AD 99-15-06

This amendment adopts a new airworthiness directive (AD), applicable to AlliedSignal Inc. Model ALF502R-5 and ALF502R-3A turbofan engines, that requires incorporation of an improved fan core inlet anti-ice system. This amendment is prompted by reports of uncommanded reduction of engine thrust (rollback) and loss of thrust control in icing conditions. The actions specified by this AD are intended to prevent ice accretion on the fan core inlet stator vane surfaces, which can result in engine rollback and loss of thrust control in icing conditions.

Final rule.

99-15-06 ALLIEDSIGNAL INC.: Amendment 39-11225. Docket 98-ANE-42-AD.
Applicability: AlliedSignal Inc. (formerly Textron Lycoming) ALF502R-5 and ALF502R-3A model turbofan engines, installed on but not limited to British Aerospace (BAe) 146-100A, -200A and -300A series aircraft.
Note 1: 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 (c) 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: Required as indicated, unless accomplished previously.
To prevent uncommanded reduction of engine thrust and loss of thrust control in icing conditions, accomplish the following:
(a) At the next engine shop visit after the effective date of this AD, but not later than December 31, 2002, install an improved fan core inlet anti-ice system in accordance with Accomplishment Instructions, Paragraphs 2.B. through 2.I.(1-4), of AlliedSignal Inc. Service Bulletin (SB) No. ALF/LF 72-1020, Revision 2, dated September 30, 1998. In order to install engines with the required modifications onto BAe 146-100A, -200A and -300A series aircraft, accomplish BAe Regional Aircraft SB No. 26-40-01601A, dated March 25, 1998, and BAe Regional Aircraft SB No. 71-68-01581A, Revision 1, dated March 25, 1998.
(b) For the purpose of this AD, an engine shop visit is defined as maintenance that includes separation of either the fan module or the combustor turbine module from the remainder of the engine.
(c) 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. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Engine Certification Office.
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.
(d) 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 airplane to a location where the requirements of this AD can be accomplished.
(e) The actions required by this AD shall be done in accordance with the following SB's:

Document No
Pages
Revision
Date
AlliedSignal Inc

No. ALF/LF 72-1020
1
2
September 30, 1998

2
1
June 3, 1998

3-14
Original
March 11, 1998

15
1
June 3, 1998

16
Original
March 11, 1998

17
1
June 3, 1998

18-20
2
September 30, 1998

21,22
Original
March 11, 1998

23,24
1
June 3, 1998

25
Original
March 11, 1998

26-29
2
September 30, 1998

30-33
Original
March 11, 1998

34,35
2
September 30, 1998

36
1
June 3, 1998

37
2
September 30, 1998

38
1
June 3, 1998
Total Pages: 38.

BAe Regional Aircraft
No. 26-40-01601A
1-7
Original
March 25, 1998
Total Pages: 7.

BAe Regional Aircraft
No. 71-68-01581A
1-3
4-18
1
Original
March 25, 1998
August 14, 1997
Total Pages: 18.

