Source: https://www.federalregister.gov/documents/2007/09/04/E7-17369/airworthiness-standards-aircraft-engine-standards-for-engine-life-limited-parts
Timestamp: 2018-04-22 14:50:02
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Federal Register :: Airworthiness Standards; Aircraft Engine Standards for Engine Life-Limited Parts
Airworthiness Standards; Aircraft Engine Standards for Engine Life-Limited Parts
72 FR 50855
50855-50861 (7 pages)
Docket No.: FAA-2006-23732
Amendment No. 33-22
2120-AI72
E7-17369
Definitions of Terms Used in the Rule
Regulations Affecting Static Parts
Definition of “Likely to Result”
Costs of Rule
Parts Manufacturer Approval Standards
Required Information, Use, and Respondents
https://www.federalregister.gov/d/E7-17369 https://www.federalregister.gov/d/E7-17369
The FAA is amending the certification standards for original and amended type certificates for aircraft engines by modifying the standards for engine life-limited parts. This final rule establishes new and uniform standards for the design and testing of life-limited parts for aircraft engines certificated by the FAA and the European Aviation Safety Agency (EASA). This rule retains the current lifing requirements, introduces damage tolerance requirements into the design process, and strengthens cooperation between engineering, manufacturing, and service elements of turbine engine manufacturers. These new requirements provide an added margin of safety and will reduce the number of life-limited parts failures due to material, manufacturing, and service induced anomalies. Additionally, this action adds new standards for the design of reciprocating engine turbocharger rotors.
This rulemaking is promulgated under the authority described in Subtitle VII, Part A, Subpart III, Section 44701, “General Requirements.” Under that section, the FAA is charged with prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce, including minimum safety standards for aircraft engines. This regulation is within the scope of that authority because it updates the existing regulations for aircraft engine life-limited parts.
Manufacturing-induced anomalies in engine disks have caused several fatal airplane accidents, notably in Sioux City, Iowa, in 1989, and in Pensacola, Florida, in 1996. The DC-10 crash in Sioux City was caused by a titanium material anomaly created during the material melting process. The MD-88 accident in Pensacola was attributed to a fatigue crack which initiated from an abnormal microstructure created during manufacturing. Most of the uncontained engine failures have been traced to material, manufacturing or operations/maintenance induced anomalies. Recent examples include:
Failure of a CF6 engine high pressure stage 1 turbine disk on a Boeing 767 airplane during a ground test at Los Angeles International Airport in June 2006, that was attributed to a manufacturing-induced anomaly in a rim slot; and
In-flight failure of a CF34 engine fan disk on a Bombardier CRJ-200 airplane departing Denver International Airport on January 25, 2007. The root cause of this failure is currently under investigation.
Industry data has shown that manufacturing-induced anomalies have caused about 40 percent of recent rotor cracking and failure events. Data for the period 1984 to 1989 indicates that uncontained engine failures due to material, manufacturing and maintenance induced anomalies occur at the rate of 1.2 per 10 million flights or approximately 3 events per year. Due to these accidents and the supporting data, the FAA determined the need to revise engine certification standards related to the design of engine parts whose failure would result in a hazardous engine condition.
In addition, a group representing the FAA, the engine industry, and European aviation authorities has worked since 1989 to revise and harmonize the U.S. and European engine certification requirements. This rule, which is based on this group's recommendations, creates common U.S. and European engine requirements for turbine engine life-limited parts (called “critical parts” in European regulations).
The following definitions are provided, but are not part of the rule itself:
Primary failure: Failure of a part that is not the result of a prior failure of another part or system.
Failure: Separation of a part into two or more pieces such that the part is no longer whole or complete.
Likely to result: Possible outcomes on an engine or aircraft when a part fails, regardless of probability of occurrence.
The following safety recommendation, issued by National Transportation Safety Board (NTSB), is addressed by this rule:
NTSB Safety Recommendation A-90-90 was issued as a result of the United Airlines accident on July 19, 1989, in Sioux City, Iowa, where 111 people died and 172 were injured. The NTSB recommended that the FAA amend 14 CFR part 33 “to require that turbine engines certificated under this rule are evaluated to identify those engine components that, if they should fracture and separate, could pose a significant threat to the structure or systems of an airplane; and require that a damage tolerance evaluation of these components be performed.”
