[Federal Register Volume 64, Number 67 (Thursday, April 8, 1999)]
[Proposed Rules]
[Pages 17130-17133]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-8687]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-275-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 777 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Supplemental notice of proposed rulemaking; reopening of 
comment period.

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SUMMARY: This document revises an earlier proposed airworthiness 
directive (AD), applicable to certain Boeing Model 777 series 
airplanes, that would have required 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. That proposed AD also would have provided for 
optional terminating action for the repetitive inspections. That 
proposal was prompted by reports indicating that excessive wear was 
found on the safety spring wear plate doublers on the APU

[[Page 17131]]

firewall of Boeing Model 777 series airplanes. This new action revises 
the proposed rule by extending the compliance time for a certain action 
and referencing a new service bulletin. For certain airplanes, this new 
action also adds a one-time inspection to detect improper clearance 
between the safety spring wear plate doubler and the APU firewall, and 
corrective action, if necessary. The actions specified by this new 
proposed 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: Comments must be received by May 3, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 98-NM-275-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056. Comments may be inspected at this 
location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except 
Federal holidays.
    The service information referenced in the proposed rule 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.

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:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed 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 above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained in this notice may be changed in 
light of the comments received.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed 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 summarizing each FAA-public contact concerned with 
the substance of this proposal 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-NM-275-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of NPRMs

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, Transport Airplane Directorate, ANM-114, Attention: Rules 
Docket No. 98-NM-275-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    A proposal to amend part 39 of the Federal Aviation Regulations (14 
CFR part 39) to add an airworthiness directive (AD), applicable to 
certain Boeing Model 777 series airplanes, was published as a notice of 
proposed rulemaking (NPRM) in the Federal Register on November 23, 1998 
(63 FR 64659). That NPRM would have required 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. That proposed AD also would have provided for 
optional terminating action for the repetitive inspections. That NPRM 
was 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. That condition, if not corrected, could result in 
a hole in the APU firewall, and consequent decreased fire protection 
capability.

Explanation of New Service Information

    Since the issuance of that NPRM, the FAA has reviewed and approved 
Boeing Service Bulletin 777-53A0018, Revision 1, dated February 11, 
1999. That service bulletin describes procedures for repetitive 
inspections of the safety spring wear plate doublers attached to the 
APU firewall, measurement of wear of the doublers, and follow-on 
actions, if necessary. Those procedures are essentially identical to 
the procedures described in Boeing Alert Service Bulletin 777-53A0018, 
dated June 29, 1998 (which was referenced as the appropriate source of 
service information for the actions proposed in the NPRM). However, 
among other things, Revision 1 of the service bulletin adds procedures 
for a one-time visual inspection to detect improper clearance between 
the safety spring wear plate doubler and the APU firewall, and 
installation of shims, if necessary, on certain airplanes that were 
modified previously in accordance with the original issue of the 
service bulletin. Improper clearance is defined in the service bulletin 
as the wear plate doubler being in contact with a chemically milled 
pocket in the APU firewall. Revision 1 of the service bulletin also 
describes procedures for an optional installation of wear sleeves on 
the ends of the APU door safety springs to provide additional 
protection against doubler wear. The new service bulletin revision also 
adds airplanes to the effectivity listing of the service bulletin.
    This supplemental NPRM would require accomplishment of the actions 
specified in Revision 1 of the service bulletin described previously, 
except as discussed below.

Differences Between the Service Bulletin and the Supplemental NPRM

    Operators should note that, although Revision 1 of the service 
bulletin specifies that the manufacturer may be contacted for 
disposition of certain repair conditions, this proposal would require 
the repair of those conditions to be accomplished in accordance with a 
method approved by the FAA.
    Operators also should note that, as described previously, Revision 
1 of the service bulletin describes procedures for an optional 
installation of wear sleeves on the ends of the APU door safety springs 
to provide additional protection against doubler wear. The FAA finds 
that installation of such wear sleeves does not eliminate the need for 
repetitive inspection of the existing wear plate doublers or 
replacement of the existing wear plate doublers with new stainless 
steel doublers. Therefore, the supplemental NPRM does not propose a 
requirement for the installation of such wear sleeves.
    Related to the optional installation, operators should note that 
this AD is applicable to Boeing Model 777 series airplanes, having line 
numbers 001 through 156 inclusive. Though Boeing Model 777 series 
airplanes after line number 156 have stainless steel wear plate 
doublers installed prior to delivery, Model 777 series airplanes having 
line numbers 157 through 183 inclusive have been included in the 
effectivity listing of the service bulletin to allow operators of these 
airplanes the

