[Federal Register Volume 61, Number 221 (Thursday, November 14, 1996)]
[Rules and Regulations]
[Pages 58318-58323]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-28688]
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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39
[Docket No. 94-NM-221-AD; Amendment 39-9810; AD 96-23-05]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 747 Series Airplanes
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final rule.
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SUMMARY: This amendment adopts a new airworthiness directive (AD),
applicable to certain Boeing Model 747 series airplanes, that requires
repetitive inspections to detect cracks and/or corrosion of the girt
bar support fitting at certain main entry doors (MED); and repair or
replacement of the support fitting. This amendment also provides for
various terminating actions for the repetitive inspections. This
amendment is prompted by reports that, during scheduled deployment
tests of main entry door slides, corrosion was found on the floor
structure supports for the escape slides of the main deck entry doors
on these airplanes. The actions specified by this AD are intended to
prevent such corrosion, which could result in separation of the escape
slide from the lower door sill during deployment, and subsequently
prevent proper operation of the escape slides at the main entry doors
during an emergency.
DATES: Effective December 16, 1996.
The incorporation by reference of certain publications listed in
the regulations is approved by the Director of the Federal Register as
of December 16, 1996.
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: Robert Breneman, Aerospace Engineer,
Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle
Aircraft Certification Office, 1601 Lind Avenue, SW., Renton,
Washington 98055-4056; telephone (206) 227-2776; fax (206) 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 February 8, 1995 (60
FR 7482). That action proposed to require repetitive detailed visual
inspections to detect cracks and/or corrosion of the girt bar support
fitting at MED's 1 through 5, inclusive; repair or replacement of the
support fitting; and reinstallation of the threshold assembly. The
action also proposed to require, under certain conditions, replacing
the support fittings with new support fittings having new fasteners;
refinishing uncorroded support fittings; and removing the corrosion and
refinishing corroded support fittings. When accomplished, these latter
actions will constitute terminating action for the repetitive visual
inspections.
Interested persons have been afforded an opportunity to participate
in the making of this amendment. Due consideration has been given to
the comments received.
Support for the Proposal
One commenter supports the proposal.
Request for Clarification of Requirements for Different Configurations
of Airplanes
One commenter requests that the proposed rule be revised to clarify
the actions that are required for variously configured airplanes. The
FAA has considered each of the commenter's requests, which are iterated
below:
Doors With Escape Slide/Raft Not Installed or Deactivated
This commenter requests that the proposal clarify instructions for
addressing airplanes having doors where an escape slide or slide/raft
is not installed or is not being used for passenger egress, such as a
deactivated door 3, at doors 4 and/or 5 of an airplane being operated
in the ``combi'' configuration, or any door not used for passenger
egress on a convertible. The commenter suggests that, for these
airplanes, the proposed requirements of the rule be ``postponed'' until
such time that any door was reactivated for passenger egress use.
The FAA concurs with the commenter's suggestion, and has added a
NOTE in the final rule to indicate this.
Airplanes With Improved Door Fittings Installed
This commenter requests that the proposal be revised to indicate
that airplanes on which support fittings have been replaced in
accordance with Boeing Alert Service Bulletin 747-25A2831, dated August
29, 1991, require no further action at the replaced fitting locations.
The FAA concurs. The service bulletin mandated by this AD replaces
Boeing Alert Service Bulletin 747-25A2831. The FAA has determined that
the modifications specified in Alert Service Bulletin 747-25A2831 are
acceptable for compliance with this AD. This AD requires no further
action on fittings that were replaced or modified in accordance with
that service bulletin. This final rule has been revised to
[[Page 58319]]
include a new paragraph (m), which clarifies this issue.
Airplanes With Main Entry Door (MED) 1 Fittings
This commenter states that proposed paragraph (b) should be more
specific as to the requirements for certain airplanes with Main Entry
Door 1. As proposed, that paragraph would require that, if no corrosion
or cracking was found during the initial inspection, operators may
accomplish either one of two actions:
1. install a new fitting with new fasteners and reinstall the
threshold assembly with new corrosion-resistant fasteners; or
2. reinstall the threshold assembly with new corrosion-resistant
fasteners and, thereafter, repetitively inspect the girt bar support
fittings.
