[Federal Register Volume 64, Number 156 (Friday, August 13, 1999)]
[Rules and Regulations]
[Pages 44110-44112]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-20501]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-275-AD; Amendment 39-11251; AD 99-17-02]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 777 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 777 series airplanes, that requires 
repetitive inspections of the safety spring wear plate doublers 
attached to the auxiliary power unit (APU) firewall, measurement of 
wear of the doublers, and follow-on actions, if necessary. For certain 
airplanes, this amendment also requires a one-time inspection to detect 
improper clearance between the safety spring wear plate doubler and the 
APU firewall, and corrective action, if necessary. This amendment also 
provides for optional terminating action for the repetitive 
inspections. This amendment is prompted by reports indicating that 
excessive wear was found on the safety spring wear plate doublers on 
the APU firewall of Boeing Model 777 series airplanes. The actions 
specified by this AD are intended to detect and correct wear of the 
safety spring wear plate doublers on the APU firewall, which could 
result in a hole in the APU firewall, and consequent decreased fire 
protection capability.

DATES: Effective September 17, 1999.

    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of September 17, 1999.

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: Ed Hormel, Aerospace Engineer, 
Propulsion Branch, ANM-140S, FAA, Transport Airplane Directorate, 
Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (425) 227-2681; 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 777 series 
airplanes was published as a supplemental notice of proposed rulemaking 
(NPRM) in the Federal Register on April 8, 1999 (64 FR 17130). That 
action proposed to require repetitive inspections of the safety spring 
wear plate doublers attached to the auxiliary power unit (APU) 
firewall, measurement of wear of the doublers, and follow-on actions, 
if necessary. For certain airplanes, that action also proposed to 
require a one-time inspection to detect improper clearance between the 
safety spring wear plate doubler and the APU firewall, and corrective 
action, if necessary. That action also provided for optional 
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 for Extension of the Compliance Time

    One commenter requests that the compliance time for the actions 
specified by paragraphs (a), (b), and (c) of the proposed AD be 
extended. The commenter states that it operates 34 airplanes affected 
by the proposed rule, including airplanes that have accumulated as many 
as 15,000 total flight hours. The commenter states that it has begun 
accomplishing the terminating action, and thus far, none of the removed 
wear plates show wear levels approaching penetration. Although the 
commenter supports the decision to mandate Boeing Alert Service 
Bulletin 777-53A0018, Revision 1, dated February 11, 1999, it feels 
that the inspection compliance times specified in paragraphs (a), (b), 
and (c) of the proposal are unnecessarily conservative.
    The FAA does not concur with the commenter's request to extend the 
compliance time. In developing an appropriate compliance time for this 
action, the FAA considered the safety implications, parts availability, 
and normal maintenance schedules for timely accomplishment of the 
modification. In consideration of these items, as well as the 
variability in the reported wear rate of the safety spring wear plate 
doublers attached to the APU firewall, the FAA has determined that the 
compliance times specified in paragraphs (a), (b), and (c) of the AD 
will not place an undue hardship on the majority of affected operators, 
and an acceptable level of safety can be maintained. No change to the 
final rule is necessary.

Explanation of Changes Made to the Applicability

    The final rule has been revised to correct the applicability of the 
AD. In the preamble to the supplemental NPRM, the FAA discussed the 
difference between the effectivity listing of the alert service 
bulletin and the applicability of the AD. The supplemental NPRM stated 
that Model 777 series airplanes after line number 156 have stainless 
steel wear plate doublers installed prior to delivery. Since the 
issuance of the supplemental NPRM, the FAA has determined that there 
are four airplanes having line numbers less than 157 (line numbers 94, 
102, 104, and 120) that had the stainless

[[Page 44111]]

steel wear plate doublers installed prior to delivery. The alert 
service bulletin identifies airplanes having line numbers 94, 102, 104, 
120, and 157 through 183 inclusive, as Group 3 airplanes. None of these 
airplanes would be subject to the unsafe condition described above; 
therefore, the applicability of the final rule has been revised to 
include only Groups 1 and 2 airplanes, as listed in the alert service 
bulletin. The four affected airplanes were not included in the cost 
impact in the proposed rule; therefore, no change is required to the 
cost impact.

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 152 airplanes of the affected design in the 
worldwide fleet. The FAA estimates that 35 airplanes of U.S. registry 
will be affected by this AD.
    It will take approximately 2 work hours per airplane to accomplish 
the required inspection to detect wear of the safety spring wear plate 
doublers, at an average labor rate of $60 per work hour. Based on these 
figures, the cost impact of this inspection required by this AD on U.S. 
operators is estimated to be $4,200, 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 proposed 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 be required to accomplish the temporary repair, 
it will take approximately 2 work hours per airplane to accomplish the 
repair, at an average labor rate of $60 per work hour. Based on these 
figures, the cost impact of the temporary repair is estimated to be 
$120 per airplane.
    Should an operator be required to accomplish the inspection to 
detect improper clearance between the safety spring wear plate doubler 
and the APU firewall, it will take approximately 1 work hour per 
airplane to accomplish the inspection, at an average labor rate of $60 
per work hour. Based on these figures, the cost impact of this 
inspection is estimated to be $60 per airplane.
    Should an operator be required or elect to accomplish the 
replacement of the wear plate doublers, it will take approximately 3 
work hours per airplane to accomplish the replacement, at an average 
labor rate of $60 per work hour. Required parts, if acquired from the 
manufacturer, will cost approximately $193 per airplane. Based on these 
figures, the cost impact of replacement of the wear plate doublers is 
estimated to be $373 per airplane.

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.
    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.


Sec. 39.13  [Amended]

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

99-17-02  Boeing: Amendment 39-11251. Docket 98-NM-275-AD.

