[Federal Register Volume 61, Number 91 (Thursday, May 9, 1996)]
[Rules and Regulations]
[Pages 21068-21070]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-11407]



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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 96-NM-84-AD; Amendment 39-9611; AD 96-10-06]
RIN: 2120-AA64


Airworthiness Directives; Boeing Model 737 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This amendment adopts a new airworthiness directive (AD) that 
is applicable to certain Boeing Model 737 series airplanes. This action 
requires repetitive inspections to detect cracks of the lower gate 
hinge of the forward galley service door, and replacement of any 
cracked hinge. This action also provides an optional terminating 
replacement for the repetitive inspections. This amendment is prompted 
by reports of fatigue cracks found in the lower gate hinge on the 
forward galley service door. The actions specified in this AD are 
intended to prevent such fatigue cracking, which could lead to the 
failure of the lower gate hinge on the forward galley service door and 
subsequent loss of cabin pressure. If the hinge fails, the hinge and 
its associated mechanisms and the emergency escape slide could separate 
from the airplane and be ingested into the engine, or could strike and 
damage the flight control surfaces.

DATES: Effective May 24, 1996.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of May 24, 1996.
    Comments for inclusion in the Rules Docket must be received on or 
before July 8, 1996.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 96-NM-84-AD, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056.
    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 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.

FOR FURTHER INFORMATION CONTACT: Roy Boffo, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington; telephone (206) 227-2780; 
fax (206) 227-1181.

SUPPLEMENTARY INFORMATION: The FAA has received several reports of 
cracks found in the lower gate hinge on the forward galley service door 
on Boeing Model 737 series airplanes. In two of these cases, the hinge 
was severed completely and the lower gate separated from the airplane 
while in flight, which resulted in loss of cabin pressure. In one of 
these cases, the emergency escape slide was slowly pulled through the 
gate opening, and, subsequently, it separated from the airplane. These 
airplanes had accumulated between 13,700 and 66,000 total flight 
cycles. Investigation revealed that the cause of such cracking was due 
to fatigue. The effects of such fatigue cracking could lead to the 
failure of the lower gate hinge on the forward galley service door and 
subsequent loss of cabin pressure. If the hinge fails, the hinge and 
its associated mechanisms and the emergency escape slide could separate 
from the airplane and be ingested into the engine, or could strike and 
damage the flight control surfaces.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Alert Service Bulletin 
737-52A1124, dated January 11, 1996, which describes procedures for 
repetitive detailed visual inspections to detect cracks of the lower 
gate hinge of the forward galley service door, and replacement of any 
cracked hinge found. The service bulletin also describes procedures for 
replacement of the lower gate hinge of the forward galley service door 
with an improved hinge, which will eliminate the need for the 
repetitive inspections.

Explanation of the Requirements of the AD

    Since an unsafe condition has been identified that is likely to 
exist or develop on other Boeing Model 737 series airplanes of the same 
type design, this AD is being issued to prevent fatigue cracking and 
subsequent failure of the lower gate hinge on the forward galley 
service door. This AD requires repetitive detailed visual inspections 
to detect cracks of the lower gate hinge of the forward galley service 
door, and replacement of any cracked hinge found. This AD also provides 
for an optional replacement of the lower gate hinge of the forward 
galley service door with an improved hinge, which constitutes 
terminating action for the repetitive inspection requirements. The 
actions are required to be accomplished

[[Page 21069]]

in accordance with the alert service bulletin described previously.

