[Federal Register Volume 64, Number 243 (Monday, December 20, 1999)]
[Rules and Regulations]
[Pages 70997-71000]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-32509]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 98-NM-189-AD; Amendment 39-11466; AD 99-26-07]
RIN 2120-AA64
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 supersedes 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 amendment requires accomplishment of the previously
optional terminating action. This amendment 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 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 January 24, 2000.
The incorporation by reference of certain publications listed in
the regulations is approved by the Director of the Federal Register as
of January 24, 2000.
The incorporation by reference of Boeing Service Bulletin 737-71-
1289, dated August 19, 1993, as listed in the regulations, was approved
previously by the Director of the Federal Register as of May 18, 1994
(59 FR 18294, April 18, 1994).
ADDRESSES: The service information referenced in this AD may be
obtained
[[Page 70998]]
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: 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: A proposal to amend part 39 of the Federal
Aviation Regulations (14 CFR part 39) by superseding AD 91-09-14 R1,
amendment 39-8876 (59 FR 18294, April 18, 1994), which is applicable to
all Boeing Model 737-100, -200, and -200C series airplanes, was
published in the Federal Register on October 2, 1998 (63 FR 52992). The
action proposed to continue to require periodic inspections to detect
missing nuts and/or damaged secondary support hardware adjacent to the
aft engine mount, and replacement, if necessary. The action also
proposed to mandate accomplishment of the previously optional
terminating action.
Comments
Interested persons have been afforded an opportunity to participate
in the making of this amendment. Due consideration has been given to
the comments received.
Support for the Proposed Rule
Two commenters support the proposed rule.
Requests to Revise Compliance Time of Paragraph (c) of the Proposed
AD
Two commenters request that the compliance time in paragraph (c) of
the proposed AD be revised by removing the threshold ``at next engine
removal'' and setting the threshold simply to ``within 8,000 flight
hours after the effective date of this AD.'' One commenter states that
the requirement to accomplish the terminating action (i.e.,
installation of Boeing Secondary Support, Kit Number 65C37057-1) is
overly restrictive. Operators would have to be prepared to modify the
secondary support (i.e., install the secondary support kit) at any
unscheduled engine change, even though the conditions that lead to an
unscheduled engine removal are not likely to affect safety of the
secondary support. Another commenter states that the threshold of ``at
next engine removal'' in paragraph (c) of the proposed rule is too
harsh. The commenter states that it accomplishes a magnetic particle
inspection of the aft engine mount cone bolt during each engine
removal, and that these inspections are more than adequate to ensure
the integrity of the aft mount cone bolt until the modification is
accomplished at 8,000 flight hours.
The FAA partially concurs with the commenters' request to revise
the compliance time specified in paragraph (c) of the AD. The FAA's
intent was to require installation at the next ``scheduled'' engine
removal, or within 8,000 flight hours after the the effective date of
this AD, whichever occurs first, which is the typical interval between
scheduled engine changes/overhauls. The FAA agrees that the threshold
should not be subject to ``unscheduled'' engine removals, but does not
agree that the threshold should be set solely to ``within 8,000 flight
hours,'' as suggested by the commenters. The FAA has determined that a
compliance time at the next ``scheduled'' engine removal, or within
8,000 flight hours after the effective date of the AD, whichever occurs
first, will provide operators adequate time to procure and install the
secondary support kit, and will not be an unnecessary burden on
operators.
In addition, the FAA does not agree with the second commenter that
a magnetic particle inspection of the cone bolt during the engine
removal will ensure that cracks will not initiate prior to the next
engine removal. The magnetic inspection only ensures that the bolts
being installed have no detectable cracks. In light of the results of
testing conducted by Boeing and the two occurrences of failure of the
aft engine mount cone bolts after the bolts had been subjected to
ultrasonic inspections, the FAA finds that installation of a new,
improved secondary support at the next scheduled engine removal, or
within 8,000 flight hours after the effective date of this AD,
whichever occurs first, is necessary to address the identified unsafe
condition.
Therefore, the FAA has revised the compliance time of paragraph (c)
of the final rule accordingly.
One commenter requests that the compliance time in paragraph (c) of
the proposed AD coincide with its hush kit installation schedule. The
commenter states that its hush kit schedule will occur prior to the
proposed 8,000-flight hour threshold, but may not occur prior to the
next engine removal. The commenter also states that aligning the
compliance time with the hush kit installation will avoid the dual cost
of installing the Boeing secondary support kit at the next engine
removal at a cost of $10,600 per aircraft, and replacing it within one
year as part of the NORDAM hush kit installation.
The FAA partially concurs with the commenter's request to revise
the subject compliance time. The FAA finds that a threshold of ``at the
next engine removal'' may result in the unnecessary installation and
removal of the Boeing secondary support kit for those operators
currently working to a schedule for incorporation of the NORDAM hush
kit. However, the FAA finds that a compliance time of at the next
``scheduled'' engine removal, or within 8,000 flight hours after the
effective date of the AD, whichever occurs first, will preclude any
unnecessary installation and removal of the Boeing secondary support
kit. The FAA based its determination on an expectation that operators
will not schedule an engine change/overhaul within 12 months prior to
installing a hush kit, but rather will schedule both to coincide in
order to minimize down time. As discussed previously, the FAA has
revised the threshold of paragraph (c) to at the next ``scheduled''
engine removal.
Requests to Allow an Alternative Method of Compliance (AMOC)
Two commenters request that paragraph (c) of the proposed AD be
revised to include a statement that installation of certain NORDAM hush
kits is an AMOC to the requirement to install the Boeing secondary
support, Kit Number 65C37057-1. The commenters state that they are
currently installing a certain NORDAM hush kit, and that this hush kit
has been approved by the Seattle Aircraft Certification Office (SACO),
FAA, Transport Airplane Directorate, as an AMOC to AD 91-09-14 R1.
Specifically, the installation of NORDAM Low Gross Weight (LGW) Hush
Kit [i.e., Supplementary Type Certificate (STC) ST00131SE] has been
approved by the FAA as terminating action for the inspections mandated
by AD 91-09-14 R1, with the exception of the repetitive inspections of
the aft cone bolt failure indicator required in paragraph (a)(1) of AD
91-09-14 R1. The commenters state that this approval indicates that the
secondary support that is installed as part of the NORDAM hush kit
should provide an acceptable level of safety and meet the intent of the
proposed rule.
The FAA concurs with the commenters' request to include a statement
in paragraph (c) of the final rule to clarify this point. The FAA has
revised the final rule to include a new
[[Page 70999]]
NOTE to specify that installation of certain NORDAM hush kits is
considered an acceptable AMOC to the requirements of this AD, and is
considered terminating action for the inspections mandated by this AD,
except for the repetitive inspections of the aft cone bolt failure
indicator required in paragraph (a)(1) of this AD. The repetitive
inspections of the aft cone bolt failure indicator specified in
paragraph (a)(1) are still required. In addition, the FAA finds that
paragraph (d)(2) of the final rule also must be revised to clarify this
point.
Requests to Not Mandate Replacement of Secondary Support
One commenter requests that the FAA continue to require the current
inspections required by AD 91-09-14 R1 and continue to provide the
optional terminating action (i.e., replacement of the secondary support
of the aft engine mount with a new, improved secondary support) rather
than mandating it. Another commenter questions the necessity of the
proposed rule based upon existing mandates that will provide an
equivalent means of compliance with a similar time period. One
commenter states that it has been inspecting the aft mount cone bolt
indicator for alignment during every over-night check in accordance
with its maintenance policy and has been inspecting the secondary
support hardware (i.e., the aft mount cone bolt and nut) in accordance
with AD 91-09-14 R1. The commenter also states that it has been
replacing the forward and aft mount cone bolt, nut, and vibration
isolator every 6,000 flight hours or engine hard time, or at any engine
removal, whichever occurs first. The commenter notes that it has not
detected a failure of the secondary support hardware in the aft mount
cone bolt, or detected loosening of the nut.
The FAA does not concur with the commenter's request to not mandate
accomplishment of the previously optional terminating action. As
discussed in the preamble of the proposed rule, 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 transport
airplane fleet. The 45-day inspection interval of the aft cone bolt
failure indicator, as specified in the existing AD, may not detect a
broken aft cone bolt in a timely manner, as cracks in the aft cone bolt
may go undetected using the current ultrasonic inspection procedures.
