[Federal Register Volume 62, Number 240 (Monday, December 15, 1997)]
[Rules and Regulations]
[Pages 65597-65600]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-32590]



[[Page 65597]]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 96-NM-147-AD; Amendment 39-10244; AD 97-26-01]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-100, -200, -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 737-100, -200, -300, -400, and -500 
series airplanes, that requires repetitive inspections to detect 
galling on the input shaft and bearing of the standby rudder power 
control unit (PCU), and replacement of the standby rudder actuator with 
a serviceable actuator, if necessary. This amendment also requires 
eventual replacement of the input bearing of the standby PCU with an 
improved bearing, which constitutes terminating action for the 
inspections to detect galling. This amendment is prompted by a review 
of the design of the flight control systems on Model 737 series 
airplanes. The actions specified by this AD are intended to prevent 
galling on the input shaft and bearing of the standby PCU, which could 
result in uncommanded movement of the rudder or increased pedal forces. 
These conditions, if not corrected, could result in reduced 
controllability of the airplane.

DATES: Effective January 20, 1998.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of January 20, 1998.

ADDRESSES: The service information referenced in this AD may be 
obtained from Dowty Aerospace Los Angeles, 1700 Business Center Drive, 
Duarte, California 91010-2859. 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: Kenneth W. Frey, 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) 227-2673; fax (425) 
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 all Boeing Model 737-100, -200, -
300, -400, and -500 series airplanes was published in the Federal 
Register on August 28, 1996 (61 FR 44234). That action proposed to 
require operational tests of the standby rudder power control unit 
(PCU) to ensure correct operation of the rudder, and correction of any 
discrepancy found; and repetitive inspections to detect galling on the 
input shaft and bearing of the standby PCU, and replacement of the 
standby rudder actuator with a serviceable actuator, if necessary. That 
action also proposed to require eventual replacement of the input 
bearing of the standby PCU with an improved bearing, which would 
constitute terminating action for the inspections to detect galling.

Actions Since the Issuance of the Proposal

    Since the issuance of the proposal, the FAA has reviewed and 
approved Dowty Aerospace Los Angeles Service Bulletin 1150-27-04, dated 
December 5, 1996, which describes procedures to replace the input shaft 
assembly and related hardware with a new, improved input shaft. The new 
input shaft uses radial bearings, which will prevent galling on the 
input shaft and bearing. Paragraph (b) of this final rule has been 
revised to reference the Dowty Aerospace service bulletin as an 
appropriate source of service information for accomplishment of the 
replacement.
    In addition, since the issuance of the proposal, the manufacturer 
has advised the FAA that the replacement of the input bearing of the 
standby PCU with an improved bearing has been incorporated on airplanes 
having line numbers 2815 and subsequent. Therefore, the FAA has revised 
the applicability of this final rule to include only airplanes having 
line numbers 1 through 2814 inclusive.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.

Request To Revise Statement of Findings of Critical Design Review 
Team

    One commenter requests the second paragraph of the Discussion 
section that appeared in the preamble to the proposed rule be revised 
to accurately reflect the findings of the Critical Design Review (CDR) 
team. The commenter asks that the FAA delete the one sentence in that 
paragraph that reads: ``The recommendations of the team include various 
changes to the design of the flight control systems of these airplanes, 
as well as correction of certain design deficiencies.'' The commenter 
suggests that the following sentences should be added: ``The team did 
not find any design issues that could lead to a definite cause of the 
accidents that gave rise to this effort. The recommendations of the 
team include various changes to the design of the flight control 
systems of these airplanes, as well as incorporation of certain design 
improvements in order to enhance its already acceptable level of 
safety.''
    The FAA does not find that a revision to this final rule in the 
manner suggested by the commenter is necessary, since the Discussion 
section of a proposed rule does not reappear in a final rule. The FAA 
acknowledges that the CDR team did not find any design issue that could 
lead to a definite cause of the accidents that gave rise to this 
effort. However, as a result of having conducted the CDR of the flight 
control systems on Boeing Model 737 series airplanes, the team 
indicated that there are a number of recommendations that should be 
addressed by the FAA for each of the various models of the Model 737. 
In reviewing these recommendations, the FAA has concluded that they 
address unsafe conditions that must be corrected through the issuance 
of AD's. Therefore, the FAA does not concur that these design changes 
merely ``enhance [the Model 737's] already acceptable level of 
safety.''

