AD 98-02-02

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AD Number:
98-02-02
Document Type:
AD Final Rules
Docket Number:
97-NM-267-AD
Subject Heading:
Airworthiness Directives; Boeing Model 747 Series Airplanes
Subject:
Forward Engine Mount Bulkhead
Status:
Current
Citation:
(Federal Register: January 16, 1998 (Volume 63, Number 11))
Citation Publish Date:
01/16/1998
Effective Date:
02/02/1998
Make:
The Boeing Company
Model:
747-100 Series | 747-100B Series | 747-100B SUD Series | 747-200B Series | 747-200C Series | 747-200...Show more
Product Type:
Aircraft
Product Subtype:
Large Airplane
Affected AD:
Superseded AD:
Affected By:
Superseded By:
Service/Office:
Office of Primary Responsibility:
CFR Part Reference:
Part 39 (63 FR 2593 NO. 11 01/16/98)
Comments:
AIRWORTHINESS DIRECTIVES FINAL RULES: 98-02-02
CITATION:   [Federal Register: January 16, 1998 (Volume 63, Number 11)]

PAGE NUMBER:   [Page 2593]

DOCKET NUMBER:   97-NM-267-AD

AMENDMENT:   39-10284

AD NUMBER:   98-02-02

SUBJECT HEADING:   Airworthiness Directives; Boeing Model 747 Series Airplanes

ACTION:   Final rule; request for comments

SUMMARY:  
This amendment supersedes an existing airworthiness directive (AD), applicable to certain Boeing Model 747 series airplanes, that currently requires repetitive inspections for discrepancies of the forward engine mount bulkhead of the nacelle strut, and corrective action, if necessary. That AD also provides for optional terminating action for the repetitive inspections. For certain airplanes, this amendment adds repetitive inspections for discrepancies in the forward engine mount bulkhead and in the forward lower spar web, and corrective actions, if necessary. For other airplanes, this amendment adds a one-time inspection to detect stop drilled cracks of the exterior of the forward engine mount chord, and replacement of the chord with a new chord, if necessary. This amendment also adds an additional optional terminating action for the repetitive inspections. This amendment is prompted by reports that fatigue cracking was found in an area adjacent to the inspection area specified in the existing AD. The actions specified in this AD are intended to detect and correct such fatigue cracking, which could lead to the failure of the forward engine mount bulkhead and consequent separation of the engine from the airplane.

DATES:   Effective February 2, 1998. The incorporation by reference of certain publications listed in the regulations is approved by the Director of the Federal Register as of February 2, 1998. Comments for inclusion in the Rules Docket must be received on or before March 17, 1998.

ADDRESSES:  
Submit comments in triplicate to the Federal Aviation Administration (FAA),
Transport Airplane Directorate, ANM-103, Attention: Rules Docket No. 97-NM-267-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

The service information referenced in this AD may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT:  
Tamara L. Dow, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2771; fax (425) 227-1181.

SUPPLEMENTARY INFORMATION:  
On October 2, 1982, the FAA issued AD 82-22-02, amendment 39-4476 (47 FR 46842, October 21, 1982), applicable to certain Boeing Model 747 series airplanes, to require repetitive inspections for discrepancies of the forward engine mount bulkhead of the nacelle strut, and corrective action, if necessary. That AD also provides for optional terminating action (installation of a new doubler) for the repetitive inspections. That action was prompted by reports of cracks in doublers that were installed as terminating action for AD 80-03-09, amendment 39-3832. The actions required by AD 82-22-02 are intended to prevent failure of the forward engine mount bulkhead and possible separation of an engine from the airplane.

Actions Since Issuance of Previous Rule

Since the issuance of AD 82-22-02, the FAA has received two reports of fatigue cracking in an area adjacent to the inspection area specified in that AD on the affected airplanes. In one incident, a 5-inch long crack was found in the forward lower spar web aft of the bulkhead-to-firewall channel, and a 2-inch long crack was found in the bend radius of the chord of the forward mount bulkhead. These cracks occurred on the number 4 pylon. The airplane had accumulated 15,200 total landings and 67,600 total flight hours. In the other incident, a 2.5-inch crack was found in the chord of the forward mount bulkhead, and a 1.5-inch and 4-inch cracks were found in the forward lower spar web. These cracks occurred on the number 3 pylon.

Such fatigue cracking, if not detected and corrected in a timely manner, could lead to the failure of the forward engine mount bulkhead and consequent separation of the engine from the airplane.