However, this commenter points out that for certain airplanes, line
numbers 12 through 36, with MED 1 support fittings specified in Figure
3, Details II, III, or IV, of Boeing Service Bulletin 747-53A2378, the
instructions in the service bulletin specify that these fittings can
only be replaced (per item 1, above).
The FAA acknowledges that the commenter is correct with regard to
these airplanes, and that the wording of the notice was not clear. By
referring to Boeing Service Bulletin 747-53A2378, Revision 1, the FAA
intended that operators follow the appropriate actions specified in it.
The FAA intended that, based on the configuration of the airplane,
operators would accomplish the actions that are applicable to their
airplanes, as defined in the service bulletin. To make this eminently
clearer, the FAA has revised paragraph (b) of the final rule to clarify
that operators are to accomplish the action in accordance with the
``applicable instruction'' in the service bulletin; by doing so,
operators will be directed to that portion of the service bulletin that
contains the instructions applicable for their specific airplanes.
Different Configurations of Airplanes Have Different MED Numbers
This commenter requests that the proposal be revised to clarify the
fact that:
Model 747 airplanes that are not ``SP's'' have MED 1, 2,
3, 4, and 5;
Model 747SP airplanes have MED 1, 2, 3, and 4.
However, MED 3 and 4 on the Model 747SP correspond in their
configuration to MED 4 and 5 on the non-SP models. In light of this,
the commenter requests that the proposed requirements of paragraph (e)
be clarified to account for these various configurations. Additionally,
proposed paragraph (i), which relates to MED 3, should be revised to
indicate that its requirements are applicable only to non-SP airplanes.
In addition, the commenter points out that the referenced Boeing
Service Bulletin makes this differentiation in its relevant
instructions.
The FAA concurs and has revised paragraphs (e) and (i) of the final
rule to specify the model and corresponding door number of those
airplanes subject to the requirements of those paragraphs.
Airplanes With Different Configuration at MED 5
This commenter states that Boeing Service Bulletin 747-53A2378,
Revision 1, does not address the configuration of some airplanes at MED
5 where the support fitting is more like that at MED 1 than at MED 2
and 4. The commenter states that the service bulletin is being revised
to contain instructions that will address the access, inspection,
removal, and replacement of this different type of MED 5 fitting. The
commenter requests that the proposed rule be revised to contain those
new instructions.
The FAA concurs that some additional procedures may be necessary
for those airplanes. However, at this time, the revised service
bulletin referred to by the commenter has not been approved and is not
available. When it is available, the FAA may consider requests for
approval of the use of it as an alternative method of compliance with
the requirements of this AD, as provided by paragraph (n).
Request To Make AD Requirements Parallel To Service Bulletin
Instructions
One commenter suggests that, if the requirements of the AD are
identical to the instructions of the Boeing Service Bulletin 747-
53A2378, Revision 1, then the AD should merely state this, instead of
reiterating each requirement. Another commenter, the airframe
manufacturer, requests that, if the intent of the proposed AD is to
mandate the same actions described in that service bulletin, then the
wording of certain portions of the proposal must be clarified.
In general, the FAA responds by stating that it did not intend for
requirements of this AD to deviate significantly from the service
bulletin instructions. However, certain portions of the AD, such as the
initial compliance time and other items explained elsewhere in this
preamble, do differ from the service bulletin. In light of this, a
statement indicating that the ``AD is identical to the service
bulletin'' would be incorrect. As for the suggested wording changes
relative to this issue, each is discussed below:
Actions When Little Corrosion Is Found
The commenter requests that paragraph (d)(2)(ii) be clarified by
reordering the required steps to match what is specified in the
referenced service bulletin. As written, the proposed paragraph could
be interpreted to mean that operators must first reinstall a repaired
fitting, and then immediately follow that step by installing a new
fitting [as specified in proposed paragraph (d)(2)(ii)(A)]. The
commenter points out that, if the intent of the paragraph is to follow
the logical sequence of steps as defined in the service bulletin,
paragraph (d)(2)(ii) should be changed as follows:
(ii) If blend out of corrosion does not exceed 10 percent of
original material thickness, accomplish either paragraph
(d)(2)(ii)(A) or (d)(2)(ii)(B) of this AD:
(A) Install a new fitting with new fasteners, and reinstall
threshold assembly with new corrosion-resistant fasteners, in
accordance with the service bulletin. After these actions are
accomplished, no further action is required by paragraph (d) of this
AD. Or
(B) Install the repaired fitting with new fasteners and
reinstall the threshold assembly with corrosion-resistant fasteners,
in accordance with the service bulletin. Repeat the inspection
required by paragraph (a) of this AD thereafter at intervals not to
exceed 6 years.