Request To Delete Operational Test Requirement

    Several commenters request that the requirement to perform the 
operational tests to cycle hydraulic fluid through the standby rudder 
PCU and to ensure correct operation of the rudder when the standby 
hydraulic system is powered) be deleted from the proposal. These 
commenters point out that the Boeing Service Letter referenced in 
paragraph (a) of the proposal does not provide a description of 
procedures to perform the operational tests and does not include 
instructions to correct any discrepancies found. Another commenter 
requests that paragraph (a) be deleted from the proposal because it is 
not a technically sound approach to eliminating galling. This commenter 
states that the only way to prevent galling is to upgrade the input 
bearing of the standby hydraulic system.

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    The FAA concurs that replacement of the input bearing of the 
standby hydraulic system with a new, improved (upgraded) input bearing 
is a technically sound approach to eliminate galling. The requirement 
to replace the input bearing with a new, improved input bearing within 
3 years, as specified in the proposed AD, supports that approach. 
Accordingly, this final rule has been revised to delete the proposed 
requirement for operational tests. The FAA finds that, until the 
replacement of the input bearing is required, repetitive inspections to 
detect galling of the input shaft and bearing, and replacement with a 
serviceable standby rudder actuator, if necessary (as specified in the 
proposed AD), will positively address the unsafe condition.

Request To Extend the Compliance Time for Operational Tests

    Several commenters request that the compliance time be extended for 
the operational tests discussed previously. The commenters request that 
the compliance time for the repetitive operational tests be extended 
from the proposed ``at intervals not to exceed 250 hours time-in-
service'' to ``at intervals not to exceed 800 hours time-in-service.'' 
The commenters state that the recent FAA MSG-3 analysis on the 
hydraulic fluid compound revealed that the appropriate interval for the 
operational test is every 800 hours time-in-service.
    As explained previously, the FAA has removed the requirement for 
operational tests from the final rule; however, this final rule is 
considered to be interim action. The FAA may consider further 
rulemaking to require operational tests of the standby system and 
correction of any discrepancies. The FAA will consider the results of 
the previously discussed MSG-3 analysis in determining an appropriate 
compliance time for future proposed operational tests.

Request To Extend the Compliance Times for Inspections for Galling

    Several commenters request that the compliance time for the initial 
and repetitive inspections for galling be extended from 3,000 hours 
time-in-service to ``18 months or 4,500 hours time-in-service'' for the 
proposed inspections to detect galling on the input shaft and bearing 
of the standby rudder PCU. The commenters state that 18 months or 4,500 
hours time-in-service closely corresponds to a ``C'' check, which 
allows operators to schedule maintenance at a heavy maintenance base 
without impacting safety. One commenter suggests that the initial 
inspection and repetitive interval inspections should be extended to 
46,000 flight hours. (The FAA infers that the ``46,000'' flight hours 
is a typographical error and that the commenter actually requests an 
extension to 4,600 flight hours.)
    The FAA concurs with the commenters' request to revise the 
compliance time to 18 months or 4,500 hours time-in-service (whichever 
occurs later) since the last inspection. The FAA finds that this 
extension of the compliance time will not adversely affect safety, and 
will more closely correspond to the operators' scheduled ``C'' checks. 
The FAA has revised paragraph (a) of this final rule accordingly.

