[Federal Register Volume 68, Number 48 (Wednesday, March 12, 2003)]
[Proposed Rules]
[Pages 11764-11770]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 03-5857]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2003-NM-47-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 747 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the supersedure of two existing 
airworthiness directives (AD), applicable to all Boeing Model 747 
series airplanes, which currently require that the FAA-approved 
maintenance inspection program be revised to include inspections that 
will give no less than the required damage tolerance rating for each 
structural significant item, and repair of cracked structure. Those ADs 
were prompted by a structural re-evaluation that identified additional 
structural elements where, if damage were to occur, supplemental 
inspections may be required for timely detection of fatigue cracking. 
This action would require additional and expanded inspections, and 
repair of cracked structure. This action also would expand the 
applicability of the existing ADs to include additional airplanes. The 
actions specified by the proposed AD are intended to ensure the 
continued structural integrity of the entire fleet of Model 747 series 
airplanes.

DATES: Comments must be received by April 28, 2003.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 2003-NM-47-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. 2003-NM-47-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 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 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) 917-6421; fax (425) 
917-6590.

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

[[Page 11765]]

in this action may be changed in light of the comments received.
    Submit comments using the following format:
    [sbull] 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.
    [sbull] For each issue, state what specific change to the proposed 
AD is being requested.
    [sbull] 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 2003-NM-47-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. 2003-NM-47-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    In the early 1980's, as part of its continuing work to maintain the 
structural integrity of older transport category airplanes, the FAA 
concluded that the incidence of fatigue cracking may increase as these 
airplanes reach or exceed their design service objective (DSO). A 
significant number of these airplanes were approaching or had exceeded 
the DSO on which the initial type certification approval was 
predicated. In light of this, and as a result of increased utilization, 
longer operational lives, and the high levels of safety expected of the 
currently operated transport category airplanes, we determined that a 
supplemental structural inspection program (SSIP) was necessary to 
ensure a high level of structural integrity for all airplanes in the 
transport fleet.

Issuance of Advisory Circular

    As a follow-on from that determination, the FAA issued Advisory 
Circular (AC) No. 91-56, ``Supplemental Structural Inspection Program 
for Large Transport Category Airplanes,'' dated May 6, 1981. That AC 
provides guidance material to manufacturers and operators for use in 
developing a continuing structural integrity program to ensure safe 
operation of older airplanes throughout their operational lives. This 
guidance material applies to transport airplanes that were certified 
under the fail-safe requirements of part 4b (``Airplane Airworthiness, 
Transport Categories'') of the Civil Air Regulations or damage 
tolerance structural requirements of part 25 (``Airworthiness 
Standards: Transport Category Airplanes'') of the Federal Aviation 
Regulations (FAR) (14 CFR part 25), and that have a maximum gross 
weight greater than 75,000 pounds. The procedures set forth in that AC 
are applicable to transport category airplanes operated under subpart D 
(``Special Flight Operations'') of part 91 of the FAR (14 CFR part 91); 
part 121 (``Operating Requirements: Domestic, Flag, and Supplemental 
Operations''); part 125 (``Certification and Operations: Airplanes 
having a Seating Capacity of 20 or More Passengers or a Maximum Payload 
of 6,000 Pounds or More''); and part 135 (``Operating Requirements: 
Commuter and On-Demand Operations'') of the FAR (14 CFR parts 121, 125, 
and 135). The objective of the SSIP was to establish inspection 
programs to ensure timely detection of fatigue cracking.

Development of the SSIP

    In order to evaluate the effect of increased fatigue cracking with 
respect to maintaining fail-safe design and damage tolerance of the 
structure of Boeing Model 747 series airplanes, Boeing conducted a 
structural reassessment of those airplanes, using modern damage 
tolerance evaluation techniques. Boeing accomplished this reassessment 
using the criteria contained in AC No. 91-56, as well as Amendment 
(Amdt.) 25-45 of section 25.571 (``Damage-tolerance and fatigue 
evaluation of structure'') of the FAR (14 CFR 25.571). During the 
reassessment, members of the airline industry participated with Boeing 
in working group sessions and developed the SSIP for Model 747 series 
airplanes. Engineers and maintenance specialists from the FAA also 
attended these sessions to observe these developments. Subsequently, 
based on the working group's recommendations, Boeing developed the 
Supplemental Structural Inspection Document (SSID).

