Federal Aviation Administration, DOT.
Notice of proposed rulemaking (NPRM).
This document proposes to adopt a new airworthiness directive (AD), applicable to Rolls-Royce Corporation, (formerly Allison Engine Company), AE 2100 and AE 3007 series engines. This proposed AD would require a one-time acid etch inspection of the 2nd stage high pressure turbine (HPT) wheel for cracks. If the wheel is cracked, this proposed AD would require replacement of the turbine wheel with a serviceable part. This proposed AD is prompted by a report of a 2nd stage turbine wheel that was returned from the field with cracks in the aft bore face. The actions specified by this proposed AD are intended to detect and prevent early development of cracks due to low cycle fatigue of the HPT 2nd stage wheel in the aft bore face that can lead to wheel failure, power loss, and possible damage to the airplane.
Comments must be received by February 12, 2001.
Submit comments to the Federal Aviation Administration (FAA), New England Region, Office of the Regional Counsel, Attention: Rules Docket No. 2000-NE-27-AD, 12 New England Executive Park, Burlington, MA 01803-5299. Comments may also be sent via the Internet using the following address: “firstname.lastname@example.org”. Comments sent via the Internet must contain the docket number in the subject line. Comments may be inspected at this location between 8 a.m. and 4:30 p.m., Monday through Friday, except Federal holidays.Start Further Info
FOR FURTHER INFORMATION CONTACT:
Michael Downs, Aerospace Engineer, Chicago Aircraft Certification Office, Start Printed Page 77529FAA, Small Airplane Directorate, 2300 E. Devon Ave., Des Plaines, IL 60018; telephone (847) 294-7870, fax (847) 294-7834.End Further Info End Preamble Start Supplemental Information
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 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 2000-NE-27-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. 2000-NE-27-AD, 12 New England Executive Park, Burlington, MA 01803-5299.
The Federal Aviation Administration (FAA) has received a report of cracks in the aft bore face of a 2nd stage high pressure turbine wheel from an AE 2100A engine that was returned from the field. Review of the manufacturing process revealed the cracks were caused by contact between the bore vertical face and a carbide tool bit during machining of the under side of the seal arm lip. This condition, if not corrected, could result in an early development of cracks due to low cycle fatigue of the HPT 2nd stage wheel in the aft bore face that can lead to wheel failure power loss, and possible damage to the airplane.
The inspection intervals for the early manufactured turbine wheels (P/N 23050912) were set to maintain a risk of a wheel burst event to levels at or below 1x10 EE-8 events per cycle. This determination is made based on the crack growth rates observed in the one field returned turbine wheel, the specific missions flown for each engine model, and the probability of a turbine wheel having been damaged. The inspection interval for the remaining engine models was set at “next shop visit” based on the lower risk of having been damaged, the shot peen benefits, and the projected shop visit rate for these models.
The “one-time” inspection is adequate because it identifies (via acid etch) those turbine wheels which were damaged during manufacturing and removes them from service thereby eliminating the risk of a premature wheel failure.
Service Bulletins (SB's)
The FAA has reviewed and approved the technical contents of Rolls-Royce Alert Service Bulletins (ASB's): AE2100A-A-72-234, Revision 2; AE2100C-A-72-183, Revision 2; AE2100D3-A-72-179, Revision, 2, dated October 17, 2000 and AE3007A-A-72, Revision 2, and AE3007C-A-72-153, Revision 2, dated October 17, 2000, that describe the procedures for examining the turbine wheels for damage using the one-time acid etch procedure.
Since an unsafe condition has been identified that is likely to exist or develop on other products of this same type design, the proposed AD would require a one-time acid etch inspection of the 2nd-stage high pressure turbine wheel for damage. If the wheel is damaged, this proposal would require replacement of the turbine wheel with a serviceable part. The actions would be required to be done in accordance with the alert service bulletins described previously.
There are approximately 1,376 engines of the affected design in the worldwide fleet. The FAA estimates that approximately 470 engines installed on airplanes of US registry would be affected by this proposed AD. The FAA estimates that disassembly to perform the acid etch inspection and reassembly will take approximately 130 work hours, which includes teardown to HPT, inspection and reassembly, and that the average labor rate is $60 per work hour. Labor costs to perform the disassembly/reassembly are $7,800, and a test stand run will cost about $5,000, for a total cost of $12,800 per engine to conduct the acid etch inspection. Based on these figures, the FAA estimates that the total cost impact of performing the acid etch inspection on US operators will be $6,016,000. If a wheel must be replaced, the cost of a replacement wheel is $18,000, and it will take an additional 30 work hours to replace the wheel, at $60 per work hour. Therefore the total cost of parts and labor for replacing the wheel will total $19,800.00 per wheel. If all wheels needed to be replaced, the total cost impact of the proposed AD on U.S. operators would be $15,322,000. The FAA estimates, however, that not all wheels will need replacement and that some labor costs required to accomplish the requirements of this proposed AD maybe reimbursed by the manufacturer, thus reducing the total cost impact of the proposed AD on US operators.
