[Federal Register Volume 64, Number 91 (Wednesday, May 12, 1999)]
[Rules and Regulations]
[Pages 25426-25428]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-11783]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 99-NM-97-AD; Amendment 39-11166; AD 99-10-13]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 737-300, -400, -500, -600,
-700, and -800 Series Airplanes Equipped with Vickers Combined
Stabilizer Trim Motors
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 and functional tests of a trailing edge
flap limit switch to verify proper operation, and replacement of the
existing limit switch with a new limit switch, if necessary. This AD
also requires modification of the stabilizer control system, which
constitutes terminating action for the repetitive inspections and
tests. This amendment is prompted by reports of uncommanded stabilizer
trim motion due to failure of the trailing edge flap limit switch. The
actions specified in this AD are intended to prevent such failure,
which could result in uncommanded (nose down) stabilizer trim motion
and consequent reduced controllability of the airplane.
DATES: Effective May 27, 1999.
The incorporation by reference of certain publications listed in
the regulations is approved by the Director of the Federal Register as
of May 27, 1999.
Comments for inclusion in the Rules Docket must be received on or
before July 12, 1999.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-114,
Attention: Rules Docket No. 99-NM-97-AD, 1601 Lind Avenue, SW., Renton,
Washington 98055-4056.
[[Page 25427]]
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: R.C. Jones, Aerospace Engineer,
Systems and Equipment Branch, ANM-130S, FAA, Transport Airplane
Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue,
SW., Renton, Washington 98055-4056; telephone (425) 227-1118; fax (425)
227-1181.
SUPPLEMENTARY INFORMATION: The FAA has received reports of several
incidents of uncommanded nose down stabilizer trim motion on certain
Boeing Model 737 series airplanes having Vickers type combined manual-
autopilot stabilizer trim motors (STM). Investigation revealed the
cause as a single point failure in the stabilizer control system, in
conjunction with a design deficiency in the STM. Analysis of the S245
trailing edge flap limit switch of the stabilizer control system
revealed that the switch had failed due to moisture penetration into
the switch contacts, resulting in corrosion and an electrical short
circuit. This short circuit caused an erroneously energized STM and
subsequent uncommanded stabilizer trim motion in the airplane nose down
direction. This condition, if not corrected, could result in reduced
controllability of the airplane.
Explanation of Relevant Service Information
The FAA has reviewed and approved Boeing Alert Service Bulletins
737-27A1227 (for Model 737-300, -400, and -500 series airplanes) and
737-27A1228 (for Model 737-600, -700, and -800 series airplanes), both
dated April 8, 1999, which describe procedures for repetitive
inspections and functional tests of the S245 trailing edge flap limit
switch to verify proper operation, and replacement of any
malfunctioning limit switch with a new limit switch.
Explanation of the Requirements of the Rule
Since an unsafe condition has been identified that is likely to
exist or develop on other airplanes of the same type design, this AD is
being issued to prevent failure of the S245 trailing edge flap limit
switch, and subsequent uncommanded (nose down) stabilizer trim motion,
which could result in reduced controllability of the airplane. This AD
requires accomplishment of the actions specified in the alert service
bulletins described previously. This AD also requires that operators
submit a report of findings of malfunctioning to the FAA.
Additionally, this AD requires modification of the stabilizer
control system, which constitutes terminating action for the repetitive
inspections and tests required by this AD.
Interim Action
This is considered to be interim action until final action is
identified, at which time the FAA may consider further rulemaking.
Differences Between This AD and Alert Service Bulletins
Operators should note that, although the alert service bulletins do
not specify procedures for terminating action for the repetitive
inspections and tests, this AD mandates, within 3 months, incorporation
of an improved design of the stabilizer control system as terminating
action for the repetitive inspections and tests.
The FAA has determined that long-term continued operational safety
will be better assured by design changes to remove the source of the
problem, rather than by repetitive inspections and tests. Long-term
inspections and tests may not be providing the degree of safety
assurance necessary for the transport airplane fleet. This, coupled
with a better understanding of the human factors associated with
numerous continual inspections, has led the FAA to consider placing
less emphasis on inspections and more emphasis on design improvements.
Incorporation of an improved design of the stabilizer control system
requirement is in consonance with these conditions.
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 99-NM-97-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.