The FAA has regulated static parts for more than a decade under § 33.19(a), which requires the engine be designed and constructed to minimize the development of an unsafe condition between overhaul periods. Experience with several types of static parts has shown that fatigue failures can result in hazardous engine effects. For example, high-pressure casing fatigue failures have led to high pressure vessel bursts and fire. Issue papers initiated by the FAA, based on § 33.19, have resulted in engine manufacturers classifying a limited number of static parts as “life-limited.” Life-limited parts are included in the Airworthiness Limitations Section of the Instructions for Continued Airworthiness.
The new § 33.70 affects only those static parts whose failure could result in a hazardous engine effect. Therefore, only a limited number of static parts will be classified as “life-limited parts” and affected by the new rule. Those static parts formerly regulated under § 33.19 are more properly located under § 33.70, which is based on whether the failure of a part could cause a hazardous Start Printed Page 50857engine effect rather than whether a part rotates or is static.
New § 33.70 replaces § 33.14. Section 33.70 introduces the term “engine life-limited parts” to cover rotating structural parts, as well as major static structural parts, whose primary failure is likely to result in a hazardous engine effect, as listed in § 33.75, and whose failure mode is either cycle (fatigue) or time (creep) dependent. This rule addresses all parts, rotating or static, that meet the definition of an engine life-limited part. The rule requires FAA approval of the procedures used to establish life limits and address anomalies.
This rule retains the current life methodology which limits the useful rotor life to the minimum number of flight cycles required to initiate a crack approximately 0.030 inches in length by 0.015 inches in depth. The rule requires sufficient analysis and testing to evaluate the effects of elevated temperatures and hold times as well as the interaction with other failure mechanisms (for example, high cycle fatigue, creep, and cold-dwell). The methodology used to establish life limits for static parts is similar to those used for rotating parts. For static parts, the life limit may be based on the crack initiation life plus a portion of the residual crack growth life, providing a safe margin is maintained between part retirement life and failure.
The rule also requires applicants to develop coordinated engineering, manufacturing, and service management plans for each life-limited part. This will ensure the attributes of a part that determine its life are identified and controlled so that the part will be consistently manufactured and properly maintained during service operation.
The rule introduces new requirements for applicants to conduct damage tolerance assessments to limit the potential for failure from material, manufacturing, and service induced anomalies. Applicants can use a variety of methods to conduct damage tolerance assessments. For example, applicants can use probabilistic risk assessments or design a part to have a specified crack growth life. The introduction of damage tolerance does not allow rotor components to remain in service with cracks. Rotor parts must be removed from service when the parts reach the end of their useful life as defined by the minimum number of flight cycles required to initiate a crack.
This rule removes turbocharger rotor life requirements from § 33.14 and places them in a new § 33.34.
The FAA published a Notice of Proposed Rulemaking (NPRM) entitled Airworthiness Standards: Aircraft Engine Standards for Engine Life-Limited Parts on February 2, 2006 (71 FR 5770). Nine commenters responded to the NPRM request for comments. The commenters included three turbine engine manufacturers; two domestic airplane operators, who submitted through their representative association; two foreign regulatory authorities; a domestic parts manufacturer; and an individual. The turbine engine manufacturers fully support the rule while proposing minor changes. Other commenters, including two airline operators and a parts manufacturer, believe that inclusion of structural static parts as life-limited parts in the rule would substantially increase their costs and affect the potential of small businesses to repair life-limited parts.
Those static parts that meet the definition of “life-limited,” as established by § 33.70, require FAA approval of the procedures used to establish life limits and address anomalies related to those parts.
Two airline operators and a parts manufacturer stated that the rule should not impose life limits on static parts. American Airlines stated that the FAA is introducing a new requirement that “all structural parts, both rotating and static are to be addressed as Engine Life-Limited Parts.” American noted that based on Continued Airworthiness Assessment Methodologies (CAAM) data from 1992 to 2000 “the probability of occurrence of case ruptures is very small” and “there does not seem to be a good reason to consider static cases or other static parts as life-limited, and they should not be.” Similarly, United Airlines “does not see imposing life limits on this static hardware as enhancing safety.” Chromalloy Gas Turbine Corporation found “that the FAA has not identified sufficient, nor appropriate substantiating cause to make such a bold change as to include static structures (high pressure turbine casings) under the term life-limited parts.”
