[Federal Register Volume 63, Number 226 (Tuesday, November 24, 1998)]
[Rules and Regulations]
[Pages 64857-64859]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-31325]


-----------------------------------------------------------------------

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-NM-157-AD; Amendment 39-10912; AD 97-09-15 R1]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-100, -200, -300, -400, 
and -500 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.


[[Page 64858]]


ACTION: Final rule.

-----------------------------------------------------------------------

SUMMARY: This amendment revises an existing airworthiness directive 
(AD), applicable to all Boeing Model 737-100, -200, -300, -400, and -
500 series airplanes, that currently requires a one-time inspection to 
determine the part number of the engage solenoid valve of the yaw 
damper on the rudder power control unit, and replacement of the valve 
with a valve having a different part number, if necessary. That AD was 
prompted by a review of the design of the flight control systems on 
Model 737 series airplanes. The actions specified by that AD are 
intended to prevent sudden uncommanded yawing of the airplane due to 
potential failures within the yaw damper system, and consequent injury 
to passengers and crewmembers. This amendment makes certain editorial 
changes to clarify the requirements of the existing AD.

EFFECTIVE DATE: December 29, 1998.

ADDRESSES: Information pertaining to this AD may be examined at the 
Federal Aviation Administration (FAA), Transport Airplane Directorate, 
Rules Docket, 1601 Lind Avenue, SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT: Tin Truong, Aerospace Engineer, ANM-
130S, FAA, Transport Airplane Directorate, Seattle Aircraft 
Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-
4056; telephone (425) 227-2764; fax (425) 227-1181.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal 
Aviation Regulations (14 CFR part 39) by revising AD 97-09-15, 
amendment 39-10011 (62 FR 24325, May 5, 1997), which is applicable to 
all Boeing Model 737-100, -200, -300, -400, and -500 series airplanes, 
was published in the Federal Register on November 13, 1997 (62 FR 
60808). The action proposed to continue to require a one-time 
inspection to determine the part number of the engage solenoid valve of 
the yaw damper on the rudder power control unit (PCU), and replacement 
of the valve with a valve having a different part number, if necessary. 
The action also proposed to make certain editorial changes to clarify 
the requirements of the existing AD.
    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

    Two commenters support the proposal.

Request To Withdraw the Proposed AD

    One commenter states that the proposed AD is unwarranted because it 
is purely editorial rather than technical in nature and requests that 
it be withdrawn. The commenter states that there is only one solenoid 
valve of the part number identified in AD 97-09-15 that is used in the 
yaw damper system, so it should be evident that the valve in question 
is that of the PCU. In addition, the commenter states that, although 
the vendor part numbers are not contained in AD 97-09-15, they are easy 
to convert to the appropriate vendor numbers from cross references 
located in the Illustrated Parts Catalog (IPC) and the Component 
Maintenance Manual (CMM). The commenter also states that, although the 
aircraft maintenance manual chapter referenced in AD 97-09-15 is 
technically incorrect for certain Model 737-100 and -200 series 
airplanes, the obvious intent of AD 97-09-15 is to ensure that the 
specified solenoid valve is installed, and the procedures for 
replacement should obviously be those applicable for routine valve 
replacement. The commenter also notes that AD 97-14-04, amendment 39-
10061 (62 FR 35068, June 30, 1997), which requires modification of the 
rudder PCU, will drive the inspection to be done in a shop environment, 
which would then require the use of the rudder PCU CMM, rather than the 
aircraft maintenance manual, for this inspection. Further, the 
commenter states that although the vendor name labeled on the affected 
parts may vary, the part number, function, and location do not.
    The FAA does not concur that the revision is unwarranted. The FAA 
agrees that there is only one solenoid valve of the part number 
identified in AD 97-09-15 that is used in the yaw damper system; 
however, this final rule is clearer and will prevent confusion. In 
addition, it is not appropriate to determine the vendor part number 
using the IPC because the IPC is not an FAA-approved document and its 
use does not ensure correlation of the appropriate part number. 
Therefore, it is necessary to identify all Boeing and vendor part 
numbers in the AD to ensure appropriate installation. Also, the FAA 
does not agree with the commenter that maintenance manual references in 
AD 97-09-15 are sufficient to ensure the use of proper maintenance 
procedures for valve installation. The FAA also does not agree with the 
comment that compliance with AD 97-14-04 will ensure that the required 
inspection will be done only in a shop environment. This final rule 
allows operators the flexibility to perform this inspection on the 
airplane or in the shop. The FAA agrees that, although the vendor name 
labeled on the affected parts may vary, the part number, function, and 
location do not; however, this final rule is clearer and will prevent 
confusion.

Request To Revise Corrective Action

    One commenter requests that the requirement to replace a suspect 
engage solenoid valve prior to further flight be deleted. The commenter 
states that this requirement is too restrictive and could lead to 
unnecessary airplane grounding if a valve having the appropriate part 
number is unavailable. The FAA does not concur. 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 installing the required modification 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 specified compliance period. No change to the 
rule is necessary.

