[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