[Federal Register Volume 61, Number 251 (Monday, December 30, 1996)]
[Rules and Regulations]
[Pages 68566-68569]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-32053]


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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 96-NM-23-AD; Amendment 39-9860; AD 96-25-17]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-300, -400, and -500 
Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD), 
applicable to certain Boeing Model 737-300, -400, and -500 series 
airplanes, that requires inspections to detect bent or damaged tie 
links and washers of the elevator feel and centering unit, and 
replacement of the centering unit with a new or serviceable unit, if 
necessary. This amendment also provides an optional replacement of the 
centering unit, which, if accomplished with the installation of 
supports and a stop bolt, constitutes terminating action for the 
repetitive inspections. This amendment is prompted by a report of high 
control column forces that occurred during takeoff and landing. The 
actions specified by this AD are intended to prevent such high forces, 
which could result in restriction of elevator control during takeoff, 
climbout, and landing.

DATES: Effective February 3, 1997.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of February 3, 1997.

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: Kristin Larson, Aerospace Engineer, 
Systems and Equipment Branch, ANM-130S, FAA, Seattle Aircraft 
Certification Office, 1601 Lind Avenue, SW., Renton, Washington; 
telephone (206) 227-1760; fax (206) 227-1181.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal 
Aviation Regulations (14 CFR part 39) to include an airworthiness 
directive (AD) that is applicable to certain Boeing Model 737-300, -
400, and -500 series airplanes was published in the Federal Register on 
June 26, 1996 (61 FR 33049). That action proposed to require repetitive 
visual inspections to detect bent or damaged tie links of the elevator 
centering unit, and replacement of the elevator centering unit with a 
new or serviceable unit, if necessary.
    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 Proposal

    One commenter supports the rule.

Request to Extend the Initial Inspection Compliance Time

    Several commenters request that the proposed compliance time of 6 
months for the initial inspection be extended to at least 12 or 15 
months. The commenters express concern that there may be a shortage of 
available tie link units to use as replacement units since the proposed 
rule would require replacement of damaged tie links with new or 
serviceable parts prior to further flight.
    The FAA does not concur with the commenters' request to extend the 
compliance time. Replacement of the feel and centering unit prior to 
further flight is required only if the tie links have damage that 
exceeds the limits as specified in Boeing Alert Service Bulletin 737-
27A1194. The manufacturer specifically devised the inspection plan 
described in the service bulletin to address the concern of the 
availability of an ample number of replacement tie link units. Damage 
found to be within the service bulletin's specified limits requires 
certain repetitive inspections until the elevator

[[Page 68567]]

feel and centering unit can be serviced or replaced. This is intended 
to allow relief for the operators if a spare feel and centering unit is 
not readily available. In developing an appropriate compliance time for 
this proposal, the FAA considered the safety implications and the parts 
availability, and finds no basis to extend the 6-month compliance time. 
However, paragraph (f) of the final rule does provide affected 
operators the opportunity to request an adjustment of the compliance 
time if data are presented to justify such an extension.

