AD 98-21-23

This amendment adopts a new airworthiness directive (AD) that is applicable to CFM International, S.A. (CFMI) CFM56-7B series turbofan engines. This action supersedes telegraphic AD T98-18-51 that currently requires an inspection of electronic engine control (EEC) fault messages on both engines for the presence of any of the hydromechanical unit (HMU) fuel metering valve (FMV) signal faults identified in the All Operators Wire every 20 flight cycles or 3 calendar days, whichever occurs first, and, if necessary, removing the HMU and replacing it with a serviceable HMU. This action also requires installation of improved EEC software that constitutes terminating action to the repetitive fault message inspections. This amendment is prompted by development of improved EEC software that obviates the need for the repetitive fault message inspections. The actions specified by this AD are intended to prevent an uncommanded engine acceleration event, or inflight engine shutdown.

Final rule; request for comments.

98-21-23 CFM International, S.A.: Amendment 39-10831. Docket No. 98-ANE-65-AD. Supersedes telegraphic AD T98-18-51.
Applicability: CFM International, S.A. (CFMI) CFM56-7B series turbofan engines, with electronic engine control (EEC) software, part numbers (P/Ns) 1853M78P07, 1853M78P08, 1853M78P10, or 1853M78P11 installed. These engines are installed on, but not limited to, Boeing 737-600, 737-700, and 737-800 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 (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: Required as indicated, unless accomplished previously.
To prevent an uncommanded engine acceleration event, or inflight engine shutdown, accomplish the following:
(a) Inspect for the presence of engine EEC fault messages for both engines installed on the aircraft within 20 flight cycles after the effective date of this AD, or within three calendar days, whichever occurs first, in accordance with CFM56-7B All Operators Wire 98/CFM56/312R1, dated August 28, 1998.
(1) If any of the faults identified in the All Operators Wire are detected on only one of the engines, remove and replace the hydromechanical unit (HMU) with a serviceable HMU, and ensure the faults are cleared prior to further flight.
(2) If any of the faults identified in the All Operators Wire are detected on both engines, remove and replace the HMU on the engine that has logged the fault for more flight cycles, replace with a serviceable HMU, and ensure that the faults are cleared prior to further flight. Remove and replace the HMU on the other engine with a serviceable HMU, after accumulating at least three flight cycles, but not to exceed ten flight cycles, and ensure the faults are cleared.
(3) Thereafter, inspect for the presence of engine EEC fault messages on both engines of the aircraft at intervals not to exceed 20 flight cycles since last inspection, or within three calendar days since last inspection, whichever occurs first. If any of the faults identified in the All Operators Wire are detected, remove and replace the HMU in accordance with paragraph (a)(1) or (a)(2) of this AD, as applicable.
Note 2: Installation of a serviceable HMU in accordance with paragraphs (a)(1) or (a)(2) of this AD does not constitute terminating action to the repetitive inspections required by paragraph (a)(3) of this AD.
(b) For the purpose of this AD, a serviceable HMU is defined as an HMU with P/N 1853M56P06 or AlliedSignal P/N 442098.
(c) Within 75 cycles in service after the effective date of this AD, or by November 9, 1998, whichever occurs first, install EEC software, P/N 1853M78P12, in accordance with CFMI CFM56-7B Alert Service Bulletin (ASB) No. 73-A024, dated September 2, 1998. Installation of this improved software constitutes terminating action to the inspections required by paragraph (a) of this AD.
(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. 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 3: Information concerning the existence of approved alternative methods of compliance with this airworthiness directive, if any, may be obtained from the Engine Certification Office.
(e) The actions required by this AD shall be accomplished in accordance with the following CFMI service documents:

Document No.
Page
Date
All Operators Wire 98/CFM56/312R1
1-2
August 28, 1998
Total Pages: 2.

CFM56-7B ASB No. 73-A024
1-23
September 2, 1998
Total Pages: 23.

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 CFM International, S.A., Technical Publications Department, 1 Neumann Way, Cincinnati, OH 45215; telephone (513) 552-2981, fax (513) 552-2816. 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 supersedes telegraphic AD T98-18-51, issued August 28, 1998.
(g) This amendment becomes effective on November 2, 1998.

On August 28, 1998, the Federal Aviation Administration (FAA) issued telegraphic airworthiness directive (AD) T98-18-51, applicable to CFM International, S.A. (CFMI) CFM56-7B series turbofan engines, which requires an inspection of electronic engine control (EEC) fault messages on both engines for the presence of any of the hydromechanical unit (HMU) fuel metering valve (FMV) signal faults identified in the all operators wire every 20 flight cycles or 3 calendar days, whichever occurs first. If any of the HMU FMV signal faults identified in CFMI All Operators Wire 98/CFM56/312R1, dated August 28, 1998, are detected on only one of the engines, that AD requires, prior to further flight, removal from service of the HMU and replacement with a serviceable HMU. If any of the HMU FMV signal faults identified in the All Operators Wire are detected on both engines, that AD requires removing the HMU and replacing it with a serviceable HMU, prior to further flight, on the engine that has logged the faults for the most flight cycles; and after accumulating at least three flight cycles, but not to exceed ten flight cycles, removing the HMU and replacing it with a serviceable HMU on the other engine.
That action was prompted by reports of 3 uncommanded engine acceleration events, one of which resulted in an inflight engine shutdown. The cause of the uncommanded acceleration events has been attributed to faults in channel B of the HMU FMV resolver. The investigation has not yet identified the root cause for these faults on all three events. Under current time-limited dispatch (TLD) guidelines, these faults are classified as short or long time dispatch faults, and therefore, they are not annunciated in the cockpit. A review of the EEC non-volatile memory following these events has indicated that the faults had been present for previous flight cycles. These faults were not detected under the current TLD guidelines. Therefore, the FAA has determined that these faults need to be reclassified as no dispatch faults, and that the inspection frequency must be increased. That condition, if not corrected, could result in an uncommanded engine acceleration event, or inflight engine shutdown.
Since the issuance of that telegraphic AD, the manufacturer has developed improved EEC software that changes the dispatch level for the HMU FMV signal faults identified in the All Operators Wire to engine control light level/no dispatch.
The FAA has reviewed and approved the technical contents of CFMI CFM56-7B All Operators Wire 98/CFM56/312R1, dated August 28, 1998, that describes procedures for inspection for the presence of engine EEC fault messages; and CFM56-7B Alert Service Bulletin (ASB) No. 73-A024, dated September 2, 1998, that describes procedures for installation of the improved software.
Since an unsafe condition has been identified that is likely to exist or develop on other engines of this same type design, this AD supersedes telegraphic AD T98-18-51 to require installation of improved EEC software, within 75 cycles in service (CIS) after the effective date of this AD, or by November 9, 1998, whichever occurs first. The calendar end-date was determined based upon risk analysis. Installation of this improved software constitutes terminating action to the repetitive fault message inspections required by this AD. The actions are required to be accomplished in accordance with the ASB described previously.
Since a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for prior public comment hereon are impracticable, and that good cause exists for making this amendment effective in less than 30 days. Comments Invited
Although this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded by notice and an opportunity for public comment, comments are invited on this rule. Interested persons are invited to comment on this 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 under the caption "ADDRESSES." All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would be needed.
Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the 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 that summarizes each FAA-public contact concerned with the substance of this AD will be filed in the Rules Docket.
Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this notice must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 98-ANE-65-AD." The postcard will be date stamped and returned to the commenter.
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.
The FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and is not a "significantregulatory action" under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket. A copy of it, if filed, 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: