AD 2000-03-22

[Federal Register Volume 65, Number 35 (Tuesday, February 22, 2000)]
[Rules and Regulations]
[Pages 8640-8642]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 00-3797]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-339-AD; Amendment 39-11582; AD 2000-03-22]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 747-100, -200, and 747SP 
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, -200, and 747SP series 
airplanes, that requires repetitive detailed visual and ultrasonic 
inspections to detect missing, damaged, or broken taperlock bolts in 
the diagonal brace underwing fittings; and corrective actions, if 
necessary. This AD also requires eventual replacement of the aft 10 
taperlock bolts with new bolts, which constitutes terminating action 
for the repetitive inspections. This amendment is prompted by reports 
of damaged, broken, and corroded taperlock bolts of the diagonal brace 
underwing fittings on the outboard strut due to stress corrosion 
cracking. The actions specified by this AD are intended to prevent loss 
of the underwing fitting load path due to missing, damaged, or broken 
taperlock bolts, which could result in separation of the engine and 
strut from the airplane.

DATES: Effective March 28, 2000.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of March 28, 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, -
200, and 747SP series airplanes was published in the Federal Register 
on August 31, 1999 (64 FR 47440). That action proposed to require 
repetitive detailed visual and ultrasonic inspections to detect 
missing, damaged, or broken taperlock bolts in the diagonal brace 
underwing fittings; and corrective actions, if necessary. That action 
also proposed to require eventual replacement of the aft 10 taperlock 
bolts with new bolts as terminating action for the repetitive 
inspections.

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.

Support for the Proposal

    One commenter supports the proposed rule.

Request to Reference Other Terminating Action

    One commenter requests that the FAA revise the notice of proposed 
rulemaking (NPRM) to reference accomplishment of Boeing Service 
Bulletin 747-57-2288 as terminating action for the repetitive 
inspection requirements proposed in the NPRM. The commenter states that 
accomplishment of the replacement of the diagonal brace underwing 
fitting in accordance with Figures 5 through 9 of that service 
bulletin, or the clearance adjustment in accordance with Figure 10 of 
that service bulletin, includes replacement of the same taperlock bolts 
with new bolts as described in the NPRM and in Boeing Alert Service 
Bulletin 747-57A2308, dated August 6, 1998 (which was referenced as the 
appropriate source of service information for the actions proposed in 
the NPRM). The commenter states that if the taperlocks that are the 
subject of this AD have already been replaced with the same new bolts 
that are specified in this AD, the operator should not be required to 
do the inspections proposed in the NPRM or apply for approval of an 
alternative method of compliance. The commenter states that if its 
request is granted and incorporated in the final rule, operators and 
the FAA will not have to process as many applications for alternative 
methods of compliance.
    The FAA concurs with the commenter's request. The FAA finds that 
accomplishment of the replacement of the diagonal brace underwing 
fitting or the clearance adjustment described in Boeing Service 
Bulletin 747-57-2288, Revision 1, dated June 26, 1997, is acceptable 
for compliance with the requirements of paragraph (d) of this AD. 
Accordingly, a new NOTE 3 has been added to this final rule. However, 
the FAA finds that accomplishment of such replacement or clearance 
adjustment in accordance with the original issue of Boeing Service 
Bulletin 747-57-2288, dated September 15, 1994, is not acceptable for 
compliance with paragraph (d) of this AD, because that service bulletin 
does not specify to replace the taperlock bolts that are subject to 
this AD.

Request to Clarify ``Spares'' Paragraph

    One commenter requests that the FAA revise paragraph (e) of the 
NPRM to change the words ``on any airplane'' to ``on any Boeing 747 
airplane that is listed in the effectivity of [Boeing Service Bulletin] 
747-57A2308.'' The commenter states that an operator was confused about 
the meaning of the paragraph as it is phrased in the NPRM.
    The FAA concurs with the intent of the commenter's request. The FAA 
acknowledges that the language used in the NPRM may confuse some 
operators. Therefore, paragraph (e) of this final rule has been revised 
to state that, ``. . . no person shall install a bolt, part number 
BACB30PE( ) * ( ), or any other bolt made of 4340, 8740, or PH13-8 Mo 
steel, in the locations specified in this AD, on any airplane listed in 
the applicability of this AD.''

