PO Box 31,Derby DE24 8BJ,England

Telephone: +44 (0) 1332 249292

Fax: +44 (0) 01332 245328

January 21, 2014

U.S. Department of Transportation 

Docket Management Facility 

1200 New Jersey Avenue, SE 

West Building Ground Floor Room W12-140 

Washington, DC 20590

Subject: Petition for exemption from § 33.27(f)(6) of Title 14, Code of Federal Regulations

 (14 C.F.R.); Docket No. FAA-2013-1049

Dear Sir or Madam:

Attached please find a revised petition providing the additional information in support of the petition 

presented in our letter to the FAA dated December 9, 2013. This submission specifically responds to 

a letter we received from the FAA, Aircraft and Propeller Directorate, Aircraft Certification Service, 

dated December 31, 2013. The first three items identified in the FAA’s December 31, 2013, letter are 

addressed in the following parts of the revised petition:

Extent of the exemption: Section C of the petition.

Extended justification to address § 11.81(d): Section D of the petition.

Extended justification to address § 11.81(e): Section E of the petition.

In addition, the FAA’s December 31, 2013, letter requested copies of the relevant references listed in 

the substantiating report, DNS192492. These documents were supplied on a confidential basis as 

proprietary information to Mr Robert Green, the FAA Engineering Certification Office focal point, on 

January 14, 2014.

Rolls-Royce would appreciate the FAA’s consideration of this revised petition on an expedited basis,

to the extent consistent with its internal processes. The exemption, if granted, will facilitate

completion of cross-validation of the Trent 1000 engine models identified in the petition, which is 

necessary to support introduction of the Boeing 787-9.

Sincerely,

Iain Park

Airworthiness Specialist

Tel. (+44) 1332 249292

Fax (+44) 1332 245328 

cc: Colleen M. D’Alessandro, Assistant Manager, Engine and Propeller Directorate,

 Aircraft Certification Service 

 Tara Fitzgerald, Project Officer, Engine and Propeller Directorate, 

 Aircraft Certification Service

 Robert Green, Engineering Certification Office Focal Point, Engine and Propeller Directorate, 

 Aircraft Certification Service
Revised Petition for Exemption

from 14 C.F.R. § 33.27(f)(6), amendment 31

A. Name, Address and Contact Information of the Petitioner 

Iain Park

Airworthiness Specialist

ML-52

Rolls-Royce plc

PO Box 31

Derby

DE24 8BJ

England

Tel (+44) 1332 249292

Iain.Park@rolls-royce.com

B. Pertinent Section of the Code of Federal Regulations

Rolls-Royce hereby petitions for an exemption from 14 C.F.R. § 33.27(f)(6). This exemption is 

requested for the HP shaft system only, for the Trent 1000 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 turbosupercharger rotor overspeed.

(f) Failure of a shaft section may be excluded from consideration in determining the highest 

overspeed that would result from a complete loss of load on a turbine rotor if the applicant:

(6) Does not exclude 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 of the 

following Trent 1000 engine models:

Model Rating x 1000 lbs.

Trent 1000-K2 74 Hot and High

Trent 1000-J2 74

Trent 1000-L2 70 Hot and High + 24°C Kink point

Trent 1000-D2 70 Hot and High + 20°C Kink point

Trent 1000-C2 70

Trent 1000-G2 67

Trent 1000-A2 64

Trent 1000-H2 58

Trent 1000-E2 53

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 granting of the exemption from § 33.27(f)(6) 

requested herein.
Relief from § 33.27(f)(6) is sought because analysis has failed to show that failure of the HP shaft 

system can never result in overspeed to burst. The design of the HP shaft system is not amenable to 

analysis by shaft section. Rolls-Royce therefore seeks an exemption from § 33.27(f)(6) 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. However, as demonstrated in Section E below, the 

level of safety afforded by compliance with § 33.27 for the HP shaft system will be unaffected by the 

granting of an exemption from § 33.27(f)(6).

