### Petition for Exemption from 14 C.F.R. 

## § 33.27(1)(6), Amendment 33·31
A. 

### Name, Address and Contact Informationotthe Petitioner Tunde Oyinloye Airworthiness Engineer ML-52 Rolls-Royce pic PO Box 31 Derby DE24 8BJ England Tel (+44) 1332 249294 Tunde.oyinloye@rolls-royce.com 

### B. Pertinent Section ot the Code of Federal Regulations 

# I Rolls-Royce

Rolls-Royce hereby petitions for an exemption from 14 

### C.F.R. § 33.27(1)(6). This exemption is requested for the HP shaft system only, forthe Trent XWB engine models identified in Section 

### C below. The pertinent provisions of 14 

### C.F
.R. § 33.27 are: 14 C.F.R. 

### § 33.27 Turbine, compressor, fan, and turbosuperchargerrotor overspeed. (f) 

### Failure ofa shaft section maybe excluded from consideration in detennining the highest overspeed that would result from a complete loss ofload on a turbine rotor iftha applicant: (6} Does notexclude the entire shaft. 

### C. The Exemption Being Sought Rolls-Royce requests an exemption from 14 

### C.F.R. § 33.27(f}(6} for the HP shaft system or the following Trenl XWB engine models: 

### Model
Trent XWB-84 Trent XWB-798 Trent XWB-79 Trent XWB-75 

### Rating x 1000 lbs.
84 79 79 75
No exemption is sought for other shaft systems on these, or any other, engine models. The HP shaft system will comply with 

### § 33.27, subject to the granling of the exemption from 

### § 33.27(f)(6) requested herein.



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# Rolls-Royce

Rolls-Royce seeks an exemption from 

### § 33.27(f)(6} to exclude the entire HP shaft system from consideration in determining the highest overspeed that would resultfrom a complete loss of load on a turbine rotor. As demonstrated in Section E below and in the substantiating report, the level of safety afforded by compliance with 

### § 33.27 for the HP shaft system will be unaffected by thegranting of an exemption from 

### § 33.27(f)(6}. The FAA has previously determined that allowing disc burst speed to be less than 100% rotor terminal speed could result in a hazardous condition, and that to ensurethat safety is not adverselyaffected because of an HPshaft failure, the HPturbine disc burst speed must be greaterthan the terminal speed. The FAA also determinedthatthe data (field experience, design similarity, Failure Modes and Effects Analysis, and terminal speed methodology} previously provided by Rolls-Royce regarding otherTrent engine models was sufficient to reduce from the 105%terminal speed requirement of 14 C.F.A. 

### § 33.27 without adversely affecting safety. Rolls-Royce requests that the exemptionfrom 

### § 33.27(f}(6} be grantedonthe basis of Rolls-Royce's demonstration that for each of the listed Trent XWB-84K engine models the HP turbine discburstspeed is greaterthan 100% rotor terminal speed resulting from HPshaft system failure. In sum, Rolls-Royce is requesting this exemption because compliance with 

### § 33.27 cannot be shown absent an exemption from 

### § 33.27(f}(6). However, compliance can be shown, without adversely affecting safety to that required to meet 

### § 33.27, 

### if the exemption is granted. 

### D. Statement 

### of Public 

### Interest Granting this exemption will promote and serve the public interest because:
• The state-of-the-artengine models (and the HP shaft system} at issue in this petition represent the latest generation of engines and engine technology from the Trent engine family

. TheTrent line of engines has established an outstanding track record of performance and safetyfor over 41 years and more than 250 million service flight hours. Thus, the engine models and shaft system at issue in this petition are based on proven expertise and in-service-verified design styles and practices. This experience and track record helps to ensure the reliability and safety ol the product. As explained further in the statements immediately below, the introduction ofthese engine models into service will generate valuable publicbenefits.
• The granting of the requested exemption will expedite the entry into service of superior engines and engine technology that will enhance the safety and reliability of airline operations, and increase the efficiency of aircraft performance, thereby promoting U.S

