[Federal Register Volume 67, Number 126 (Monday, July 1, 2002)]
[Proposed Rules]
[Pages 44116-44119]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 02-16406]


-----------------------------------------------------------------------

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2002-NM-24-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 747 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

-----------------------------------------------------------------------

SUMMARY: This document proposes the supersedure of an existing 
airworthiness directive (AD), applicable to certain Boeing Model 747 
series airplanes, that currently requires inspection of the flap tracks 
of the wing trailing edge flaps for adequate cadmium plating and for 
corrosion of certain bolt holes of the fail-safe bar, and plating of 
such holes, if necessary. This new action would require post-
modification inspections of certain bolt holes of the fail-safe bar of 
the flap tracks of the wing trailing edge flaps for discrepancies, and 
corrective actions, if necessary. This proposal is prompted by reports 
of corrosion and cracks found in certain bolt holes reworked according 
to the existing AD. The actions specified by the proposed AD are 
intended to find and fix discrepancies of the bolt holes, which could 
result in fracture of the flap track, separation of the flap, and 
consequent loss of control of the airplane. This action is intended to 
address the identified unsafe condition.

DATES: Comments must be received by August 15, 2002.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 2002-NM-24-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056. Comments may be inspected at this 
location between 9 a.m. and 3 p.m., Monday through Friday, except 
Federal holidays. Comments may be submitted via fax to (425) 227-1232. 
Comments may also be sent via the Internet using the following address: 
[email protected]. Comments sent via fax or the Internet must 
contain ``Docket No. 2002-NM-24-AD'' in the subject line and need not 
be submitted in triplicate. Comments sent via the Internet as attached 
electronic files must be formatted in Microsoft Word 97 for Windows or 
ASCII text.
    The service information referenced in the proposed rule may be 
obtained from

[[Page 44117]]

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: Tamara Anderson, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 
227-2771; 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 action may be changed in 
light of the comments received.
    Submit comments using the following format:
     Organize comments issue-by-issue. For example, discuss a 
request to change the compliance time and a request to change the 
service bulletin reference as two separate issues.
     For each issue, state what specific change to the proposed 
AD is being requested.
     Include justification (e.g., reasons or data) for each 
request.
    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 action must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 2002-NM-24-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. 2002-NM-24-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    On January 24, 1991, the FAA issued AD 91-03-17, amendment 39-6884 
(56 FR 4534, February 5, 1991), applicable to certain Boeing Model 747 
series airplanes, to require inspection of the flap tracks of the 
trailing edge for adequate cadmium plating and to find corrosion of 
certain bolt holes of the fail-safe bar, and plating of such holes, if 
necessary. That action was prompted by reports of missing cadmium 
plating and corrosion in certain flap track fail-safe bar bolt holes. 
The requirements of that AD are intended to prevent fracture of the 
trailing edge flap track, separation of the flap supported by the 
track, and resultant reduction of the controllability of the airplane 
and/or damage to other structure from impact with the departing debris.

Actions Since Issuance of Previous Rule

    Since the issuance of AD 91-03-17, there have been reports of 
additional corrosion and cracks found in certain forward bolt holes of 
the fail-safe bar of the flap tracks of the wing trailing edge flaps on 
certain Boeing Model 747 series airplanes. The corrosion and cracks 
were found AFTER the bolt holes were reworked or replated with cadmium, 
as required by that AD. Boeing Service Bulletins 747-57-2256, dated 
March 8, 1990, and Revision 1, dated November 15, 1990, were the 
sources of service information specified in that AD for accomplishment 
of those actions. Boeing Service Bulletin 747-57-2256, Revision 2, 
dated March 5, 1992, was approved by the FAA after that AD was issued 
and has since been revised. In light of these findings, the terminating 
actions (replating with cadmium and rework of the bolt holes), and the 
option to defer bolt rework if corrosion is found, as specified in that 
AD, are no longer valid and have not been included in this proposed AD. 
In addition, although the effectivity specified in the most recently 
revised service bulletin (below) has not changed from the applicability 
of the existing AD, the applicability section in this proposed AD has 
been changed to specify Revision 3 of the service bulletin instead of 
the original issue.