The FAA believes it is essential to include a limited number of structural static parts in the rules as service experience has demonstrated that failure of these parts may result in hazardous consequences to an aircraft. We also find that inclusion of certain static parts under § 33.70 does not impose a new requirement for turbine engine manufacturers who currently meet the requirements of § 33.19, Durability, and EASA certification requirements. We find that turbine engine manufacturers, based on § 33.19 and issue papers, have classified a limited number of static parts as “life-limited” for at least the last decade. Examples of engines with static parts classified as “life-limited” include: The CF34 (GE) family of engines, installed on Bombardier and Embraer regional jets; GE90 Growth family of engines, installed on the Boeing 777; Engine Alliance's (General Electric and Pratt & Whitney) GP7200 engine, installed on the Airbus A-380; and GEnx engine, to be installed on the Boeing 787.
All engine manufacturers who desire certification in Europe must also meet EASA engine certification requirements. Under EASA requirements, CS-E 515, Engine Critical Parts, turbine engine manufacturers already classify a limited number of static parts as “life-limited” and include these parts in the Airworthiness Limitations Section of the Instructions for Continued Airworthiness. Imposing two different standards for engine certification on U.S. engine manufacturers increases the costs of developing and certifying aircraft turbine engines with no associated safety benefits.
We note that CAAM data covers the period from 1982 to 1996. Based on this data, rupture of engine cases was the 10th leading cause of level 3 or 4 events (significant damage or total loss to aircraft, or minor injuries or loss of life).
Section 33.70 establishes that “Engine life-limited parts are rotor and major static structural parts whose primary failure is likely to result in a hazardous engine effect.” The term “likely to result” in this rule refers to possible consequences that may occur from an engine part failure.
American Airlines took issue with the definition and use of the term “likely to result.” American commented that “likely to result” is “not clearly defined” and “does not agree with the SAE (Society of Automotive Engineers) interpretation for CAAM analysis.” American also believes that the definition goes beyond the current § 33.14 and forces consideration of all failures no matter how remote the possibility of occurrence.
We have clarified that “likely to result” refers to possible consequences to an engine or aircraft that may occur from an engine part failure. The consequence of failure determines if a part is considered a life-limited part.
The commenter's reference to an SAE interpretation of “likely to result,” used Start Printed Page 50858during CAAM analysis, deals with failures that have already occurred in service. The SAE interpretation is appropriate for analysis of failures that already occurred, but is not appropriate for a certification rule that applies to an engine manufacturer during the design and certification process. The definition of “likely to result” does not apply or alter the corresponding definition used by CAAM techniques.
The definition is consistent with current § 33.14 that states a life limit must be established for each rotor part, “the failure of which could produce a hazard to the aircraft.” It is absolutely essential to safety that the consequences of failure are anticipated to ensure appropriate engine parts are designated as life-limited parts. Once a part is designated as life-limited, a vast array of quality standards is applied to the part to prevent the unsafe consequences.
American Airlines expressed concern that the rule would result in “unjustifiable additional costs.” United Airlines stated that the rule will “significantly drive up operator's costs.” United claimed that “the slightest defect, insignificant or otherwise, will result in a part being held-up in its repair cycle, while FAA Approved Data is sought. * * * To compensate, operators will be forced to increase inventory levels of this expensive hardware.”
The rule may result in a small increase in the number of static parts classified as “life-limited” beyond those few major structural static parts currently classified as life-limited under existing regulations. In addition, static parts are usually designed to have a life consistent with the life of the engine. Unlike rotor parts, static parts are repaired and their life is extended, provided their life limits are re-established using approved methods. The classification of static parts as life-limited requires engine manufacturers to design these parts to a higher standard including validation of life. The design of these parts to a higher standard, as well as the need to meet higher quality control manufacturing standards, has the potential to reduce the number of required repairs.