Discussion of Relevant Service Information

Subsequent to the finding of this new cracking, the FAA reviewed and approved Boeing Alert Service Bulletin 747-54A2069, Revision 9, dated May 29, 1997. The revised alert service bulletin continues to describe procedures identical to those described in Revision 2 of the alert service bulletin (which was referenced in AD 82-22-02 as the appropriate source of service information). However, the revised alert service bulletin also describes new procedures for various repetitive inspections to detect discrepancies (i.e., cracks, damage, loose fasteners) in the forward engine mount bulkhead and in the forward lower spar web, and corrective actions, if necessary. The revised alert service bulletin also deletes the procedures for stop drilling cracks in the bulkhead chords.

The FAA also has reviewed and approved the following Boeing service information:

Alert Service Bulletin 747-54A2069, Revision 3, dated May 23, 1980;
Alert Service Bulletin 747-54A2069, Revision 4, dated November 26, 1980;
Service Bulletin 747-54A2069, Revision 5, dated August 21, 1981;
Alert Service Bulletin 747-54A2069, Revision 6, dated October 22, 1982;
Service Bulletin 747-54A2069, Revision 7, dated July 28, 1988; and
Service Bulletin 747-54A2069, Revision 8, dated June 9, 1994.

The inspection procedures specified in Revisions 3 through 8 of the service bulletin are similar to those specified in Revision 2 of the service bulletin. Therefore, the FAA has included in this AD references to these service bulletin revisions as additional sources of service information.

Explanation of Requirements of Rule

Since an unsafe condition has been identified that is likely to exist or develop on other airplanes of this same type design, this AD supersedes AD 82-22-02 to continue to require repetitive inspections for discrepancies of the forward engine mount bulkhead of the nacelle strut, and corrective action, if necessary. This AD adds various repetitive inspections to detect discrepancies (i.e., cracks, damage, loose fasteners) in the forward engine mount bulkhead and in the forward lower spar web, and corrective actions, if necessary. This AD also adds an additional optional terminating action for the repetitive inspections. Unlike the requirements of AD 82-22-02, this AD does not permit further flight with cracks in the bulkhead chords.

Differences Between the AD and the Relevant Service Information

Operators should note that, although the referenced service bulletins specify that the manufacturer must be contacted for disposition of certain conditions, this AD requires the repair or replacement of any cracked chord and/or web to be accomplished in accordance with a method approved by the FAA.

The referenced service bulletins also specify that accomplishment of AD 95-10-16, amendment 39-9233 (59 FR 65733, December 21, 1994), is terminating action for the repetitive inspections. However, for airplanes on which the strut/wing modification required by AD 95-10-16 has been accomplished, this AD requires a one-time detailed visual inspection to detect stop drilled cracks of the exterior of the forward engine mount chord. The FAA has determined that accomplishment of this inspection will ensure that all chords with stop drilled cracks are replaced.

Determination of Rule's Effective Date

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 shall 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 rule must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 97-NM-267-AD." The postcard will be date stamped and returned to the commenter.

Regulatory Impact

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 that it is not a "significant regulatory 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 removing amendment 39-4476 (47 FR 46842, October 21, 1982), and by adding a new airworthiness directive (AD), amendment 39-10284, to read as follows:

REGULATORY TEXT:  
98-02-02 BOEING: Amendment 39-10284. Docket 97-NM-267-AD. Supersedes AD 82-22-02, Amendment 39-4476.

Applicability: Model 747 series airplanes; as listed in Boeing Alert Service Bulletin 747-54A2069, Revision 9, dated May 29, 1997; certificated in any category.

NOTE 1: The airplanes specified in the applicability of this AD are the same as those specified in the applicability of AD 82-22-02.

NOTE 2: This AD applies to each airplane 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 airplanes 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: Required as indicated, unless accomplished previously.

To detect and correct fatigue cracking of the forward engine mount bulkhead, which could lead to the failure of the forward engine mount bulkhead and consequent separation of the engine from the airplane, accomplish the following:

(a) For airplanes on which the terminating action specified in AD 80-03-09, amendment 39-3832, has been accomplished: Within 300 hours time-in-service after October 27, 1982 (the effective date of 82-22-02, amendment 39-4476), accomplish paragraphs (a)(1), (a)(2), and (a)(3) of this AD. Repeat the inspections thereafter at intervals not to exceed 4,000 flight hours, until accomplishment of the inspections required by paragraphs (c)(1) and (c)(2) of this AD or the terminating action specified in paragraph (e) of this AD.

