[Federal Register Volume 60, Number 26 (Wednesday, February 8, 1995)]
[Proposed Rules]
[Pages 7482-7485]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-3074]
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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39
[Docket No. 94-NM-221-AD]
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 adoption of a new airworthiness
directive (AD) that is applicable to certain Boeing Model 747 series
airplanes. This proposal would require repetitive inspections to detect
cracks and/or corrosion of the girt bar support fitting at certain main
entry doors; and repair or replacement of the support fitting. This
proposal would also provide for various terminating actions for the
repetitive inspections. This proposal 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 the
proposed 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: Comments must be received by April 6, 1995.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
[[Page 7483]] Administration (FAA), Transport Airplane Directorate,
ANM-103, Attention: Rules Docket No. 94-NM-221-AD, 1601 Lind Avenue,
SW., Renton, Washington 98055-4056. Comments may be inspected at this
location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except
Federal holidays.
The service information referenced in the proposed rule may be
obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle,
Washington 98124-2207. This information may be examined at the FAA,
Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton,
Washington.
FOR FURTHER INFORMATION CONTACT: Steven C. Fox, Aerospace Engineer,
Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle
Aircraft Certification Office, 1601 Lind Avenue, SW., Renton,
Washington 98055-4056; telephone (206) 227-2777; fax (206) 227-1181.
SUPPLEMENTARY INFORMATION:
Comments Invited
Interested persons are invited to participate in the making of the
proposed rule by submitting such written data, views, or arguments as
they may desire. Communications shall identify the Rules Docket number
and be submitted in triplicate to the address specified above. All
communications received on or before the closing date for comments,
specified above, will be considered before taking action on the
proposed rule. The proposals contained in this notice may be changed in
light of the comments received.
Comments are specifically invited on the overall regulatory,
economic, environmental, and energy aspects of the proposed rule. All
comments submitted will be available, both before and after the closing
date for comments, in the Rules Docket for examination by interested
persons. A report summarizing each FAA-public contact concerned with
the substance of this proposal will be filed in the Rules Docket.
Commenters wishing the FAA to acknowledge receipt of their comments
submitted in response to this notice must submit a self-addressed,
stamped postcard on which the following statement is made: ``Comments
to Docket Number 94-NM-221-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-03, Attention: Rules
Docket No. 94-M-21-D, 1601 Lind Avenue, SW., Renton, Washington 98055-
4056.
Discussion
The FAA has received reports from operators that, during scheduled
deployment tests of a main entry door slide, corrosion was found on the
floor structure supports for the escape slides of the main deck entry
doors on Boeing Model 747 series airplanes.
In three reported incidents, the escape slides disconnected from
the lower door sill and fell to the ground. In all three incidents, the
girt bar supports were found to have moderate to severe corrosion. In
two cases, the fasteners that attach the serrated plate assembly to the
girt bar supports were corroded and broken. One of these incidents
occurred at Main Entry Door (MED) 2 and the other two incidents
occurred at MED 5. These airplanes had accumulated 15 to 20 years of
service since date of manufacture.
In three other reported incidents, corrosion was found on the
support fitting and the fastener. The corrosion was so severe that the
escape slide would have fallen off the airplane, if the slide had been
deployed. Two of these incidents occurred at MED 1, and the other
incident occurred at MED 4. These airplanes had accumulated 11 to 20
years of service since date of manufacture.
Additionally, four more reported incidents of corrosion were found
on the girt bar supports at seven doors on six other airplanes. One of
these incidents occurred at MED 2, two occurred at MED 3, three
occurred at MED 4, and one occurred at MED 5. These airplanes had
accumulated 9 to 18 years of service since date of manufacture.
Following these reports, the manufacturer conducted a structural
review of all entry doors on Model 747 series airplanes. This review
found that corrosion could occur at any main deck entry door. Each main
entry door has two girt bar chock support fittings; when the escape
slide is deployed, these fittings attach the escape slide to the sill
of the MED. Corrosion on these fittings, if not detected and corrected
in a timely manner, could result in separation of the escape slide from
the lower door sill during deployment, which would prevent proper
operation of the escape slides at the main entry doors during an
emergency.
