[Federal Register Volume 59, Number 74 (Monday, April 18, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-8418]
[[Page Unknown]]
[Federal Register: April 18, 1994]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 93-NM-170-AD; Amendment 39-8876; AD 91-09-14 R1]
Airworthiness Directives; Boeing Model 737-100, -200, and -200C
Series Airplanes
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final rule.
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SUMMARY: This amendment revises 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
engine aft mount, and replacement, if necessary. This amendment
provides for the optional installation of a new, modified support,
which, if accomplished, constitutes terminating action for certain
required inspections. This amendment is prompted by the development of
a modification that will prevent wearing of the secondary support. The
actions specified by this 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: Effective May 18, 1994.
The incorporation by reference of certain publications listed in
the regulations is approved by the Director of the Federal Register as
of May 18, 1994.
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: Thomas Rodriguez, Aerospace Engineer,
Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle
Aircraft Certification Office (ACO), 1601 Lind Avenue SW., Renton,
Washington 98055-4056; telephone (206) 227-2779; fax (206) 227-1181.
SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal
Aviation Regulations by revising AD 91-09-14, Amendment 39-6972 (56 FR
18696, April 24, 1991), which is applicable to all Boeing Model 737-
100, -200, and -200C series airplanes, was published in the Federal
Register on December 29, 1993 (58 FR 68787). Among other things, AD 91-
09-14 currently requires periodic inspections to detect missing nuts
and/or damaged secondary support hardware, and replacement, if
necessary. The notice proposed to revise AD 91-09-14 to provide for the
optional replacement of the existing aft engine mount secondary support
with a new, modified secondary support. If accomplished, such
replacement would constitute terminating action for certain of the
currently required 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.
All of the commenters support the proposal.
One commenter, Boeing, notes that the number of work hours
necessary to accomplish the optional modification is closer to 60 work
hours rather than 30 work hours, as was indicated in the cost impact
information presented in the preamble to the notice. The FAA
acknowledges this updated figure and has revised the cost impact
information, below, to reflect it.
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 as proposed.
There are approximately 1,144 Model 737 series airplanes of the
affected design in the worldwide fleet. The FAA estimates that 432
airplanes of U.S. registry will be affected by this AD.
The actions currently required by AD 91-09-14 take approximately 3
work hours per airplane to accomplish, at an average labor rate of $55
per work hour. Based on these figures, the total cost impact of the
currently required actions on U.S. operators is estimated to be
$71,280, or $165 per airplane, per inspection cycle.
This revision of AD 91-09-14 adds no new additional costs to
operators, since it merely provides for an optional installation that
would provide terminating action for certain requirements. Should an
operator elect to accomplish the installation, the associated actions
will take approximately 60 work hours per airplane to accomplish, at an
average labor rate of $55 per work hour. Required parts will cost
approximately $6,818 per airplane. Based on these figures, the total
cost of accomplishing the optional installation is estimated to be
$10,118 per airplane.
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 14 CFR part
39 of the Federal Aviation Regulations 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 removing amendment 39-6972 (56 FR
18696, April 24, 1991), and by adding a new airworthiness directive
(AD), amendment 39-8876, to read as follows:
91-09-14 R1 Boeing: Amendment 39-8876. Docket 93-NM-170-AD. Revises
AD 91-09-14, Amendment 39-6972.
Applicability: All Model 737-100, -200, and -200C series
airplanes, certificated in any category.
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 engine separation 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 above 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 every 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, 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) Replacement of the existing aft engine mount secondary
support with a new, modified secondary support, Kit Number 65C37057-
1, in accordance with Boeing Service Bulletin 737-71-1289, dated
August 19, 1993, constitutes terminating action for the inspections
required by paragraphs (a)(2), (b), (b)(1), and (b)(2) of this AD.
(d) 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.
(e) Special flight permits may be issued in accordance with
Federal Aviation Regulations (FAR) 21.197 and 21.199 to operate the
airplane to a location where the requirements of this AD can be
accomplished.
(f) The optional replacement shall be done in accordance with
Boeing Service Bulletin 737-71-1289, dated August 19, 1993. 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.
(g) This amendment becomes effective on May 18, 1994.
Issued in Renton, Washington, on April 4, 1994.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 94-8418 Filed 4-15-94; 8:45 am]
BILLING CODE 4910-13-U