    Applicability: Model 777 series airplanes listed as Groups 1 and 
2 airplanes in Boeing Service Bulletin 777-53A0018, Revision 1, 
dated February 11, 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 (h) 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 wear of the safety spring wear plate 
doublers on the auxiliary power unit (APU) firewall, which could 
result in a hole in the APU firewall, and consequent decreased fire 
protection capability, accomplish the following:

Initial Inspection

    (a) Perform a visual inspection of the two safety spring wear 
plate doublers on the APU firewall, and measure any wear of the 
doublers, in accordance with Boeing Service Bulletin 777-53A0018, 
Revision 1, dated February 11, 1999, at the time specified in 
paragraph (a)(1), (a)(2), or (a)(3) of this AD, as applicable.
    (1) For airplanes that have accumulated 6,000 total flight hours 
or less as of the effective date of this AD: Inspect and measure 
prior to the accumulation of 6,300 total flight hours.
    (2) For airplanes that have accumulated more than 6,000 but less 
than 10,000 total flight hours as of the effective date of this AD: 
Inspect and measure within 30 days after the effective date of this 
AD.
    (3) For airplanes that have accumulated 10,000 total flight 
hours or more as of the effective date of this AD: Inspect and 
measure within 10 days after the effective date of this AD.

    Note 2: Inspections, repairs, and modifications accomplished 
prior to the effective date of this AD in accordance with Boeing 
Alert Service Bulletin 777-53A0018, dated June 29, 1998, are 
considered acceptable for compliance with this AD, provided that the 
actions required by paragraph (f) of this AD, as applicable, are 
accomplished in accordance with Boeing Service Bulletin 777-53A0018, 
Revision 1, dated February 11, 1999.

[[Page 44112]]

Repetitive Inspections

    (b) If, during the inspection required by paragraph (a) of this 
AD, the wear on each doubler measures less than 0.045 inch, repeat 
the inspection and measurement required by paragraph (a) of this AD 
thereafter at intervals not to exceed 60 days, in accordance with 
Boeing Service Bulletin 777-53A0018, Revision 1, dated February 11, 
1999; until paragraph (g) of this AD has been accomplished.
    (c) If, during the inspection required by paragraph (a) of this 
AD, the wear on either doubler measures greater than or equal to 
0.045 inch, but does not penetrate into or through the APU firewall: 
Repeat the inspection and measurement required by paragraph (a) of 
this AD thereafter at intervals not to exceed 30 days, in accordance 
with Boeing Service Bulletin 777-53A0018, Revision 1, dated February 
11, 1999; until paragraph (g) of this AD has been accomplished.

Corrective Actions

    (d) If, during the inspection required by paragraph (a) of this 
AD, any wear penetrates through either doubler and into or through 
the APU firewall: Within 20 days after detection of the wear, 
accomplish either paragraph (d)(1) or (d)(2) of this AD in 
accordance with Boeing Service Bulletin 777-53A0018, Revision 1, 
dated February 11, 1999.
    (1) Install a temporary stainless steel patch on both doublers, 
and within 4,000 flight cycles after installation of the temporary 
patch, accomplish the requirements of paragraph (e) of this AD.
    (2) Accomplish the requirements of paragraph (e) of this AD.
    (e) For airplanes on which wear is detected that penetrates 
through either doubler and into or through the APU firewall: 
Accomplish the requirements of paragraphs (e)(1) and (e)(2) of this 
AD at the time specified in paragraph (d) of this AD, as applicable.
    (1) Repair the damage to the APU firewall in accordance with a 
method approved by the Manager, Seattle Aircraft Certification 
Office (ACO), FAA, Transport Airplane Directorate.
    (2) Replace both existing wear plate doublers of the APU 
firewall with new stainless steel wear plate doublers in accordance 
with Boeing Service Bulletin 777-53A0018, Revision 1, dated February 
11, 1999. Such replacement constitutes terminating action for the 
repetitive inspection requirements of paragraphs (b) and (c) of this 
AD.

One-Time Inspection

    (f) For airplanes having L/N 001 through 037 inclusive that have 
been modified prior to the effective date of this AD in accordance 
with Boeing Alert Service Bulletin 777-53A0018, dated June 29, 1998: 
Within 4 years after the effective date of this AD, perform a one-
time visual inspection to detect improper clearance between the 
safety spring wear plate doublers and the APU firewall, in 
accordance with Boeing Service Bulletin 777-53A0018, Revision 1, 
dated February 11, 1999.
    (1) If the doublers are not in contact with the chemically 
milled pocket of the APU firewall, no further action is required by 
this paragraph.
    (2) If the doublers are in contact with the chemically milled 
pocket of the APU firewall, prior to further flight, install shims 
between the safety spring wear plate doublers and the APU firewall, 
in accordance with Part 6 of the Accomplishment Instructions of the 
service bulletin.

Optional Terminating Action

    (g) Replacement of the existing wear plate doublers of the APU 
firewall with new stainless steel wear plate doublers, in accordance 
with Boeing Service Bulletin 777-53A0018, Revision 1, dated February 
11, 1999, constitutes terminating action for the repetitive 
inspection requirements of paragraphs (b) and (c) of this AD.

Alternative Methods of Compliance

    (h) 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 3: 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

    (i) Special flight permits may be issued in accordance with 
Secs. 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

    (j) Except as provided by paragraph (e)(1) of this AD, the 
actions shall be done in accordance with Boeing Service Bulletin 
777-53A0018, Revision 1, dated February 11, 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.
    (k) This amendment becomes effective on September 17, 1999.

    Issued in Renton, Washington, on August 4, 1999.

D. L. Riggin,

Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-20501 Filed 8-12-99; 8:45 am]
BILLING CODE 4910-13-P