Airworthiness Directives; Boeing Model 737-600, -700, -700C, and -800 Series Airplanes

[Federal Register Volume 67, Number 81 (Friday, April 26, 2002)]
[Rules and Regulations]
[Pages 20628-20630]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 02-10244]



[[Page 20628]]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2002-NM-76-AD; Amendment 39-12732; AD 2002-08-20]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-600, -700, -700C, and 
-800 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 all Boeing Model 737-600, -700, -700C, and 800 series 
airplanes. This action requires inspecting the airplane following any 
suspected limit cycle oscillation (LCO) of the elevator tab; and 
revising the airplane flight manual (AFM) to limit airspeeds under 
certain conditions and to provide the flight crew with information 
regarding elevator tab LCO. This action also requires repetitive 
cleaning of the elevator tab and a one-time cleaning of the elevator 
balance bays. This action provides for the option to repetitively clean 
the elevator tab and balance bays following every deicing/anti-icing of 
the horizontal stabilizer, which would temporarily allow airspeeds 
exceeding those limited by the AFM revision. For certain airplanes, 
this action requires trimming the elevator balance panel seals, which 
will terminate the optional repetitive cleaning procedures for the 
balance bays. This action is necessary to prevent the accumulation of 
fluid or residue in the balance bays and foreign substances on the 
external surfaces of the elevator tab, which can lead to limit cycle 
oscillation, severe vibration, flutter, and loss of controllability of 
the airplane. This action is intended to address the identified unsafe 
condition.

DATES: Effective May 13, 2002.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of May 13, 2002.
    Comments for inclusion in the Rules Docket must be received on or 
before June 25, 2002.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 2002-NM-76-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. Comments may be submitted via fax to (425) 227-1232. 
Comments may also be sent via the Internet using the following address: 
[email protected]. Comments sent via fax or the Internet must 
contain ``Docket No. 2002-NM-76-AD'' in the subject line and need not 
be submitted in triplicate. Comments sent via the Internet as attached 
electronic files must be formatted in Microsoft Word 97 for Windows or 
ASCII text.
    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: Steve O'Neal, Aerospace Engineer, 
Flight Test Branch, ANM-160S, telephone (425) 227-2699 (for operations-
related questions); or Nancy Marsh, Aerospace Engineer, Airframe 
Branch, ANM-120S, telephone (425) 227-2028 (for airframe-related 
questions); FAA, Seattle Aircraft Certification Office, 1601 Lind 
Avenue, SW., Renton, Washington 98055-4056; fax (425) 227-1180.
    Other Information: Sandi Carli, Airworthiness Directive Technical 
Editor/Writer; telephone (425) 227-1120, fax (425) 227-1232. Questions 
or comments may also be sent via the Internet using the following 
address: [email protected]. Questions or comments sent via the 
Internet as attached electronic files must be formatted in Microsoft 
Word 97 for Windows or ASCII text.

SUPPLEMENTARY INFORMATION: The FAA has received reports of numerous 
incidents of severe airframe vibration, or limit cycle oscillation 
(LCO), in flight after the horizontal stabilizer had been deiced/anti-
iced on the ground. The reported incidents occurred on Boeing Model 
737-600, -700, and -800 series airplanes. The empennage structure on 
these, as well as Model 737-700C series airplanes, is identical; 
therefore, all of these airplanes are subject to the identified unsafe 
condition. These events have been attributed to an accumulation of 
deicing/anti-icing fluid or other residue in the elevator balance panel 
cavities and on the external surfaces of the elevator tab. The 
accumulation of fluid in the balance bays has been attributed to 
inadequate drainage provisions. Drainage provisions on Model 737-900 
series airplanes are improved over those on the airplanes affected by 
this AD.
    Preliminary results of the investigation of the incidents indicated 
that only Type I and Type II deicing/anti-icing fluids were susceptible 
to this type of accumulation; however, a recent LCO event occurred 
following deicing/anti-icing with Type I and Type IV fluid on one 
affected airplane. One operator reported finding up to 30 liters of 
fluid trapped in the balance bays on one airplane. Other operators have 
reported visible accumulations of foreign substances on the external 
surfaces of the elevator tab. The additional weight of accumulated 
residue on the tab can initiate LCO. The elevator tab is so 
aerodynamically sensitive that repairing and painting the subject area 
have been prohibited by related existing ADs. The reported airspeeds at 
the onset of the incidents have ranged from 276 to 325 knots.
    Fluid or residue accumulated in the balance bays, or foreign 
substances accumulated on the external surfaces of the elevator tab, in 
combination with normally recommended maximum operating airspeeds, can 
initiate LCO or flutter and result in loss of controllability of the 
airplane.

Related Rulemaking

    The FAA has issued related ADs on Model 737-600, -700, and -800 
series airplanes: AD 2001-04-08, amendment 39-12127 (66 FR 13229, March 
5, 2001); AD 2001-08-09, amendment 39-12186 (66 FR 20194, April 20, 
2001); and AD 2001-14-05, amendment 39-12315 (66 FR 36145, July 12, 
2001). Those ADs prohibit painting or repairing the elevator tab 
because of its sensitivity to changes in mass characteristics. This 
action further addresses the accumulation of foreign substances on the 
elevator tab, and the resulting associated sensitivity to the 
additional mass caused by these accumulations.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Alert Service Bulletin 
737-55A1084, dated March 7, 2002, which describes procedures for 
modifying the elevator balance panel seals on the inboard side of the 
balance panels in bays 2, 3, and 4. The modification, which involves 
trimming the seals to specified dimensions, will reduce the possibility 
of fluid accumulating in the elevator balance bays. This modification 
is incorporated in production on airplanes having line numbers 1092 and 
subsequent.

[[Page 20629]]

    The FAA has reviewed Boeing Service Letter 737-SL-12-017, dated 
April 10, 2002, which describes procedures for cleaning deicing/anti-
icing fluid residue from the elevator balance panel cavity area.

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 the accumulation of fluid or residue in the 
balance bays and foreign substances on the external surfaces of the 
elevator tab, which can lead to LCO, severe vibration, flutter, and 
loss of controllability of the airplane. This AD requires inspecting 
the airplane following any suspected LCO of the elevator tab; and 
revising the airplane flight manual (AFM) to limit airspeeds following 
deicing/anti-icing of the horizontal stabilizer, and to provide the 
flight crew with information regarding elevator tab LCO. This action 
requires repetitive cleaning of the elevator tab and a one-time 
cleaning of the elevator balance bays. This action provides for the 
option to repetitively clean the elevator tab and balance bays 
following every deicing/anti-icing of the horizontal stabilizer, which 
would temporarily allow airspeeds exceeding those limited by the AFM 
revision. For certain airplanes, this action requires trimming the 
elevator balance panel seals, which will terminate the optional 
repetitive cleaning procedures for the balance bays.

Interim Action

    This is considered to be interim action. The manufacturer has 
advised that it is currently developing an elevator tab with an 
improved design, which, when installed, would terminate the 
requirements of this AD. Once the redesigned elevator tab is developed, 
approved, and available, the FAA may consider additional rulemaking.

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.
    Submit comments using the following format:
    <bullet> Organize comments issue-by-issue. For example, discuss a 
request to change the compliance time and a request to change the 
service bulletin reference as two separate issues.
    <bullet> For each issue, state what specific change to the AD is 
being requested.
    <bullet> Include justification (e.g., reasons or data) for each 
request.
    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 2002-NM-76-AD.'' The postcard will be date stamped and 
returned to the commenter.

Regulatory Impact

    The regulations adopted herein will not have a substantial direct 
effect 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, it 
is determined that this final rule does not have federalism 
implications under Executive Order 13132.
    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 U.S.C. 106(g), 40113, 44701.


Sec. 39.13  [Amended]

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

2002-08-20  Boeing: Amendment 39-12732. Docket 2002-NM-76-AD.
    Applicability: All Model 737-600, -700, -700C, and -800 series 
airplanes; certificated in any category.

    Note 1:
    The applicability of this AD includes ALL Model 737-700 series 
airplanes, including Model 737-700 BBJ airplanes.


    Note 2:
    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 (i) 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 the accumulation of fluid or residue in the elevator 
balance bays, and foreign substances on the external surfaces of the 
elevator tab, which can lead to limit cycle oscillation, flutter, 
and loss of controllability of the airplane, accomplish the 
following:

[[Page 20630]]

Revision of the Airplane Flight Manual (AFM)--Airspeed Limitations

    (a) Within 10 days after the effective date of this AD, revise 
the Limitations section of the FAA-approved AFM to include the 
following procedures (this may be accomplished by inserting a copy 
of this AD into the AFM):
    ``After any ground deicing/anti-icing of the horizontal 
stabilizer, airspeed must be limited to 270 KIAS until the crew has 
been informed that applicable maintenance procedures have been 
accomplished that would allow exceedance of 270 KIAS. Once the 
applicable maintenance procedures have been accomplished, exceeding 
270 KIAS is permissible only until the next deicing/anti-icing.''

Optional Post-Deicing/Anti-Icing Cleaning

    (b) Accomplishment of the applicable cleaning procedures 
specified by paragraphs (b)(1) and (b)(2) of this AD allows the 
temporary operation of the airplane at airspeeds exceeding 270 
KIAS--until the next deicing/anti-icing of the horizontal 
stabilizer.
    (1) For all airplanes: Clean the external aerodynamic surfaces 
of the elevator tab to remove accumulated deicing/anti-icing fluid, 
residue, or other foreign substances, in accordance with the 
procedures for Airplane Cleaning in Section 12-40-00 (G) of Boeing 
737-600/700/800/900 Maintenance Manual Document D633A101.
    (2) For airplanes having line numbers 1 through 1091 inclusive: 
Until the actions required by paragraph (f) of this AD have been 
accomplished, clean the elevator balance bays in accordance with a 
method approved by the Manager, Seattle Aircraft Certification 
Office (ACO), FAA. For a cleaning method to be approved by the 
Manager, Seattle ACO, as required by this paragraph, the Manager's 
approval letter must specifically reference this AD.