Worn secondary support components that exceed the wear limits allowed
in the AD 91-09-14 R1 may not be reliably detected due to human factors
and may, in the event of the failure of an aft cone bolt, render the
secondary support incapable of supporting the aft end of the engine
until the next inspection of the aft cone bolt failure indicator.
Therefore, the FAA has determined that the repetitive inspections may
not be adequate to preclude an engine separation, and finds that
installation of the new Boeing secondary support kit should be
mandated.
Conclusion
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 with the changes previously
described. The FAA has determined that these changes will neither
increase the economic burden on any operator nor increase the scope of
the AD.
Cost Impact
There are approximately 1,045 Model 737-100, -200, and -200C series
airplanes of the affected design in the worldwide fleet. The FAA
estimates that 382 airplanes of U.S. registry will be affected by this
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 inspections on U.S. operators is
estimated to be $68,760, or $180 per airplane, per inspection cycle.
The replacement that is required by this AD will take approximately
60 work hours per airplane to accomplish, at an average labor rate of
$60 per work hour. Required parts will cost approximately $7,000 per
airplane. Based on these figures, the cost impact of the new
requirements of 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 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 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 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), amendment 39-11466, to read as follows:
99-26-07 Boeing: Amendment 39-11466. Docket 98-NM-189-AD.
Supersedes AD 91-09-14 R1, Amendment 39-8876.
Applicability: All Model 737-100, -200, and -200C 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 (e)(1)
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.
[[Page 71000]]
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:
Restatement of Requirements of AD 91-09-14, Amendment 39-6972
Repetitive Inspections and Replacement, If Necessary
(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.
Follow-On Inspections, Replacement, and Torque Check
(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.
New Actions Required by This AD
Replacement
(c) At the next scheduled 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.
Optional Installation
(d) Installation of Nordam hush kits modified in accordance with
the following Supplemental Type Certificate is considered acceptable
for compliance with the requirements of paragraphs (a)(2), (b), and
(c) of this AD, but are not considered acceptable for compliance
with the requirements of paragraph (a)(1) of this AD.
SA5730NM, issued on June 26, 1992 and amended on
October 2, 1992; or
ST00131SE, issued on November 8, 1994, and amended on
January 26, 1995, May 13, 1996, September 13, 1996, and February 20,
1997.
Alternative Methods of Compliance
(e)(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.
Note 2: Information concerning the existence of approved
alternative methods of compliance with this AD, if any, may be
obtained from the Seattle ACO.
(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 the requirements of this AD,
except for the requirements of paragraph (a)(1) of this AD.
Special Flight Permits
(f) 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.
Incorporation by Reference
(g) The inspection required by paragraph (a)(2) of this AD shall
be done in accordance with Boeing Service Bulletin 737-71-1250,
dated June 14, 1990. The inspection required by paragraph (b)(1) of
this AD shall be done in accordance with Boeing Alert Service
Bulletin 737-71A1212, dated December 22, 1987. The replacement
required by paragraph (c) of this AD shall be done in accordance
with Boeing Service Bulletin 737-71-1289, dated August 19, 1993, as
revised by Notice of Status Change 737-71-1289 NSC 1, dated
September 2, 1993, Notice of Status Change 737-71-1289 NSC 2, dated
January 26, 1995, and Notice of Status Change 737-71-1289 NSC 03,
dated October 3, 1996.
(1) The incorporation by reference of Boeing Service Bulletin
737-71-1250, dated June 14, 1990; Boeing Alert Service Bulletin 737-
71A1212, dated December 22, 1987, Boeing Service Bulletin Notice of
Status Change 737-71-1289 NSC 1, dated September 2, 1993, Boeing
Service Bulletin Notice of Status Change 737-71-1289 NSC 2, dated
January 26, 1995, and Boeing Service Bulletin Notice of Status
Change 737-71-1289 NSC 03, dated October 3, 1996; is approved by the
director of the Federal Register in accordance with 5 U.S.C. 552(a)
and 1 CFR part 51.
(2) The incorporation by reference of Boeing Service Bulletin
737-71-1289, dated August 19, 1993, as listed in the regulations,
was approved previously by the Director of the Federal Register as
of May 18, 1994 (59 FR 18294, April 18, 1994).
(3) 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.
(h) This amendment becomes effective on January 24, 2000.
Issued in Renton, Washington, on December 9, 1999.
D.L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 99-32509 Filed 12-17-99; 8:45 am]
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