(1) Perform an inspection to detect loose or missing fasteners of the fasteners attaching the forward engine mount bulkhead of the nacelle strut to the horizontal fire wall, in accordance with one of the following service bulletins listed below. If any loose or missing fastener is detected, prior to further flight, replace all fasteners in both rows of fasteners, in accordance with the service bulletin.

Boeing Alert Service Bulletin 747-54A2069, Revision 2, dated February 1, 1980;
Boeing Alert Service Bulletin 747-54A2069, Revision 3, dated May 23, 1980;
Boeing Alert Service Bulletin 747-54A2069, Revision 4, dated November 26, 1980;
Boeing Service Bulletin 747-54A2069, Revision 5, dated August 21, 1981;
Boeing Alert Service Bulletin 747-54A2069, Revision 6, dated October 22, 1982;
Boeing Service Bulletin 747-54A2069, Revision 7, dated July 28, 1988;
Boeing Service Bulletin 747-54A2069, Revision 8, dated June 9, 1994; or
Boeing Alert Service Bulletin 747-54A2069, Revision 9, dated May 29, 1997.

(2) Remove by hand the protective coating of the area to be penetrant inspected using 400 grit or equivalent abrasive, and perform a penetrant inspection to detect cracks of the bulkhead chords, in accordance with one of the service bulletins listed below:



Boeing Alert Service Bulletin 747-54A2069, Revision 2, dated February 1, 1980;
Boeing Alert Service Bulletin 747-54A2069, Revision 3, dated May 23, 1980;
Boeing Alert Service Bulletin 747-54A2069, Revision 4, dated November 26, 1980;
Boeing Service Bulletin 747-54A2069, Revision 5, dated August 21, 1981;
Boeing Alert Service Bulletin 747-54A2069, Revision 6, dated October 22, 1982;
Boeing Service Bulletin 747-54A2069, Revision 7, dated July 28, 1988;
Boeing Service Bulletin 747-54A2069, Revision 8, dated June 9, 1994; or
Boeing Alert Service Bulletin 747-54A2069, Revision 9, dated May 29, 1997.

(i) If any crack is detected on the outside radius of the chord, and it is within the limits specified in the service bulletin, prior to further flight, perform a penetrant inspection to detect cracks on the inside radius of the chord, in accordance with the service bulletin.
(A) If any crack is detected on the inside radius of the chord, and it is within the limits specified in the service bulletin, prior to further flight, rework the cracked part in accordance with the service bulletin. Repeat the penetrant inspection required by paragraph (a)(2) of this AD thereafter at intervals not to exceed 600 flight hours, until accomplishment of the inspections required by paragraphs (c)(1) and (c)(2) of this AD or the terminating action specified in paragraph (e) of this AD.

(B) If any crack is detected on the inside radius of the chord, and it is outside the limits specified in the service bulletin, prior to further flight, replace the cracked part with a new part, in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate.

(ii) If any crack is detected on the outside radius of the chord, and it is outside the limits specified in the service bulletin, prior to further flight, replace the cracked part with a new part in accordance with a method approved by Seattle ACO.

(3) Perform an inspection to detect evidence of looseness of the fasteners attaching the forward engine mount fittings to the strut bulkhead. If any loose fastener is detected, prior to further flight, replace it with a new fastener.

(b) For airplanes on which only loose fasteners have been replaced as required by telegraphic AD T79-NW-21, amendment 39-3687: Within 600 hours time-in-service after October 27, 1982, replace all fasteners in both rows of fasteners with new fasteners in accordance with one of the service bulletins listed below:

Boeing Alert Service Bulletin 747-54A2069, Revision 2, dated February 1, 1980;
Boeing Alert Service Bulletin 747-54A2069, Revision 3, dated May 23, 1980;
Boeing Alert Service Bulletin 747-54A2069, Revision 4, dated November 26, 1980;
Boeing Service Bulletin 747-54A2069, Revision 5, dated August 21, 1981;
Boeing Alert Service Bulletin 747-54A2069, Revision 6, dated October 22, 1982;
Boeing Service Bulletin 747-54A2069, Revision 7, dated July 28, 1988;
Boeing Service Bulletin 747-54A2069, Revision 8, dated June 9, 1994; or
Boeing Alert Service Bulletin 747-54A2069, Revision 9, dated May 29, 1997.

(c) For airplanes on which the strut/wing modification required by AD 95-10-16, amendment 39-9233, has not been accomplished: Within 90 days after the effective date of this AD, accomplish paragraphs (c)(1) and (c)(2) of this AD.