. economic interests (including those of U.S. airlines and their employees and shareholders} as well as those ofthe traveling public, while also reducing adverse effects onthe environment. All of these enhancementsconstitute substantial public benefits

.
• Certification ofthe XWB engine by the U.S. will make additional aircraft models availablefor purchase byU.S. airlines. Such choices are in the economic interest ofthe U

.S

. through promotion of a more competitive marketfor large commercial transport aircraft.
• These state-of-the-art engine models will reduce the operating costs of aircraft, and the airlines that operate them, relative to costs associated with aircraft that are currently in service

. Such a reduction in operating costs will benefit U.S. and international airlines, their employees and shareholders. Moreover, such reduced operating costs provide the opportunity for airlines to offer more numerous, and less expensive, air service options to the traveling public

. • The Trent XWB models will be installed on the Airbus A350, which has customers both within and outside the United States.
• Certificationof state-of
-the-artengine models, when operated in the Airbus A350, will reduce fuel bum, thereby reducing harmful emissions such as carbon dioxide (CO·) and NO. from ro11s-royce.com**~II> ~e** pk legb!eredofroc.e,**~** &ucklngh.lmG.l!e
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# Rolls-Royce

levels experiencedwith engines currently in service.

• The Trent XWB is built with U.S. supplied parts that constituting approximately 16% of the engine value. Sales of the engine contribute to the U.S. economy, support U.S. jobs, and enhance the U.S. balance of trade and gross domestic product, all ofwhich promote the U.S. public interest.

• Certification of the XWB engine in the U.S. promotes the regulatory standards ofthe U.S. as global bench mark for airworthiness. Promotion of the U.S. regulatory standards is in the public interest asthis increases the numberof goods and services available to U.S. citizens that are compliant with U.S. regulatory standards, and since many countriesvoluntarily adopt U.S. standardsthis process does not increase the burden on the U.S. government.


### E. Statement of No Adverse 

### Effect on Safety The FAA's grant ofthis requested exemption will have no adverse effect on safety. Compliance with 

### § 33.27 is significant for safety purposes because it demonstratesthat an engine's rotors will not fail under a varying range of potential operating conditions. The requirements contained in 

### § 33.27(1} are significant for safety because this subsection allows failures of shaft sections to be excluded from the range of conditions considered under§ 33.27, but only if a design organization can demonstratethat the risk of such shaft section failures is sufficiently remote. Subsection 33.27(1)(6) does not in itself impose any additional safety requirement. Clearly, if risk of failure of the whole shaft system is considered and shown to be at least as remote as is acceptable for Nshaft sections,w then the overall level of safety must be at least equal to circumstances in which only Nshaft sections" are considered, as provided for under 

### § 33.27(f}. Subsection 33.27(f)(6) was included in Section 33.27 based on a history offailures associated with conventional shalt systems, which raised doubt about the ability of design organizationsto fully assess the potential failure modes (and failure rate) of an entire shaft system. However, forthe HP shaft system of the Trent 

### XWB (and indeed for other Rolls-Royce modern 

### 3 shaft engines), this analysis can be carried out with high fidelity because: 1. The HP shaft system design utilized across the Trent engine family differs significantly from conventional shaft systems. For example, it features no bearings oroil system components, has high stiffness and significant clearance relative to other shafts; consequently,the threats associated with the features of a conventional shaft do not apply. A Failure Mode and Effect Analysis has determined that there are no known or potential environmentalthreats to the integrity of the HP shaft system componentsthat could lead to a loss of load failure. 2. In order to ensure a high level of integrity, the special controls applied to the torquetransmitting components (i.e., the HP compressor rear drum and the HP turbine disc of the HP shaft system) are of a higher standard than those of many other shaft systems in the past. These mandated controls address, but are not limited to:
• Material specifications; • Material properties (e.g., low cycle fatigue, high cycle fatigue, creep); • Manufacturing induced anomalies; • Service induced damage tolerance assessment; • Safe life mandatory inspections; and • Mandatory cycle life limitation. 