The FAA concurs. The intent of the requirements of that paragraph
was that operators would follow the procedures specified in the
referenced service bulletin. The FAA finds that the change in wording
suggested by the commenter suggestion will help to clarify these
instructions. The final rule has been revised accordingly.
Installing New Fasteners After Primer Application
The commenter points out that proposed paragraph (f) would require
removal of the inspected fitting and reinstallation of it with a new
coat of primer. Likewise, proposed paragraph (j) would require the
removal of the inspected girt bar support angle, and reinstallation of
it with a new coat of primer. However, the commenter requests that
these paragraphs be clarified to state that when, the fitting or angle
is reinstalled, new fasteners must be used. This is specified in the
service bulletin, but is not called out precisely in the proposed rule;
therefore, the commenter considers that operators may be unsure as to
whether or not new fasteners must be used.
The FAA concurs that clarification is necessary. As stated
previously, the intent of this AD is to parallel the
[[Page 58320]]
actions described in the service bulletin. In the particular case of
proposed paragraphs (f) and (j), the FAA assumed that operators would
use new fasteners when reinstalling the subject components since that
action is specified in the instructions laid out in the service
bulletin, and since those paragraphs state that the required actions
are to be accomplished ``in accordance with'' that service bulletin.
However, the FAA acknowledges that this may not be clear to affected
operators. Therefore, the FAA has revised the two paragraphs to include
a statement indicating the installation of new fasteners is a necessary
part of the process of reinstalling the components.
Correct Terminology of Inspection Item
The commenter requests that proposed paragraph (i) be corrected to
indicate that the inspection is required to be performed on the ``girt
bar support angles,'' not the ``girt bar support fitting.'' The follow-
on corrective actions specified in proposed paragraph (j) and (k)
correctly refer to the ``support angles.''
The FAA acknowledges this error and has corrected the terminology
in paragraph (i) accordingly.
Addressing Cracking at Support Angles
This commenter requests that proposed paragraph (k) be revised to
clarify that the cracking that is to be addressed is any that is found
``common to the support angles.'' Additionally, proposed paragraph
(l)(2)(i), which is a follow-on action to paragraph (k), should be
revised to specify this same language. The commenter points out that
this language is used in the referenced Boeing service bulletin and
likewise should be used in the AD to avoid confusion for operators.
The FAA concurs, and has revised paragraph (k) and (l)(2)(i) of the
final rule accordingly.
Inspections of the Support Angles Corner Castings
The commenter requests that paragraph (k) be clarified to include
the instructions for addressing cracking that is found in the corner
casting of the support angles during the inspection required by
proposed paragraph (i). The commenter points out that special
instructions are contained in the referenced Boeing service bulletin to
address this cracking, but these instructions were not specified in the
proposal. The service bulletin provides for repair of cracks found in
corner castings, rather than the immediate installation of new angles
and fasteners if such cracking is found, as would be required by the
proposal. The commenter maintains that allowing operators to repair
these cracks rather than replace the components would provide operators
with time to obtain the replacement corner casting without having to
ground the airplane. A repaired corner casting would be structurally
acceptable, since it is not primary load carrying structure.
The FAA concurs that this repair action should be provided as an
option to replacement in cases of cracking in the corner casting.
However, the service bulletin does not sufficiently describe all of the
actions that are necessary to repair the part. The FAA considers that
cracked corner castings should be addressed on a case-by-case basis.
Therefore, operators that prefer to repair a cracked corner casting, as
an option to replacing it, should request an alternative method of
compliance with this portion of the AD, as provided by paragraph (n).
Paragraph (k)(2) of this final rule has been revised accordingly.