Explanation of Revised Service Information

    The FAA has reviewed and approved Boeing Service Bulletin 747-57-
2256, Revision 3, dated June 21, 2001, which describes procedures for 
post-modification inspections of certain bolt holes of the fail-safe 
bar of the flap tracks of the trailing edge for discrepancies 
(corrosion, cracks, damaged cadmium plating), and corrective actions 
(rework, repair, or replate with cadmium the affected bolt holes), if 
necessary. The service bulletin revises the procedures specified in the 
original issue, Revision 1, and Revision 2 of the service bulletin as 
follows: changes the post-modification inspection; adds separate post-
modification and rework instructions in Part 2; changes the type of 
bolts in Figure 4, Table II, to ``K'' material-type bolts (corrosion-
resistant); and eliminates the option to defer bolt hole rework if 
corrosion is found. The service bulletin specifies that no more work is 
necessary on airplanes that had cadmium plating installed during 
production and on which no corrosion was found after doing the initial 
inspection specified in the service bulletin. Accomplishment of the 
actions specified in the service bulletin is intended to adequately 
address the identified unsafe condition.

Explanation of Requirements of Proposed Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other products of this same type design, the 
proposed AD would supersede AD 91-03-17 to continue to require 
inspection of the flap tracks of the trailing edge for adequate cadmium 
plating of certain bolt holes of the fail-safe bar, and plating of such 
holes, if necessary. This new action would require post-modification 
inspections of certain bolt holes of the fail-safe bar of the flap 
tracks of the trailing edge for discrepancies, and corrective action, 
if necessary. The actions would be required to be accomplished in 
accordance with the service bulletin described previously, except as 
discussed below.

Difference Between Service Bulletin and Proposed AD

    The service bulletin specifies that the manufacturer may be 
contacted for disposition of certain repair conditions. This proposed 
AD requires the repair of those conditions to be accomplished per a 
method approved by the FAA, or per data meeting the type certification 
basis of the airplane approved by a Boeing Company Designated 
Engineering Representative who has been authorized by the Manager, 
Seattle Aircraft Certification Office, to make such findings.

[[Page 44118]]

Cost Impact

    There are approximately 553 airplanes of the affected design in the 
worldwide fleet. The FAA estimates that 169 airplanes of U.S. registry 
would be affected by this proposed AD.
    The actions that are currently required by AD 91-03-17 take 
approximately 50 work hours per airplane to accomplish, at an average 
labor rate of $60 per work hour. Based on these figures, the cost 
impact of the currently required actions is estimated to $3,000 per 
airplane.
    The borescope inspection proposed in this AD action would take 
approximately 32 work hours per airplane to accomplish, at an average 
labor rate of $60 per work hour. Based on these figures, the cost 
impact of the proposed requirements of this AD on U.S. operators is 
estimated to be $324,480, or $1,920 per airplane.
    The cost impact figures discussed above are based on assumptions 
that no operator has yet accomplished any of the current or proposed 
requirements of this AD action, and that no operator would accomplish 
those actions in the future if this AD were not adopted. The cost 
impact figures discussed in AD rulemaking actions represent only the 
time necessary to perform the specific actions actually required by the 
AD. These figures typically do not include incidental costs, such as 
the time required to gain access and close up, planning time, or time 
necessitated by other administrative actions.
    Should an operator be required to accomplish the eddy current 
inspection, it would take approximately 40 work hours 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 $2,400 per airplane.
    Should an operator be required to accomplish the modification of 
the bolt holes, it would take approximately 256 work hours per airplane 
to accomplish the modification, at an average labor rate of $60 per 
work hour. Based on these figures, the cost impact of the modification 
is estimated to be $15,360 per airplane.

Regulatory Impact

    The regulations proposed herein would 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 proposal would not have federalism implications 
under Executive Order 13132.
    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 removing amendment 39-6884 (56 FR 
4534, February 5, 1991), and by adding a new airworthiness directive 
(AD), to read as follows:

Boeing: Docket 2002-NM-24-AD. Supersedes AD 91-03-17, Amendment 39-
6884.

    Applicability: Model 747 series airplanes, as listed in Boeing 
Service Bulletin 747-57-2256, Revision 3, dated June 21, 2001, 
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)(1) 
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 find and fix discrepancies of certain bolt holes of the fail-
safe bar of the flap tracks of the wing trailing edge flaps, which 
could result in separation of the flap and consequent loss of 
control of the airplane, accomplish the following:

Restatement of Certain Requirements of AD 91-03-17

Inspections

    (a) Prior to the accumulation of 30,000 total flight hours, or 8 
years time-in-service on current production flap tracks, whichever 
is first; or within 2,000 flight cycles after March 11, 1991 (the 
effective date of AD 91-03-17, amendment 39-6884); whichever is 
later: Perform a borescope inspection of the forward four bolt holes 
on each side of the affected trailing edge flap tracks for corrosion 
and adequate cadmium plating, in accordance with the procedures 
specified in Boeing Service Bulletin 747-57-2256, dated March 8, 
1990; Revision 1, dated November 15, 1990; Revision 2, dated March 
5, 1992; or Revision 3, dated June 21, 2001. If the cadmium plating 
is adequate, as specified in the service bulletin, and no corrosion 
or cracks are found, no further action is required for this 
paragraph. If the cadmium plating is not adequate, or if corrosion 
exists in any bolt hole, prior to further flight, conduct an eddy 
current inspection of the bolt hole for cracks, in accordance with 
the service bulletin. After the effective date of this AD only 
Revision 3 of the service bulletin may be used.

