Airworthiness Directives; Boeing Model 737 Series Airplanes

[Federal Register Volume 64, Number 238 (Monday, December 13, 1999)]
[Rules and Regulations]
[Pages 69392-69394]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-32193]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-383-AD; Amendment 39-11175; AD 99-11-05]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; correction.

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SUMMARY: This document corrects and clarifies information in an 
existing airworthiness directive (AD) that applies to all Boeing Model 
737 series airplanes. That AD currently requires repetitive 
displacement tests of the secondary slide in the dual concentric servo 
valve of the power control unit (PCU) for the rudder, and replacement 
of the valve assembly with a modified valve assembly, if necessary. 
This document corrects certain PCU part and serial numbers and 
clarifies that PCU's with certain other serial numbers are not required 
to comply with the requirements of this AD. This correction is 
necessary to prevent failure of the secondary slide and consequent 
rudder hardover and reduced controllability of the airplane.

DATES: Effective June 28, 1999.
    The incorporation by reference of certain publications, as listed 
in the regulations, was approved previously by the Director of the 
Federal Register as of June 28, 1999 (64 FR 27905, May 24, 1999).

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: On May 13, 1999, the Federal Aviation 
Administration (FAA) issued AD 99-11-05, amendment 39-11175 (64 FR 
27905, May 24, 1999), which applies to all Boeing Model 737 series 
airplanes. That AD requires repetitive displacement tests of the 
secondary slide in the dual concentric servo valve of the power control 
unit (PCU) for the rudder, and replacement of the valve assembly with a 
modified valve assembly, if necessary. That AD was prompted by reports 
of cracking found in PCU secondary servo valve slides. The actions 
specified by that AD are intended to prevent failure of the secondary 
slide and consequent rudder hardover and reduced controllability of the 
airplane.

Need for the Correction

    Information received recently from the manufacturer indicates that 
the following clarifications and corrections are necessary. Paragraph 
(a)(2) of this AD was intended to address certain PCU's that are 
installed only after the effective date of the AD, and has been revised 
to clarify that intent. [Paragraph (a) of this AD already addresses

[[Page 69393]]

airplanes on which these PCU's had been installed before the effective 
date.] As reflected in the applicable service bulletin referenced in 
this AD, paragraph (a)(2) also was intended to address the PCU's having 
part number 65C37053-(XX), but that reference was omitted from the 
final rule. Similarly, as reflected in the applicable service bulletin, 
paragraph (a)(3) was intended to address only identified airplanes that 
are equipped with certain PCU's. However, as adopted, the final rule 
was not so limited. [Airplanes having other PCU's are subject to the 
longer compliance time specified in paragraph (a)(4)]. The references 
to these part numbers have been added to this AD.
    Finally, the FAA has revised paragraph (c) of this AD to more 
clearly specify the actuators that may be installed after the effective 
date of this AD. The FAA has determined that some PCU's (referenced in 
Boeing Alert Service Bulletin 737-27A1221, Revision 1, and Boeing Alert 
Service Bulletin 737-27A1222, Revision 1, both dated January 28, 1999) 
have been displacement tested, but have not been vibro engraved with 
the letter ``C.'' (Subsequent serial numbers greater than those 
specified in this AD are displacement tested as part of the certified 
production process, and are not vibro engraved.) The FAA has determined 
that, for PCU's having the specified serial numbers, only those that 
are vibro engraved with the letter ``C'' are in compliance with the 
requirements of this AD. Therefore, paragraph (c) of this AD has been 
corrected by removing the phrase ``or letters greater than `C'.''

Correction of Publication

    This document corrects the error and correctly adds the AD as an 
amendment to section 39.13 of the Federal Aviation Regulations (14 CFR 
39.13).
    The AD is reprinted in its entirety for the convenience of affected 
operators. The effective date of the AD remains June 28, 1999.
    Since this action only corrects and clarifies the current 
requirements, it has no adverse economic impact and imposes no 
additional burden on any person. Therefore, the FAA has determined that 
notice and public procedures are unnecessary.

List of Subject in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

Adoption of the Correction

    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  [Corrected]

    2. Section 39.13 is amended by correctly adding the following 
airworthiness directive (AD):

99-11-05  Boeing: Amendment 39-11175. Docket 98-NM-383-AD.

    Applicability: All Model 737 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 (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 secondary servo valve slide in the 
rudder power control unit (PCU) due to cracking of the slide, and 
consequent rudder hardover and reduced controllability of the 
airplane, accomplish the following:

Displacement Testing

    (a) Perform a displacement test of the secondary slide in the 
dual servo valve in the rudder PCU, in accordance with Boeing Alert 
Service Bulletin 737-27A1221, Revision 1, dated January 28, 1999 
(for Model 737-100, -200, -300, -400, and -500 series airplanes); or 
737-27A1222, Revision 1, dated January 28, 1999 (for Model 737-600, 
-700, and -800 series airplanes); at the applicable time specified 
by paragraph (a)(1), (a)(2), (a)(3), or (a)(4) of this AD. Repeat 
the displacement test on that PCU thereafter at intervals not to 
exceed 24,000 flight hours.

    Note 2: Accomplishment of the initial displacement testing 
required by paragraph (a) of this AD in accordance with Boeing Alert 
Service Bulletin 737-27A1221, dated January 14, 1999 (for Model 737-
100, -200, -300, -400, and -500 series airplanes); or 737-27A1222, 
dated January 14, 1999 (for Model 737-600, -700, and -800, series 
airplanes) is acceptable only for the initial compliance 
requirements of this AD.

    (1) For Model 737-100, -200, -300, -400, and -500 series 
airplanes: Conduct the displacement test within 16 months after the 
effective date of this AD.
    (2) For airplanes on which a PCU specified in paragraph 
(a)(2)(I) or (a)(2)(ii) of this AD is installed within 16 months 
after the effective date of this AD: Conduct the displacement test 
within 16 months after the effective date of this AD.
    (i) Part number 65-44861-12 and having serial number (S/N) 3509A 
or lower,
    (ii) Part number 65C37053-(XX).
    (3) For Model 737-600, -700, and -800 series airplanes having 
line numbers 1 through 222 inclusive that are equipped with PCU's 
having P/N 251A301-(XX) and serial number 299 or lower: Conduct the 
displacement test within 16 months after the effective date of this 
AD.
    (4) For all other airplanes: Conduct the displacement test prior 
to the accumulation of 24,000 total flight hours on the PCU, or 
within 30 days after the effective date of this AD, whichever occurs 
later.

Corrective Actions

    (b) If the results of the displacement test required by 
paragraph (a) of this AD are outside the limits specified by Boeing 
Alert Service Bulletin 737-27A1221, Revision 1, dated January 28, 
1999 (for Model 737-100, -200, -300, -400, and -500 series 
airplanes), or 737-27A1222, Revision 1, dated January 28, 1999 (for 
Model 737-600, -700, and -800 series airplanes): Prior to further 
flight, accomplish the actions specified in paragraphs (b)(1) and 
(b)(2) of this AD.
    (1) Replace the valve assembly, in accordance with the 
applicable alert service bulletin, with a serviceable valve 
assembly. And
    (2) Following installation of the replacement valve assembly in 
accordance with paragraph (b)(1) of this AD, perform the 
displacement test required by paragraph (a) of this AD on that 
assembly, in accordance with the applicable alert service bulletin. 
If the test results are outside the limits specified by the 
applicable alert service bulletin, prior to further flight, replace 
the valve assembly with a serviceable valve assembly in accordance 
with the applicable alert service bulletin, and repeat the 
displacement test required by paragraph (a) of this AD on that 
assembly.

    Note 3: Boeing Alert Service Bulletin 737-27A1222, Revision 1, 
dated January 28, 1999, refers to Parker Service Bulletin 381500-27-
01, dated December 22, 1998, as an additional source of service 
information for accomplishment of the displacement test for Model 
737-600, -700, and -800 series airplanes.

    (c) As of 16 months after the effective date of this AD, no 
person shall install a main rudder PCU specified in paragraph (c)(1) 
or (c)(2) of this AD unless that PCU's nameplate has been vibro-
engraved with the letter ``C'' following the serial number. 
(Subsequent serial numbers greater than those listed below are 
displacement tested as part of the certified production process, and 
do not require the letter ``C'' to be vibro-engraved.)
    (1) For Boeing Model 737-100, -200, -300, -400, and -500 series 
airplanes: A PCU having P/N 65-44861-12 and a serial number (S/N) 
3509A or lower; or any PCU having P/N 65C37053-(XX).
    (2) For Boeing Model 737-600, -700, and -800 series airplanes: A 
PCU having P/N 251A301-(X) and a S/N 0299 or lower.

[[Page 69394]]

    (d)(1) Within 30 days after accomplishing the initial 
displacement test required by paragraph (a) of this AD: Submit a 
report of the testing to the Manager, Seattle Aircraft Certification 
Office (ACO), FAA, Transport Airplane Directorate, 1601 Lind Avenue, 
SW., Renton, Washington 98055-4056; fax (425) 227-1181. The report 
must include the displacement testing results (both positive and 
negative findings), test data for any failed valve assemblies, a 
description of any discrepancies if found, the part number and 
serial number of each rudder PCU tested, and the airplane serial 
number.
    (2) Within 30 days after accomplishing any repetitive 
displacement testing required by paragraph (a) of this AD: Submit a 
report of any failed valve assembly to the Manager, Seattle Aircraft 
Certification Office (ACO), FAA, Transport Airplane Directorate, 
1601 Lind Avenue, SW., Renton, Washington 98055-4056; fax (425) 227-
1181. The report must include the displacement testing results of 
any failed valve assembly, test data for any failed valve 
assemblies, a description of any discrepancies found, the part 
number and serial number of each rudder PCU with a failed valve 
assembly, and the airplane serial number.
    (3) Within 30 days after accomplishing the initial displacement 
test required by paragraph (a) of this AD: Submit failed valve 
assemblies for analysis to Parker Hannifin Corporation, Chief 
Engineer, Customer Support Operations, 16666 Von Karman Avenue, 
Irvine, California 92606.
    (4) 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 4: 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) The actions shall be done in accordance with Boeing Alert 
Service Bulletin 737-27A1221, Revision 1, dated January 28, 1999, or 
Boeing Alert Service Bulletin 737-27A1222, Revision 1, dated January 
28, 1999. This incorporation by reference of those documents was 
previously approved by the Director of the Federal Register as of 
June 28, 1999 (64 FR 27905, May 24, 1999). 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) The effective date of this amendment remains June 28, 1999.

    Issued in Renton, Washington, on December 7, 1999.
D.L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-32193 Filed 12-10-99; 8:45 am]
BILLING CODE 4910-13-P

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