[Federal Register Volume 63, Number 244 (Monday, December 21, 1998)]
[Rules and Regulations]
[Pages 70316-70319]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-33541]
=======================================================================
-----------------------------------------------------------------------
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 97-NM-59-AD; Amendment 39-10954; AD 98-26-13]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 747 Series Airplanes
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final rule.
-----------------------------------------------------------------------
SUMMARY: This amendment adopts a new airworthiness directive (AD),
applicable to certain Boeing Model 747 series airplanes, that requires
a one-time inspection to determine the material type of the stop
support fittings of the main entry doors. This AD also requires
repetitive visual inspections to detect cracks of certain stop support
fittings of the main entry doors, and replacement of any cracked stop
support fitting with a certain new stop support fitting. This amendment
is prompted by reports that stress corrosion cracking was found on
certain stop support fittings of the main entry doors. The actions
specified by this AD are intended to detect and correct such stress
corrosion cracking, which could lead to failure of the stop support
fittings. Failure of the stop support fittings could result in loss of
a main entry door and consequent rapid decompression of the airplane.
DATES: Effective January 25, 1999.
The incorporation by reference of certain publications listed in
the regulations is approved by the Director of the Federal Register as
of January 25, 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: Bob Breneman, Aerospace Engineer,
Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle
Aircraft Certification Office, 1601 Lind Avenue, SW., Renton,
Washington 98055-4056; telephone (425) 227-2776; fax (425) 227-1181.
SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal
Aviation Regulations (14 CFR part 39) to include an airworthiness
directive (AD) that is applicable to certain Boeing Model 747 series
airplanes was published in the Federal Register on March 20, 1998 (63
FR 13566). That action proposed to require a one-time
[[Page 70317]]
inspection to determine the material type of the stop support fittings
of the main entry doors. That action also proposed to require
repetitive visual inspections to detect cracks of certain stop support
fittings of the main entry doors, and replacement of any cracked stop
support fitting with a certain new stop support fitting.
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
Several commenters support the proposed rule.
Request to Include a Threshold for Initial Inspection
Two commenters request that the proposed compliance time for the
initial high frequency eddy current (HFEC) inspection to determine the
material type of the stop support fittings of the main entry doors be
revised from 18 months after the effective date of this AD, as stated
in the proposal, to 6 years after delivery of the airplane or 18 months
after the effective date of the AD, whichever occurs later. One of the
commenters points out that cracking of the fittings has been attributed
to stress corrosion and that, when corrosion prevention is performed
properly [i.e., in accordance with the Corrosion Prevention and Control
Program (CPCP)], the growth of corrosion cracking is very slow. The
commenter notes that corrosion and stress corrosion cracking is
unlikely to occur on younger airplanes.
The FAA does not concur with the commenters' request to include a
threshold for the initial inspection. As stated previously in the
notice of proposed rulemaking (NPRM), the FAA has determined that all
affected airplanes are older than 6 years since the date of manufacture
of the airplane. The youngest airplane has been in service for more
than seven years. Therefore, all operators are required to perform the
initial inspection of the affected airplanes within 18 months after the
effective date of this AD. No change to the final rule is necessary in
this regard.
Request to Limit the Area of Inspection
One commenter requests that the proposed HFEC inspection to
determine the material type of the stop support fittings of the main
entry doors should be required only if the material of the stop support
fittings is unknown, as specified in Figure 3, Table 1, of the
referenced service bulletin.
The FAA concurs with the commenter that the HFEC inspection
required by this AD should be required only for those stop support
fittings. The FAA's intent is that the HFEC inspection be accomplished
only at the locations specified in the referenced service bulletin,
where the material type is unknown. The visual inspection must be
accomplished only on those stop support fittings of the main entry
doors that are made from either 7079-T651 or 7075-T651 material. The
FAA has revised paragraph (a) of the final rule to clarify this point.
Request to Extend Repetitive Inspection Intervals
Several commenters request that the repetitive interval for
accomplishment of the visual inspections to detect cracks of certain
stop support fittings of the main entry doors be extended from the
proposed 18 months to 36 months, as specified in Boeing Service
Bulletin 747-53-2358, dated August 26, 1993 (which was referenced as
the appropriate source of service information in the NPRM). One of the
commenters notes that the cracks on the affected stop support fittings
are attributed to stress corrosion, which is a function of environment
and time. As such, the inspection interval specified in the service
bulletin is based on results of inspections of the fleet of Model 747
series airplanes, and on the degree of corrosion or cracking found
during those inspections. Another commenter notes that the growth rate
of stress corrosion cracks depends mainly on the environment and the
age of the airplane, and that growth of such cracks is relatively slow
when corrosion prevention measures are accomplished properly in
accordance with the CPCP.