Request To Include All Applicable Maintenance Manual Chapters

    One commenter states that Boeing Maintenance Manual Chapter 22-12-
21 is applicable for some operators of Model 737-100 and -200 series 
airplanes and that use of the procedures contained in Chapter 22-12-21 
should be allowed to accomplish the actions in this AD. The FAA concurs 
and has revised paragraph (a) of the final rule accordingly.

Request for Credit of Previously Accomplished Work

    One commenter requests that, because the proposed revisions to the 
AD are editorial in nature, a statement be added to the AD to state 
that work already accomplished on any airplanes affected by AD 97-09-15 
should not require additional action. The commenter also requests that 
all previously approved alternative methods of compliance should remain 
valid and in effect.
    The FAA agrees with the commenter that this AD does not change the 
required actions of AD 97-09-15 and that any airplanes inspected and 
modified in accordance with AD 97-09-15 would not require additional 
action. However, operators are always given credit for work previously 
performed in accordance with the existing AD by means of the phrase in 
the compliance

[[Page 64859]]

section of the AD that states, ``Required * * * unless accomplished 
previously.'' Further, no alternative methods of compliance have been 
approved for the AD 97-09-15. Therefore, no change to the rule is 
necessary in this regard.

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 change previously 
described. The FAA has determined that this change will neither 
increase the economic burden on any operator nor increase the scope of 
the AD.

Cost Impact

    There are approximately 2,675 Boeing Model 737 series airplanes of 
the affected design in the worldwide fleet. The FAA estimates that 
1,091 airplanes of U.S. registry will be affected by this AD.
    It will take approximately 1 work hour per airplane to accomplish 
the required one-time inspection, at an average labor rate of $60 per 
work hour. Based on these figures, the cost impact of the inspection 
required by this AD on U.S. operators is estimated to be $65,460, or 
$60 per airplane. The requirements of this AD will add no new costs to 
affected operators.
    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, 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 39-10011 (62 FR 
24325, May 5, 1997), and by adding a new airworthiness directive (AD), 
amendment 39-10912, to read as follows:

97-09-15 R1 Boeing: Amendment 39-10912. Docket 97-NM-157-AD. Revises 
AD 97-09-15, Amendment 39-10011.

    Applicability: All Model 737-100, -200, -300, -400, and -500 
series 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 (b) 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 sudden uncommanded yawing of the airplane due to 
potential failures within the yaw damper system, and consequent 
injury to passengers and crewmembers, accomplish the following:
    (a) Perform a one-time inspection of the engage solenoid valve 
of the yaw damper on the rudder power control unit (PCU) to 
determine the part number (P/N) of the valve. If any valve having 
Parker P/N 59600-5011 (Boeing P/N 10-60811-9), Parker P/N 59600-5007 
(Boeing P/N 10-60811-3), or Parker P/N 59600-5003 (Boeing P/N 10-
60811-1) is installed, prior to further flight, replace it with a 
valve having Parker P/N 881600-1001 (Boeing P/N 10-60811-13), Sterer 
P/N 45080-1 (Boeing P/N 10-60811-8), or Sterer P/N 45080 (Boeing P/N 
10-60811-3). Accomplish the actions in accordance with procedures 
specified in Chapters 22-11-61 or 22-12-21 (for Model 737-100 and -
200 series airplanes), as applicable; or Chapter 22-12-21 (for Model 
737-300, -400, and -500 series airplanes) of the Boeing Maintenance 
Manual, as applicable. Accomplish the inspection at the earlier of 
the times specified in paragraphs (a)(1) and (a)(2) of this AD.
    (1) Within 5 years or 15,000 flight hours after June 9, 1997 
(the effective date of AD 97-09-15, amendment 39-10011), whichever 
occurs first.
    (2) At the next time the PCU is sent to a repair facility.

    Note 2: Boeing In-Service Activities Report 95-03-2725-10, dated 
February 16, 1995 (for Model 737-100 and -200 series airplanes), or 
95-04-2725-10, dated February 24, 1995 (for Model 737-300, -400, and 
-500 series airplanes), provides additional information concerning 
interchangeability of solenoid valve part numbers.

    Note 3: Operators should note that, as specified in paragraph 
(a) of this AD, both the Parker and Sterer P/N's have the same 
Boeing P/N (10-60811-3). If, upon inspection, Boeing P/N 10-60811-3 
is found to be installed, operators must ascertain the vendor P/N. 
Parts having Boeing P/N 10-60811-3 and Parker P/N 59600-5007 must be 
replaced and are not considered to be acceptable replacement parts. 
In addition, some engage solenoid valves may be labeled with only 
the name ``Bertea,'' rather than ``Parker'' or ``Parker-Bertea.''

    (b) 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 4: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

    (c) 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.
    (d) This amendment becomes effective on December 29, 1998.

    Issued in Renton, Washington, on November 18, 1998.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 98-31325 Filed 11-23-98; 8:45 am]
BILLING CODE 4910-13-U