Request to Revise Inspection Times and Mandate the Terminating 
Action

    Another commenter requests that:
    1. The compliance time for the initial inspection be extended to 12 
months,
    2. Repetitive inspections be required every 12 months thereafter, 
and
    3. ``the modification'' specified in Boeing Alert Service Bulletin 
737-27A1194 should be required to be installed within 2 years.
    This commenter states that changing the elevator feel and centering 
unit is labor-intensive and would require at least 8 hours to 
accomplish. However, this commenter offered no data or technical basis 
for revising the compliance times or for mandating the terminating 
action provided in paragraph (e) of the proposed rule.
    As for the commenter's request to extend the compliance time to 
extend the compliance time of the initial and repetitive inspections, 
the FAA does not concur. As previously explained, the FAA considered 
the safety implications, parts availability, and maintenance schedules 
when developing the compliance time. The commenter has offered no new 
technical data that would indicate a need to revise the compliance 
times. However, paragraph (f) of the final rule does provide affected 
operators the opportunity to request an adjustment of the compliance 
time if data are presented to justify such an extension.
    As for the commenter's request to mandate ``the modification,'' the 
FAA infers that the modification the commenter is referring to is that 
of the feel and centering unit. (The referenced Boeing alert service 
bulletin actually describes two different modifications: modification 
of the supports and stop-bolt, and modification of the feel and 
centering unit.) The FAA does not concur with this request. The 
commenter offered no data to justify a compliance time of 2 years for 
mandating the installation of this modification. The FAA considers 
that, by providing the modification as an optional terminating action 
for this AD, prudent operators may accomplish that action at a time of 
their own discretion. Additionally, the optional terminating action 
does not preclude any operator from installing the modification before 
an arbitrary 2-year period, as suggested by the commenter. Further, the 
FAA finds that the required inspections, and replacement action as 
necessary, are both adequate and appropriate in addressing the subject 
damage associated with the elevator feel and centering unit.

Request to Extend the Repetitive Inspection Interval

    Two commenters state that, when the stop bolt and support are 
installed, they will prevent excessive travel of the elevator feel 
actuator and preclude further damage to the tie links. Therefore, one 
of these commenters requests that, once the stop bolt and support are 
installed, the repetitive inspection intervals be extended from those 
intervals specified in proposed paragraph (c) (and specified in Figure 
1 of Boeing Alert Service Bulletin 737-27A1194). This commenter, an 
operator, proposes that the inspection intervals be increased to 
coincide with the current maintenance schedules established for its 
fleet of airplanes.
    The FAA does not concur. The commenter provided no substantiating 
evidence to justify extending the repetitive inspection intervals; and 
the FAA does not consider it appropriate to revise provisions in an AD 
to accommodate a single operator's maintenance schedule. The FAA has 
determined that the repetitive inspection interval described in Boeing 
Alert Service Bulletin 737-27A1194 (the appropriate service information 
for this AD) will ensure that any damage to the tie links is identified 
and corrected in a timely manner. However, paragraph (f) of the final 
rule does provide affected operators the opportunity to request an 
adjustment of the compliance time if data are presented to justify such 
an extension.

Request to Clarify Damage Limits

    One commenter, the manufacturer, states that the phrase ``* * * and 
damage is within limits specified in Figure 1 * * *'', as used in 
paragraphs (c) and (d) of the proposal is confusing. The manufacturer 
notes that Figure 1 of Boeing Alert Service Bulletin 737-27A1194, which 
is referenced as the appropriate source of service information in the 
proposal, has two action paths: One path depicts actions to follow if 
damage is within acceptable limits (which starts an inspection 
program); the other path depicts actions to follow if damage is outside 
the acceptable limits (which specifies replacement of the unit). The 
manufacturer requests that the phrase be clarified to read ``* * * and 
damage is within acceptable limits as specified in Figure 1 * * *''.
    The FAA concurs and has revised paragraphs (c) and (d) of the AD 
accordingly.

Request to Clarify the Unsafe Condition

    The manufacturer also suggests that the wording, ``Since an unsafe 
condition has been identified that is likely to exist or develop * * 
*.'', which appeared in the preamble to the notice, be changed. The 
manufacturer requests that this language be revised to specify that a 
``possible unsafe condition'' has been identified. The manufacturer 
states that this change of wording is warranted, since the worst 
scenario that has been identified is ``high control column forces'' 
and, even in that situation, an airplane still would be controllable.
    The FAA does not concur with the commenter's suggestion. First, all 
unsafe conditions are ``possible'' events that ``could occur.'' In 
fact, they are described in the regulations as conditions that are 
``likely to exist or develop'' in aircraft. Second, as for this 
specific AD, in the event that the tie links were to become bent, it 
could lead to the elevator control forces being higher than normal, 
thus restricting the elevator control. This would be especially 
noticeable when larger elevator inputs are necessary, such as during 
takeoff, climb, and landing. The FAA considers this restriction of 
elevator control during these critical flight regimes to be an unsafe 
condition. (Further, since that language is not repeated in this final 
rule, no change is necessary.)