AFM Revision--Non-Normal Procedures

    (c) Within 10 days after the effective date of this AD, revise 
the Non-Normal Procedures section of the FAA-approved AFM (Boeing 
Document D631A001) to include the following procedures (this may be 
accomplished by inserting a copy of this AD into the AFM):

Elevator Tab Limit Cycle Oscillation

    An Elevator Tab Limit Cycle Oscillation (LCO) will be 
characterized by a high frequency, possibly severe vibration, 
originating in the tail of the airplane, and emanating forward 
through the airframe structure. LCO events have previously occurred 
at airspeeds greater than 275 KIAS, and in an altitude range between 
10,000 and 25,000 feet following ground deicing/anti-icing of the 
horizontal stabilizer. This vibration may, or may not, be felt in 
the control column. Cabin crew may be able to confirm the source of 
any airframe vibrations. If LCO is suspected in flight, immediately 
reduce airspeed (WITHOUT use of speed brakes, or changing aircraft 
configuration) to 270 KIAS, or until the vibration ceases, whichever 
indicated airspeed is lower.

DO NOT USE SPEED BRAKES FOR THE REMAINDER OF THE FLIGHT.

    Use of the speed brakes in other emergencies is at the 
discretion of the flight crew. Remain at or below the indicated 
airspeed at which the vibration ceased for the remainder of the 
flight, but do not exceed 270 KIAS. Evaluate the need to land at the 
nearest practicable airport. Landing airport selection should be 
based upon consideration of all pertinent factors such as: weather, 
distance to destination, range available at the reduced airspeed, 
maximum landing weight, and possible airframe damage. Use of ground 
spoilers during landing rollout is permitted.''

Elevator Tab Cleaning

    (d) Within 250 flight cycles or 90 days after the effective date 
of this AD, whichever occurs first: Clean the external aerodynamic 
surfaces of the elevator tab to detect accumulated deicing/anti-
icing fluid, residue, or other foreign substances, in accordance 
with the procedures for Airplane Cleaning in Section 12-40-00 (G) of 
Boeing 737-600/700/800/900 Maintenance Manual Document D633A101. 
Thereafter, repeat the tab cleaning procedure at least every 250 
flight cycles or 90 days, whichever occurs first.

Balance Bay Cleaning

    (e) For airplanes having line numbers 1 through 1091 inclusive: 
Prior to or concurrently with the accomplishment of the seal trim 
required by paragraph (f) of this AD, clean the elevator balance 
bays in accordance with Boeing Service Letter 737-SL-12-017, dated 
April 10, 2002. If the balance bays have been cleaned at least one 
time in accordance with paragraph (b)(2) of this AD, and if the seal 
trim has been accomplished in accordance with paragraph (f) of this 
AD, it is not necessary to repeat this procedure.

Seal Trim

    (f) For airplanes having line numbers 1 through 1091 inclusive: 
Within 90 days after the effective date of this AD, trim the 
elevator balance bay seals in accordance with Boeing Alert Service 
Bulletin 737-55A1084, dated March 7, 2002. Following accomplishment 
of the seal trim required by this paragraph and the balance bay 
cleaning required by paragraph (e) of this AD, the optional 
repetitive cleaning procedures specified by paragraph (b)(2) of this 
AD are no longer necessary.

Post-LCO Inspection

    (g) Before the next revenue flight following any suspected limit 
cycle oscillation (LCO) of the elevator tab: Inspect the airplane in 
accordance with a method approved by the Manager, Seattle ACO, FAA. 
For an inspection method to be approved by the Manager, Seattle ACO, 
as required by this paragraph, the Manager's approval letter must 
specifically refer to this AD.

Spare Parts

    (h) As of the effective date of this AD, no person may install 
on any airplane an elevator balance panel bay seal having part 
number 183A9140-1, -5, or -9.

Alternative Methods of Compliance

    (i) 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, FAA. 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

    (j) 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, provided the 
maximum operating airspeed is 270 knots indicated airspeed (KIAS) 
during the ferry flight.

Incorporation by Reference

    (k) The modification required by paragraph (f) of this AD must 
be done in accordance with Boeing Alert Service Bulletin 737-
55A1084, dated March 7, 2002; and Boeing Service Letter 737-SL-12-
017, dated April 10, 2002. 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.

Effective Date

    (l) This amendment becomes effective on May 13, 2002.

    Issued in Renton, Washington, on April 19, 2002.
Lirio Liu-Nelson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 02-10244 Filed 4-25-02; 8:45 am]
BILLING CODE 4910-13-U

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