Requests To Extend the Compliance Time
Several commenters request that the proposal be revised to require
operators to perform the initial visual inspections prior to an
airplane accumulating 16 years of service or 18 months--rather than the
proposed 15 months--after the effective date of the final rule,
whichever is later:
1. One of these commenters states that the Corrosion Prevention and
Control Program, which was mandated by AD 90-25-05 [amendment 39-6790,
(55 FR 31401, November 27, 1990)], already requires inspections in this
area at 18-month intervals. Allowing the proposed inspections to be
accomplished at this same interval would reduce the economic burden on
affected operators, since they would not have to special schedule
airplanes for those inspections.
2. Another commenter states that some of the proposed inspections
will necessarily require that the galley be removed from the airplanes.
This removal activity is so extensive that it is normally accomplished
at main base locations when airplanes are undergoing their regularly
scheduled 18-month ``C'' check activity. By extending the proposed
compliance time to correspond with this activity, operators would not
be required to schedule special times for the accomplishment of this
inspection, at considerable additional expense. Additionally, it will
allow the inspections and any necessary installation or repair to be
performed at a main maintenance base where special equipment and
trained maintenance personnel will be available, if necessary.
3. Finally, another commenter points out that the lead time for
obtaining some of the parts that may be necessitated by the proposed
actions may take as long as 37 months; the proposed 15-month compliance
time would make it very difficult to place a parts order in time to
comply with the AD.
The FAA concurs that the compliance time may be extended to 18
months. In consideration of all of the factors raised by the
commenters, as well as the demonstrated reliability and safety features
of the Model 747, and the likelihood of having to perform an emergency
evacuation during the compliance period, the FAA finds that extending
the compliance time by a modest 3 additional months will have an
insignificant effect on safety, while significantly reducing the burden
on the affected operators.
Request To Shorten the Compliance Time
One commenter supports the proposal, but requests that it be
revised to require operators to perform the initial visual inspections
prior to an airplane accumulating 16 years of service or 6 months--
rather than the proposed 15 months--after the effective date of the
final rule, whichever is later. The commenter provided no technical
justification for this request, but indicated that it was based on its
general feeling that the proposed AD is vital to the safety and well-
being of the traveling public. This commenter considers the problem
addressed to be an extremely hazardous situation that could endanger
the lives of both passengers and cabin crew.
The FAA does not concur with this commenter's request. While the
FAA does not intend in any way to depreciate the commenter's statements
relative to the unsafe condition, as discussed previously, the FAA is
obligated to weigh many other factors in addition to safety when
developing an appropriate compliance time. In the case of this AD, the
FAA considered not only the safety implications, but normal maintenance
schedules for timely accomplishment of the actions, parts availability,
recommendations of the airframe manufacturer based on crack analysis
and service reports, the reliability of the affected fleet, and the
probability of an incident occurring that is associated with the
problem addressed by the AD. In light of all of these factors, the FAA
has determined that a reduction of the compliance time is not
warranted.
[[Page 58321]]
Request To Clarify Replacement Requirements
One commenter requests that the proposal be revised to clarify that
the replacement of fittings or fasteners is required only if cracking
or corrosion is found. The commenter states that, as the proposal is
written, if an inspection shows that no cracking or corrosion is
present, an operator may accomplish one of two possible actions:
1. install a new fitting with new fasteners in the cracking
location; or
2. reinstall corrosion-resistant fasteners in the threshold
assembly and repeat the inspection thereafter every 6 years.
The commenter states that one could conclude from the wording of
this second option that the operators would have to install corrosion-
resistant fasteners every six years, regardless of whether or not
corrosion was present. If this is not the FAA's intent, the commenter
requests that this requirement be clarified.
The FAA concurs that clarification is necessary. It is not the
FAA's intent that fasteners be replaced at every inspection, regardless
of whether corrosion is present or not. The only time that the
replacement must be accomplished is if corrosion is detected during the
inspection. The FAA has added wording to the appropriate portions of
the final rule to clarify this requirement.
Conclusion
After careful review of the available data, including the comments
noted above, the FAA has determined that air safety and the public
interest require the adoption of the rule with the changes previously
described. The FAA has determined that these changes will not increase
the economic burden on any operator. Additionally, these changes do not
increase the scope of the AD, and are a logical outgrowth of the notice
that does not necessitate providing an additional opportunity for
public comment.