[[Page 25428]]
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 adding the following new
airworthiness directive:
99-10-13 Boeing: Amendment 39-11166. Docket 99-NM-97-AD.
Applicability: Model 737-300, -400, -500, -600, -700, and -800
series airplanes, certificated in any category; equipped with
Vickers combined stabilizer trim motors.
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) 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 failure of the trailing edge flap limit switch, which
could result in uncommanded (nose down) stabilizer trim motion and
reduced controllability of the airplane, accomplish the following:
Inspections and Tests
(a) Perform a special detailed inspection and functional test to
verify proper operation of the S245 trailing edge flap limit switch,
in accordance with the applicable Boeing Alert Service Bulletin 737-
27A1227 (for Model 737-300, -400, and -500 series airplanes) or 737-
27A1228 (for Model 737-600, -700, and -800 series airplanes), both
dated April 8, 1999; as applicable; at the time specified in
paragraph (a)(1) or (a)(2) of this AD, as applicable.
(1) For airplanes that have accumulated less than 1,000 total
flight hours as of the effective date of this AD: Inspect and test
prior to the accumulation of 1,000 total flight hours, or within 10
days after the effective date of this AD, whichever occurs later.
Repeat the inspection and test thereafter at intervals not to exceed
300 flight hours, until accomplishment of paragraph (c) of this AD.
(2) For airplanes that have accumulated 1,000 or more total
flight hours as of the effective date of this AD: Inspect and test
within 5 days after the effective date of this AD. Repeat the
inspection and test thereafter at intervals not to exceed 300 flight
hours, until accomplishment of paragraph (c) of this AD.
Note 2: Any inspection and test of the S245 trailing edge flap
limit switch accomplished prior to the effective date of this AD in
accordance with the Accomplishment Instructions of either Boeing
Alert Service Bulletin 737-27A1227 (for Model 737-300, -400, and -
500 series airplanes) or 737-27A1228 (for Model 737-600, -700, and -
800 series airplanes), both dated April 8, 1999, as applicable, is
considered acceptable for compliance with the initial inspection and
test specified in paragraph (a) of this AD.
Corrective Action
(b) If any malfunction is detected during any inspection and
test required by paragraph (a) of this AD, prior to further flight,
replace the existing limit switch with a new limit switch in
accordance with the Boeing Alert Service Bulletin 737-27A1227 (for
Model 737-300, -400, and -500 series airplanes) or 737-27A1228 (for
Model 737-600, -700, and -800 series airplanes), both dated April 8,
1999, as applicable. Repeat the inspection and test thereafter at
intervals not to exceed 300 flight hours, until accomplishment of
paragraph (c) of this AD.
(c) Within 3 months after the effective date of this AD:
Incorporate an improved design of the stabilizer control system in
accordance with a method approved by the Manager, Seattle Aircraft
Certification Office (ACO), FAA, Transport Airplane Directorate.
Incorporation of an improved design, as required by this paragraph,
constitutes terminating action for the repetitive inspection and
test requirements of this AD.
Reporting Requirement
(d) Within 10 days after accomplishing the inspection and test
required by paragraph (a) of this AD, submit a report of the
inspection and test results (positive findings of malfunctioning
only) to the Manager, Seattle ACO, FAA, Transport Airplane
Directorate, 1601 Lind Avenue SW., Renton, Washington, 98055-4056.
The report must include the inspection results, the airplane serial
number, and the total number of landings and flight hours on the
airplane. Information collection requirements contained in this
regulation have been approved by the Office of Management and Budget
(OMB) under the provisions of the Paperwork Reduction Act of 1980
(44 U.S.C. 3501 et seq.) and have been assigned OMB Control Number
2120-0056.
Alternative Methods of Compliance
(e) 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 ACO. 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 3: Information concerning the existence of approved
alternative methods of compliance with this AD, if any, may be
obtained from the Seattle ACO.
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) Except as provided by paragraph (c) of this AD, the actions
shall be done in accordance with Boeing Alert Service Bulletin 737-
27A1227, dated April 8, 1999; or Boeing Alert Service Bulletin 737-
27A1228, dated April 8, 1999; as applicable. 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.
(h) This amendment becomes effective on May 27, 1999.
Issued in Renton, Washington, on May 4, 1999.
D.L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 99-11783 Filed 5-11-99; 8:45 am]
BILLING CODE 4910-13-P