Requests To Revise the Compliance Time for Replacement of the Input 
Bearing

    One commenter (the airplane manufacturer) requests that the 
proposed compliance time for replacement of the input bearing be 
changed from 3 to 4 years after the effective date of the AD. The 
commenter states that the inspection should be accomplished at least 
once in 4 years, and the inspection should detect any units that are 
galled. Another commenter requests that the replacement be required by 
August 1, 1997. This commenter states that the National Transportation 
Safety Board (NTSB) suggests that date in a recommendation to the FAA.
    The FAA does not concur that the compliance time should be revised. 
In developing an appropriate compliance time for this action, the FAA 
considered not only the degree of urgency associated with addressing 
the subject unsafe condition, but the availability of required parts 
and the practical aspect of accomplishing the required replacement 
within an interval of time that parallels normal scheduled maintenance 
for the majority of affected operators. The manufacturer has advised 
that an ample number of required parts will be available for 
modification of the U.S. fleet within the compliance period. However, 
under the provisions of this final rule, the FAA may approve requests 
for adjustments to the compliance time if data are submitted to 
substantiate that such adjustments would provide an acceptable level of 
safety.

Request To Delete (or Make Optional) the Replacement Requirement

    Several commenters request that the proposed replacement 
requirement be deleted to provide more time to review the retrofit 
program. One commenter suggests that the requirement should be 
optional, as long as the inspection to detect galling on the PCU input 
shaft is carried out repetitively every 46,000 flight hours. The 
commenter does not provide a justification for the recommended 46,000 
flight hours. (The FAA infers that the ``46,000'' flight hours is a 
typographical error and that the commenter actually requests a 
compliance time of 4,600 flight hours.)
    The FAA does not concur with the commenters' requests. Although the 
repetitive inspections required by this final rule may detect galled 
units before the galling progresses to a level that would affect the 
flight control system, the inspections do not ensure that galling will 
not occur. The replacement of the input bearing with a new, improved 
bearing, as described in the Dowty Aerospace service bulletin discussed 
previously, will positively address the subject unsafe condition and 
provide an acceptable level of safety.
    The FAA has determined that long term continued operational safety 
will be better assured by modifications or design changes to remove the 
source of the problem, rather than by repetitive inspections. Long term 
inspections 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 repetitive 
inspections, has led the FAA to consider placing less emphasis on 
special procedures and more emphasis on design improvements. The 
replacement requirement is in consonance with these considerations.

Request To Revise the Cost Estimate

    One commenter, the airplane manufacturer, requests that the cost 
estimate for the proposed inspections be revised from $60 to $120 per 
airplane, per inspection cycle. The FAA acknowledges that the correct 
cost estimate is $120 per airplane, per inspection cycle, and has 
revised the cost impact information, below, accordingly.

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 
significantly increase the economic burden on any operator nor increase 
the scope of the AD.

[[Page 65599]]

Cost Impact

    There are approximately 2,830 Model 737 series airplanes of the 
affected design in the worldwide fleet. The FAA estimates that 1,037 
airplanes of U.S. registry would be affected by this proposed AD.
    The FAA estimates that it will take approximately 2 work hours per 
airplane to accomplish the required inspections, at an average labor 
rate of $60 per work hour. Based on these figures, the cost impact of 
the required inspections on U.S. operators is estimated to be $124,440, 
or $120 per airplane, per inspection cycle.
    The FAA estimates that it will take approximately 2 work hours per 
airplane to accomplish the required replacement, at an average labor 
rate of $60 per work hour. The cost of the replacement parts is 
estimated to be $793 per airplane. Based on these figures, the cost 
impact of the required replacement is estimated to be $946,781, or $913 
per airplane.
    The cost impact figures discussed above are based on assumptions 
that no operator has yet accomplished any of the proposed 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:

97-26-01  Boeing: Amendment 39-10244. Docket 97-NM-147-AD.