The FAA has reviewed and approved Boeing Service Bulletin 747-
53A2378, Revision 1, dated March 10, 1994, which describes procedures
for 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. This service bulletin also
describes procedures for 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 actions eliminate the need for the
repetitive visual inspections. (The new support fitting has inserts of
cadmium plated alloy steel that are less susceptible to corrosion.)
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 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 proposed AD would
also 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 would
constitute terminating action for the repetitive visual inspections.
The actions would be required to be accomplished in accordance with the
service bulletin described previously.
As a result of recent communications with the Air Transport
Association (ATA) of America, the FAA has learned that, in general,
some operators may misunderstand the legal effect of AD's on airplanes
that are identified in the applicability provision of the AD, but that
have been altered or repaired in the area addressed by the AD. The FAA
points out that all airplanes identified in the applicability provision
of an AD are legally subject to the AD. If an airplane has been altered
or repaired in the affected area in such a way as to affect compliance
with the AD, the owner or operator is required to obtain FAA approval
for an alternative method of compliance with the AD, in accordance with
the paragraph of each AD that provides for such approvals. A note has
been included in this notice added to this final rule to clarify this
requirement.
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 would be affected by this proposed AD.
[[Page 7484]]
The proposed inspection of MED 1 would take approximately 81 work
hours per door to accomplish, at an average labor rate of $60 per work
hour. Based on these figures, the total cost impact of the proposed
inspection on U.S. operators is estimated to be $4,860 per door.
The proposed inspection of MED's 2, 4, and 5 would take
approximately 7 work hours per door to accomplish, at an average labor
rate of $60 per work hour. Based on these figures, the total cost
impact of the proposed inspection on U.S. operators is estimated to be
$420 per door.
The proposed 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 total cost impact of the proposed
inspection on U.S. operators is estimated to be $780 per door.
The proposed replacement of both support fittings would take
approximately 37 work hours per door to accomplish, at an average labor
rate of $60 per work hours. Based on these figures the total cost
impact of the proposed replacement on U.S. operators is estimated to be
$2,200 per door.
The regulations proposed herein would not have substantial direct
effects on the States, on the relationship between the national
government and the States, or on the distribution of power and
responsibilities among the various levels of government. Therefore, in
accordance with Executive Order 12612, it is determined that this
proposal would not have sufficient federalism implications to warrant
the preparation of a Federalism Assessment.
For the reasons discussed above, I certify that this proposed
regulation (1) is not a ``significant regulatory action'' under
Executive Order 12866; (2) is not a ``significant rule'' under the DOT
Regulatory Policies and Procedures (44 FR 11034, February 26, 1979);
and (3) if promulgated, will not have a significant economic impact,
positive or negative, on a substantial number of small entities under
the criteria of the Regulatory Flexibility Act. A copy of the draft
regulatory evaluation prepared for this action is contained in the
Rules Docket. A copy of it may be obtained by contacting the Rules
Docket at the location provided under the caption ADDRESSES.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Safety.
The Proposed Amendment
Accordingly, pursuant to the authority delegated to me by the
Administrator, the Federal Aviation Administration proposes to amend
part 39 of the Federal Aviation Regulations (14 CFR part 39) as
follows:
PART 39--AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C.
106(g); and 14 CFR 11.89.
Sec. 39.13 [Amended]
2. Section 39.13 is amended by adding the following new
airworthiness directive:
Boeing: Docket 94-M-21-D.
Applicability: Model 747 series airplanes; line numbers 1
through 868 inclusive, excluding freighters and special freighters;
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 use the authority
provided in paragraph (m) to request approval from the FAA. This
approval may address either no action, if the current configuration
eliminates the unsafe condition; or different actions necessary to
address the unsafe condition described in this AD. Such a request
should include an assessment of the effect of the changed
configuration on the unsafe condition addressed by this AD. In no
case does the presence of any modification, alteration, or repair
remove any airplane from the applicability of this AD.
Compliance: Required as indicated, unless accomplished
previously.
