Daily Rules, Proposed Rules, and Notices of the Federal Government
For service information identified in this proposed AD, contact Pratt & Whitney, 400 Main St., East Hartford, CT 06108; phone: 860-565-4321. You may review copies of the referenced service information at the FAA, Engine & Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803. For information on the availability of this material at the FAA, call 781-238-7125.
You may examine the AD docket on the Internet at
We invite you to send any written relevant data, views, or arguments about this proposal. Send your comments to an address listed under the
We will post all comments we receive, without change, to
We have received reports of 3rd and 4th stage vane fractures in the LPT of certain PW4000-94″ and PW4000-100″ turbofan engines. These fractures caused an uncontained engine failure, an LPT case puncture, and multiple in flight shutdowns. We have identified four primary root causes for LPT vane failures:
1. Inadequate retention of the vane in the case due to dimensional tolerances which causes 3rd stage vane liberations. This AD requires dimensional inspections of the 3rd stage vanes at their retention points and case at LPT assembly after overhaul.
2. Non-uniform airfoil fillet radii found on vanes produced prior to 2005 which causes 4th stage vane fractures. This AD removes these vanes, identified by the casting identifier, from service at the next LPT overhaul.
3. Multiple strip-and-recoat repairs of the 4th stage vanes which degrade the structural integrity of the vanes and cause 4th stage vane fractures. This AD removes from service 4th stage vanes with multiple strip-and-recoat repairs. This AD also prohibits approving for return to service any 4th stage vane with more than one strip-and-recoat repair.
4. Aerodynamic excitation of the vanes which causes 4th stage vane fractures. The excitation is attributed to the rotor assembly methods for the upstream rotor stages. This AD requires reassembling the 2nd stage HPT blades at the next HPT overhaul and the 3rd stage LPT blades at the next LPT overhaul, using the latest assembly technique.
The actions proposed in this AD are intended to address each of the root causes identified above. This condition, if not corrected, could result in 3rd and 4th stage vane fractures in the LPT, which could damage the LPT rotor and lead to an uncontained engine failure and damage to the airplane.
We are proposing this AD because we evaluated all the relevant information and determined the unsafe condition described previously is likely to exist or develop in other products of the same type designs.
This proposed AD would require dimensional inspections of 3rd stage vanes and the rear turbine case. This AD also requires inspection of 4th stage vanes at the next LPT overhaul and removal of vanes with non-conforming airfoil fillet radii and vanes with more than one strip and recoat repair. This AD also requires disassembly and reassembly of the 2nd stage HPT rotor and 3rd stage LPT rotor at the next HPT and LPT overhauls.
We estimate that this proposed AD affects 807 engines installed on airplanes of U.S. registry. We estimate that it would take 2 work-hours per engine to perform the LPT 3rd stage vane cluster assembly and rear turbine case inspections. The average labor rate
Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, section 106, describes the authority of the FAA Administrator. Subtitle VII: Aviation Programs, describes in more detail the scope of the Agency's authority.
We are issuing this rulemaking under the authority described in subtitle VII, part A, subpart III, section 44701: “General requirements.” Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.
We determined that this proposed AD would not have federalism implications under Executive Order 13132. This proposed AD 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.
(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),
(3) Will not affect intrastate aviation in Alaska, and
(4) 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.
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.
Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 14 CFR part 39 as follows:
1. The authority citation for part 39 continues to read as follows:
49 U.S.C. 106(g), 40113, 44701.
2. The FAA amends § 39.13 by adding the following new airworthiness directive (AD):
We must receive comments by May 1, 2012.
This AD applies to the following Pratt & Whitney Division (PW) turbofan engines:
(1) PW4000-94″ engine models PW4050, PW4052, PW4056, PW4152, PW4156, PW4650, PW4060, PW4060A, PW4060C, PW4062, PW4062A, PW4156A, PW4158, PW4160, PW4460, and PW4462 including models with any dash number suffix.
(2) PW4000-100″ engine models PW4164, PW4164C, PW4164C/B, PW4168, PW4168A, PW4164-1D, PW4164C-1D, PW4164C/B-1D, PW4168-1D, PW4168A-1D, and PW4170.
This AD was prompted by reports of 3rd and 4th stage vane fractures in the low pressure turbine (LPT) of certain PW4000-94″ and PW4000-100″ turbofan engines. These fractures caused an uncontained engine failure and an LPT case puncture, and resulted in multiple in flight shutdowns. We are issuing this AD to prevent 3rd and 4th stage vane fractures in the LPT, which could damage the LPT rotor and lead to an uncontained engine failure and damage to the airplane.
Comply with this AD within the compliance times specified, unless already done.
(1) At the next LPT overhaul do the following:
(i) Remove LPT 4th stage vanes from service if more than one strip and recoat repair has been performed, or if the number of strip and recoat repairs are unknown. After the effective date of this AD, do not install or reinstall into any engine any LPT 4th stage vanes that have had more than one strip and recoat repair.
(ii) Re-assemble the 3rd stage LPT rotor blades using a method that will alternate heavy blades next to light blades and balance blades of similar weights 180 degrees across the rotor.
(iii) Inspect the LPT 3rd stage vane cluster assembly. Ensure adequate engagement between the vane cluster assembly and the rear turbine case.
(iv) Examine the vane and airseal engagement slots on the rear turbine case where the 3rd stage vane is installed. Ensure adequate engagement exists for assembly of the 3rd stage vane cluster assembly and the rear turbine case.
(v) Inspect the 44 LPT 4th stage vane cluster assemblies PN 52N774-01 for casting identification “51N554AT 1447 2S1C1” and PN 52N674-01 for casting identification “51N454AT 655 2S1C1.” Remove the vane cluster assembly from service if either of these casting identifications is found.
(2) At the next HPT overhaul, re-assemble the 2nd stage HPT rotor blades using a method that will alternate heavy blades next to light blades and balance blades of similar weights 180 degrees across the rotor.
The Manager, Engine Certification Office, may approve AMOCs for this AD. Use the procedures found in 14 CFR 39.19 to make your request.
(1) Guidance on the assembly method of paragraph (e)(1)(ii) of this AD can be found in the applicable engine manual: PN 50A605 or PN 50A822 Task 72-53-03-440-001, dated September 15, 2006; or PN 50A443 Task 72-53-03-440-001, dated May 1, 2007; or PN 51A342 Task 72-53-03-440-002-003, dated September 15, 2006.
(2) Guidance on the dimensional inspection of paragraph (e)(1)(iii) of this AD can be found in the Clean Inspect Repair Manual, PN 51A357 Task 72-53-23-200-004, dated January 15, 2011.
(3) Guidance on the dimensional inspections of paragraph (e)(1)(iv) of this AD can be found in the Clean Inspect Repair Manual, PN 51A357 Subtask 72-53-17-220-060, dated September 15, 2009.
(4) Guidance on the assembly method of paragraph (e)(2) of this AD can be found in the applicable engine manual: PN 50A605, PN50A822, or PN50A443 Task 72-52-02-440-001, dated May 1, 2010; or PN 51A342 Task 72-52-02-440-001, dated September 15, 2011.
(5) For more information about this AD, contact James Gray, Aerospace Engineer, Engine Certification Office, FAA, 12 New England Executive Park; phone: 781-238-7742; fax: 781-238-7199; email:
(6) For service information identified in this AD, contact Pratt & Whitney, 400 Main St., East Hartford, CT 06108; phone: 860-565-4321. You may review copies of the referenced service information at the FAA,