03-12109. Airworthiness Directives; Rolls-Royce plc Model RB211 Turbofan Engines

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Final rule.

SUMMARY:

This amendment adopts a new airworthiness directive (AD), that is applicable to Rolls-Royce plc (RR) model RB211-535E4-37, RB211-535E4-B-37, and RB211-535E4-B-75 turbofan engines. This amendment requires removal from service of certain high pressure (HP) turbine discs before they reach newly established life limits. This amendment is prompted by the manufacturer's inspections and analysis of HP turbine discs that have accumulated high cycles. The actions specified by this AD are intended to prevent machining-induced cracking of the HP turbine disc which could cause an uncontained HP turbine disc failure and damage to the airplane.

DATES:

Effective June 20, 2003.

ADDRESSES:

Information regarding this action may be examined, by appointment, at the Federal Aviation Administration (FAA), New England Region, Office of the Regional Counsel, 12 New England Executive Park, Burlington, MA.

FOR FURTHER INFORMATION CONTACT:

Ian Dargin, Aerospace Engineer, Engine Certification Office, FAA, Engine and Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803-5299, telephone [phone]; fax [phone].

SUPPLEMENTARY INFORMATION:

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an AD that is applicable to RR model RB211-535E4-B-37 and RB211-535E4-B-75 turbofan engines was published in the Federal Register on November 6, 2002 (67 FR 69160). That action proposed to require removal from service of certain HP turbine discs before they reach newly established life limits.

Comments

Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.

Change Explanation for Cracking

One commenter states that the explanation for cracking in the HP disc rim cooling hole area is machining damage from new manufacture, and has nothing to do with the discs being sensitive to corrosion-induced cracking, as stated in the proposal. The commenter also states that RR had previously indicated that the proposed life reduction was due to the condition described in RR Mandatory Service Bulletin (MSB) No. 72-C817. This MSB states that HP turbine discs part numbers (P/Ns) UL10323, UL27680, and UL27681 are sensitive to cracking in the disc rim cooling hole area due to machining damage from new manufacture.

The FAA agrees. The cracking has been identified as occurring at the disc rim cooling hole area on the disc rear face. Although problems have been reported during overhaul, presumably due to rework or repair associated with, in part, corrosion, the primary explanation for this AD is machining damage. Therefore, in the final rule the explanation for cracking is changed to machining damage.

Clarification of Part Numbers

One commenter requests that HP turbine discs P/Ns UL39766 and UL39767 be removed from the applicability and disc P/N UL10323 be added. The commenter states that disc P/N UL39766 is not listed in the RR Engine Illustrated Parts Catalogue or the Time Limits Manual. The commenter states that disc P/N UL39767 was introduced by RR Service Bulletin (SB) No. 72-C817 and is not subject to damage by machining. The commenter also states that disc P/N UL10323 is listed in the Time Limits Manual with a life limit of 14,800 cycles-since-new (CSN). Service Bulletin No. 72-C817 lists disc P/N UL10323, indicating that it is sensitive to cracking due to machining damage from manufacture.

The FAA agrees. We determined that HP turbine disc P/N UL39766 was never produced by RR and is, therefore, removed from the final rule. Also, disc P/N UL39767 was introduced as a new part to replace disc P/N UL27681, and has, therefore, been removed from the final rule. Disc P/N UL10323 is affected by machining damage and is added to the final rule applicability with a life limit of 14,800 CSN.

Add Engine Model to Applicability

One commenter asks if the RB211-535E4-37 engine should be included in the applicability.

The FAA agrees that this AD should be applicable to engine model RB211-535E4-37. Therefore, this model is now listed in the final rule.

After careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the changes described previously. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD.

Economic Analysis

There are approximately 400 RR model RB211-535E4-37, RB211-535E4-B-37, and RB211-535E4-B-75 turbofan engines in the worldwide fleet containing the affected HP turbine discs, P/Ns UL10323, UL27680, and UL27681. The FAA estimates that 346 engines installed on airplanes of U.S. registry will be affected by this AD, that it will take approximately 112 work hours per engine to replace an affected disc, and that the average labor rate is $60 per work hour. The FAA estimates that the prorated cost of the life reduction per engine would be approximately $64,000. Based on these figures, the total cost of the AD to remove HP turbine discs P/Ns UL27680 and UL27681 from service before accumulating 15,000 cycles-since-new (CSN) and HP turbine discs P/N UL10323 from service before accumulating 14,800 CSN, rather than the former life limit of 20,000 CSN, is estimated to be $24,469,120.

Regulatory Analysis

This final rule does not have federalism implications, as defined in Executive Order 13132, because it would not have a substantial direct effect 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. Accordingly, the FAA has not consulted with state authorities prior to publication of this final rule.

For the reasons discussed above, I certify that this action (1) is not a “significant regulatory action” under Executive Order 12866; (2) is not a “significant rule” under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act. A final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained by contacting the Rules Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• 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. 106(g), 40113, 44701.

§ 39.13

[Amended]

2. Section 39.13 is amended by adding a new airworthiness directive to read as follows:

2003-10-03 Rolls-Royce plc: Amendment 39-13148. Docket No. 2002-NE-12-AD.

Applicability: This airworthiness directive (AD) is applicable to model RB211-535E4-37, RB211-535E4-B-37 and RB211-535E4-B-75 turbofan engines with high pressure (HP) turbine disc, P/N UL10323, UL27680, and UL27681, installed. These engines are installed on, but not limited to Boeing 757 and Tupolev Tu204 airplanes.

Note 1:

This AD applies to each engine identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For engines that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (d) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.

Compliance: Compliance with this AD is required as indicated, unless already done.

To prevent machining-induced cracking of the HP turbine disc, which could cause an uncontained HP turbine disc failure and damage to the airplane, do the following:

(a) Remove HP turbine discs P/Ns UL27680 and UL27681 from service before accumulating 15,000 cycles-since-new (CSN).

(b) Remove HP turbine discs P/N UL10323 from service before accumulating 14,800 CSN.

(c) After the effective date of this AD, do not install any HP turbine disc P/N UL27680 or UL27681 that exceeds 15,000 CSN, or any HP turbine disc P/N UL10323 that exceeds 14,800 CSN.

Alternative Methods of Compliance

(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 (ECO). Operators must submit their request through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, ECO.

Note 2:

Information concerning the existence of approved alternative methods of compliance with this airworthiness directive, if any, may be obtained from the Engine Certification Office.

Special Flight Permits

(e) Special flight permits may be issued in accordance with §§ 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be done.

Effective Date

(f) This amendment becomes effective on June 20, 2003.

Issued in Burlington, Massachusetts, on May 9, 2003.

Jay J. Pardee,

Manager, Engine and Propeller Directorate, Aircraft Certification Service.