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 AlliedSignal Engines, P.O. Box 5218, Phoenix, AZ85072-2181, telephone (602) 365-2493, fax (602) 365-5577. Copies may be inspected at the FAA, New England Region, Office of the Regional 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.
(f) This amendment becomes effective on September 17, 1999.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to AlliedSignal Inc. Model ALF502R-5 and ALF502R-3A turbofan engines was published in the Federal Register on December 14, 1998 (63 FR 68708). That action proposed to require installation of an improved fan core inlet anti-ice system, at the next shop visit, but no later than December 31, 2002.
Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.
Two commenters state that they should be allowed to use the altitude and operating restrictions, currently mandated by AD 96-14-09, rather than to require incorporation of the proposed engine anti-icing system modifications. One of the commenters proposes adoption of the altitude and operating restrictions regardless of icing conditions being present; while theother commenter proposes permanent use of AD 96-14-09 restrictions in icing conditions only. The commenters state that no rollback events have occurred below 26,000 feet, and that the unsafe icing conditions are not prevalent at altitudes below 26,000 feet. The commenters also state that the modifications are economically burdensome due to increased engine operating costs, and airplane air traffic control restrictions in congested areas. The FAA does not concur. The FAA acknowledges that no known rollback events have occurred below 26,000 feet altitude. However, the FAA considers the total operating hours accrued below that altitude, and the hours accrued in icing conditions below that altitude, to be insufficient to conclude that the interim restrictions, successfully imposed by AD 96-14-09, would provide an acceptable level of safety for long-term unrestricted operation of an unmodified engine below that altitude. In addition, the technical data available to the FAA, includingthat provided by the commenters, does not show that significant mixed phase icing conditions are isolated to altitudes above 26,000 feet, or that the unmodified ALF502R-5 and ALF502R-3A engines are capable of long-term unrestricted operation in the icing conditions present below that altitude.
Moreover, the FAA is aware of two instances of ALF502R-5 engine rollback which occurred during inadvertent encounters of icing conditions at altitudes above 26,000 feet, after altitude and operating restrictions were originally established by AD 94-07-09, and superseded by AD 96-14-09. Accordingly, the FAA considers the current altitude restriction and operating procedures in icing conditions to be acceptable only for a finite period as necessary for implementation of engine modifications, rather than relying on interim changes to operating procedures.
Therefore, based on the relatively limited fleet experience below the altitude limitation of 26,000 feet, the absence of sufficient engineand meteorological data to confidently isolate the ALF502R-5 engine rollback phenomenon to altitudes above 26,000 feet, and the demonstrated possibility of inadvertent operation in icing conditions above 26,000 feet, the FAA does not concur that an acceptable long-term level of safety would be provided by limiting the operating envelope of unmodified engines to altitudes below 26,000 feet.
One commenter proposes that the AD allow temporary installation of a single unmodified engine without requiring re-imposition of airplane operating restrictions. The change was proposed in order to reduce the frequency of aircraft being reidentified from restricted operation to unrestricted operation and back, to minimize airplane flight manual changes, and to reduce the likelihood of mis-placarding or pilot error. The commenter further states that the change is justifiable by statistical analysis of rollback likelihood. The FAA does not concur. The proposed AD is intended to require specificactions for incorporating ALF502R-5 engine modifications, rather than to address broader requirements with regard to airplane operation. Therefore, this submitted comment and response would not directly impact the requirements of the proposed rule.
The actions proposed by the submitted comment would intentionally allow operation of an engine beyond its known operating capability, including unrestricted operation in icing conditions associated with engine rollback and power loss. The FAA recognizes that reinstallation of a single unmodified engine may require more instances of airplane flight manual changes and cockpit placard changes than would be required otherwise. However, the FAA does not consider the need for these additional tasks to warrant allowing operation of an unmodified engine beyond its known operating capability. Moreover, installation of cockpit placards and airplane flight manual revisions are currently required by AD 96-14-09, and these tasks are considered appropriate for notifying crews of applicable altitude restrictions and operating procedures for unmodified engines. Accordingly, the FAA does not consider that the potential for mis-placarding or crew error to necessitate consideration of other measures.
In summary, because of the likelihood of rollback and power loss if ALF502R-5 engines are allowed to operate unrestricted in icing conditions, the FAA considers it necessary to continue to impose the operating restrictions in AD 96-14-09 if a single unmodified engine is installed and operated in icing conditions. The FAA continues to consider the installation of cockpit placards and flight manual revisions as acceptable means to identify when an unmodified engine is installed and requires AD 96-14-09 restrictions.
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 as proposed.
There are approximately 982 engines of the affected design in the worldwide fleet. The FAA estimates that 100 engines installed on aircraft of U.S. registry will be affected by this AD, that it will take approximately 30 work hours per engine to accomplish the required actions, and that the average labor rate is $60 per work hour. Required parts will cost approximately $75,000 per engine. Based on these figures, the cost impact of the AD's required incorporation of engine modifications for U.S. operators is estimated to be $7,680,000.
In addition to the above engine modifications, further aircraft modifications specified by BAe SB No. 71-68-01581A, and BAe SB No. 26-40-01601A, Revision 1, are required prior to installation of modified engines onto BAe 146 aircraft. The FAA estimates that 20 aircraft of U.S. registry will be affected by this proposed AD, that it will take approximately 33 work hours per aircraft to accomplish the required actions, and that the average labor rate is $60 per work hour. Required parts will cost approximately $2,400 per aircraft. Based on these figures, the cost impact for incorporation of aircraft modifications required by the AD on U.S. operators is estimated to be $87,600.
Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $7,767,600.
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.
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 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 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. 106(g), 40113, 44701. 39.13 [Amended]
2. Section 39.13 is amended by adding the following new airworthiness directive:

U.S. Department of Transportation Federal Aviation Administration The following Airworthiness Directive issued by the Federal Aviation Administration in accordance with the provisions of Federal Aviation Regulations, Part 39, applies to an aircraft model of which our records indicate you may be the registered owner. Airworthiness Directives affect aviation safety and are regulations which require immediate attention. You are cautioned that no person may operate an aircraft to which an Airworthiness Directive applies, except in accordance with the requirements of the Airworthiness Directive (reference FAR Subpart 39.3).