One of these commenters also requests that the repetitive interval
for the visual inspections be extended from the proposed 18 months to
2,000 flight cycles or 36 months, whichever occurs first. That
commenter points out that the 18-month intervals specified in the
proposal are not consistent with the inspection intervals of 2,000
flight cycles that are specified for inspections of similar fittings at
main entry door 5 that are required by AD 92-02-01, amendment 39-8137
(57 FR 5373, February 14, 1992).
The FAA concurs with the commenters' requests to extend the
repetitive visual inspection intervals. As a result of these comments,
the FAA has reviewed results from inspections of similar fittings of
main entry door 5 that were accomplished in accordance with AD 92-02-
01. Based on this review, the FAA has determined that repetitive
inspections of fittings that are accomplished at 2,000-flight-cycle
intervals are sufficient to detect cracked fittings in a timely manner.
Therefore, the FAA has revised paragraph (a)(2)(i) of the final rule to
state, ``. . . repeat the visual inspection thereafter at intervals not
to exceed 36 months or 2,000 flight cycles, whichever occurs first.''
Request to Allow Continued Use of Subject Stop Support Fittings
One commenter requests that the proposal be revised to allow
cracked stop support fittings of the main entry doors to be replaced
with new stop support fittings that are made from either 7079-T651 or
7075-T651 material, provided that repetitive inspections of the
replacement parts are performed at intervals of 36 months. The
commenter states that a non-cracked stop support fitting made from
7079-T651 or 7075-T651 material provides the required strength
capability. The commenter also notes that discarding all spares of stop
support fittings made from 7079-T651 or 7075-T651 material is a waste
of resources.
The FAA infers that the commenter is requesting that paragraph
(a)(2)(ii) of the proposal be revised to allow installation of new
parts made from either 7079-T651 or 7075-T651 material, or parts made
from 7075-T73 material, and that paragraph (c) of the proposal not be
included in the final rule. The FAA does not concur with the
commenter's request to allow continued use of the subject stop support
fittings. The FAA has determined that the cracking of the stop support
fittings of the main entry doors is caused by a combination of internal
residual stress resulting from the manufacturing process, clamp-up
stress from the installation of the fittings, operational stress due to
pressurization of the airplane, and stress corrosion. Other parts made
from 7079-T651 or 7075-T651 material previously have been found to
crack while in storage, due to internal residual stress. While the FAA
is not requiring the replacement of uncracked stop support fittings of
the main entry doors, the FAA will not promote long-term inspections of
the stop support fittings by approving the installation of replacement
parts that are subject to the same unsafe condition. No change to the
final rule is necessary in this regard.
Request to Amend Aging Fleet Inspection and Modification Program
One commenter suggests that Boeing Service Bulletin 747-53-2358 be
reviewed by the 747 Structures Task Group (STG) for possible inclusion
in
[[Page 70318]]
the aging aircraft inspection or modification program.
The FAA infers that the commenter is requesting that the FAA delay
issuance of the final rule until the STG has reviewed Boeing Service
Bulletin 747-53-2358 and considered including that service bulletin in
Boeing Document No. D6-35999, dated March 1989, ``Aging Airplane
Service Bulletin Structural Modification Program, Model 747.'' [The FAA
previously issued AD 90-06-06, amendment 39-6490 (55 FR 8374, March 7,
1990), which requires incorporation of certain structural modifications
in accordance with Boeing Document No. D6-35999.]
The FAA does not concur. The FAA has determined that rulemaking is
necessary to address the unsafe condition (stress corrosion cracking on
certain stop support fittings of the main entry doors, which could
result in failure of the stop support fittings, loss of a main entry
door, and consequent rapid decompression of the airplane). By issuing
this new rule, the FAA has taken action to ensure that the stop support
fittings of the main entry doors on the affected Boeing Model 747
series airplanes are inspected and replaced, if necessary, in a timely
manner. This action does not preclude a review of Boeing Service
Bulletin 747-53-2358 by the STG for possible inclusion in Boeing
Document No. D6-35999. However, the FAA finds that to delay this action
would be inappropriate in light of the identified unsafe condition.