    Applicability: Model 737-100, -200, -300, -400, and -500 series 
airplanes, having line numbers 1 through 2814 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 (c) 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 uncommanded movement of the rudder or increased 
rudder pedal forces, and consequent reduced controllability of the 
airplane, accomplish the following:
    (a) Within 18 months or 4,500 hours time-in-service after the 
effective date of this AD, whichever occurs later; and thereafter at 
intervals not to exceed 18 months or 4,500 hours time-in-service, 
whichever occurs later: Perform an inspection to detect galling on 
the input shaft and bearing of the standby rudder PCU by 
accomplishing paragraphs (a)(1) through (a)(10) of this AD.
    (1) Shut off all hydraulic power.
    (2) Gain access to the standby rudder actuator.
    (3) Disconnect the input rod from the standby actuator.
    (4) Using a push/pull spring scale (minimum +/-10% accuracy at 
1.0 pound; preferably one having a peak load memory function), push 
on the standby rudder actuator input lever with sufficient force to 
move the lever from the neutral position up to, but not touching, 
the aft stop. The scale must be contacting the input lever at 
approximately the clevis bolt centerline. While applying the load 
required to move the lever, the scale must be maintained at an angle 
perpendicular to the lever arm (not to exceed 20 degrees from 
perpendicular). The force required to move the input lever 
throughout this range of motion must not exceed one pound.
    (5) Repeat the test specified in paragraph (a)(4) of this AD, 
moving the lever arm from the aft stop position up to the forward 
stop, but not touching. The force required to move the input lever 
throughout this range of motion must not exceed one pound.
    (6) Repeat the test specified in paragraph (a)(4) of this AD, 
moving the lever arm from the forward stop position back to the 
neutral position. The force required to move the input lever 
throughout this range of motion must not exceed one pound.
    (7) If the actuator force encountered during any of the 
procedures required by paragraph (a)(4), (a)(5), or (a)(6) of this 
AD exceeds one pound, prior to further flight, replace the standby 
rudder actuator with a serviceable actuator, and test the standby 
rudder actuator in accordance with the procedure specified in 
paragraph (a)(9) of this AD.
    (8) If the actuator force encountered during any of the 
procedures required by paragraph (a)(4), (a)(5), or (a)(6) of this 
AD is one pound or less, prior to further flight, reconnect the 
input rod to the standby rudder actuator, and test the standby 
rudder actuator in accordance with the procedure specified in 
paragraph (a)(9) of this AD.
    (9) Perform a functional test of the standby rudder actuator in 
accordance with Maintenance Manual 737-100/-200, Chapter 27-21-141, 
removal/installation (for Model 737-100 and -200 series airplanes); 
or maintenance Manual 737-300/-400/-500, Chapter 27-21-24, removal/
installation (for Model 737-300, -400, and -500 series airplanes).
    (10) Restore the airplane to its normal condition.
    (b) Within 3 years after the effective date of this AD, replace 
the input bearing of the standby rudder PCU with an improved bearing 
in accordance with Dowty Aerospace Los Angeles Service Bulletin 
1150-27-04, dated December 5, 1996; or in accordance with a method 
approved by the Manager, Seattle Aircraft Certification Office 
(ACO), FAA, Transport Airplane Directorate. Replacement of the input 
bearing with an improved bearing in accordance with the service 
bulletin constitutes terminating action for the requirements of this 
AD.
    (c) 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, 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.

    (d) 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.

[[Page 65600]]

    (e) Except as provided by paragraph (b) of this AD, the 
replacement shall be done in accordance with Dowty Aerospace Los 
Angeles Service Bulletin 1150-27-04, dated December 5, 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 Dowty Aerospace Los Angeles, 1700 
Business Center Drive, Duarte, California 91010-2859. 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.
    (f) This amendment becomes effective on January 20, 1998.

    Issued in Renton, Washington, on December 8, 1997.
Stewart R. Miller,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 97-32590 Filed 12-12-97; 8:45 am]
BILLING CODE 4910-13-U