Current Model 747 Series Airplanes ADs

    On July 18, 1994, the FAA issued AD 94-15-12, amendment 39-8983 (59 
FR 37933, July 26, 1994), applicable to certain Boeing Model 747-100SR 
series airplanes. Additionally, on July 22, 1994, we issued AD 94-15-
18, amendment 39-8989 (59 FR 41233, August 11, 1994), applicable to 
certain Boeing Model 747 series airplanes. Both of those ADs currently 
require that the FAA-approved maintenance inspection program be revised 
to include inspections that will give no less than the required damage 
tolerance rating (DTR) for each structural significant item (SSI), and 
repair of cracked structure. AD 94-15-12 references Boeing Document No. 
D6-35655, ``Supplemental Structural Inspection Document (SSID) for 747-
100SR,'' dated April 2, 1986; and AD 94-15-18 references Boeing 
Document No. D6-35022, ``Supplemental Structural Inspection Document 
(SSID) for Model 747 Airplanes,'' Revision E, dated June 17, 1993; as 
the appropriate sources of service information. Those actions were 
prompted by a structural re-evaluation that identified additional 
structural components where fatigue cracking is likely to occur. The 
requirements of those ADs are intended to ensure the continued 
structural integrity of the entire Model 747 fleet in service at the 
time of issuance of those ADs.

Other ADs Regarding SSIPs

    On December 30, 1998, the FAA issued SSIP AD 98-11-03 R1, amendment 
39-10983 (64 FR 989, January 7, 1999) for Boeing Model 727 series 
airplanes and SSIP AD 98-11-04 R1 (64 FR 987, January 7, 1999) for 
Boeing Model 737 series airplanes. Those ADs, in addition to their 
primary purpose to require inspection of baseline structure, also 
address repairs, alterations, and modifications (RAMs). Those ADs 
require operators to provide damage tolerance-based inspection programs 
for RAMs that affect principal structural elements or that create new 
principal structural elements.
    This proposed AD for Boeing Model 747 series airplanes will address 
a damage tolerance-based inspection program only for the baseline 
structure and will not include RAMs. If a RAM interferes with the 
inspection of baseline structure, then this area must be addressed per 
Note 1 of the proposed AD.

[[Page 11766]]

Addressing RAMs

    In April of 2000, an FAA team was chartered to address 
standardization of the SSIP ADs with regard to RAMs. The team was 
formed due to concerns of operators regarding different approaches to 
addressing RAMs for the McDonnell Douglas series airplanes versus the 
Boeing Model 727 and 737 series airplanes. Also, since the issuances of 
AD 98-11-03 R1 and AD 98-11-04 R1, operators have had various problems 
addressing RAMs. As announced in a Notice of Public Meeting, published 
in the Federal Register on January 15, 2003 (68 FR 2103), a public 
meeting will be held to present our view and to receive comments from 
the public. Due to the many issues that have arisen in addressing RAMs, 
this proposed AD will not require damage tolerance-based inspections 
for RAMs on Boeing Model 747 series airplanes.

Aging Airplane Safety Rule (AASR)

    The AASR was published in the Federal Register on December 6, 2002 
(67 FR 72726). That rule requires the maintenance program applicable to 
affected airplanes to include damage tolerance-based inspections and 
procedures that include all major structural repairs, alterations, and 
modifications. The compliance time for these procedures is four years 
after December 8, 2003 (the effective date of the AASR). The FAA 
intends to eventually require damage tolerance-based inspections for 
RAMs during subsequent rulemaking. (See the information under the 
``Interim Action'' paragraph of this proposed AD.)

Other SSIP Issues

    Since the issuance of the current SSIP ADs for Model 747 series 
airplanes (ADs 94-15-12 and 94-15-18), the FAA has reconsidered the 
following two aspects of the existing SSIP:
    1. Candidate fleet vs. inspection threshold approach. Paragraph 4.4 
of AC No. 91-56, Change 2, dated April 15, 1983, states, ``Inspection 
thresholds for supplemental inspections should be established. These 
inspections would be supplemental to the normal inspection including 
the detailed internal inspections.'' Moreover, paragraph 4.4.2 of AC 
No. 91-56 states, `` * * * this threshold should be such as to include 
sufficient [high-cycle] airplanes in the inspection to develop added 
confidence in the integrity of the structure . . . .''
    A properly established inspection threshold ensures that: (1) The 
SSI inspections are accomplished; (2) fatigue cracks in SSIs are 
detected in a timely manner; (3) airplanes are automatically added to 
the SSIP; and (4) the SSIP includes a statistically valid number of 
airplanes.
    Among other things, SSID D6-35655 and Revision E of SSID D6-35022 
(referenced as the appropriate service information in ADs 94-15-12 and 
94-15-18) define a candidate fleet approach to ensure that fatigue 
cracks in SSIs are detected in a timely manner in the entire fleet of 
Model 747 series airplanes. The initial candidate fleet of Model 747-
100 and -200 series airplanes, as defined in SSID D6-35022, consisted 
of a number of airplanes that had exceeded 10,000 total flight cycles 
by June 30, 1983. The initial candidate fleet of Model 747SR series 
airplanes, as defined in SSID D6-35655, consisted of a number of 
airplanes that had exceeded 12,000 total flight cycles by January 1, 
1985. In other words, Boeing considered 10,000 total flight cycles for 
Model 747-100 and -200 series airplanes, and 12,000 total flight cycles 
for Model 747SR series airplanes, to be the threshold for the airplanes 
in the candidate fleets. Those airplanes were the most likely airplanes 
in the fleets to experience initial fatigue damage, because they had 
the highest number of flight cycles. Boeing produced those SSIDs with 
the assumption that the airplanes in the candidate fleets would 
continue to represent the entire fleet and would have the highest 
number of flight cycles in the fleet.
    Under the existing SSIP, Boeing intended to periodically review the 
airplanes in the candidate fleet for significant changes in fleet 
distribution, composition, or utilization, and update of the candidate 
fleet, if any significant change was detected. It was intended that the 
FAA would then mandate any change to the SSID through the rulemaking 
process.
    The FAA finds that the candidate fleet approach is deviating from 
Boeing's original philosophy in that the candidate fleet has not been 
updated to reflect changes in the fleet. This situation could result in 
a statistically invalid number of airplanes in the SSIP and undetected 
fatigue cracks in SSIs. The candidate fleet approach also does not 
automatically account for non-candidate airplanes that eventually 
accumulate more flight cycles than those of certain candidate 
airplanes. High-cycle airplanes are more likely to experience initial 
fatigue damage in the fleet. The confidence in the structural integrity 
of the fleet of airplanes could be reduced if high-cycle airplanes are 
excluded from the SSIP.
    The FAA has reconsidered the candidate fleet approach described in 
SSID D6-35655 and Revision E of SSID D6-35022 because it does not meet 
the guidelines of AC No. 91-56. We have also determined that the Model 
747 SSIP must contain inspection thresholds for all Model 747 series 
airplanes to ensure the timely detection of fatigue cracks in the SSIs.
    The FAA has reviewed the thresholds derived from Boeing's 
statistical analysis. The analysis is based on a certain probability 
that cracks will be detected in the inspected fleet before they 
initiate on other airplanes that have not been inspected. We find that 
the thresholds recommended in Revision G of SSID D6-35022 for the Model 
747 airplane fleet are acceptable. Therefore, we have determined that a 
threshold of 20,000 total flight cycles or 100,000 total flight hours, 
whichever comes first, on wing structure, and 20,000 total flight 
cycles on all other structures are necessary in order to produce a 
statistically valid assessment of the service history for these 
airplanes. The original threshold for the Model 747SR series airplane 
was set higher by the manufacturer because it was believed that these 
airplanes were not subject to the same fatigue cycles due to use of a 
lower cabin differential pressure. We have since determined that an 
adjustment of flight cycles due to a lower cabin differential pressure 
is not substantiated and will not be allowed for use in determining the 
flight cycle threshold and inspection intervals of the SSID program. 
Therefore, the threshold for Model 747SR series airplanes is now the 
same as that of other Model 747 series airplanes.
    It should be noted that, although the proposed AD specifies a 
threshold, the FAA may approve requests for adjustments to the 
compliance time (i.e., under the provisions of paragraph (g)(1) of this 
proposed AD) provided that no cracking is detected in the airplane 
structure. The request should include a new proposed inspection 
threshold and must include data to substantiate that such an adjustment 
would provide an acceptable level of safety.
    Operators also should note that the alternative inspection 
threshold may be based solely on the analysis of the data of the 
existing fleet. However, the FAA has determined that the analysis that 
derives the new inspection threshold must include: (1) Data relevant to 
a sufficient number of high-cycle airplanes, and (2) data that show 
accomplishment of the inspections of the SSIs. An adequate statistical 
sampling size will provide confidence in the structural integrity of 
the fleet of airplanes. Therefore, additional airplanes may need to be 
added to the inspected fleet until a sufficient number

[[Page 11767]]

of airplanes have been inspected with no crack findings.
    2. Transferability of airplanes. Since issuance of AD 94-15-12 and 
AD 94-15-18, the FAA has issued several ADs that implement Corrosion 
Prevention and Control Programs (CPCP) for aging airplanes. While 
developing the ADs that mandated the CPCP, we recognized that an 
operator of an airplane that has been transferred from another operator 
could revise its maintenance or inspection program to restart the 
compliance times for the required corrosion tasks. This situation could 
lead to corrosion not being detected and corrected in a timely manner, 
which could reduce the structural integrity of the airplane.
    As a result, the CPCP ADs require that operators establish a 
program for accomplishment of the subject corrosion tasks before any 
airplane can be added to an air carrier's operations specification. 
Establishment of such a program ensures that airplanes transferred from 
operator to operator are inspected and that corrosion is detected in a 
timely manner.
    The FAA's intent in AD 94-15-12 and AD 94-15-18 was that operators 
of candidate fleet airplanes that have been previously operated under 
an FAA-approved maintenance or inspection program would accomplish the 
SSID inspections within the compliance time established by the previous 
operator. We assumed that, under the existing SSIDs, these airplanes 
would be inspected in a manner similar to CPCP requirements. However, 
the SSID ADs, AD 94-15-12 and AD 94-15-18, do not specifically address 
the transfer of airplanes in the candidate fleet from one operator to 
another.
    AD 94-15-12 and AD 94-15-18 currently require that the revision to 
the maintenance inspection program be included and be implemented per 
the procedures specified in Sections 5.0 and 6.0 of the SSIDs. However, 
the FAA finds that those sections do not provide explicit instructions 
to repetitively inspect airplanes that have been transferred from one 
operator to another. Those sections also do not specify that new 
operators must continue the SSID inspections at the same frequency 
established by the previous operator.
    In addition, as AD 94-15-12 and AD 94-15-18 are currently worded, 
the FAA finds that operators, who acquire candidate fleet airplanes 
that have been previously operated under a maintenance inspection 
program, could revise their programs to restart the compliance times. 
This situation is contrary to standard AD requirements. An AD typically 
mandates an initial compliance time and a repetitive interval that 
remains unchanged for all operators of the affected airplanes.
    As a result of these omissions, the SSID inspections of a candidate 
fleet airplane could be deferred until it is required by the 
maintenance inspection program of the new operator. For airplanes that 
are transferred frequently, this situation could continue for the life 
of the airplane. As a result, the size of the candidate fleet is in 
effect reduced because fewer candidate fleet airplanes are being 
inspected. Even if airplanes are ultimately inspected under these 
circumstances, inspections would not be performed frequently enough to 
maintain the applicable DTR. The FAA has determined that such a 
reduction of the candidate fleet and the resulting reduction in the 
number of airplanes being inspected do not ensure the continued 
structural integrity of the entire fleet of Model 747 series airplanes.
    Implementation of procedures in the SSID that are similar to the 
CPCP will ensure that: (1) Airplanes transferred from operator to 
operator are inspected; (2) the SSIP includes a statistically valid 
number of airplanes; and (3) fatigue cracks are detected in a timely 
manner.
    Therefore, the FAA finds that, to ensure the continued structural 
integrity of the entire fleet of Model 747 series airplanes, AD 94-15-
12 and AD 94-15-18 must be superseded to include provisions that 
address the transfer of airplanes. We also find that a program must be 
established to ensure that inspections are accomplished before any 
applicable airplane can be added to an air carrier's operations 
specifications.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Document No. D6-35022, 
``Supplemental Structural Inspection Document'' (SSID), Revision F, 
dated May 1996, as an alternative method of compliance to AD 94-15-18. 
Revision F of SSID D6-35022 describes procedures for revising the FAA-
approved maintenance inspection program for all Model 747-100, -200B, -
200C, and -200F series airplanes. This revision of the SSID for Model 
747 series airplanes incorporates additional and expanded inspections 
from those that were contained in the previous version and mandated by 
AD 94-15-18. We also reviewed and approved Boeing Document No. D6-
35022, ``Supplemental Structural Inspection Document'' (SSID), Revision 
G, dated December 2000. Revision G affects all Model 747-SP, -SR, -100, 
-100B, -100SUD, -200B, -200C, -200F, -300, -400, -400D, and -400F 
series airplanes, and supersedes Boeing Document No. D6-35655 for 747-
SR series airplanes. This revision also adds additional inspection 
requirements. We find that accomplishment of these inspections in 
Boeing Document No. D6-35022, ``Supplemental Structural Inspection 
Document'' (SSID), Revision G, dated December 2000, will ensure the 
continuing structural integrity of the identified fleet of Model 747 
series airplanes. Accomplishment of the actions specified in Revision G 
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 94-15-12 and AD 94-15-18 to require the 
following actions:
    Paragraph (a) of the proposed AD restates the requirements of AD 
94-15-
    12. Paragraph (b) of the proposed AD restates the requirements of 
paragraph (b) of AD 94-15-18. Although AD 94-15-18 specifies Revision E 
of Boeing Document No. D6-35022 as the appropriate source of service 
information for that AD, this proposed AD also permits incorporation of 
Revision F, of Boeing Document No. D6-35022, dated May 1996, until the 
compliance time for incorporation of Revision G is reached. (Paragraph 
(a) of AD 94-15-12 is no longer necessary because that paragraph 
required an earlier revision of the SSID than that required by 
paragraph (b).)
    Paragraph (c) of the proposed AD would require incorporation of a 
revision into the FAA-approved maintenance or inspection program that 
provides no less than the required DTR for each SSI listed in Revision 
G of SSID D6-35022.
    Paragraph (d) of the proposed AD would establish specific 
compliance times for performing the initial inspection of the structure 
identified in Revision G of SSID D6-35022. Once the initial inspection 
has been performed, operators would be required to perform repetitive 
inspections at the intervals specified in Revision G of SSID D6-35022 
in order to remain in compliance with their maintenance or inspection 
programs, as specified in paragraph (c) of this proposed AD.
    Paragraph (e) of the proposed AD would require that repair of any 
cracked structure is to be accomplished per an FAA-approved method.

[[Page 11768]]

    Paragraph (f) of the proposed AD specifies the requirements of the 
inspection program for transferred airplanes. Before any airplane that 
is subject to this proposed AD can be added to an air carrier's 
operations specifications, a program for the accomplishment of the 
inspections required by this proposed AD must be established. Paragraph 
(f) of the proposed AD would require accomplishment of the following:
    1. For airplanes that have been inspected per this proposed AD, the 
inspection of each SSI must be accomplished by the new operator per the 
previous operator's schedule and inspection method, or per the new 
operator's schedule and inspection method, at whichever time would 
result in the earlier accomplishment date for that SSI inspection. The 
compliance time for accomplishment of this inspection must be measured 
from the last inspection accomplished by the previous operator. After 
each inspection has been performed once, each subsequent inspection 
must be performed per the new operator's schedule and inspection 
method.
    2. For airplanes that have not been inspected per this proposed AD, 
the inspection of each SSI must be accomplished either prior to adding 
the airplane to the air carrier's operations specification, or per a 
schedule and an inspection method approved by the FAA. After each 
inspection has been performed once, each subsequent inspection must be 
performed per the new operator's schedule.
    Accomplishment of these actions will ensure that: (1) An operator's 
newly acquired airplanes comply with its SSIP before being operated; 
and (2) frequently transferred airplanes are not permitted to operate 
without accomplishment of the inspections defined in the SSID.

Interim Action

    This is considered to be interim action. The FAA is currently 
considering requiring damage tolerance-based inspections and procedures 
that include all major structural RAMs in a superseding AD. That 
superseding AD would include appropriate recommendations from the 
previously mentioned FAA team and public meeting on how to address 
RAMs.

Differences Between SSID and Proposed AD

    Operators should note the following differences between the 
procedures specified in Revision G of SSID D6-35022 and the proposed 
requirements of this AD:
    1. Revision G of SSID D6-35022 provides for phased inspections or 
rotational sampling of inspections. This proposed AD would not allow 
phased inspections or rotational sampling.
    2. Revision G of SSID D6-35022 allows individual operators to 
combine their affected airplanes with those of other operators to 
fulfill requirements of the SSIP. This proposed AD would not allow for 
phased inspections or a candidate fleet; therefore, this proposed AD 
would not allow an operator to take credit for inspections accomplished 
on another operator's airplane.
    3. Revision G of SSID D6-35022 contains blanket provisions for 
touch-and-go training flights, which are not allowed by this proposed 
AD. Revision G of SSID D6-35022 also allows for fleet averaging, and 
arbitrary 10% escalations for flight cycles to achieve the required 
DTR. These procedures are not allowed in this proposed AD.
    4. Revision G of SSID D6-35022 does not provide an implementation 
grace period when an operator's airplane is near or passed the 
threshold. This proposed AD will allow 12 months after the effective 
date of the AD to incorporate Revision G of SSID D6-35022 into the FAA-
approved maintenance or inspection program. This proposed AD will also 
allow a grace period of 1,000 flight cycles measured from 12 months 
after the effective date of the proposed AD.

Cost Impact

    There are approximately 1,000 airplanes of the affected design in 
the worldwide fleet.
    The FAA estimates that 87 airplanes of U.S. registry are currently 
affected by the requirements of AD 94-15-12 and AD 94-15-18. Those 
required actions take approximately 1,000 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 on 
U.S. operators is estimated to be $5,220,000, or $60,000 per airplane, 
per inspection cycle.
    The FAA estimates that 181 airplanes of U.S. registry would be 
affected by this proposed AD. The new actions that are proposed in this 
AD action would take approximately 1,275 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 $13,846,500, or $76,500 per 
airplane, per inspection cycle.
    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 number of proposed work hours, as indicated above, is presented 
as if the accomplishment of the actions proposed in this AD were to be 
conducted as ``stand alone'' actions. However, in actual practice, 
these actions for the most part would be accomplished coincidentally or 
in combination with normally scheduled airplane inspections and other 
maintenance program tasks. Therefore, the actual number of necessary 
additional work hours would be minimal in many instances. Additionally, 
any costs associated with special airplane scheduling would be minimal.

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.

[[Page 11769]]

Sec.  39.13  [Amended]

    2. Section 39.13 is amended by removing amendments 39-8983 (59 FR 
37933, July 26, 1994) and 39-8989 (59 FR 41233, August 11, 1994), and 
by adding a new airworthiness directive (AD), to read as follows:

Boeing: Docket 2003-NM-47-AD. Supersedes AD 94-15-12, amendment 39-
8983, and AD 94-15-18, amendment 39-8989.