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, with at least an equal 

level of 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-art engine 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. The Trent line of engines has established an outstanding track record of performance 

and safety over 41 years and more than 228 million service flight hours. Thus, the engine 

models and shaft system at issue in this petition are based on proven expertise and inservice-verified design styles and practices. This experience and track record helps to 

ensure the reliability and safety of the product. As explained further in the points immediately 

below, the introduction of these engine models into service will generate valuable public 

benefits.

 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 Boeing, U.S. airlines, and their employees and 

shareholders) as well as those of the traveling public, while also reducing adverse effects on 

the environment. All of these enhancements constitute substantial public benefits.

 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 and less expensive air service options to the traveling 

public. 

 Certification of state-of-the-art engine models, when operated in the Boeing 787, will reduce 

fuel burn, thereby reducing harmful emissions such as carbon dioxide (CO2) and NOx from 

levels experienced with engines currently in service.

 The Trent 1000 models are installed on the Boeing 787-9 which has customers outside the 

United States. 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 of which promote the 

U.S. public interest.

E. Statement of No Adverse Effect on Safety

The FAA’s grant of this requested exemption will have no adverse effect on safety. Compliance with 

§ 33.27 is significant for safety purposes because it demonstrates that an engine’s rotors will not fail

under a varying range of potential operating conditions. The requirements contained in § 33.27(f) 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 demonstrate that 
the risk of such shaft section failures is sufficiently remote. Subsection 33.27(f)(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 “shaft sections,” then the overall 

level of safety must be at least equal to circumstances in which only “shaft 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 of failures associated with conventional shaft systems, which raised doubt about the ability of 

design organizations to fully assess the potential failure modes (and failure rate) of an entire shaft 

system. However, for the HP shaft system of the Trent 1000 (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 or oil 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 environmental threats to the 

integrity of the HP shaft system components that 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 assessment of points 1) and 2) above is supported by the service experience 

of the Rolls-Royce three shaft family of engines, all of which incorporate the same design 

style for the HP shaft system as the Trent 1000 engine models that are the subject of this 

petition. Over the course of more than 228 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 3.1 x 10-9 failures per flight 

hour.

In sum, there is ample evidence that analysis of the complete HP shaft system on the Trent 1000 

models at issue achieves the level of fidelity required for failures of shaft 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 no adverse effect on safety will result from a grant of the 

requested exemption.

F. Summary for Federal Register

In accordance with § 11.81(f), Rolls-Royce offers the following summary suitable for publication in 

the Federal Register.

Petitioner: Rolls-Royce plc

Section of 14 C.F.R. Affected: 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 

Trent1000 engine, models Trent 1000-A2, Trent 1000-C2, Trent 1000-D2, Trent 1000-E2, 
Trent 1000-G2, Trent 1000-H2, Trent 1000-J2, Trent 1000-K2, and Trent 1000-L2. 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 to those of §

33.27. The Trent 1000 engine models at issue have been certified by EASA under Type Certificate 

E.036 issue 4, which was released on September 10, 2013. To meet the requirements of CS-E 840 

and CS-3 850, 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 Equivalent 

Safety Finding was accepted by EASA on August 27, 2013.

H. Privileges of this Exemption Outside the United States

Per 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 agreements with the United States accepting FAA 14 C.F.R. Part 

33 as their airworthiness standards for transport category aircraft. The Trent 1000 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; b) the relief requested is effectively identical an Equivalent Safety Finding

previously accepted by EASA (c) delaying the action would adversely affect Rolls-Royce because the 

Trent 1000 engine models covered by this petition are currently undergoing cross-validation with the 

FAA, the timing of which is aimed at meeting Boeing requirements for entry into service of the Boeing 

787-9, and significant delays in engine validation would impact the Boeing program; and (d) this 

petition is timely filed.

Respectfully submitted,

Iain Park

Airworthiness Specialist

Rolls-Royce plc

Date: January 21, 2014