[Federal Register Volume 65, Number 25 (Monday, February 7, 2000)]
[Rules and Regulations]
[Pages 5753-5756]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-2468]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-88-AD; Amendment 39-11558; AD 2000-03-01]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 747-100 and -200 Series 
Airplanes

AGENCY:  Federal Aviation Administration, DOT.

ACTION:  Final rule.

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SUMMARY:  This amendment adopts a new airworthiness directive (AD), 
applicable to certain Boeing Model 747-100 and -200 series airplanes, 
that requires repetitive inspections of the

[[Page 5754]]

upper and lower chords of the wing front spar for cracks, and 
corrective action, if necessary. For airplanes on which no cracking is 
detected, this AD also provides an optional terminating action in lieu 
of repetitive inspections. This amendment is prompted by reports of 
cracks in the upper chord of the wing front spar. The actions specified 
by this AD are intended to detect and correct fatigue cracking of the 
upper and lower chords of the wing front spar, which could result in 
reduced structural capability and possible fuel leakage onto an engine 
and a resultant fire.

DATES:  Effective March 13, 2000.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of March 13, 2000.

ADDRESSES:  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 Federal 
Aviation Administration (FAA), Transport Airplane Directorate, Rules 
Docket, 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. Anderson, 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:  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 certain Boeing Model 747-100 and 
-200 series airplanes was published in the Federal Register on August 
20, 1999 (64 FR 45481). That action proposed to require repetitive 
inspections of the upper and lower chords of the wing front spar for 
cracks, and corrective action, if necessary.

Comments

    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.

Request to Allow Alternative Inspection Method

    One commenter requests that the FAA revise paragraph (a) of the 
proposal to allow accomplishment of an open hole high frequency eddy 
current (HFEC) inspection in lieu of the ultrasonic inspection that is 
specified in paragraph (a) of the proposal. The commenter asserts that 
accomplishment of an HFEC inspection ``equals or exceeds the capability 
of surface ultrasonic inspections'' for detecting cracking of the upper 
and lower chords of the wing front spar. The commenter states that the 
HFEC inspection should be accomplished in accordance with Figure 6 of 
Boeing Service Bulletin 747-57-2305, Revision 1, dated January 21, 1999 
(which was referenced in the proposal as the appropriate source of 
service information for accomplishment of the proposed actions).
    The FAA concurs with the commenter's request to approve the 
alternative inspection method. However, the FAA finds that, rather than 
revising paragraph (a) of this AD, it is more appropriate to add a NOTE 
stating that accomplishment of an HFEC inspection in accordance with 
Figure 6 of the service bulletin is acceptable for compliance with the 
requirements of paragraph (a) of this AD. NOTE 2 has been added to this 
final rule accordingly.

