it 
must be established that no single failure or malfunction or probable 
combination of failures will jeopardize the safe operation of the 
rotorcraft except that the failure of structural elements need not be 
considered if the probability of any such failure is extremely remote.
* * * * *
    3. Section 29.903 is amended by revising paragraph (d) to read as 
follows:


Sec. 29.903  Engines.

* * * * *
    (d) Turbine engine installation. For turbine engine installations--
    (1) Design precautions must be taken to minimize the hazards to the 
rotorcraft in the event of an engine rotor failure; and
    (2) The powerplant systems associated with engine control devices, 
systems, and instrumentation must be designed to give reasonable 
assurance that those engine operating limitations that adversely affect 
engine rotor structural integrity will not be exceeded in service.
* * * * *
    Issued in Washington, DC, on October 6, 1995.
David R. Hinson,
Administrator.
[FR Doc. 95-27225 Filed 11-1-95; 8:45 am]
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