AD 94-18-03

This amendment adopts a new airworthiness directive (AD) that is applicable to Rolls- Royce plc (R-R) RB211 series turbofan engines. This action requires removing from service intermediate pressure (IP) compressor stage 6-7 rotor shafts that exceed new, reduced cyclic life limits. This amendment is prompted by a report of an uncontained failure of an IP compressor stage 6-7 rotor shaft. The actions specified in this AD are intended to prevent an uncontained engine failure due to rupture of an IP compressor stage 6-7 rotor shaft.
The incorporation by reference of certain publications listed in the regulations is approved by the Director of the Federal Register as of September 26, 1994.
Comments for inclusion in the Rules Docket must be received on or before November 8, 1994.

Final rule; request for comments.

94-18-03 Rolls-Royce plc: Amendment 39-9016. Docket 94-ANE-16.
Applicability: Rolls-Royce plc (R-R) Model RB211-22B and -524 series turbofan engines, not incorporating thicker intermediate pressure (IP) compressor stage 6-7 rotor shafts in accordance with R-R Service Bulletin (SB) RB.211-72-5787, dated March 20, 1981, and incorporating IP compressor stage 6-7 rotor shafts that have not been reworked in accordance with R-R SB RB.211- 72-9594, Revision 5, dated February 12, 1993. These engines are installed on but not limited to Boeing 747 series and 767 series, and Lockheed L-1011 series aircraft.
Compliance: Required as indicated, unless accomplished previously.
To prevent an uncontained engine failure due to rupture of an IP compressor stage 6-7 rotor shaft, accomplish the following:
(a) For R-R RB211-22B series engines, accomplish the following:
(1) For IP compressor stage 6-7 rotor shafts that have greater than or equal to 14,000 cycles in service (CIS) on theeffective date of this AD, remove the rotor shafts within 15 days after the effective date of this AD, and replace with a serviceable part.
(2) For IP compressor stage 6-7 rotor shafts that have less than 14,000 CIS but greater than 11,000 CIS on the effective date of this AD, remove the rotor shafts at the next shop visit, or prior to 45 days after the effective date of this AD, whichever occurs first, and replace with a serviceable part.
(3) For IP compressor stage 6-7 rotor shafts that have 11,000 or less CIS on the effective date of this AD, remove the rotor shafts on or before 11,000 CIS, or 45 days after the effective date of this AD, whichever occurs later, and replace with a serviceable part.
(4) Subsequent to 45 days after the effective date of this AD, the new life limit for the IP compressor stage 6-7 rotor shafts that have not been reworked in accordance with R-R SB RB.211-72-9594, Revision 5, dated February 12, 1993, shall be 11,000 CIS.
(5) Rotor shafts that are reworked in accordance with R-R Service Bulletin No. RB.211-72-9594, Revision 5, dated February 12, 1993, may remain in service until their assigned life limits are reached.
(b) For all affected R-R RB211-524 series engines excluding R-R Models RB211-524D4, - 524G, and -524H, accomplish the following:
(1) For IP compressor stage 6-7 rotor shafts that have greater than or equal to 10,500 CIS on the effective date of this AD, remove the rotor shafts within 15 days after the effective date of this AD, and replace with a serviceable part.
(2) For IP compressor stage 6-7 rotor shafts that have less than 10,500 CIS but greater than 7,500 CIS on the effective date of this AD, remove the rotor shafts at the next shop visit, or January 31, 1995, whichever occurs first, and replace with a serviceable part.
(3) For IP compressor stage 6-7 rotor shafts that have 7,500 or less CIS on the effective date of this AD, remove the rotor shafts on or before 7,500 CIS, or January 31,1995, whichever occurs later, and replace with a serviceable part.
(4) After January 31, 1995, the new life limit for the IP compressor stage 6-7 rotor shafts that have not been reworked in accordance with R-R SB RB.211-72-9594, Revision 5, dated February 12, 1993, shall be 7,500 CIS.
(5) Rotor shafts that are reworked in accordance with R-R Service Bulletin No. RB.211-72-9594, Revision 5, dated February 12, 1993, may remain in service until their assigned life limits are reached.
(c) For R-R Models RB211-524D4, -524G, and -524H engines, and all other models of R-R RB211-524 series engines with the thicker IP compressor stage 6-7 rotor shaft in accordance with R-R SB RB.211-72-5787, dated March 20, 1981, accomplish the following:
(1) For IP compressor stage 6-7 rotor shafts that have greater than or equal to 10,500 CIS on the effective date of this AD, remove the rotor shafts within 15 days after the effective date of this AD, and replace with a serviceable part.
(2)For IP compressor stage 6-7 rotor shafts that have less than 10,500 CIS but greater than 8,500 CIS on the effective date of this AD, remove the rotor shafts at the next shop visit, or January 31, 1995, whichever occurs first, and replace with a serviceable part.
(3) For IP compressor stage 6-7 rotor shafts that have 8,500 or less CIS on the effective date of this AD, remove the rotor shafts on or before 8,500 CIS, or January 31, 1995, whichever occurs later, and replace with a serviceable part.
(4) After January 31, 1995, the new life limit for the IP compressor stage 6-7 rotor shafts shall be 8,500 CIS.
(5) Rotor shafts that are reworked in accordance with R-R Service Bulletin No. RB.211-72-9594, Revision 5, dated February 12, 1993, may remain in service until their assigned life limits are reached.
(d) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Engine Certification Office. The request should be forwarded through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Engine Certification Office. NOTE: Information concerning the existence of approved alternative methods of compliance with this airworthiness directive, if any, may be obtained from the Engine Certification Office.
(e) Special flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the aircraft to a location where the requirements of this AD can be accomplished.
(f) The rework, if accomplished, shall be done in accordance with the following service documents:

Document No.
Pages
Revision
Date
R-R SB No. RB.211-72-9594
1
5
February 12, 1993

2
Original
February 5, 1992

3
4
November 13, 1992

4
2
May 8, 1992

5
4
November 13, 1992

6-6A
2
May 8, 1992

7
Original
February 5, 1992

8-9
2
May 8, 1992

10
3
August 7, 1992

11-14
2
May 8, 1992

15-18
Original
February 5, 1992

19-20
4
November 13, 1992

21
Original
February 5, 1992

22-25
2
May 8, 1992
Supplement
1
2
May 8, 1992
Appendix 1
1-4
5
February 12, 1993

5
Original
February 5, 1992
Total pages: 32.

R-R SB No. RB.211-72-5787
1-6
Original
March 20, 1981
Supplement
1
Original
March 20, 1981
Total pages: 7.

This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Rolls-Royce plc, Technical Publications Department, P.O. Box 31, Derby, England. Copies may be inspected at the FAA, New England Region, Office of the Assistant Chief Counsel, 12 New England Executive Park, Burlington, MA; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.
(g) This amendment becomes effective onSeptember 26, 1994.

The Civil Aviation Authority (CAA), which is the airworthiness authority for the United Kingdom, recently notified the Federal Aviation Administration (FAA) that an unsafe condition may exist on Rolls-Royce plc (R-R) RB211-22B and -524 series turbofan engines. The CAA advises that they received a report of a cracked intermediate pressure (IP) compressor stage 6-7 rotor shaft that was removed from an R-R RB211-22B engine due to expiration of its life limit. The crack emanated from a corrosion pit, extending 0.45 inches radially inward from the bolt holes in the rotor shaft diaphragm. The manufacturer performed fracture mechanics analysis and determined that the rotor shaft would not reach its published life limit without cracking under normal operating conditions. Consequently, the CAA took mandatory action to reduce the life limit and remove suspect rotor shafts from service.
The CAA received an additional report of an uncontained failure of an IP compressor stage 6-7 rotor shaft installed in an R-R RB211-22B engine that failed during takeoff roll. Investigation determined that the failure may have been caused by stress corrosion cracking of the tierod bolt holes. Laboratory examination revealed that the crack originated at a corrosion pit that had been present for, at minimum, two-thirds of the rotor shaft's service life. The investigation revealed additional rotor shafts with corrosion pitting and cracking. This condition, if not corrected, can result in an uncontained engine failure due to rupture of an IP compressor stage 6-7 rotor shaft.
The R-R RB211-524 IP compressor stage 6-7 rotor shaft is similar in design and construction to the -22B, shares the same material composition, and has also exhibited bolt hole corrosion pitting and cracking. The -524 rotor shaft operates at higher stress levels than the -22B due to increased operational speeds.
Rolls-Royce plc has issued Service Bulletin (SB) No. RB.211-72-9594, Revision 5, dated February 12, 1993, that specifies rework of the IP compressor stage 6-7 rotor shaft; and SB No. RB.211-72-5787, dated March 20, 1981, that introduces a thicker IP compressor stage 6-7 rotor shaft. Rotor shafts complying with either of these SB's are not affected by this AD.
This engine model is manufactured in the United Kingdom and is type certificated for operation in the United States under the provisions of section 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and the applicable bilateral airworthiness agreement. Pursuant to this bilateral airworthiness agreement, the CAA has kept the FAA informed of the situation described above. The FAA has examined the findings of the CAA, reviewed all available information, and determined that AD action is necessary for products of this type design that are certificated for operation in the United States.
Since an unsafe condition has been identified that is likely to exist or develop on other R-R RB211 series turbofan engines of the same type design registered in the United States, this AD requires removing from service IP compressor stage 6-7 rotor shafts that exceed new, reduced cyclic life limits. This AD is not applicable to those engines that incorporate the thicker IP compressor stage 6-7 rotor shafts in accordance with R-R SB RB.211-72-5787, dated March 20, 1981. If operators elect to rework rotor shafts in accordance with R-R SB No. RB.211-72-9594, Revision 5, dated February 12, 1993, the rotor shafts may operate up to the assigned life limits.
Since a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for prior public comment hereon are impracticable, and that good cause exists for making this amendment effective in less than 30 days. Comments Invited
Although this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded by notice and an opportunityfor public comment, comments are invited on this rule. Interested persons are invited to comment on this rule by submitting such written data, views, or arguments as they may desire. Communications should identify the Rules Docket number and be submitted in triplicate to the address specified under the caption "ADDRESSES." All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would be needed.
Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report that summarizes each FAA-public contact concerned with the substance of this AD will be filed in the Rules Docket.
Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this notice must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 94-ANE-16." The postcard will be date stamped and returned to the commenter.
The regulations adopted 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 final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.
The FAA has determined that this regulation is an emergency regulation that must be issued immediately tocorrect an unsafe condition in aircraft, and is not a "significant regulatory action" under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket. A copy of it, if filed, may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES." List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.
Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows: PART 39 - AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89. 39.13 - [AMENDED]
2. Section 39.13 is amended by adding the following new airworthiness directive: