Airworthiness Directives; Pratt & Whitney PW4164, PW4168, and PW4168A Series Turbofan Engines

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The Federal Aviation Administration (FAA) proposes to revise an existing airworthiness directive (AD), applicable to Pratt & Whitney PW4164, PW4168, and PW4168A series turbofan engines. That AD currently requires initial and repetitive torque checks for loose or broken front pylon mount bolts made from INCO 718 material and MP159 material. That AD also requires initial and repetitive visual inspections of the primary mount thrust load path. This proposal extends the cycles accumulated before performing the initial inspection, and reduces the frequency of repetitive inspections for MP159 material bolts, and adds a terminating action to the primary mount thrust load path inspections by introducing a new increased durability engine mount forward mount bearing housing. This proposed revision is prompted by component testing to assess the low cycle fatigue (LCF) life of the MP159 material bolts and the development of a new design forward engine mount bearing housing that meets the 8,000 flight cycle design intent for inspection. The actions specified by the proposed AD are intended to prevent front pylon mount bolt and primary mount thrust load path failure, which could result in an engine separating from the airplane.

DATES:

Comments must be received by November 12, 2002.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), New England Region, Office of the Regional Counsel, Attention: Rules Docket No. 97-ANE-44-AD, 12 New England Executive Park, Burlington, MA 01803-5299. Comments may be inspected at this location, by appointment, between 8 a.m. and 4:30 p.m., Monday through Friday, except Federal holidays. Comments may also be sent via the Internet using the following address: “9-ane-adcomment@faa.gov.” Comments sent via the Internet must contain the docket number in the subject line.

The service information referenced in the proposed rule may be obtained from Pratt & Whitney, 400 Main St., East Hartford, CT 06108; telephone (860) 565-8860; fax (860) 565-4503. This information 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:

Tara Goodman, Aerospace Engineer, Engine Certification Office, FAA, Engine and Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803-5299; telephone (781) 238-7130; fax (781) 238-7199.

SUPPLEMENTARY INFORMATION:

Comments Invited

Interested persons are invited to participate in the making of the proposed 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 above. All communications received on or before the closing date for comments, specified above, will be considered before taking action on the proposed rule. The proposals contained in this action may be changed in light of the comments received.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the proposed 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 summarizing each FAA-public contact concerned with the substance of this proposal will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this action must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket Number 97-ANE-44-AD.” The postcard will be date stamped and returned to the commenter.

Availability of NPRM's

Any person may obtain a copy of this NPRM by submitting a request to the FAA, New England Region, Office of the Regional Counsel, Attention: Rules Docket No. 97-ANE-44-AD, 12 New England Executive Park, Burlington, MA 01803-5299.

Discussion

On August 1, 2000, the FAA issued AD 2000-16-02, Amendment 39-11856 (65 FR 49730, August 15, 2000), applicable to Pratt & Whitney PW4164, PW4168, and PW4168A series turbofan engines. That AD requires initial and repetitive torque checks for loose or broken front pylon mount bolts made from INCO 718 material and MP159 material. That AD also requires initial and repetitive visual inspections of the primary mount thrust load path. That condition, if not corrected, could result in an engine separating from the airplane.

Since AD 2000-16-02 was issued, Pratt & Whitney has determined that the cycles accumulated before performing the intitial inspections should be extended from 1,250 cycles to 4,100 cycles and that the 1,250 cycle maximum inspection interval specified in paragraph (c) of that AD should be increased to a 4,350 cycle maximum inspection interval for MP159 material bolts. In addition, Pratt & Whitney is introducing a new forward mount bearing housing (monoball housing) which constitutes terminating action for repetitive inspections. This improved housing will eliminate the 1,250 cycle maximum inspection interval of the forward engine mount primary thrust load path, presently being performed in accordance with Alert Service Bulletin (ASB) PW4G-100-A71-18, allowing the improved housing to achieve the 8,000 flight cycle inspection goal. This proposed revision is prompted by component testing that assessed the low cycle fatigue (LCF) life of MP159 material bolts, and the development of a new design forward engine mount bearing housing that meets the 8,000 flight cycle design intent for inspection. The FAA reviewed this analysis and agrees with it.

Manufacturer's Service Information

The FAA has reviewed and approved the technical contents of the following Pratt & Whitney alert service bulletins (ASB's) and service bulletin (SB):

• ASB PW4G-100-A71-9, Revision 1, dated November 24, 1997, that describes the repetitive inspection procedures for the forward mount pylon bolts and adds a note to Part B of the Accomplishment Instructions.
• ASB PW4G-100-A71-20, Revision 1, dated January 15, 2002, that describes the repetitive inspection procedures for engines with the MP159 material forward mount pylon bolts, part number (P/N) 51U615, to verify the integrity of the bolts to identify a bolt-out condition. In addition, the 1,250 maximum cycle inspection interval is increased to 4,350 cycles maximum.
• ASB PW4G-100-A71-18, Revision 2, dated January 15, 2002, that describes the procedures for visually inspecting the primary mount thrust load path; and adds Pratt & Whitney ASB PW4G-100-A71-22, dated January 15, 2002, to the references section. ASB PW4G-100-71-18 also lists ASB PW4G-100-71-22, dated January 15, 2002, as an alternate method of compliance for the periodic inspection of the primary thrust load path components.
• SB PW4G-100-A71-22, dated January 15, 2002, that introduces a new increased durability forward mount bearing housing (monoball housing), P/N 52U420.

FAA's Determination of an Unsafe Condition and Proposed Actions

Since an unsafe condition has been identified that is likely to exist or develop on other Pratt & Whitney PW4164, PW4168, and PW4168A series turbofan engines of this same type design, the proposed AD would revise AD 2000-16-02 to:

• Require extension of the cycles accumulated for performing initial inspection.
• Require an extension of the frequency of performing repetitive inspections for MP159 material bolts.
• Add a terminating action to the primary mount thrust load path inspections by introducing a new increased durability engine mount forward mount bearing housing.

Economic Analysis

There are approximately 226 engines of the affected design in the worldwide fleet. The FAA estimates that 21 engines installed on aircraft of U.S. registry would be affected by this proposed AD. The FAA also estimates that it would take approximately 3 work hours per engine to perform the proposed actions, and that the average labor rate is $60 per work hour. Required parts would cost approximately $19,000 per engine. Based on these figures, the total cost of the proposed AD to U.S. operators is estimated to be $402,780.

Regulatory Analysis

This proposed 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 proposed rule.

For the reasons discussed above, I certify that this proposed regulation (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) if promulgated, 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 copy of the draft regulatory evaluation prepared for this action 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

The Proposed Amendment

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration proposes to amend 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.