[Federal Register Volume 59, Number 76 (Wednesday, April 20, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-9337]


[[Page Unknown]]

[Federal Register: April 20, 1994]


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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 93-NM-64-AD; Amendment 39-8887; AD 91-26-05 R1]

 

Airworthiness Directives; Boeing Model 747-400 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment revises an existing airworthiness directive 
(AD), applicable to Boeing Model 747-400 series airplanes, that 
currently requires revising the FAA-approved Airplane Flight Manual 
(AFM) to impose an operational limitation that requires the right very 
high frequency (VHF) radio communication system to be operational for 
dispatch. That action was prompted by the discovery of a single point 
failure within the audio management unit (AMU) that will disable the 
transmission functions of both the left and center VHF radios. The 
actions specified by that AD are intended to prevent loss of all VHF 
radio voice communication transmission capability. This amendment 
limits the applicability of the rule, and provides an optional 
terminating action for the required AFM limitation.

EFFECTIVE DATE: May 20, 1994.

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.

FOR FURTHER INFORMATION CONTACT: Matt Wade, 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) 227-2751; fax (206) 227-1181.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal 
Aviation Regulations by revising AD 91-26-05, amendment 39-8116 (56 FR 
65181, December 16, 1991), which is applicable to all Boeing Model 747-
400 series airplanes, was published in the Federal Register on July 26, 
1993 (58 FR 39688). The action proposed to revise AD 91-26-05 to 
continue to require the addition of a limitation in the FAA-approved 
Airplane Flight Manual (AFM) requiring that the right very high 
frequency (VHF) radio communication system be operational for dispatch. 
Additionally, the action proposed to provide for replacement of the 
currently-installed audio management unit (AMU) with a modified AMU, as 
optional terminating action for the requirements of this AD for certain 
airplanes.
    The action also proposed to limit the applicability of the rule to 
exclude airplanes having variable numbers RT681 and RT682. These 
airplanes were determined not to be subject to the addressed unsafe 
condition, since they were equipped with the modified AMU during 
production.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the two comments received.
    Both commenters support the proposed rule.
    Subsequent to the issuance of the notice, the manufacturer advised 
the FAA that the proposed terminating action had been installed 
previously on certain additional airplanes. Airplanes having production 
line numbers 961 and higher were modified during production to include 
the modified AMU. In light of this, the FAA finds that these airplanes 
are not subject to the addressed unsafe condition and, therefore, has 
revised the applicability of the final rule to exclude these airplanes. 
Additionally, the applicability has been revised to call out the 
production line numbers (816 and 839), rather than the variable numbers 
(RT681 and RT682), of the two excluded airplanes that were specified in 
the notice.
    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.
    There are approximately 235 Model 747-400 series airplanes of the 
affected design in the worldwide fleet. The FAA estimates that 28 
airplanes of U.S. registry will be affected by this AD. The 
requirements of this revised rule will not add any new additional 
economic burden on affected operators. The AFM revision, currently 
required by AD 91-26-05, takes approximately 1 work hour per airplane 
to accomplish, at an average labor rate of $55 per work hour. Based on 
these figures, the total cost impact of the existing requirements of 
this AD on U.S. operators is estimated to be $1,540, or $55 per 
airplane.
    The total 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. However, based 
on the fact that the effective date of AD 91-26-05 was December 30, 
1994, the FAA assumes that all affected U.S. operators already have 
complied with the requirements of that AD. Therefore, there will be no 
future cost impact of those requirements of this rule.
    Should an operator elect to install the modified AMU as terminating 
action, it will take approximately 1 work hour per airplane to 
accomplish, at an average labor charge of $55 per work hour. The cost 
of required costs will be approximately $250 per airplane. Based on 
these figures, the total cost impact of the optional terminating action 
is expected to be $305 per airplane.
    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 14 CFR part 
39 of the Federal Aviation Regulations as follows:

PART 39--AIRWORTHINESS DIRECTIVES

    1. The authority citation for part 39 continues to read as follows:

    Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 
106(g); and 14 CFR 11.89.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by removing amendment 39-8116 (56 FR 
65181, December 16, 1991), and by adding a new airworthiness directive 
(AD), amendment 39-8887, to read as follows:

91-26-05 R1 Boeing: Amendment 39-8887. Docket 93-NM-64-AD. Revises 
AD 91-26-05, Amendment 39-8116.

    Applicability: Model 747-400 series airplanes, excluding 
airplanes having production line numbers 816, 839, and 961 and 
subsequent; certificated in any category.
    Compliance: Required as indicated, unless accomplished 
previously.

    Note 1: Paragraph (a) of this AD restates the requirements of 
paragraph (a) of AD 91-26-05, amendment 39-8116. As allowed by the 
phrase, ``unless accomplished previously,'' if the requirements of 
AD 91-26-05 have been accomplished previously, paragraph (a) of this 
revised AD does not require the insertion of the Airplane Flight 
Manual (AFM) limitation to be repeated.

    To prevent loss of all very high frequency (VHF) radio voice 
communication transmission capability, accomplish the following:
    (a) Within 14 days after December 30, 1991 (the effective date 
of AD 91-26-05, amendment 39-8116): Add the following statement to 
the Limitations Section of the FAA-approved AFM. This may be 
accomplished by placing a copy of this AD in the AFM.

``Electronic Systems

VHF Radio Voice Communications

    Right VHF radio (VHF R) communication system must be operational 
for dispatch.''
    (b) Replacement of the currently-installed audio management unit 
(AMU) of the VHF radio communication system having Boeing part 
numbers S220U000-101, -102, or -104, (Hughes-Avicom part numbers 
1167014-140, -141, or -142), with a modified AMU having Boeing part 
number S220U000-105 (Hughes part number 1167014-143), in accordance 
with Boeing Service Bulletin 747-23-2321, dated May 20, 1993, 
constitutes terminating action for the requirements of this AD. 
Following accomplishment of this replacement, the AFM limitation 
required by paragraph (a) of this AD may be removed.
    (c) As of the effective date of this AD, no AMU having Boeing 
part numbers S220U000-101, -102, or -104, (Hughes-Avicom part 
numbers 1167014-140, -141, or -142), shall be installed on any 
airplane, unless the requirements of paragraph (a) of this AD have 
been accomplished.
    (d) 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.

    (e) Special flight permits may be issued in accordance with 
Secs. 21.197 and 21.199 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.
    (f) This amendment becomes effective on May 20, 1994.

    Issued in Renton, Washington, on April 13, 1994.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 94-9337 Filed 4-19-94; 8:45 am]
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