(1) Perform various inspections to detect discrepancies (i.e., cracks, damage, loose fasteners) in the forward engine mount bulkhead and in the forward lower spar web, in accordance with Figure 1 of Boeing Alert Service Bulletin 747-54A2069, Revision 9, dated May 29, 1997. If any discrepancy is detected, prior to further flight, perform the applicable corrective action in accordance with Figure 1 of the alert service bulletin; except the repair or replacement of any cracked chord and/or web shall be accomplished in accordance with a method approved by the Manager, Seattle ACO. Repeat the inspections thereafter at intervals not to exceed 4,000 flight hours.

(2) Perform an inspection to detect evidence of looseness of the fasteners attaching the forward engine mount fittings to the strut bulkhead. If any loose fastener is detected, prior to further flight, replace it with a new fastener in accordance with Boeing Document D6-13592, "747 Structural Repair Manual (SRM)," Chapter 51, Subject 51-30-04, Revision 8, dated September 5, 1997.

(d) For airplanes on which the strut/wing modification required by AD 95-10-16, amendment 39-9233, has been accomplished: Within 90 days after the effective date of this AD, perform a detailed visual inspection to detect stop drilled cracks of the exterior of the forward engine mount chord. Inspect to the height of the engine mount fitting (approximately 12 inches). If any crack (including a stop drilled crack) is detected, prior to further flight, replace the chord with a new chord in accordance with a method approved by the Manager, Seattle ACO.

NOTE 3: Inspections required by AD 94-17-17, amendment 39-9012, are similar and somewhat overlap the inspections required by this AD.

(e) Accomplishment of either paragraphs (e)(1) and (e)(2), or paragraphs (e)(2) and (e)(3) of this AD constitutes terminating action for the requirements of this AD.

(1) Modify the fasteners and install a doubler on the forward lower spar web, or replace the doubler of the forward lower spar web with a new doubler, in accordance with Figure 2 or Figure 3, as applicable, of Boeing Alert Service Bulletin 747-54A2069, Revision 6, dated October 22, 1982; Boeing Service Bulletin 747-54A2069, Revision 7, dated July 28, 1988; Boeing Service Bulletin 747-54A2069, Revision 8, dated June 9, 1994; or Boeing Alert Service Bulletin 747-54A2069, Revision 9, dated May 29, 1997.

(2) Replace any cracked forward engine mount bulkhead chord with a new chord, and replace any cracked forward lower spar web with a new web, in accordance with a method approved by the Manager, Seattle ACO.

(3) Modify the nacelle strut and wing structure in accordance with Boeing Alert Service Bulletin 747-54A2159, dated November 3, 1994; Revision 1, dated June 1, 1995; or Revision 2, dated March 14, 1996.

(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, Seattle ACO. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Seattle ACO.
NOTE 4: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO.

(g) 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.

(h) Except as provided in paragraphs (a)(2)(i)(B), (a)(2)(ii), (c)(1), (c)(2), (d), and (e)(2) of this AD, the actions shall be done in accordance with the following Boeing service bulletins, as applicable, which contain the specified effective pages:


Service Bulletin
Referenced and Date
	
Page Number
	
Revision Level
Shown on Page
	
Date
Shown on Page

Alert Service Bulletin 747-54A2069,
Revision 2,
February 1, 1980	1-9	
2
	February 1, 1980
Alert Service Bulletin
747-54A2069,
Revision 3,
May 23, 1980	1-7


8	
3


2
	May 23, 1980


February 1, 1980
Alert Service Bulletin 747-54A2069,
Revision 4,
November 26, 1980	1, 9, 10, 12, 19-21


2-7, 11, 13-18
8	
4


3
2
	November 26, 1980


May 23, 1980
February 1, 1980
Service Bulletin 747-54A2069,
Revision 5,
August 21, 1981	1-7, 9, 10, 17


8
11, 13-16, 18
12,19-21	
5


2
3
4
	August 21, 1980


February 1, 1980
May 23, 1980
November 26, 1980
Alert Service Bulletin 747-54A2069,
Revision 6,
October 22, 1982	1-28	
6
	October 22, 1982
Service Bulletin
747-54A2069,
Revision 7,
July 28, 1988	1-5, 7-16, 24, 28


6, 17-23, 25-27	
7


6
	July 28, 1988


October 22, 1982
Service Bulletin
747-54A2069,
Revision 8,
June 9, 1994	1-28	
8
	June 9, 1994
Alert Service Bulletin
747-54A2069,
Revision 9,
May 29, 1997	1-28	
9
	May 29, 1997

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 Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

(i) This amendment becomes effective on February 2, 1998.

FOOTER: