[Federal Register Volume 63, Number 191 (Friday, October 2, 1998)]
[Proposed Rules]
[Pages 52992-52994]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-26354]
=======================================================================
-----------------------------------------------------------------------
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 98-NM-189-AD]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 737-100, -200, and -200C
Series Airplanes
AGENCY: Federal Aviation Administration, DOT.
ACTION: Notice of proposed rulemaking (NPRM).
-----------------------------------------------------------------------
SUMMARY: This document proposes the supersedure of an existing
airworthiness directive (AD), applicable to all Boeing Model 737-100, -
200, and -200C series airplanes, that currently requires periodic
inspections to detect missing nuts and/or damaged secondary support
hardware adjacent to the aft engine mount, and replacement, if
necessary. That AD also provides for optional terminating action for
certain inspections and a torque check. This action would mandate
accomplishment of the previously optional terminating action. This
proposal is prompted by the FAA's determination that the repetitive
inspections required by the existing AD may not be providing the degree
of safety assurance necessary for the transport airplane fleet. The
actions specified by the proposed AD are intended to prevent failure of
the secondary support to sustain engine loads in the event of failure
of the aft engine mount cone bolt, which could result in the separation
of the engine from the wing.
DATES: Comments must be received by November 16, 1998.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-114,
Attention: Rules Docket No. 98-NM-189-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: Greg Schneider, Aerospace Engineer,
Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle
Aircraft Certification Office, 1601 Lind Avenue, SW., Renton,
Washington 98055-4056; telephone (425) 227-2028; fax (425) 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
[[Page 52993]]
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 98-NM-189-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-114, Attention: Rules
Docket No. 98-NM-189-AD, 1601 Lind Avenue, SW., Renton, Washington
98055-4056.
Discussion
On April 4, 1994, the FAA issued AD 91-09-14 R1, amendment 39-8876
(59 FR 18294, April 18, 1994), applicable to all Boeing Model 737-100,
-200, and -200C series airplanes, to require periodic inspections to
detect missing nuts and/or damaged secondary support hardware adjacent
to the aft engine mount, and replacement, if necessary. That AD also
provides for optional installation of a new, modified support, which
would constitute terminating action for certain inspections and a
torque check. That action was prompted by the development of a
modification that will prevent wearing of the secondary support. The
requirements of that AD are intended to prevent failure of the
secondary support to sustain engine loads in the event of failure of
the aft engine mount cone bolt, which could result in the separation of
the engine from the wing.
Actions Since Issuance of Previous Rule
Since the issuance of AD 91-09-14 R1, Boeing has informed the FAA
that, based on testing conducted by Boeing, significant cracks of the
aft engine mount cone bolts may not be detected using the current
ultrasonic inspection procedures. There have been two occurrences of
failure of aft engine mount cone bolts after the bolts had been
subjected to ultrasonic inspections. In light of this information, the
FAA has determined that the repetitive inspections required by the
existing AD may not be providing the degree of safety assurance
necessary for the fleet of Boeing Model 737-100, -200, and -200C series
airplanes.
Explanation of Relevant Service Information
The FAA previously reviewed and approved Boeing Service Bulletin
737-71-1289, dated August 19, 1993. That service bulletin describes
procedures for replacement of the existing secondary support with a
new, improved secondary support. Since the issuance of AD 91-09-14 R1,
the FAA has reviewed and approved Boeing Notices of Status Change (NSC)
737-71-1289 NSC 1, dated September 2, 1993; 737-71-1289 NSC 2, dated
January 26, 1995; and 737-71-1289 NSC 03, dated October 3, 1996. These
NSC's contain certain minor editorial changes to the service bulletin.
Explanation of Requirements of Proposed Rule
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 supersede AD 91-09-14 R1, to continue to require
periodic inspections to detect missing nuts and/or damaged secondary
support hardware, and replacement, if necessary. The proposed AD would
require accomplishment of the previously optional terminating action,
which, when accomplished, would constitute terminating action for
certain inspections and for a torque check required by this AD.
Cost Impact
There are approximately 1,045 airplanes of the affected design in
the worldwide fleet. The FAA estimates that 382 airplanes of U.S.
registry would be affected by this proposed AD.
The inspections that are currently required by AD 91-09-14 R1 take
approximately 3 work hours per airplane to accomplish, at an average
labor rate of $60 per work hour. Based on these figures, the cost
impact of the currently required actions on U.S. operators is estimated
to be $68,760, or $180 per airplane, per inspection cycle.
The replacement that is proposed in this AD would take
approximately 60 work hours per airplane to accomplish, at an average
labor rate of $60 per work hour. Required parts would cost
approximately $7,000 per airplane. Based on these figures, the cost
impact of the replacement proposed by this AD on U.S. operators is
estimated to be $4,049,200, or $10,600 per airplane.
The cost impact figures discussed above are based on assumptions
that no operator has yet accomplished any of the current or proposed
requirements of this AD action, and that no operator would accomplish
those actions in the future if this AD were not adopted.
Regulatory Impact
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. 106(g), 40113, 44701.
Sec. 39.13 [Amended]
2. Section 39.13 is amended by removing amendment 39-8876 (59 FR
18294, April 18, 1994), and by adding a new airworthiness directive
(AD), to read as follows:
Boeing: Docket 98-NM-189-AD. Supersedes AD 91-09-14 R1, amendment
39-8876.
Applicability: All Model 737-100, -200, and -200C series
airplanes; certificated in any category.
Note 1: This AD applies to each airplane identified in the
preceding applicability provision, regardless of whether it has been
modified, altered, or repaired in the area subject to the
requirements of this AD. For airplanes that have been modified,
altered, or repaired so that the performance of the requirements of
this AD is affected, the owner/operator must request approval for an
alternative method of compliance in accordance with paragraph (d)(1)
of this AD. The request should include an assessment of
[[Page 52994]]
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 failure of the secondary support to sustain engine
loads in the event of failure of the aft engine mount cone bolt,
which could result in the separation of the engine from the wing,
accomplish the following:
(a) Within the next 45 landings after May 20, 1991 (the
effective date of AD 91-09-14, amendment 39-6972), accomplish the
following:
(1) Inspect the aft mount cone bolt indicator for proper
alignment. Improper alignment indicates a broken aft cone bolt.
Broken cone bolts must be replaced, prior to further flight, with
bolts that have been inspected in accordance with Boeing Alert
Service Bulletin 737-71A1212, dated December 22, 1987, using
magnetic particle inspection techniques. Repeat the inspection of
the indicator at intervals thereafter not to exceed 45 landings.
(2) Unless previously accomplished within the last 255 landings,
inspect the aft mount cone bolt improved secondary support for
missing nuts, evidence of bolt wear, and disbonded honeycomb core;
in accordance with Boeing Service Bulletin 737-71-1250, dated June
14, 1990. Except as provided in paragraph (b) of this AD, missing
nuts, bolts worn outside the limits specified in the service
bulletin, or disbonded honeycomb core must be replaced, prior to
further flight, with new or repaired identical parts. Repeat the
inspection at intervals not to exceed 300 landings.
(b) Perform the following inspections if discrepant hardware is
found during the inspections required by paragraph (a)(2) of this
AD, and replacement hardware is not immediately available:
(1) Prior to further flight, and thereafter at intervals not to
exceed 300 landings, inspect for cracks in the aft engine mount cone
bolt, in accordance with Boeing Alert Service Bulletin 737-71A1212,
dated December 22, 1987, using ultrasonic inspection techniques.
Replace cracked cone bolts, prior to further flight, with bolts that
have been inspected in accordance with the service bulletin, using
magnetic particle inspection techniques. Replacement (newly
installed) cone bolts must be ultrasonically inspected for internal
cracking in accordance with the provisions of this paragraph at
intervals not to exceed 300 landings.
(2) At the next ultrasonic inspection, as required by paragraph
(b)(1) of this AD, unless previously accomplished within 150 to 300
landings after cone bolt installation, accomplish a torque check to
verify that the cone bolt is torqued to the proper torque limit
specified in the appropriate Boeing maintenance manual. This check
is to be accomplished without loosening the bolt. After each cone
bolt installation, accomplish the torque check procedure required by
this paragraph between 150 landings and 300 landings following
installation. Replacement of discrepant hardware in accordance with
paragraph (a)(2) of this AD constitutes terminating action for the
requirements of this paragraph.
(i) If the cone bolt torque is below one-half the specified
torque, prior to further flight, remove the cone bolt and replace it
with a serviceable bolt.
(ii) If the cone bolt torque is equal to, or above one-half the
specified torque, but below the specified torque, re-torque to the
specified level and re-check the torque within the next 150 to 300
landings. If, at that time, the torque is below 90 percent of the
specified torque, replace the cone bolt with a serviceable bolt.
(c) At next engine removal, or within 8,000 flight hours after
the effective date of this AD, whichever occurs first, replace the
secondary support of the aft engine mount with a new, improved
secondary support, Kit Number 65C37057-1; in accordance with Boeing
Service Bulletin 737-71-1289, dated August 19, 1993; as revised by
Notices of Status Change 737-71-1289 NSC 1, dated September 2, 1993,
737-71-1289 NSC 2, dated January 26, 1995, and 737-71-1289 NSC 03,
dated October 3, 1996. Accomplishment of such replacement
constitutes terminating action for the repetitive inspection
requirements of paragraphs (a)(2) and (b)(1) of this AD, and for the
torque check requirement of paragraph (b)(2) of this AD.
(d)(1) 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.
(d)(2) Alternative methods of compliance, approved previously in
accordance with AD 91-09-14 R1, amendment 39-8876, are approved as
alternative methods of compliance with paragraph (a)(1) of this AD.
Note 2: Information concerning the existence of approved
alternative methods of compliance with this AD, if any, may be
obtained from the Seattle ACO.
(e) Special flight permits may be issued in accordance with
sections 21.197 and 21.199 of the Federal Aviation Regulations (14
CFR 21.197 and 21.199) to operate the airplane to a location where
the requirements of this AD can be accomplished.
Issued in Renton, Washington, on September 25, 1998.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 98-26354 Filed 10-1-98; 8:45 am]
BILLING CODE 4910-13-U