    Applicability: All Model 747 series airplanes, 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 per paragraph (g)(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 ensure the continued structural integrity of the entire fleet 
of Model 747 series airplanes, accomplish the following:

    Note 2: Where there are differences between this AD and the 
Supplemental Structural Inspection Document (SSID) specified in this 
AD, the AD prevails.

Inspection Program Required by AD 94-15-12

    (a) For Model 747-100SR series airplanes having line numbers 
346, 351, 420, 426, 427, and 601: Within 1 year after August 10, 
1994 (the effective date of AD 94-15-12, amendment 39-8983), 
incorporate a revision into the FAA-approved maintenance inspection 
program that provides no less than the required damage tolerance 
rating (DTR) for each structural significant item (SSI) listed in 
Boeing Document No. D6-35655, ``Supplemental Structural Inspection 
Document (SSID) for 747-100SR,'' dated April 2, 1986. The revision 
to the maintenance program must include and be implemented per the 
procedures specified in Sections 5.0 and 6.0 of the SSID D6-35655. 
Revision to the maintenance program shall be per the SSID D6-35655, 
dated April 2, 1986, until Revision G of the SSID D6-35022 is 
incorporated into the FAA-approved maintenance or inspection program 
per the requirements of paragraph (c) of this AD.

    Note 3: For the purposes of this AD, an SSI is defined as a 
principal structural element (PSE). A PSE is a structural element 
that contributes significantly to the carrying of flight, ground, or 
pressurization loads, and whose integrity is essential in 
maintaining the overall structural integrity of the airplane.

Inspection Program Required by AD 94-15-18

    (b) For airplanes listed in Boeing Document No. D6-35022, 
Volumes 1 and 2, ``Supplemental Structural Inspection Document 
(SSID) for Model 747 Airplanes,'' Revision E, dated June 17, 1993; 
and manufacturer's line numbers 42, 174, 221, 231, 234, 239, 242, 
and 254: Within 12 months after September 12, 1994 (the effective 
date of AD 94-15-18, amendment 39-8989), incorporate a revision into 
the FAA-approved maintenance inspection program that provides no 
less than the required DTR for each SSI listed in Boeing Document 
No. D6-35022, Volumes 1 and 2, ``Supplemental Structural Inspection 
Document (SSID) for Model 747 Airplanes,'' Revision E, dated June 
17, 1993, or Revision F, dated May 1996. (The required DTR value for 
each SSI is listed in the document.) The revision to the maintenance 
program shall include Sections 5.0 and 6.0 of the SSID D6-35022 and 
shall be implemented per the procedures contained in those sections. 
Revision to the maintenance program shall be per Revision E or F of 
SSID D6-35022, until Revision G of the SSID D6-35022 is incorporated 
into the FAA-approved maintenance or inspection program per the 
requirements of paragraph (c) of this AD.

New Inspection Program Requirements

    (c) For all Model 747 series airplanes: Prior to reaching either 
of the thresholds specified in paragraph (d)(1)(i) or (d)(2)(i) of 
this AD, or within 12 months after the effective date of this AD, 
whichever occurs later, incorporate a revision into the FAA-approved 
maintenance or inspection program that provides no less than the 
required DTR for each SSI listed in Boeing Document No. D6-35022, 
``Supplemental Structural Inspection Document,'' Revision G, dated 
December 2000 (hereinafter referred to as ``Revision G''). (The 
required DTR value for each SSI is listed in Revision G.) The 
revision to the maintenance or inspection program shall include and 
shall be implemented per the procedures in Section 5.0, excluding 
paragraphs 5.1.2, 5.1.6, item 5; 5.1.8; 5.2; 5.2.1; 5.2.2; 5.2.3; 
and 5.2.4; ``Damage Tolerance Rating (DTR) System Application;'' and 
Section 6.0, ``SSI Discrepancy Reporting;'' of Revision G. Upon 
incorporation of Revision G required by this paragraph, the revision 
required by either paragraph (a) or (b) of this AD, as applicable, 
may be removed.