Request to Refer to Terminating Action

    The manufacturer requests that reference to ``see paragraph (e) for 
terminating action'' be added to paragraph (c)(2) of the proposed rule.
    The FAA does not concur. The FAA finds that it is unnecessary to 
reference paragraph (e) for operators who may be required to accomplish 
paragraph (c)(2) of the AD, since the terminating action specified in 
paragraph (e) of this AD is not a required terminating action.

Request to Change the Date of the Referenced Alert Service Bulletin

    Additionally, the manufacturer requests that the release date of 
Boeing Alert Service Bulletin 737-27A1194 be changed from February 1, 
1996, as specified in the proposed rule, to the actual release date of 
February 8, 1996.

[[Page 68568]]

    The FAA concurs. The FAA notes that the subject alert service 
bulletin dated February 1, 1996, has been replaced with the February 8, 
1996, version. The FAA has revised the final rule accordingly.

Additional Sources of Service Information

    Since the issuance of the proposed rule, the FAA has reviewed and 
approved Boeing Notices of Status Change (NSC) 737-27A1194 NSC 01, 
dated March 7, 1996, and 737-27A1194 NSC 02, dated April 4, 1996; and 
Boeing Alert Service Bulletin 737-27A1194, Revision 1, dated September 
26, 1996. The NSC's and service bulletin revision provide further 
clarification of the inspection and modification procedures required by 
this AD. Therefore, the FAA has revised the AD to cite those documents 
as additional sources of service information.

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 1,618 Boeing Model 737-300, -400, and -500 
series airplanes of the affected design in the worldwide fleet. The FAA 
estimates that 684 airplanes of U.S. registry will be affected by this 
AD, that it will take approximately 3 work hours per airplane to 
accomplish the required actions, and that the average labor rate is $60 
per work hour. Required parts will cost approximately $140 per 
airplane. Based on these figures, the cost impact of the AD on U.S. 
operators is estimated to be $218,880, or $320 per airplane.
    The cost impact figure discussed above is 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 adding the following new 
airworthiness directive:

96-25-17  Boeing: Amendment 39-9860. Docket 96-NM-23-AD.

    Applicability: Model 737-300, -400 and -500 series airplanes 
through line position 2764, inclusive; certificated in any category.