Request to Revise Estimated Cost of Terminating Action

    One commenter requests that the FAA revise the estimated cost of 
the terminating action, as quoted in the proposed rule. The commenter 
points out that the number of work hours for accomplishment of the 
terminating action stated in the NPRM (i.e., 8 work

[[Page 8641]]

hours) is inconsistent with the estimate in Boeing Alert Service 
Bulletin 747-57A2308. The commenter estimates that 248 to 306 work 
hours per airplane is necessary to accomplish the proposed replacement 
of taperlock bolts.
    The FAA partially concurs with the commenter's request. The FAA 
does not concur with the commenter's estimate of 248 to 306 work hours, 
because that estimate includes time to gain access and close up. The 
cost analysis in AD rulemaking actions typically does not include 
incidental costs, such as the time required to gain access and close 
up, planning time, or time necessitated by other administrative 
actions. Because such incidental costs may vary significantly from 
operator to operator, they are almost impossible to calculate. However, 
the FAA finds that the number of work hours necessary for 
accomplishment of the terminating action is underestimated in the NPRM. 
The FAA estimates that the terminating action will take 68 work hours 
for airplanes in Groups 1, 2, and 5, and 125 work hours for airplanes 
in Groups 3 and 4. (These estimates coincide with Boeing's estimate for 
the number of work hours necessary to accomplish the terminating action 
if it is accomplished concurrently with other strut modifications.) The 
FAA has revised the cost impact information in this final rule 
accordingly.

Request To Delete Terminating Action Requirement

    One commenter requests that the FAA revise the NPRM to delete the 
requirement to replace the subject taperlocks within 48 months after 
the effective date of this AD. The commenter states that the diagonal-
brace-to-wing attachment can carry ultimate load with a certain number 
of failed taperlocks. The commenter asserts that the visual and 
ultrasonic inspections that are proposed in the NPRM will reliably 
detect bolt fractures before multiple fractures occur, and will ensure 
that the outboard engines and struts will not separate from the 
airplane. Furthermore, the commenter states that removing the subject 
taperlocks is a difficult and time-consuming procedure, necessitating 
costs and downtime not commensurate with the degree of enhanced flight 
safety.
    The FAA does not concur with the commenter's request. As stated in 
the ``Differences Between Proposed Rule and Service Bulletin'' section 
of the NPRM, the FAA has determined that long-term inspections may not 
provide the degree of safety assurance necessary for the transport 
airplane fleet. The commenter supplied no data (such as the crack 
growth rate after inspection, to ensure that the inspection interval is 
adequate for timely detection of cracking) to support its statement 
that inspections will reliably detect bolt fractures before multiple 
fractures occur. The FAA finds that no change to the final rule is 
necessary in this regard.

Request To Allow Installation of Cadmium-Plated Taperlock Bolts

    One commenter requests that the FAA revise paragraph (e) of the 
NPRM to state that taperlock bolts made of 4340, 8740, or PH13-8 Mo 
steel with no coating or with aluminum coating may be installed. 
[Paragraph (e) of the NPRM states that no bolt made of 4340, 8740, or 
PH13-8 Mo steel--regardless of the type of coating--may be installed.] 
The commenter states that it has had no service problems with cadmium-
plated 4340, 8740, or PH13-8 Mo steel taperlock bolts, and further 
states that such cadmium-plated 4340 and 8740 steel taperlock bolts are 
approved for use in the Boeing 747 Structural Repair Manual, which is 
approved by the FAA.
    The FAA does not concur with the commenter's request to allow use 
of cadmium-plated steel taperlock bolts. The terminating action 
required by this AD requires installation of BACB30NX*K* bolts. The 
material that these bolts are made of is less susceptible to stress 
corrosion cracking than the bolts with cadmium plating that the 
commenter specifies. In addition, the FAA has determined that 
BACB30NX*K* bolts are not listed in Boeing 747 Structural Repair 
Manual, Chapter 51-30-03, Figure 1, Sheet 37. Therefore, cadmium-plated 
4340 and 8740 steel taperlock bolts are not approved for use in place 
of the BACB30NX*K* bolts required by this AD. 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 274 Model 747-100, -200, and 747SP series 
airplanes of the affected design in the worldwide fleet. The FAA 
estimates that 122 airplanes of U.S. registry will be affected by this 
AD.
    It will take approximately 1 work hour per airplane to accomplish 
the required inspection, at the average labor rate of $60 per work 
hour. Based on these figures, the cost impact of the required 
inspection on U.S. operators is estimated to be $7,320, or $60 per 
airplane, per inspection cycle.
    It will take approximately 68 work hours per airplane to accomplish 
the required terminating action for airplanes included in Groups 1, 2, 
and 5, as specified in the service bulletin. It will take approximately 
125 work hours to accomplish the required terminating action for 
airplanes included in Groups 3 and 4, as specified in the service 
bulletin. The average labor rate is $60 per work hour. Required parts 
will cost approximately $8,008 per airplane. Based on these figures, 
the cost impact of the required terminating action on U.S. operators is 
estimated to be $12,088 per airplane, for airplanes in Groups 1, 2, and 
5; and $15,508 per airplane, for airplanes in Groups 3 and 4.
    The cost impact figures discussed above are 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.

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.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

[[Page 8642]]

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:

2000-03-22  Boeing: Amendment 39-11582. Docket 98-NM-339-AD.

    Applicability: Model 747-100, -200, and 747SP series airplanes; 
line numbers 1 through 567 inclusive; equipped with aluminum 
diagonal brace underwing fittings; 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 (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 prevent loss of the underwing fitting load path due to 
missing, damaged, or broken taperlock bolts, which could result in 
separation of the engine and strut from the airplane, accomplish the 
following:

Repetitive Inspections

    (a) Prior to the accumulation of 9,000 total flight cycles, or 
within 18 months after the effective date of this AD, whichever 
occurs later, accomplish the actions required by paragraphs (a)(1) 
and (a)(2) of this AD in accordance with Boeing Alert Service 
Bulletin 747-57A2308, dated August 6, 1998. Thereafter, repeat the 
inspections at intervals not to exceed 18 months until 
accomplishment of the actions specified in paragraph (d) of this AD.
    (1) Perform a detailed visual inspection to detect missing 
taperlock bolts in the diagonal brace underwing fitting at the 
Number 1 and Number 4 pylons.

    Note 2: For the purposes of this AD, a detailed visual 
inspection is defined as: ``An intensive visual examination of a 
specific structural area, system, installation, or assembly to 
detect damage, failure, or irregularity. Available lighting is 
normally supplemented with a direct source of good lighting at 
intensity deemed appropriate by the inspector. Inspection aids such 
as mirror, magnifying lenses, etc., may be used. Surface cleaning 
and elaborate access procedures may be required.''

    (2) Perform an ultrasonic inspection to detect damaged or broken 
taperlock bolts in the diagonal brace underwing fitting at the 
Number 1 and Number 4 pylons.

Corrective Actions

    (b) If any missing, damaged, or broken taperlock bolt is 
detected during any inspection required by paragraph (a) of this AD, 
prior to further flight, perform the applicable corrective actions 
(i.e., inspection, drill/ream, and replacement) in accordance with 
Boeing Alert Service Bulletin 747-57A2308, dated August 6, 1998; 
except as provided in paragraph (c) of this AD. Replacement of any 
taperlock bolt with a new bolt in accordance with this paragraph 
constitutes terminating action for the repetitive inspections 
required by paragraph (a) of this AD for that bolt only.
    (c) If any crack is detected during the inspection required by 
paragraph (b) of this AD and the damage to a bolt hole exceeds first 
oversize (for 0.5-inch bolts) or second oversize (for 0.4375-inch 
bolts); and the service bulletin specifies to contact Boeing for 
appropriate action: 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 a Boeing Company Designated Engineering 
Representative who has been authorized by the Manager, Seattle ACO, 
to make such findings. For a repair method to be approved by the 
Manager, Seattle ACO, as required by this paragraph, the Manager's 
approval letter must specifically reference this AD.

Terminating Action

    (d) Within 48 months after the effective date of this AD, 
accomplish the actions required by paragraphs (d)(1) and (d)(2) of 
this AD in accordance with Boeing Alert Service Bulletin 747-
57A2308, dated August 6, 1998. Accomplishment of the actions 
specified in this paragraph constitutes terminating action for the 
repetitive inspection requirements of this AD.
    (1) Prior to accomplishing the replacement required by paragraph 
(d)(2) of this AD, perform an open hole high frequency eddy current 
inspection to detect cracks at the bolt hole locations of the aft 10 
taperlock bolts. If any cracking is detected, prior to further 
flight, perform applicable corrective actions in accordance with 
paragraph (c) of this AD.
    (2) Replace the aft 10 taperlock bolts with new bolts in the 
diagonal brace underwing fitting at the Number 1 and Number 4 
pylons.

    Note 3: Accomplishment of the replacement of the diagonal brace 
underwing fitting in accordance with Figures 5 through 9 of Boeing 
Service Bulletin 747-57-2288, Revision 1, dated June 26, 1997; or 
the clearance adjustment in accordance with Figures 10 through 14 of 
that service bulletin; is acceptable for compliance with the 
requirements of paragraph (d) of this AD.

Spares

    (e) As of the effective date of this AD, no person shall install 
a bolt, part number BACB30PE() * (), or any other bolt made of 4340, 
8740, or PH13-8 Mo steel, in the locations specified in this AD, on 
any airplane listed in the applicability of this AD.

Alternate Method 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, 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

    (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.

Incorporation by Reference

    (h) Except as provided in paragraph (c) of this AD, the actions 
shall be done in accordance with Boeing Alert Service Bulletin 747-
57A2308, dated August 6, 1998. 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 March 28, 2000.

    Issued in Renton, Washington, on February 11, 2000.
Donald L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 00-3797 Filed 2-18-00; 8:45 am]
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