Initial Inspection

    (d) For all Model 747 series airplanes: Perform an inspection to 
detect cracks of all structure identified in Revision G of SSID D6-
35022 at the time specified in paragraph (d)(1) or (d)(2) of this 
AD, as applicable.
    (1) For wing structure: At the times specified in paragraph 
(d)(1)(i) or (d)(1)(ii) of this AD, whichever occurs later.
    (i) Prior to the accumulation of 20,000 total flight cycles or 
100,000 total flight hours, whichever comes first. Or,
    (ii) Within 1,000 flight cycles measured from 12 months after 
the effective date of this AD.
    (2) For all other structure: At the times specified in paragraph 
(d)(2)(i) or (d)(2)(ii) of this AD, whichever occurs later.
    (i) Prior to the accumulation of 20,000 total flight cycles, or
    (ii) Within 1,000 flight cycles measured after 12 months from 
the effective date of this AD.

    Note 4: Notwithstanding the provisions of paragraphs 5.1.2, 
5.1.6, item 5, 5.2, 5.2.1, 5.2.2, 5.2.3, and 5.2.4 of the General 
Instructions of Revision G, which would permit operators to perform 
fleet and rotational sampling inspections to perform inspections on 
less than whole airplane fleet sizes and to perform inspections on 
substitute airplanes, this AD requires that all airplanes that 
exceed the threshold be inspected per Revision G. Paragraph 5.1.8 
allows provisions for touch-and-go training flights, fleet 
averaging, and 10% escalations of flight cycles to achieve the 
required DTR. This AD does not allow for these provisions as well.


    Note 5: Once the initial inspection has been performed, 
operators are required to perform repetitive inspections at the 
intervals specified in Revision G in order to remain in compliance 
with their maintenance or inspection programs, as revised per 
paragraph (c) of this AD.

Repair

    (e) Cracked structure found during any inspection required by 
this AD shall be repaired, prior to further flight, in accordance 
with an FAA-approved method.

Inspection Program for Transferred Airplanes

    (f) Before any airplane that is subject to this AD and that has 
exceeded the applicable compliance times specified in paragraph (d) 
of this AD can be added to an air carrier's operations 
specifications, a program for the accomplishment of the inspections 
required by this AD must be established per paragraph (f)(1) or 
(f)(2) of this AD, as applicable.
    (1) For airplanes that have been inspected per this AD, the 
inspection of each SSI must be accomplished by the new operator per 
the previous operator's schedule and inspection method, or the new 
operator's schedule and inspection method, at whichever time would 
result in the earlier accomplishment date for that SSI inspection. 
The compliance time for accomplishment of this inspection must be 
measured from the last inspection accomplished by the previous 
operator. After each inspection has been performed once, each 
subsequent inspection must be performed per the new operator's 
schedule and inspection method.
    (2) For airplanes that have not been inspected per this AD, the 
inspection of each SSI required by this AD must be accomplished 
either prior to adding the airplane to the air carrier's operations 
specification, or per a schedule and an inspection method approved 
by the Manager, Seattle Aircraft Certification Office (ACO). After 
each inspection has been performed once, each subsequent inspection 
must be performed per the new operator's schedule.

[[Page 11770]]

Alternative Methods of Compliance

    (g)(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 per 
AD 94-15-12, amendment 39-8983, are approved as alternative methods 
of compliance with paragraphs (a) and (e) of this AD.
    (3) Alternative methods of compliance, approved previously per 
AD 94-15-18, amendment 39-8989, are approved as alternative methods 
of compliance with paragraphs (b) and (e) of this AD.
    (4) Alternative methods of compliance, approved previously per 
AD 94-15-18 and AD 94-15-12 that provide alternative inspections are 
approved as alternative methods of compliance for the inspections of 
that area only in this AD.

    Note 6: 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

    (h) Special flight permits may be issued per 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 March 5, 2003.
Ali Bahrami,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 03-5857 Filed 3-11-03; 8:45 am]
BILLING CODE 4910-13-P