To prevent 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 15 months after the effective date of
this AD, whichever occurs later, perform a detailed visual
inspection to detect cracks and/or corrosion of the girt bar support
fitting at the left and right MED 1, in accordance with Boeing
Service Bulletin 747-3A2378, Revision 1, dated March 10, 1994.
(b) If no cracks or corrosion is found during the inspection
required by paragraph (a) of this AD, prior to further flight,
accomplish either paragraph (b)(1) or (b)(2) of this AD in
accordance with Boeing Service Bulletin 747-3A2378, 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. Repeat the
inspection required by paragraph (a) of this AD thereafter at
intervals not to exceed 6 years.
(c) If any crack is found during the inspection required by
paragraph (a) 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 747-3A2378, Revision 1, dated March 10, 1994. After
these actions are accomplished, no further action is required by
paragraph (c) of this AD.
(d) If any corrosion is found during the inspection required by
paragraph (a) of this AD, prior to further flight, accomplish either
paragraph (d)(1) or (d)(2) of this AD, in accordance with Boeing
Service Bulletin 747-3A2378, 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 (d) of this
AD. 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 paragraph
(d) of this AD.
(ii) If blend out of corrosion does not exceed 10 percent of
original material thickness, install the repaired fitting with new
fasteners in accordance with the service bulletin, and 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) 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.
(e) For airplanes equipped with Main Entry Doors (MED) 2, 4,
and/or 5: Prior to the accumulation of 10 years of service since
date of manufacture of the airplane or within 15 months after the
effective date of this AD, whichever occurs later, perform a
detailed visual inspection to detect cracks and/or
[[Page 7485]] corrosion of the girt bar support fitting at the left
and right MED 2, 4, and 5, in accordance with Boeing Service
Bulletin 747-53A2378, Revision 1, dated March 10, 1994.
(f) If no cracks 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 Boeing Service Bulletin 747-53A2378, Revision 1,
dated March 10, 1994.
(1) Reinstall the serrated plate assembly and the girt bar floor
fitting with corrosion resistant fasteners, in accordance with the
service bulletin. Repeat the inspection required by paragraph (e) of
this AD thereafter at intervals not to exceed 6 years. Or
(2) Remove the inspected fitting and reinstall it with a new
coat of primer, 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 (f) of this AD.
(g) If any crack is found during the inspection required by
paragraph (e) 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 of this AD.
(h) If any corrosion is found during the inspection required by
paragraph (e) 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 paragraph (h) of this
AD. 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 paragraph
(h) of this AD.
(ii) If blend out of corrosion does not exceed 10 percent of
original material thickness, install 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
paragraph (h) of this AD.
(i) For airplanes equipped with Main Entry Door (MED) 3: Prior
to the accumulation of 16 years of service since date of manufacture
of the airplane, or within 15 months after the effective date of
this AD, whichever occurs later, perform a detailed visual
inspection to detect cracks and/or corrosion of the girt bar support
fitting at the left and right MED 3, in accordance with Boeing
Service Bulletin 747-53A2378, Revision 1, dated March 10, 1994.
(j) If no cracks 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 Boeing Service Bulletin 747-53A2378, Revision 1,
dated March 10, 1994.
(1) Remove inspected angles and reinstall it with a new coat of
primer, 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 (j) of this AD. Or
(2) Reinstall the corner scuff plate and the threshold apron
with corrosion resistant fasteners, in accordance with the service
bulletin. Repeat the inspection required by paragraph (i) of this AD
thereafter at intervals not to exceed 6 years.
(k) If any crack is found during the inspection required by
paragraph (i) of this AD, prior to further flight, install the new
angles 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 of this AD.
(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
accomplished, no further action is required by paragraph (l) of this
AD. 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 the new angles 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 (l) of this
AD.
(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
paragraph (l) of this AD.
(m) 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.
(n) Special flight permits may be issued in accordance with
sections 21.197 and 21.199 of the Federal Aviation Regulations (14
CFR 21.197 and 21.199) to operate the airplane to a location where
the requirements of this AD can be accomplished.
Issued in Renton, Washington, on February 2, 1995.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 95-3074 Filed 2-7-95; 8:45 am]
BILLING CODE 4910-13-U