This proposal 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 proposal.
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.Start List of Subjects
List of Subjects in 14 CFR Part 39End List of Subjects
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 Code of Federal Regulations (14 CFR part 39) as follows:Start Part Start Printed Page 77530
PART 39—AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
2. Section 39.13 is amended by adding the following new airworthiness directive:
Rolls-Royce Corporation: Docket No. 2000-NE-27-AD.
Applicability: This airworthiness directive is applicable to Rolls-Royce Corporation (formerly Allison Engine Company) models AE 2100A and AE 2100C engines with high pressure turbine (HPT) wheel 23050912 installed; AE 2100A engine with turbine wheel 23063462-serial number (S/N) MM14062 installed; AE 2100D3 and AE 3007A, AE 3007A1/1, AE 3007A1/2, AE 3007A1/3, AE 3007A1, AE 3007A1P, AE 3007A3 and AE 3007C with HPT second stage wheels with S/Ns before MM183060. These engines are installed on but not limited to Embraer (EMB) 145 and 135, Cessna Citation 750, and Industi Pesawat Terbang Nusantara (IPTN) N-250 airplanes.
This airworthiness directive (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 (f) 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 the requirements of this AD is required as indicated, unless already.
To detect and prevent early development of cracks due to low cycle fatigue of the high pressure turbine (HPT) 2nd stage wheel in the aft bore face that can lead to wheel failure power loss, and possible damage to the airplane, do the following:
(a) Perform a one-time acid etch inspection to the 2nd stage high pressure turbine wheel in accordance with the Accomplishment Instructions contained in the following Rolls-Royce Alert Service Bulletins:
|AE models||Rolls-Royce service bulletin|
|AE 2100A||AE 2100A-A-72-234, Revision 2, dated October 13, 2000.|
|AE2100C||AE 2100C-A-72-183, Revision 2, dated October 13, 2000.|
|AE2100D3||AE 2100D3-A-72-179, Revision 2, dated October 13, 2000.|
|AE3007A||AE 3007A-A-72-179, Revision 2, dated October 17, 2000.|
|AE3007C||AE 3007C-A-72-153, Revision 2, dated October 17, 2000.|
(b) Perform these inspections according to the following compliance times:
|Models||With turbine wheel||Mandatory|
|(1) AE2100A, AE2100C||23050912||Before 4800 cycles since new (CSN).|
|(2) AE2100A||23063462-S/N MM 14062||Before 4800 CSN.|
|(3) AE2100D3||23050912||Before 3200 CSN.|
|(4) All other AE2100A, AE2100C, and AE2100D3||23069592, 23063462, 23064822, 23070673, 23065892, 23069116, 233064473, 23064474, 23068072 with S/N's MM183060 and before.||Next shop visit.|
|(5) All AE3007A, AE3007A1/1, AE 3007A1/2, AE 3007A1/3, AE 3007A1, AE3007A1P, AE3007A3, and AE3007C series engines||23063462, 23065892, 23069116, 23069592, 23069438, with S/N MM183060 and before.||Next shop visit.|
(c) If cracks are discovered, replace the turbine wheel with a serviceable part.
(d) The next shop visit is defined as whenever the engine is removed and sent to a maintenance center for inspection or repair.
(e) A serviceable part is defined as any turbine wheel with a serial number greater than MM183060, or less than MM183060, that has undergone an acid etch inspection and has been determined to have no cracks.
Alternative Methods of Compliance
(f) 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, Chicago Aircraft Certification Office. Operators shall submit their request through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Chicago Aircraft Certification Office.
Information concerning the existence of approved alternative methods of compliance with this airworthiness directive, if any, may be obtained from the Chicago Aircraft Certification Office.
(g) 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 aircraft to a location where the requirements of this AD can be accomplished.
Issued in Burlington, Massachusetts, on December 1, 2000.
David A. Downey,
Assistant Manager, Engine and Propeller Directorate, Aircraft Certification Service.
[FR Doc. 00-31613 Filed 12-11-00; 8:45 am]
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