Request to Reference Alternative Terminating Action

    One commenter requests that the FAA revise paragraph (b) of the 
proposed rule to reference accomplishment of certain strut and wing 
modifications or certain other terminating actions as terminating 
action for the requirements of this AD. The commenter states that 
accomplishment of certain modifications meets the intent of the 
terminating action described in the proposed rule, provided that an 
HFEC inspection of affected fastener holes has been accomplished (in 
accordance with Boeing 747 Non-Destructive Test Manual D6-7170, Part 6, 
Subject 51-00-00, Figure 16) prior to oversizing of the holes, and the 
holes were found to be free of cracks, corrosion, or damage.
    The FAA infers that the commenter is referring to the terminating 
action specified in paragraph (c) of this AD. The FAA concurs with the 
commenter's request. The FAA finds that the strut and wing 
modifications and terminating action referenced by the commenter are 
already required by certain other AD's, which are described below.
     AD 95-10-16, amendment 39-9233 (60 FR 27008, May 22, 
1995), applies to certain Boeing Model 747 series airplanes, and 
requires, among other things, modification of the nacelle strut and 
wing structure in accordance with Boeing Alert Service Bulletin 747-
54A2159, dated November 3, 1994.
     AD 95-13-07, amendment 39-9287 (60 FR 33336, June 28, 
1995), applies to certain Boeing Model 747 series airplanes, and 
requires modification of the nacelle strut and wing structure in 
accordance with Boeing Alert Service Bulletin 747-54A2158, dated 
November 30, 1994.
     AD 99-10-09, amendment 39-11162 (64 FR 25194, May 11, 
1999), applies to certain Model 747-100, -200, and 747SP series 
airplanes, and military type E-4B airplanes. That AD provides for 
replacement of the wing front spar web with a new shot-peened wing 
front spar web, in accordance with Boeing Service Bulletin 747-57A2303, 
Revision 1, dated September 25, 1997, as an optional terminating action 
for the repetitive inspection requirements of that AD.
    The FAA has determined that accomplishment of the wing and strut 
modification specified in AD 95-10-16 or AD 95-13-07, or the optional 
terminating action specified in AD 99-10-09, constitutes terminating 
action for the repetitive inspections required by paragraph (a) of this 
AD, provided that an HFEC inspection of subject fastener holes has been 
accomplished (in accordance with Boeing 747 Non-Destructive Test Manual 
D6-7170, Part 6, Subject 51-00-00, Figure 16) prior to oversizing of 
the holes, and the holes were found to be free of cracks, corrosion, or 
damage. The FAA has added NOTE 3 to this final rule accordingly.

Request to Delete Certain Supplemental Structural Inspection 
Document Inspections

    One commenter requests that the FAA revise the proposal by adding a 
paragraph that eliminates the requirement for certain inspections to be 
accomplished in accordance with the Supplemental Structural Inspection 
Document (SSID). The commenter justifies its request by saying that 
oversizing the web-to-chord fastener holes, as described in the 
optional terminating action in Boeing Service Bulletin 747-57-2305, 
Revision 1, will ``zero time'' the fastener holes, renewing the fatigue 
life. The commenter states that, if this optional terminating action is 
accomplished, SSID inspections W-24B at the front spar web-to-chord 
fastener holes between the upper link fittings and W-24C at the front 
spar web-to-chord fastener holes at the outboard upper link fittings 
would no longer be necessary.
    The FAA partially concurs with the commenter's request. The FAA 
acknowledges that, following accomplishment of the optional

[[Page 5755]]

terminating action, fatigue life will be renewed in the affected web-
to-chord fastener holes. However, the SSID inspections that the 
commenter references are required, along with various other 
inspections, by AD 94-15-12, amendment 39-8983 (59 FR 37933, July 26, 
1994), and AD 94-15-18, amendment 39-8989 (59 FR 41233, August 11, 
1994). The FAA finds that deleting SSID inspections required by other 
AD's is not an appropriate action to take in this AD. Therefore, no 
change to the final rule is necessary in this regard.

Request to Allow Use of Original Issue of Service Bulletin

    One commenter requests that the FAA revise paragraphs (a), (b), and 
(c) of the proposal to reference the original issue of Boeing Service 
Bulletin 747-57-2305, dated October 8, 1998, in addition to Revision 1 
of the service bulletin, as appropriate sources of service information 
for the actions required by this AD. The commenter states that there is 
no substantial difference between the two versions of the service 
bulletin, and the inspection methods and procedures for terminating 
action are the same. The commenter states that Revision 1 adds missing 
fastener codes and revises grip lengths of fasteners. Further, the 
commenter states that operators that accomplished inspections or 
terminating action in accordance with the original issue of the service 
bulletin should not be required to perform the inspections or 
terminating action in accordance with Revision 1, nor should they be 
required to apply for an alternative means of compliance.
    The FAA does not concur with the commenter's request. The FAA 
considers the grip length of fasteners (one of the items changed 
between the original issue and Revision 1) important for proper clamp-
up, and the FAA has been advised that certain fasteners specified in 
the original issue of the service bulletin had grip lengths that were 
too long. In addition, the FAA considers the fact that certain fastener 
codes were missing from the original issue of the service bulletin to 
be significant, in that it could result in installation of fasteners 
that are not structurally satisfactory. Also, Revision 1 of the service 
bulletin deleted inspections of the fasteners in the upper and lower 
chords between the upper link fittings. For these reasons, the FAA does 
not find that accomplishment of the actions required by this AD in 
accordance with the original issue of the service bulletin is 
acceptable for compliance with this AD. No change to the final rule is 
necessary in this regard.

Request to Revise Statement of Unsafe Condition

    One commenter, the airplane manufacturer, requests that the FAA 
revise the reason for issuing the proposed rule. The proposed rule 
states that ``the actions specified by the proposed AD are intended to 
detect and correct fatigue cracking of the upper and lower chords of 
the wing front spar, which could result in reduced structural 
capability and possible fuel leakage onto an engine and a resultant 
fire.'' The commenter states that the correct reason for issuing the AD 
is that cracks addressed by Boeing Service Bulletin 747-57-2305 are 
subject to Item W-24A and W-24B in Boeing Document D6-35022, 
``Supplemental Structural Inspection Document.'' The commenter also 
states that the service bulletin was issued to address undetected 
cracks in the front spar chords that could result in extensive labor 
hours and downtime if the cracks propagate to the extent that 
replacement of a section of chord is necessary. The commenter concludes 
that there are no safety-of-flight issues associated with such 
cracking, and that fuel leakage due to undetected cracks is very 
unlikely because, for leakage to occur, cracks in the chord would have 
to grow through the thickness of the chord, beyond the upper or lower 
edges of the front spar web, and beyond the fillet seal.
    The FAA does not concur with the commenter's request. The statement 
of unsafe condition, as stated in the proposal, specifies what could 
happen if the inspections of the front spar upper and lower chords that 
will be required by this AD are not accomplished. The fact that fuel 
leaks have not been detected to date does not preclude leaks from 
occurring in the future. For example, even though an operator may have 
accomplished the strut and wing modification required by another AD (as 
discussed previously), if an HFEC inspection to detect cracking of the 
fastener holes was not accomplished, a crack may still be present and 
could grow to the point that fuel leakage occurs. The FAA finds no 
justification for revising the statement of unsafe condition as the 
commenter suggested. Therefore, no change to the final rule is 
necessary in this regard.

Conclusion

    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 with the changes previously 
described. The FAA has determined that these changes will neither 
increase the economic burden on any operator nor increase the scope of 
the AD.

Cost Impact

    There are approximately 332 Model 747-100 and -200 series airplanes 
of the affected design in the worldwide fleet. The FAA estimates that 
137 airplanes of U.S. registry will be affected by this AD, that it 
will take approximately 2 work hours per airplane to accomplish the 
required inspection, and that the average labor rate is $60 per work 
hour. Based on these figures, the cost impact of the inspection 
required by this AD on U.S. operators is estimated to be $16,440, or 
$120 per airplane, per inspection cycle.
    The cost impact figure discussed above is based on assumptions that 
no operator has yet accomplished any of the requirements of this AD 
action, and that no operator would accomplish those actions in the 
future if this AD were not adopted.
    Should an operator elect to accomplish the optional terminating 
action rather than continue the repetitive inspections, it will take 
approximately 37 work hours per airplane to accomplish the 
modification, at an average labor rate of $60 per work hour. Required 
parts will cost approximately $5,000 per airplane. Based on these 
figures, the cost impact of this optional terminating action is 
estimated to be $7,220 per airplane.

Regulatory Impact

    The regulations adopted herein will 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. Therefore, it 
is determined that this final rule does not have federalism 
implications under Executive Order 13132.
    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.

