[Federal Register Volume 61, Number 221 (Thursday, November 14, 1996)]
[Rules and Regulations]
[Pages 58316-58318]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-28689]


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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 96-NM-06-AD; Amendment 39-9809; AD 96-23-04]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-100 and -200 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 and -200 series airplanes, 
that requires replacement of the 250 volt-ampere (VA) rated static 
inverters with 410 VA or 500 VA rated static inverters, and an 
operational test of the standby electrical power system. This amendment 
is prompted by a report that accomplishment of a certain modification 
could result in overload of the static inverter on these airplanes. The 
actions specified by this AD are intended to prevent overload of the 
static inverter, which could result in the loss of the 115 volt 
alternating current (VAC) standby bus and the associated flight 
instruments when the airplane is operating on standby electrical power.

DATES: Effective December 19, 1996.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of December 19, 1996.

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: Stephen Oshiro, 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 (206) 227-2793; 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 737-100 and -
200 series airplanes was published in the Federal Register on June 7, 
1996 (61 FR 29038). That action proposed to require replacement of the 
250 VA rated static inverters with certain 410 VA or 500 VA-rated 
static inverters.
    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 proposed rule.

Request To Revise the Applicability of the Proposed Rule

    The manufacturer requests that the applicability of the proposed 
rule be revised to specify that the only Model 737-100 and -200 series 
airplanes affected by the AD are those that are listed in Boeing Alert 
Service Bulletin 737-24A1113, dated February 29, 1996. The manufacturer 
indicates that it has reviewed the loading of the 115 VAC standby 
electrical power bus of the Model 737-100 and -200 series airplanes 
that were delivered with 250 VA static inverters and modified in 
accordance with Boeing Service Bulletin 737-24-1051. This review 
verified that the 115 VAC standby bus of some of the 250VA static 
inverters installed on airplanes that had been modified in accordance 
with Boeing Service Bulletin 737-24-1051 are less heavily loaded than 
others and, therefore, are not susceptible to the addressed unsafe 
condition. The commenter states that, for 21 of the airplanes specified 
in the applicability of the proposal, the currently-installed 250 VA 
static inverter is adequate and need not be replaced.
    The FAA concurs. The FAA's initial assessment of the unsafe 
condition concluded that all Model 737-100 and -200 series airplanes 
equipped with 250

[[Page 58317]]

VA static inverters and modified in accordance with Boeing Service 
Bulletin 737-24-1051 were susceptible to overloading of the static 
inverters. Since issuance of the proposal, however, the FAA has 
reviewed the electrical load analysis conducted by the manufacturer and 
agrees that, for the 21 identified airplanes, the 250 VA static 
inverter does possess sufficient capacity to preclude the unsafe 
condition. The FAA finds that the airplanes listed in the effectivity 
listing of Boeing Alert Service Bulletin 737-24A1113, dated February 
29, 1996, are the only ones subject to the unsafe condition addressed 
by this AD action. Accordingly, the applicability of this final rule 
has been revised to indicate this. Additionally, the cost impact 
information, discussed below, has been revised to clarify the number of 
affected airplanes.

Request To Allow Replacement With Any FAA-Approved Static Inverter

    One commenter requests that paragraph (a) of the proposal be 
revised to allow any FAA-approved 410 VA-rated or 500 VA-rated static 
inverter to be used as a replacement part, instead of requiring the 
installation of specific static inverters by part number. This 
commenter considers that such a change to the proposed rule would 
alleviate the need for operators to obtain approvals for use of 
alternative methods of compliance in the event that a new static 
inverter with a new part number is developed in the future.
    The FAA does not concur with the commenter's request. While other 
static inverters may be FAA-approved, the static inverters having the 
part numbers specified in this AD are the only 410 VA and 500 VA 
inverters that have been approved specifically for use in Boeing Model 
737-100 and -200 series airplanes. These units have been demonstrated 
to be compatible with the electrical power system and the 
electromagnetic environment of those airplane models. The FAA must 
ensure that only these units, which have been tested for compatibility 
with the affected airplane models, be used to satisfy the requirements 
of this AD.

Request To Include Additional Maintenance Manual Reference

    One commenter requests that paragraph (a) of the proposal be 
revised to indicate that the operational test of the standby electrical 
power system may be performed in accordance with Section 24-54-2, as 
well as Section 24-54-0, of the Model 737 Maintenance Manual. The 
commenter points out that, for some of the affected operators, the 
operational test is located in Section 24-54-2 instead of Section 24-
54-0 (which was the only Section specified in the proposal).
    The FAA concurs with the commenter's request and has revised 
paragraph (a) of this final rule accordingly.
    The FAA also has revised paragraph (a) to include Boeing Alert 
Service Bulletin 737-24A1113 as an additional source of appropriate 
service instructions for accomplishing both the replacement of the 
static inverter and the operational test of the associated system.

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 52 Boeing Model 737-100 and -200 series 
airplanes of the affected design in the worldwide fleet. The FAA 
estimates that 1 airplane of U.S. registry will be affected by this AD, 
that it will take approximately 2 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 $10,500 per airplane. 
Based on these figures, the cost impact of the AD on the single 
affected U.S. operator is estimated to be $10,620.
    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:

96-23-04  Boeing: Amendment 39-9809. Docket 96-NM-06-AD.

    Applicability: Model 737-100 and -200 series airplanes; as 
listed in Boeing Alert Service Bulletin 737-24A1113, dated February 
29, 1996; 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 (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 overload of the static inverter, which could 
result in the loss of the 115 VAC standby power and the associated 
flight instruments, accomplish the following:
    (a) Within 10 months after the effective date of this AD, 
replace the 250 VA rated static inverters either with 500 VA-rated 
static inverters having Boeing part number (P/N) 60B40023-2, or with 
410 VA-rated

[[Page 58318]]

static inverters having Jet Electronics and Technology P/N 
3S2060DV109B1, in accordance with Boeing Alert Service Bulletin 737-
24A1113, dated February 29, 1996; or in accordance with Section 20-
10-111 of the Boeing 737 Airplane Maintenance Manual. Prior to 
further flight following the replacement, perform an operational 
test of the standby electrical power system in accordance with the 
service bulletin; or in accordance with Section 24-54-0 or 24-54-2 
of the maintenance manual.
    (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 2: 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) Except as provided by paragraph (a) of this AD, the 
replacement and operational test shall be done in accordance with 
Boeing Alert Service Bulletin 737-24A1113, dated February 29, 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.
    (e) This amendment becomes effective on December 19, 1996.

    Issued in Renton, Washington, on October 31, 1996.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 96-28689 Filed 11-13-96; 8:45 am]
BILLING CODE 4910-13-U