[Federal Register Volume 61, Number 161 (Monday, August 19, 1996)]
[Rules and Regulations]
[Pages 42776-42777]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-20873]


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


DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 95-NM-177-AD; Amendment 39-9717; AD 96-17-08]
RIN 2120-AA64


Airworthiness Directives; McDonnell Douglas Model DC-10-10, -15, 
-30, -40, and KC-10A (Military) Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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

SUMMARY: This amendment adopts a new airworthiness directive (AD), 
applicable to certain McDonnell Douglas Model DC-10-10, -15, -30, -40, 
and KC-10A (military) series airplanes, that requires modification of 
the AC generator control units. This amendment is prompted by reports 
of loss of electrical power from two generators and an engine that 
flamed out due to an overfrequency condition of a generator. The 
actions specified by this AD are intended to prevent an overfrequency 
condition of a generator, which could lead to the loss of all 
electrical power of the airplane.

DATES: Effective September 23, 1996.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of September 23, 1996.

ADDRESSES: The service information referenced in this AD may be 
obtained from McDonnell Douglas Corporation, 3855 Lakewood Boulevard, 
Long Beach, California 90846, Attention: Technical Publications 
Business Administration, Department C1-L51 (2-60). 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 FAA, Los Angeles Aircraft Certification Office, 
Transport Airplane Directorate, 3960 Paramount Boulevard, Lakewood, 
California; or at the Office of the Federal Register, 800 North Capitol 
Street, NW., suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Natalie Phan-Tran, Aerospace Engineer, 
Systems and Equipment Branch, ANM-130L, FAA, Los Angeles Aircraft 
Certification Office, 3960 Paramount Boulevard, Lakewood, California 
90712; telephone (310) 627-5343; fax (310) 627-5210.

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 McDonnell Douglas Model 
DC-10-10, -15, -30, -40, and KC-10A (military) series airplanes was 
published in the Federal Register on January 3, 1996 (61 FR 134). That 
action proposed to require modification of the AC generator control 
units.
    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

    Three commenters support the proposed rule.

Request Not to Adopt the Rule

    One commenter requests that the proposed AD not be adopted as 
proposed. The commenter states that the modification (i.e., addition of 
a circuit that will provide overfrequency protection) proposed by the 
AD causes a significant reduction in the reliability of the generator 
control unit (GCU). The commenter notes that, following accomplishment 
of the proposed modification, it has experienced an increase of GCU 
removals and bus tie relay (BTR) lockouts on in-service airplanes. The 
commenter acknowledges that the subject modification may add a margin 
of operating safety to the electrical generator system of Model DC-10 
series airplanes; however, the commenter notes that the margin may be 
eliminated with the reduction in the reliability of the GCU and 
increased BTR lockouts. Therefore, the commenter concludes that the FAA 
should investigate the root cause of the failure of the constant speed 
drive (CSD).
    The FAA does not concur with the commenters request that the 
proposal not be adopted. The FAA acknowledges that the subject 
modification may cause a reduction in the reliability of the GCU, which 
may lead to increased removals of the GCU; and may cause an increase in 
the BTR lockouts. However, the FAA has determined that the GCU's have a 
low failure rate, since the overfrequency protection circuit contains a 
minimum of parts; therefore, the reduction in the reliability of the 
GCU will be minimal. In addition, the FAA recognizes that the BTR 
lockouts may be a nuisance; however, the FAA finds that such lockouts 
will not adversely affect the safety of the fleet. Furthermore, the FAA 
has evaluated the root cause of the CSD failure and concluded that 
there are no assurances that could prevent the failure of the CSD. 
Therefore, the FAA finds that modification of the GCU's is necessary to 
provide overfrequency protection as a result of failure of the CSD. An 
overfrequency condition of a generator, if not corrected, could lead to 
the loss of all electrical power of the airplane.

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 as proposed.

Cost Impact

    There are approximately 419 Model DC-10-10, -15, -30, -40, and KC-
10A (military) series of the affected design in the worldwide fleet. 
The FAA estimates that 276 airplanes of U.S. registry will be affected 
by this AD, that it will take approximately 5 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 $2,896 per 
generator control unit; there are 4 units per airplane. Based on these 
figures, the cost impact of the AD on U.S. operators is estimated to be 
$3,279,984, or $11,884 per airplane.
    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

[[Page 42777]]

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:

96-17-08 McDonnell Douglas: Amendment 39-9717. Docket 95-NM-177-AD.

    Applicability: Model DC-10-10, -15, -30, -40, and KC-10A 
(military) series airplanes, as listed in McDonnell Douglas Service 
Bulletin DC10-24-111 RO1, Revision 1, dated August 14, 1995; 
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 an overfrequency condition of the generator, which 
could result in loss of all electrical power of the airplane, 
accomplish the following:
    (a) Within 2 years after the effective date of this AD, modify 
the AC generator control units (GCU) in accordance with McDonnell 
Douglas Service Bulletin DC10-24-111 RO1, Revision 1, dated August 
14, 1995.
    (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, Los Angeles 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, Los Angeles ACO.

    Note 2: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Los Angeles 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) The modification shall be done in accordance with McDonnell 
Douglas Service Bulletin DC10-24-111 RO1, Revision 1, dated August 
14, 1995. 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 McDonnell Douglas 
Corporation, 3855 Lakewood Boulevard, Long Beach, California 90846, 
Attention: Technical Publications Business Administration, 
Department C1-L51 (2-60). Copies may be inspected at the FAA, 
Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, 
Washington; or at the FAA, Los Angeles Aircraft Certification 
Office, Transport Airplane Directorate, 3960 Paramount Boulevard, 
Lakewood, California; or at the Office of the Federal Register, 800 
North Capitol Street, NW., suite 700, Washington, DC.
    (e) This amendment becomes effective on September 23, 1996.

    Issued in Renton, Washington, on August 9, 1996.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service. -
[FR Doc. 96-20873 Filed 8-16-96; 8:45 am]
BILLING CODE 4910-13-P