Corrective Actions

    (b) If the cadmium plating is not adequate and no corrosion or 
cracks are found during the inspection required by paragraph (a) of 
this AD: Within 1,000 flight cycles after accomplishment of the 
inspection required by paragraph (a) of this AD, cadmium plate the 
affected bolt holes in accordance with Boeing Service Bulletin 747-
57-2256, dated March 8, 1990; Revision 1, dated November 15, 1990; 
Revision 2, dated March 5, 1992; or Revision 3, dated June 21, 2001; 
and conduct the inspections of the affected track as specified in 
paragraphs (b)(1), (b)(2), and (b)(3) of this AD, in accordance with 
the service bulletin. Restoration of the cadmium plating terminates 
the inspections required by this paragraph.

Inspections

    (1) Within 50 flight cycles after accomplishment of the 
inspection required by paragraph (a) of this AD: Perform a close 
visual inspection of each side of the track, at the lower chord, for 
cracks emanating from the forward four fail-safe bar bolt holes, and 
repeat the inspection thereafter at intervals not to exceed 50 
flight cycles.
    (2) Within 250 flight cycles after accomplishment of the 
inspection required by paragraph (a) of this AD: Perform an eddy 
current inspection for cracks of the bolt holes, and repeat the 
inspection thereafter at intervals not to exceed 250 flight cycles.
    (3) Prior to each flight on which a fifth engine is to be 
carried, perform a close visual inspection of each side of the 
track, at the lower chord, for cracks emanating from the forward 
four fail-safe bar bolt holes.

[[Page 44119]]

New Requirements of This AD

Cadmium Plating Applied During Production

    (c) For airplanes on which cadmium plating of the forward four 
bolt holes was applied during production: No further action is 
required by this AD. If operator records indicate that during the 
inspection required by paragraph (a) of this AD cadmium plating was 
applied during production (not during rework or replating), no 
further action is required by this AD. (Indications of rework 
include oversized fasteners and/or fasteners with repair sleeves, 
and/or flap track dash numbers that have been changed per the 
service bulletin.)

Compliance Time for Borescope Inspection

    (d) For airplanes on which cadmium plating of the forward four 
bolt holes was NOT applied during production: Do the action required 
by paragraph (e) of this AD at the later of the times given in 
paragraphs (d)(1) and (d)(2) of this AD.
    (1) Within 2 years or 2,000 flight cycles after the effective 
date of this AD, whichever is first; or
    (2) Within 6 years after doing the initial bolt hole rework per 
AD 91-03-17.

Borescope Inspection

    (e) Do a borescope inspection of the forward four bolt holes on 
each side of the fail-safe bar of the flap tracks of the trailing 
edge flaps for discrepancies (corrosion, cracks, damaged cadmium 
plating), per Part 2 of the Work Instructions of Boeing Service 
Bulletin 747-57-2256, Revision 3, dated June 21, 2001. Then, do the 
actions specified in paragraph (e)(1), (e)(2), or (e)(3) of this AD, 
as applicable, and repeat the borescope inspection every 8 years or 
8,000 flight cycles, whichever is first. Accomplishment of the 
actions specified in this paragraph terminates the requirements of 
paragraph (a) of this AD.

Corrective Actions

    (1) If the cadmium plating is damaged, but no corrosion or 
cracking is found: Before further flight, do the eddy current 
inspection specified in and per Part 2.F. of the Work Instructions 
of the service bulletin. If no cracking is found, before further 
flight, cadmium plate the affected bolt holes per Part 2.F. of the 
Work Instructions of the service bulletin.
    (2) If any corrosion is found, before further flight, rework the 
affected bolt holes as specified in and per Part 2.G. of the Work 
Instructions of the service bulletin.
    (3) If any cracking is found, before further flight, repair per 
a method approved by the Manager, Seattle Aircraft Certification 
Office (ACO), or per data meeting the type certification basis of 
the airplane approved by 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.

Alternative Methods of Compliance

    (f)(1) 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.
    (2) Alternative methods of compliance, approved previously in 
accordance with AD 91-03-17, amendment 39-6884, are approved as 
alternative methods of compliance with paragraphs (a) and (b) of 
this AD.

    Note 2: 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.

    Issued in Renton, Washington, on June 24, 2002.
Kalene C. Yanamura,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 02-16406 Filed 6-28-02; 8:45 am]
BILLING CODE 4910-13-P