    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been 
otherwise 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 (f) 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 restriction of elevator control during takeoff, 
climbout, and landing, due to higher than normal elevator control 
forces caused by damaged tie links in the elevator centering unit, 
accomplish the following:
    (a) Within 6 months after the effective date of this AD: Perform 
a visual inspection to detect any bent or damaged tie links of the 
elevator feel and centering unit, in accordance with Boeing Alert 
Service Bulletin 737-27A1194, dated February 8, 1996, as revised by 
Boeing Notice of Status Change 737-27A1194 NSC 01, dated March 7, 
1996, and Boeing Notice of Status Change 737-27A1194 NSC 02, dated 
April 4, 1996; or Boeing Alert Service Bulletin 737-27A1194, 
Revision 1, dated September 26, 1996.
    (b) If no tie link is found to be broken, bent, or damaged 
during the inspection required by paragraph (a) of this AD: 
Accomplish either paragraph (b)(1) or (b)(2) of this AD, in 
accordance with Boeing Alert Service Bulletin 737-27A1194, dated 
February 8, 1996, as revised by Boeing Notice of Status Change 737-
27A1194 NSC 01, dated March 7, 1996, and Boeing Notice of Status 
Change 737-27A1194 NSC 02, dated April 4, 1996; or Boeing Alert 
Service Bulletin 737-27A1194, Revision 1, dated September 26, 1996.
    (1) Prior to further flight, install supports and a stop-bolt on 
the elevator centering unit. Once this installation is accomplished, 
no further action is required by this AD. Or
    (2) Repeat the inspection required by paragraph (a) of this AD 
thereafter at intervals not to exceed 1,000 flight cycles. 
Installation of supports and a stop-bolt in accordance with the 
alert service bulletin, constitutes terminating action for the 
repetitive inspections required by this AD, provided that no damage 
is detected during any inspection required by paragraph (a) of this 
AD.
    (c) If any tie link is found to be bent or damaged during the 
inspection required by paragraph (a) of this AD, and damage is 
within acceptable limits as specified in Figure 1 of Boeing Alert 
Service Bulletin 737-27A1194, dated February 8, 1996, Boeing Notice 
of Status Change 737-27A1194 NSC 01, dated March 7, 1996, and Boeing 
Notice of Status Change 737-27A1194 NSC 02, dated April 4, 1996; or 
as specified in Boeing Alert Service Bulletin 737-27A1194, Revision 
1, dated September 26, 1996: Accomplish paragraphs (c)(1) and (c)(2) 
of this AD in accordance with the alert service bulletin:
    (1) Repeat the inspection required by paragraph (a) of this AD 
thereafter at intervals not to exceed those specified in Figure 1 of 
the alert service bulletin. And
    (2) Within 6 months after the effective date of this AD, install 
supports and a stop-bolt on the elevator centering unit. This 
installation does not terminate the repetitive inspection 
requirements of this paragraph.
    (d) If any tie link is found to be bent or damaged during any 
inspection required by this AD, and the damage is beyond the 
acceptable limits as specified in Figure 1 of Boeing Alert Service 
Bulletin 737-27A1194, dated February 8, 1996, Boeing Notice of 
Status Change 737-27A1194 NSC 01, dated

[[Page 68569]]

March 7, 1996, and Boeing Notice of Status Change 737-27A1194 NSC 
02, dated April 4, 1996; or Boeing Alert Service Bulletin 737-
27A1194, Revision 1, dated September 26, 1996: Prior to further 
flight, replace the elevator centering unit with a new or 
serviceable unit and accomplish either paragraph (d)(1) or (d)(2) of 
this AD in accordance with the alert service bulletin:
    (1) Install supports and a stop-bolt on the elevator centering 
unit; or
    (2) Repeat the inspection required by paragraph (a) of this AD 
thereafter at intervals not to exceed 1,000 flight cycles until the 
installation specified in paragraph (d)(1) of this AD is 
accomplished.
    (e) Replacement of the elevator centering unit with a unit in 
which the tie links have been inspected and determined to be 
acceptable and in which supports and a stop-bolt have been 
installed, in accordance with Boeing Alert Service Bulletin 737-
27A1194, dated February 8, 1996, as revised by Boeing Notice of 
Status Change 737-27A1194 NSC 01, dated March 7, 1996, and Boeing 
Notice of Status Change 737-27A1194 NSC 02, dated April 4, 1996; or 
Boeing Alert Service Bulletin 737-27A1194, Revision 1, dated 
September 26, 1996, constitutes terminating action for the 
requirements of this AD.
    (f) 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.

    (g) 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.
    (h) The actions shall be done in accordance with Boeing Alert 
Service Bulletin 737-27A1194, dated February 8, 1996, as revised by 
Boeing Notice of Status Change 737-27A1194 NSC 01, dated March 7, 
1996, and Boeing Notice of Status Change 737-27A1194 NSC 02, dated 
April 4, 1996; or in accordance with Boeing Alert Service Bulletin 
737-27A1194, Revision 1, dated September 26, 1996. 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.
    (i) This amendment becomes effective on February 3, 1997.

    Issued in Renton, Washington, on December 11, 1996.
James V. Devany,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 96-32053 Filed 12-27-96; 8:45 am]
BILLING CODE 4910-13-U