Chromalloy Gas Turbine Corporation commented that “With regard to static structural parts, there are many small entities that perform the maintenance tasks on these parts in direct competition with Original Engine Manufacturers.” Chromalloy further claimed that “The proposed rule change will severely affect the ability of these many entities to develop and perform repairs for the static structural parts independent of the Original Engine Manufacturers.”
We do not agree that the rule prevents any entities from performing maintenance on life-limited parts (“static” or “rotating”). Any entity, however, that repairs critical aircraft engine parts must possess the necessary inspection, design, analysis, and engineering skills to evaluate whether a repair is done properly. The safety of the part depends on the applicant possessing these skills.
Rolls-Royce Corporation noted that the rule requires a Service Management Plan that defines in-service processes for maintenance and repair, and that these processes become part of the Instructions for Continued Airworthiness (ICA). Rolls-Royce commented that the “rule could be interpreted to require that all engine life-limited repair processes be defined by the Design Approval Holder (DAH) and subsequently `made available' under the normal ICA requirements. * * *”
We revised the rule to require an applicant to specify the “limitations” associated with a part's repair instead of actually defining the repair process.
Transport Canada commented that life-limited parts are not acceptable candidates for Parts Manufacturer Approval (PMA) and FAA should reconsider PMA standards.
PMA standards are beyond the scope of this rule. Therefore, we did not make any changes in response to this comment.
As required by the Paperwork Reduction Act of 1995 (44 U.S.C. 3507(d)), the FAA submitted a copy of the amended information collection requirements(s) in this final rule to the Office of Management and Budget (OMB) for its review. OMB approved the collection of this information and assigned OMB Control Number 2120-0665.
This final rule consists of regulatory changes that will affect operators and individuals performing repairs. Some of those changes will require additional information collection. Comments received about these requirements and the FAA's responses are discussed earlier in this document, under the Comments section. The new information requirements and the persons who would be required to provide that information are described below.
Operators 995 $ 49,750
Maintenance Providers 498 37,350
Additional recordkeeping will occur, because operators will be required to track the life of the part.
Additional engineering analysis will be performed anytime an affected part is repaired.
One-thousand nine-hundred and ninety (1,990) is the average number of affected aircraft and the corresponding estimated number of engine removals is 498 (1,990 × 25%).
The recordkeeping cost estimate includes estimates of shop and records personnel time for tracking the part when an engine is removed. The total estimated recordkeeping time requirement is 2 hours per additional part per engine removal.
We calculate the annual recordkeeping hours by multiplying the additional number of parts (1), by the number of hours per part (2). That product is then multiplied by the annual number of engine removals (498), to arrive at the annual hour Start Printed Page 50859estimate of 995. When combined with the burdened labor rate of $50 per hour, the estimated annual cost is $49,750.
Additional engineering analysis will be required because operators and maintenance providers handle repairs differently on life-limited parts because of the critical nature of the part. More detailed analysis is performed, in addition to life methodology checks, when a life-limited part is repaired.
We calculated the annual engineering hours of 498 by multiplying the additional number of hours per part (10) by the annual number of engine removals (498) and then by the 10% repair factor. When combined with the burdened labor rate of $75 per hour, the estimated annual cost is $37,350.
Changes to Federal regulations must undergo several economic analyses. First, Executive Order 12866 directs that each Federal agency shall propose or adopt a regulation only upon a reasoned determination that the benefits of the intended regulation justify its costs. Second, the Regulatory Flexibility Act of 1980 (Pub. L. 96-354) requires agencies to analyze the economic impact of regulatory changes on small entities. Third, the Trade Agreements Act (Pub. L. 96-39) prohibits agencies from setting standards that create unnecessary obstacles to the foreign commerce of the United States. In developing U.S. standards, this Trade Act requires agencies to consider international standards and, where appropriate, that they be the basis of U.S. standards. Fourth, the Unfunded Mandates Reform Act of 1995 (Pub. L. 104-4) requires agencies to prepare a written assessment of the costs, benefits, and other effects of proposed or final rules that include a Federal mandate likely to result in the expenditure by State, local, or tribal governments, in the aggregate, or by the private sector, of $100 million or more annually (adjusted for inflation with base year of 1995). This portion of the preamble summarizes the FAA's analysis of the economic impacts of this final rule. Readers seeking greater detail may read the full regulatory evaluation, a copy of which we have placed in the docket for this rulemaking.