Therefore, no change to the final rule is necessary in this regard.
Explanation of Additional Changes Made to This Final Rule
In the proposal, paragraph (a)(1) reads, ``If the fitting is made
from 7075-T73 material, no further action is required by this AD.''
Since the issuance of the NPRM, the FAA has determined that such
language could be misleading to operators, because follow-on actions
are required for any stop support fitting of the main entry door that
is made from 7079-T651 or 7075-T651 material, regardless of whether
other stop support fittings are made from 7075-T73 material. Therefore,
paragraph (a)(1) of the final rule has been revised to read, ``. . . no
further action is required by this AD for that fitting.''
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 described
previously. 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 515 Boeing Model 747 series airplanes of
the affected design in the worldwide fleet. The FAA estimates that 164
airplanes of U.S. registry will be affected by this AD.
It will take approximately 1 work hour per door to accomplish the
required HFEC inspection, at an average labor rate of $60 per work
hour. Based on these figures, the cost impact of the HFEC inspection
required by this AD on U.S. operators is estimated to be $60 per door.
The cost impact figure discussed above is based on assumptions that
no operator has yet accomplished any of the requirements of this AD
action, and that no operator would accomplish those actions in the
future if this AD were not adopted.
Should an operator be required to accomplish the required visual
inspection, it will take approximately 2 work hours per door to
accomplish the required actions, at an average labor rate of $60 per
work hour. Based on these figures, the cost impact of the visual
inspection required by this AD on U.S. operators is estimated to be
$120 per door.
Should an operator elect to accomplish the optional terminating
action that is provided by this AD action, the number of hours required
to accomplish it would be approximately 124 work hours per door, at an
average labor rate of $60 per work hour. Required parts would cost
approximately $13,000 per door. Based on these figures, the cost impact
of the optional terminating action on U.S. operators is estimated to be
$20,440 per door.
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:
98-26-13 BOEING: Amendment 39-10954. Docket 97-NM-59-AD.
Applicability: Model 747-100, -100B, -200, -200B, -200C, -300, -
400, and 747SR series airplanes; having line numbers 1 through 830
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 (d) 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 stress corrosion cracking of the stop
support fittings of the main entry doors and the resultant failure
of the stop support fittings, which could result in loss of a main
entry door and consequent rapid decompression of the airplane,
accomplish the following:
(a) Within 18 months after the effective date of this AD,
perform a high frequency eddy current inspection to determine the
material type of the stop support fittings of
[[Page 70319]]
the main entry doors, in accordance with the Accomplishment
Instructions of Boeing Service Bulletin 747-53-2358, dated August
26, 1993. Perform the inspection only at those locations where the
material type of the stop support fittings is unknown, as specified
in Figure 3, Table 1, of the service bulletin.
(1) If the fitting is made from 7075-T73 material, no further
action is required by this AD for that fitting.
(2) If the fitting is NOT made from 7075-T73 material, prior to
further flight, perform a visual inspection to detect cracks of the
stop support fitting of the main entry doors, in accordance with the
service bulletin.
(i) If no crack is detected, repeat the visual inspection
thereafter at intervals not to exceed 36 months or 2,000 flight
cycles, whichever occurs first.
(ii) If any crack is detected, prior to further flight, replace
the fitting with a stop support fitting made from 7075-T73 material,
in accordance with the service bulletin.
(b) Replacement of the stop support fitting of the main entry
doors with a stop support fitting made from 7075-T73 material, in
accordance with Boeing Service Bulletin 747-53-2358, dated August
26, 1993, constitutes terminating action for the repetitive
inspection requirements of this AD for the replaced fitting.
(c) As of the effective date of this AD, no person shall install
a stop support fitting made from either 7079-T651 or 7075-T651
material on any airplane.
(d) 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 Aircraft Certification
Office (ACO), FAA, Transport Airplane Directorate. 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 2: Information concerning the existence of approved
alternative methods of compliance with this AD, if any, may be
obtained from the Seattle ACO.
(e) 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.
(f) The actions shall be done in accordance with Boeing Service
Bulletin 747-53-2358, dated August 26, 1993. 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.
(g) This amendment becomes effective on January 25, 1999.
Issued in Renton, Washington, on December 14, 1998.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 98-33541 Filed 12-18-98; 8:45 am]
BILLING CODE 4910-13-U