Cost Impact
There are approximately 868 Boeing Model 747 series airplanes of
the affected design in the worldwide fleet. The FAA estimates that 169
airplanes of U.S. registry will be affected by this AD.
The inspection of MED 1 will take approximately 81 work hours per
door to accomplish, at an average labor rate of $60 per work hour.
Based on these figures, the cost impact of this required inspection on
U.S. operators is estimated to be $4,860 per door.
The inspection of MED's 2, 4, and 5 (MED 2, 3, and 4 on Model 747
SP series airplanes) will take approximately 7 work hours per door to
accomplish, at an average labor rate of $60 per work hour. Based on
these figures, the cost impact of this required inspection on U.S.
operators is estimated to be $420 per door.
The inspection of MED 3 would take approximately 13 work hours per
door to accomplish, at an average labor rate of $60 per work hour.
Based on these figures, the cost impact of this required inspection on
U.S. operators is estimated to be $780 per door.
The replacement of both support fittings will take approximately 37
work hours per door to accomplish, at an average labor rate of $60 per
work hour. Based on these figures the cost impact of the required
replacement on U.S. operators is estimated to be $2,200 per door.
The cost impact figures 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.
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:
96-23-05 Boeing: Amendment 39-9810. Docket 94-NM-221-AD.
Applicability: Model 747 series airplanes; line numbers 1
through 868 inclusive, excluding freighters and special freighters;
certificated in any category.
Note 1: The requirements of this AD are not applicable to doors
where an escape slide or slide/raft is not installed or is not used
for passenger egress (such as a deactivated door 3, at doors 4 and/
or 5 of an airplane being operated in the ``combi'' configuration,
or any door not used for passenger egress on a convertible). The
requirements of this rule become applicable at the time when an
escape slide or slide/raft is installed on such doors, or when such
doors are activated and/or converted for passenger use. The
requirements also become applicable at the time an airplane
operating in an all-cargo configuration is converted to a passenger
or passenger/cargo configuration.
Note 2: 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 (n) 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 corrosion on girt bar support fittings,
which could result in separation of the escape slide from the lower
door sill during deployment, and subsequently prevent operation of
the escape slides at the main entry doors during an emergency,
accomplish the following:
(a) For airplanes equipped with Main Entry Door (MED) 1: Prior
to the accumulation of 16 years of service since date of manufacture
of the airplane, or within 18 months after the effective date of
this AD, whichever occurs later, perform a detailed visual
inspection to detect cracking and/or corrosion of the girt bar
support fitting at the left and right MED 1, in accordance with
Boeing Service Bulletin 747-53A2378, Revision 1, dated March 10,
1994.
(b) If no cracking or corrosion is found during the inspection
required by paragraph
[[Page 58322]]
(a) of this AD, prior to further flight, accomplish either paragraph
(b)(1) or (b)(2) of this AD, in accordance with the applicable
instructions specified in Boeing Service Bulletin 747-53A2378,
Revision 1, dated March 10, 1994.
(1) Install a new fitting with new fasteners, and reinstall the
threshold assembly with new corrosion-resistant fasteners, in
accordance with the service bulletin. After these actions are
accomplished, no further action is required by paragraph (b) of this
AD. Or
(2) Reinstall the threshold assembly with corrosion-resistant
fasteners, in accordance with the service bulletin. Thereafter,
repeat the inspection required by paragraph (a) of this AD at
intervals not to exceed 6 years.
(c) If any cracking is found during the inspection required by
paragraph (a) or (b)(2) of this AD, prior to further flight, install
a new fitting with new fasteners, and reinstall the threshold
assembly with new corrosion-resistant fasteners, in accordance with
Boeing Service Bulletin 747-53A2378, Revision 1, dated March 10,
1994. After these actions are accomplished, no further action is
required by this paragraph.
(d) If any corrosion is found during the inspection required by
paragraph (a) or (b)(2) of this AD, prior to further flight,
accomplish either paragraph (d)(1) or (d)(2) of this AD, in
accordance with Boeing Service Bulletin 747-53A2378, Revision 1,
dated March 10, 1994.
