[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]]
_______________________________________________________________________
Part III
Department of Transportation
_______________________________________________________________________
Federal Aviation Administration
_______________________________________________________________________
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.
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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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