[[Page 17132]]

option of installing wear sleeves on the ends of the APU door safety 
springs. Because the FAA is not requiring installation of such wear 
sleeves, Model 777 series airplanes having line numbers 157 through 183 
inclusive would not be subject to this AD. Therefore, no change to the 
applicability of the supplemental NPRM is necessary.

Comments

    Due consideration has been given to the comments received in 
response to the NPRM. One comment that has prompted a change in the 
proposal is explained below.

Request To Revise Proposed AD To Parallel the Service Bulletin

    One commenter, the manufacturer, requests that the proposal be 
revised to parallel the Accomplishment Instructions specified in Boeing 
Alert Service Bulletin 777-53A0018, dated June 29, 1998. The commenter 
states that the AD, as proposed, would require repair of any damage to 
the APU firewall within 20 days after detection of wear. The service 
bulletin, however, recommends that, if any wear is through either 
doubler and into or through the firewall, temporary stainless steel 
patches should be installed within 20 days and the firewall should be 
repaired within 4,000 flight cycles after installation of the temporary 
patches. The commenter also points out that paragraph (e) of the 
proposed rule, which requires the repair of wear into or through the 
APU firewall within 20 days after detection, contradicts statements in 
the ``Explanation of Requirements of the Proposed Rule'' in the 
proposal, which reflects the recommendations of the service bulletin 
(repair with temporary patches within 20 days and permanent repair of 
the firewall within 4,000 flight cycles after installation of the 
temporary patches).
    The FAA concurs with the commenter's request to revise the proposed 
AD to parallel the service bulletin. The FAA has reviewed the 
Accomplishment Instructions in the original issue of the alert service 
bulletin, and has determined that, in converting the instructions in 
the alert service bulletin into the proposed corrective actions stated 
in the NPRM, the FAA erroneously stated the compliance time for 
accomplishment of repairs if any wear penetrates into or through the 
APU firewall. Therefore, the FAA has revised paragraph (c) of this 
supplemental NPRM to clarify that the paragraph applies to conditions 
in which wear does not extend into the APU firewall. In addition, the 
FAA has revised paragraphs (d) and (e) of this supplemental NPRM to 
reflect the compliance times recommended in the service bulletin.

Conclusion

    Since the changes described previously expand the scope of the 
originally proposed rule, the FAA has determined that it is necessary 
to reopen the comment period to provide additional opportunity for 
public comment.

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 
would be affected by this proposed AD.
    It would take approximately 2 work hours per airplane to accomplish 
the proposed 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 proposed 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 would 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 action 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 would 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 proposed by this AD is estimated to be $60 per airplane.
    Should an operator be required or elect to accomplish the 
replacement of the wear plate doublers, it would 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, would 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 proposed herein would 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 
proposal would not have sufficient federalism implications to warrant 
the preparation of a Federalism Assessment.
    For the reasons discussed above, I certify that this proposed 
regulation (1) is not a ``significant regulatory action'' under 
Executive Order 12866; (2) is not a ``significant rule'' under the DOT 
Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); 
and (3) if promulgated, 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 copy of the draft 
regulatory evaluation prepared for this action is contained in the 
Rules Docket. A copy of it may be obtained by contacting the Rules 
Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
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:

Boeing: Docket 98-NM-275-AD.

    Applicability: Model 777 series airplanes, line numbers (L/N) 
001 through 156 inclusive, 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.

[[Page 17133]]

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 between 6,001 and 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 10,001 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.

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 
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.

    Issued in Renton, Washington, on April 1, 1999.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-8687 Filed 4-7-99; 8:45 am]
BILLING CODE 4910-13-U