[[Page 5756]]

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.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:

2000-03-01  Boeing: Amendment 39-11558. Docket 99-NM-88-AD.

    Applicability: Model 747-100 and -200 series airplanes, listed 
in Boeing Service Bulletin 747-57-2305, Revision 1, dated January 
21, 1999; certificated in any category.

    Note 1:  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 (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 detect and correct fatigue cracking of the upper and lower 
chords of the wing front spar, which could result in reduced 
structural capability and possible fuel leakage onto an engine and a 
resultant fire, accomplish the following:

Inspections and Corrective Action

    (a) Prior to the accumulation of 12,000 total flight cycles, or 
within 24 months after the effective date of this AD, whichever 
occurs later, accomplish an ultrasonic inspection for cracking of 
the upper and lower chord of the wing front spar, in accordance with 
Boeing Service Bulletin 747-57-2305, Revision 1, dated January 21, 
1999.

    Note 2:  Accomplishment of an open hole high frequency eddy 
current inspection in accordance with Figure 6 of Boeing Service 
Bulletin 747-57-2305, Revision 1, dated January 21, 1999, is 
acceptable for compliance with the inspection requirement of 
paragraph (a) of this AD.


    (1) If no cracking is found, repeat this inspection thereafter 
at intervals not to exceed 6,000 flight cycles, until the 
requirements of paragraph (c) of this AD have been accomplished.
    (2) If any cracking is found, prior to further flight, 
accomplish ``Part 2--Terminating Action'' of the Accomplishment 
Instructions of the service bulletin, except as provided by 
paragraph (b) of this AD. Accomplishment of this action constitutes 
terminating action for the requirements of this AD.
    (b) During accomplishment of the terminating action required by 
paragraph (a)(2) of this AD, if any crack is found in the upper 
chord that is outside the limits specified in Boeing Service 
Bulletin 747-57-2305, Revision 1, dated January 21, 1999; or if any 
crack is found in the lower chord; prior to further flight, repair 
in accordance with a method approved by the Manager, Seattle 
Aircraft Certification Office (ACO), FAA, Transport Airplane 
Directorate; or in accordance with data meeting the type 
certification basis of the airplane approved by a Boeing Company 
Designated Engineering Representative who has been authorized by the 
FAA to make such findings. For a repair method to be approved by the 
Manager, Seattle ACO, as required by this AD, the Manager's approval 
letter must specifically reference this AD.

Optional Terminating Action

    (c) Accomplishment of ``Part 2--Terminating Action'' of the 
Accomplishment Instructions of Boeing Service Bulletin 747-57-2305, 
Revision 1, dated January 21, 1999, constitutes terminating action 
for the requirements of this AD.

    Note 3:  Accomplishment of the wing and strut modification 
specified in AD 95-10-16, amendment 39-9233, or AD 95-13-07, 
amendment 39-9287, or the optional terminating action specified in 
AD 99-10-09, amendment 39-11162, constitutes terminating action for 
the repetitive inspections required by paragraph (a) of this AD, 
provided that an HFEC inspection of subject fastener holes has been 
accomplished in accordance with Boeing 747 Non-Destructive Test 
Manual D6-7170, Part 6, Subject 51-00-00, Figure 16, prior to 
oversizing of the holes in accordance with AD 95-10-16, AD 95-13-07, 
or AD 99-10-09, and the holes were found to be free of cracks, 
corrosion, or damage.

Alternative Methods of Compliance

    (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, 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.

Special Flight Permits

    (e) 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.

Incorporation by Reference

    (f) Except as provided by paragraph (c) of this AD, the actions 
shall be done in accordance with Boeing Service Bulletin 747-57-
2305, Revision 1, dated January 21, 1999. 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.
    (g) This amendment becomes effective on March 13, 2000.

    Issued in Renton, Washington, on January 31, 2000.
Donald L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 00-2468 Filed 2-4-00; 8:45 am]
BILLING CODE 4910-13-U