(1) Install a new fitting with new fasteners, and reinstall the
threshold assembly with new corrosion-resistant fasteners in
accordance with the service bulletin. After these actions are
accomplished, no further action is required by this paragraph. Or
(2) Blend out corrosion in accordance with the service bulletin.
(i) If blend out of corrosion is beyond 10 percent of original
thickness or any crack is found during accomplishment of the blend
out procedures, install a new fitting with new fasteners, and
reinstall the threshold assembly with new corrosion-resistant
fasteners, in accordance with the service bulletin. After these
actions are accomplished, no further action is required by this
paragraph.
(ii) If blend out of corrosion does not exceed 10 percent of
original material thickness, accomplish either paragraph
(d)(2)(ii)(A) or (d)(2)(ii)(B) of this AD:
(A) Install a new fitting with new fasteners, and reinstall
threshold assembly with new corrosion-resistant fasteners, in
accordance with the service bulletin. After these actions are
accomplished, no further action is required by this paragraph. Or
(B) Install the repaired fitting with new fasteners and
reinstall the threshold assembly with corrosion-resistant fasteners,
in accordance with the service bulletin. Thereafter, repeat the
inspection, and corrective actions as necessary, required by
paragraph (a) of this AD at intervals not to exceed 6 years.
(e) For airplanes equipped with Main Entry Doors (MED) 2, 4,
and/or 5 (MED 2, 3, and/or 4 on Model 747SP series airplanes): Prior
to the accumulation of 10 years of service since date of manufacture
of the airplane, or within 18 months after the effective date of
this AD, whichever occurs later, perform a detailed visual
inspection to detect cracking and/or corrosion of the girt bar
support fitting at the left and right MED 2, 4, and 5 (MED 2, 3, and
4 on Model 747SP series airplanes), in accordance with Boeing
Service Bulletin 747-53A2378, Revision 1, dated March 10, 1994.
(f) If no cracking or corrosion is found during the inspection
required by paragraph (e) of this AD, prior to further flight,
accomplish either paragraph (f)(1) or (f)(2) of this AD, in
accordance with the applicable instructions in Boeing Service
Bulletin 747-53A2378, Revision 1, dated March 10, 1994.
(1) Remove the inspected fitting and reinstall it with a new
coat of primer and new fasteners; and reinstall the threshold
assembly with new corrosion-resistant fasteners; in accordance with
the service bulletin. After these actions are accomplished, no
further action is required by this paragraph. Or
(2) Reinstall the serrated plate assembly and the girt bar floor
fitting with corrosion-resistant fasteners, in accordance with the
service bulletin. Thereafter, repeat the inspection required by
paragraph (e) of this AD at intervals not to exceed 6 years.
(g) If any cracking is found during the inspection required by
paragraph (e) or (f)(2) of this AD, prior to further flight, install
a new fitting with new fasteners, and reinstall the threshold
assembly with new corrosion-resistant fasteners, in accordance with
Boeing Service Bulletin 747-53A2378, Revision 1, dated March 10,
1994. After these actions are accomplished, no further action is
required by this paragraph.
(h) If any corrosion is found during the inspection required by
paragraph (e) or (f)(2) of this AD, prior to further flight,
accomplish either paragraph (h)(1) or (h)(2) of this AD, in
accordance with Boeing Service Bulletin 747-53A2378, Revision 1,
dated March 10, 1994.
(1) Install a new fitting with new fasteners, and reinstall the
threshold assembly with new corrosion-resistant fasteners, in
accordance with the service bulletin. After these actions are
accomplished, no further action is required by this paragraph. Or
(2) Blend out corrosion in accordance with the service bulletin.
(i) If blend out of corrosion is beyond 10 percent of original
thickness or any crack is found during accomplishment of the blend
out procedures, install a new fitting with new fasteners, and
reinstall the threshold assembly with new corrosion-resistant
fasteners, in accordance with the service bulletin. After these
actions are accomplished, no further action is required by this
paragraph.
(ii) If blend out of corrosion does not exceed 10 percent of
original material thickness, install the repaired fitting with new
fasteners, and reinstall the threshold assembly with new corrosion-
resistant fasteners, in accordance with the service bulletin. After
these actions are accomplished, no further action is required by
this paragraph.