### 3. The theoretical assessmentof points 

### 1 ) and 2) above is supported bythe service experience of the Rolls-Royce three shaft family of engines, all ofwhich Incorporate the same design style for the HP shaft system as the Trent 

### XWB engine models that are the subject of this petition. Over the course of more than 

### 250 million service flight hours, there have been no failures of the HP shaft system torque path on the Trent family of engines. This performance reflects an extremely remote potential failure rate of less than 2.8 

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# I Rolls-Royce

In addition, in its Partial Grant of Exemption, Exemplion No. 10964, issued March 28, 2014 in Regulatory Docket No. FAA-2013-1049, the FAA concluded that granting Rolls-Royce's recent petition requesting an identical exemption forother Rolls-Royce Trent engine family models had noadverse effectonsafetyand was in the public interest, subjecttothe condition that the HPturbine disc burst speed is greaterthan 100% rotorterminal speed dueto HP shaftsystem failure. In sum, there is ample evidence that analysis of the complete HP shaft system on the Trent XWB models at issue achieves the level of fidelity required forfailures ofshaft sections under§33.27(f). Therefore, the level of safety under the requested exemption will be at least equal to that otherwise provided by§ 33.27, thereby assuring that noadverse effect on safety will result from a grant of the requested exemption. 

### F. Summary for Federal Register As setforth in section I below, Rolls-Royce is requesting that this petition be processed without publication in the Federal Register. If, however, the FAA determines that publication in the Federal Register is warranted, in accordancewith § 11.81(f), Rolls-Royce offers the following summary suitable for publication inthe Federal Register. Petitioner. Rolls-Royce pic Section of 14 C.F.R. Artected: 14 C.F.R. 

### § 33.27(f)(6) Description of Relief Sought: Rolls-Royce requests an exemption from 14 C.F.R. § 33.27(f)(6) to be applied to Rolls-Royce Trent XWB engine, models XWB-84, XWB-798, XWB-79 and XWB-75. Rolls-Royce seeks to exclude the entire HP shaft system from consideration In determining the highest overspeed that would result from a complete loss of load on a turbine rotor. 

### G. Additional Supporting 

### Information EASA Certification requirements CS-E 840 and CS-E 850 are similar requirements tothose of§ 33.27. The Trent XWB engine models at issue have been certified by EASA under Type Certificate E.111, which was released on 7 February 2013. To meet the requirements of CS-E 840 and CS-E 850, EASA granted an Equivalent Safety Finding. The evidence provided to support this Equivalent Safety Finding was similar to that provided in this petition for exemption. The EquivalentSafety Finding was accepted by EASA on 15January 2013. 

### H. Privileges of this Exemption Outside the United States Pursuantto 14 C

.F.R. § 11.81(h), Rolls-Royce requests that the privileges of this exemption be extended outside the United States. This extension of privileges Is necessary for operations based within foreign countries having bilateral agreementswith the United States accepting FAA 14 C.F.R. Part 33 as their airworthinessstandards for transport category aircraft. The Trent XWB is intended for the global marketplace,with customers based in countries utilizing the U.S

. airworthiness standards. 

### I. Good Cause Exists to Issue the Exemption without Notice and Comment Pursuant to 14 C.F.R. 

### § 11.87, Rolls-Royce requests that this petition be processed without publication in the Federal Register for notice and comment, as may otherwise be required. RollsRoyce believes that good cause exists to not delay this action because: a) granting of this petition will not set a precedent since the petition seeks the same exemption granted bythe FAA on March 28, 2014 in Exemption No. 10964, Regulatory Docket No. FAA-2013-1049; b) the relief requested is ertectively identical tothat granted in Exemption No. 10964 and in the Equivalent Safety Finding previously accepted by EASA; (c) delaying the action would adversely affect Rolls-Royce because theTrent XWB engine models covered bythis petition are currently undergoingcross-validation with the FAA expected to complete in September2014; and (d) thispetition is timely filed. 

### rotls-royce.com

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# ~::(fsz;;:;**tyr** Tunde Oyinloye Airworthiness Engineer Rolls-Royce pic

Date: Wednesday 13th August, 2014



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# I Rolls-Royce