There will be an overall benefit to manufacturers as a result of having common certification processes in the United States and in Europe. In addition to these benefits, the requirements contained in this final rule will provide an added margin of safety by reducing the number of failures in life-limited parts due to material, manufacturing and service induced anomalies. The FAA believes it is essential to include a limited number of structural static parts in the rules as service experience has demonstrated that failure of these parts can result in hazardous consequences to an aircraft. This final rule will prevent a portion of uncontained engine failures. If only one event is averted over the period of analysis, the benefits will be $11.6 million ($3.5 million present value).
The FAA estimates the total costs from implementing this final rule are roughly $3.6 million ($1.0 million present value). These costs are comprised of engineering and recordkeeping costs.
The estimated benefits of at least $11.6 million ($3.5 million present value) are greater than the estimated cost of $3.6 million ($1.0 million present value). Accordingly, the final rule is cost-beneficial.
Part 33 Engine Manufacturers
Operators of future part 33 engines
Entities performing maintenance and repairs
Period of analysis—2008 through 2050
The purpose of this analysis is to provide the reasoning underlying the FAA determination. The FAA has determined that:
There will not be a significant impact on a substantial number of part 33 manufacturers.
There will not be a significant impact on a substantial number of small entities that perform maintenance or repairs on affected parts.
There will not be a significant impact on a substantial number of small operators.
Part 33 manufacturers will receive the certification harmonization savings that will arise as a result of this final rule. There will not be a significant impact on a substantial number of small entities performing maintenance or repairs on affected parts because their expected revenue will be greater than the expected cost. There will not be a significant impact on a substantial number of small airline operators because the ratio of compliance cost to revenue was below 0.03 (three hundredths) of one percent for 49 small entities where data was available.
A full discussion of the agency's regulatory flexibility analysis can be found in the final regulatory evaluation, which has been placed in the docket for this rulemaking. Start Printed Page 50860
You may search the electronic form of all comments received in any of our dockets by the name of the individual submitting the comment (or signing the comment, if submitted on behalf of an association, business, labor union, etc.). You may review DOT's complete Privacy Act statement in the Federal Register published on April 11, 2000 (Volume 65, Number 70; Pages 19477-78) or you may visit http://dms.dot.gov.
§ 33.14
2. Remove § 33.14.
3. Add new § 33.34 to read as follows:
4. Add new § 33.70 to read as follows:
Engine life-limited parts.
By a procedure approved by the FAA, operating limitations must be established which specify the maximum allowable number of flight cycles for each engine life-limited part. Engine life-limited parts are rotor and major static structural parts whose primary failure is likely to result in a hazardous engine effect. Typically, engine life-limited parts include, but are not limited to disks, spacers, hubs, shafts, high-pressure casings, and non-redundant mount components. For the purposes of this section, a hazardous engine effect is any of the conditions listed in § 33.75 of this part. The applicant will establish the integrity of each engine life-limited part by:
(a) An engineering plan that contains the steps required to ensure each engine life-limited part is withdrawn from service at an approved life before hazardous engine effects can occur. These steps include validated analysis, test, or service experience which ensures that the combination of loads, material properties, environmental influences and operating conditions, including the effects of other engine parts influencing these parameters, are sufficiently well known and predictable Start Printed Page 50861so that the operating limitations can be established and maintained for each engine life-limited part. Applicants must perform appropriate damage tolerance assessments to address the potential for failure from material, manufacturing, and service induced anomalies within the approved life of the part. Applicants must publish a list of the life-limited engine parts and the approved life for each part in the Airworthiness Limitations Section of the Instructions for Continued Airworthiness as required by § 33.4 of this part.
Issued in Washington, DC, on August 27, 2007.
End Signature1 1 End Supplemental Information
[FR Doc. E7-17369 Filed 8-31-07; 8:45 am]