Differences Between the AD and the Relevant Service Information

    Operators should note that, unlike the various recommended 
compliance times specified in the alert service bulletin for 
accomplishing the initial inspection of airplanes (specified as 1,200 
flight cycles after receipt of the service bulletin for airplanes with 
10,000 to 12,000 total flight cycles; 800 flight cycles after receipt 
for airplanes with 12,000 to 13,000 total flight cycles; and 400 flight 
cycles after receipt for airplanes with 13,000 or more total flight 
cycles), this AD requires that all airplanes be inspected within 400 
flight cycles after the effective date of the AD. In consideration of 
not only the manufacturer's recommendation, but the degree of urgency 
associated with addressing the subject unsafe condition, the average 
utilization of the affected fleet, and the time necessary to perform 
the inspection (3 hours), the FAA has determined that the various 
intervals specified in that alert service bulletin would not address 
the identified unsafe condition in a timely manner. In addition, the 
FAA has reviewed the available data and determined that the length of 
cracking is not necessarily related to the airplane's flight cycles, 
but instead is related to the number of door cycles. In light of all of 
these factors, the FAA finds that a 400-flight cycle compliance time 
for initiating the required actions is warranted, in that it represents 
an appropriate interval of time allowable for affected airplanes to 
continue to operate without compromising safety.

Determination of Rule's Effective Date

    Since a situation exists that requires the immediate adoption of 
this regulation, it is found that notice and opportunity for prior 
public comment hereon are impracticable, and that good cause exists for 
making this amendment effective in less than 30 days.

Comments Invited

    Although this action is in the form of a final rule that involves 
requirements affecting flight safety and, thus, was not preceded by 
notice and an opportunity for public comment, comments are invited on 
this rule. Interested persons are invited to comment on this 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 under the caption ADDRESSES. All 
communications received on or before the closing date for comments will 
be considered, and this rule may be amended in light of the comments 
received. Factual information that supports the commenter's ideas and 
suggestions is extremely helpful in evaluating the effectiveness of the 
AD action and determining whether additional rulemaking action would be 
needed.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the rule that might 
suggest a need to modify the 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 that 
summarizes each FAA-public contact concerned with the substance of this 
AD will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this rule must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 96-NM-84-AD.'' The postcard will be date stamped and 
returned to the commenter.

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.
    The FAA has determined that this regulation is an emergency 
regulation that must be issued immediately to correct an unsafe 
condition in aircraft, and that it is not a ``significant regulatory 
action'' under Executive Order 12866. It has been determined further 
that this action involves an emergency regulation under DOT Regulatory 
Policies and Procedures (44 FR 11034, February 26, 1979). If it is 
determined that this emergency regulation otherwise would be 
significant under DOT Regulatory Policies and Procedures, a final 
regulatory evaluation will be prepared and placed in the Rules Docket. 
A copy of it, if filed, 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 USC 106(g), 40113, 44701.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:

96-10-06  Boeing: Amendment 39-9611. Docket 96-NM-84-AD.

    Applicability: Model 737 series airplanes, as listed in Boeing 
Alert Service Bulletin 737-52A1124, dated January 11, 1996; on which 
the actions specified in Boeing Service Bulletin 737-52-1097, 
Revision 1, dated April 6, 1989, or Revision 2, dated January 11, 
1990, have not been accomplished; certificated in any category.

    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been 
otherwise 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 (c) 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 prevent fatigue cracking of the lower gate hinge on the 
forward galley service door, accomplish the following:
    (a) Within 400 flight cycles after the effective date of this 
AD, perform a detailed visual inspection to detect cracks of the 
lower gate hinge of the forward galley service door, in accordance 
with Boeing Alert Service Bulletin 737-52A1124, dated January 11, 
1996.
    (1) If no cracks are detected, repeat the inspection thereafter 
at intervals not to exceed 4,500 flight cycles.
    (2) If any crack is detected, prior to further flight, replace 
the lower gate hinge with a new hinge, in accordance with the alert 
service bulletin. Accomplishment of the replacement constitutes 
terminating action for this AD.

[[Page 21070]]

    (b) Replacement of the lower gate hinge of the forward galley 
service door with an improved hinge, in accordance with Boeing Alert 
Service Bulletin 737-52A1124, dated January 11, 1996, constitutes 
terminating action for the requirements of this AD.
    (c) 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.

    (d) 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.
    (e) The inspection and replacement shall be done in accordance 
with Boeing Alert Service Bulletin 737-52A1124, dated January 11, 
1996. 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.
    (f) This amendment becomes effective on May 24, 1996.

    Issued in Renton, Washington, on May 1, 1996.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 96-11407 Filed 5-8-96; 8:45 am]
BILLING CODE 4910-13-U