(i) For airplanes equipped with Main Entry Door (MED) 3 (this
paragraph does not apply to Model 747SP series airplanes): Prior to
the accumulation of 16 years of service since date of manufacture of
the airplane, or within 18 months after the effective date of this
AD, whichever occurs later, perform a detailed visual inspection to
detect cracking and/or corrosion of the girt bar support angles at
the left and right MED 3, in accordance with Boeing Service Bulletin
747-53A2378, Revision 1, dated March 10, 1994.
(j) If no cracking or corrosion is found during the inspection
required by paragraph (i) of this AD, prior to further flight,
accomplish either paragraph (j)(1) or (j)(2) of this AD in
accordance with the applicable instructions in Boeing Service
Bulletin 747-53A2378, Revision 1, dated March 10, 1994.
(1) Remove inspected angle and reinstall it with a new coat of
primer and new fasteners; and reinstall the threshold assembly with
new corrosion-resistant fasteners, in accordance with the service
bulletin. After these actions are accomplished, no further action is
required by this paragraph. Or
(2) Reinstall the corner scuff plate and the threshold apron
with corrosion-resistant fasteners, in accordance with the service
bulletin. Thereafter, repeat the inspection required by paragraph
(i) of this AD at intervals not to exceed 6 years.
(k) If any crack common to the support angles is found during
the inspection required by paragraph (i) or (j)(2) of this AD, prior
to further flight, accomplish the actions specified in paragraph
(k)(1) or (k)(2), as applicable, in accordance with Boeing Service
Bulletin 747-53A2378, Revision 1, dated March 10, 1994:
(1) Install the new angles with new fasteners, and reinstall the
threshold assembly with new corrosion-resistant fasteners. After
these actions are accomplished, no further action is required by
this paragraph of this AD.
(2) For any cracking found only in the corner casting as
specified in the service bulletin, accomplish either paragraph
(k)(2)(i) or (k)(2)(ii) prior to further flight:
(i) Replace the corner casting in accordance with the service
bulletin. Or
(ii) Repair the cracked part in accordance with a method
approved by the Manager, Seattle Aircraft Certification Office
(ACO), FAA, Transport Airplane Directorate. Refer to paragraph (n)
of this AD for the appropriate procedure for seeking such an
approval. (This option is provided in order to give operators time
to obtain a replacement corner casing without grounding an
airplane.) This repair is considered temporary action only;
replacement of the corner casting eventually must be accomplished in
accordance with a schedule prescribed by the Manager, Seattle ACO.
(l) If any corrosion is found during the inspection required by
paragraph (i) of this AD, prior to further flight, accomplish either
paragraph (l)(1) or (l)(2) of this AD, in accordance with Boeing
Service Bulletin 747-53A2378, Revision 1, dated March 10, 1994.
(1) Install the new angles with new fasteners, and reinstall the
threshold assembly with new corrosion-resistant fasteners, in
accordance with the service bulletin. After these actions are
[[Page 58323]]
accomplished, no further action is required by this paragraph. Or
(2) Blend out corrosion in accordance with the service bulletin.
(i) If blend out of corrosion is beyond 10 percent of original
thickness, or if any crack common to the support angles is found
during accomplishment of the blend out procedures, install the new
angles with new fasteners, and reinstall the threshold assembly with
new corrosion-resistant fasteners, in accordance with the service
bulletin. After these actions are accomplished, no further action is
required by this paragraph.
(ii) If blend out of corrosion does not exceed 10 percent of
original material thickness, install the repaired angles with new
fasteners, and reinstall the threshold assembly with new corrosion-
resistant fasteners, in accordance with the service bulletin. After
these actions are accomplished, no further action is required by
this paragraph.
(m) Installation of a girt bar support fitting in accordance
with Boeing Service Bulletin 747-25A2831, dated August 29, 1991, is
considered acceptable for compliance with the requirements of this
AD for each affected fitting location.
(n) 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 request 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.
(o) 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.
(p) The actions shall be done in accordance with Boeing Service
Bulletin 747-53A2378, Revision 1, dated March 10, 1994. 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.
(q) This amendment becomes effective on December 16, 1996.
Issued in Renton, Washington, on October 31, 1996.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 96-28688 Filed 11-13-96; 8:45 am]
BILLING CODE 4910-13-U