[Federal Register Volume 64, Number 30 (Tuesday, February 16, 1999)]
[Rules and Regulations]
[Pages 7498-7499]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-3591]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-SW-61-AD; Amendment 39-11036; AD 99-04-12]
RIN 2120-AA64


Airworthiness Directives; McDonnell Douglas Helicopter Systems 
Model 369D, 369E, 369FF, 369H, MD500N, and MD600N Helicopters

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD), 
applicable to McDonnell Douglas Helicopter Systems (MDHS) Model 369D, 
369E, 369FF, 369H, MD500N, and MD600N helicopters, that requires a one-
time visual inspection of certain input shaft coupling assemblies for 
pitting. This amendment is prompted by three operators' reports of 
discovering pitting on the internal spline teeth. The actions specified 
by this AD are intended to prevent failure of the spline teeth in the 
input shaft coupling assembly, loss of drive to the main rotor system, 
and subsequent loss of control of the helicopter.

EFFECTIVE DATE: March 23, 1999.

FOR FURTHER INFORMATION CONTACT: Bruce Conze, Aerospace Engineer, Los 
Angeles Aircraft Certification Office, 3960 Paramount Blvd., Lakewood, 
California, 90712, telephone (562) 627-5261, fax (562) 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 MDHS Model 369D, 369E, 369FF, 
369H, MD500N, and MD600N helicopters was published in the Federal 
Register on May 15, 1998 (63 FR 27011). That action proposed to require 
a one-time visual inspection of certain input shaft coupling assemblies 
for pitting.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.
    One commenter states that the addition of a calendar period to 
supplement the time-in-service compliance time is necessary to account 
for the effects of corrosion which caused the internal spline pitting. 
The FAA does not concur for the following reasons:
     The original corrosion occurred during the manufacturing 
process due to exposure of unprotected machined parts and porosity in 
the material. The corrosion was subsequently removed in normal 
processing and parts coated with dry lube. The corrosion is not a 
result of time-in-service.
     After examining parts returned from the field, there is no 
evidence suggesting that the original corrosion damage increases with 
time.
    The same commenter also states that there are no guidelines or 
references to Boeing instructions, service bulletins, or manuals given 
to strip the input shaft coupling assembly and perform the visual 
inspection. The FAA does not concur; Note 2 states that Boeing Service 
Bulletin SB369H-240, SB369E-085, SB500N-013, SB369D-192, SB369F-072, 
SB600N-003, dated September 26, 1997, pertains to the subject of the 
AD. No additional guidelines for stripping shaft coupling assembly and 
performing the visual inspection are deemed necessary because the 
corrosion on the input shaft coupling assemblies is obvious and easily 
discernible with the naked eye without stripping the shaft coupling 
assembly.
    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.
    The FAA estimates that 82 helicopters of U.S. registry will be 
affected by this AD, that it will take approximately 3 work hours per 
helicopter to accomplish the required actions, and that the average 
labor rate is $60 per work hour. Required parts will cost approximately 
$638 per coupling assembly. Based on these figures, the total cost 
impact of the AD on U.S. operators is estimated to be $67,076 if the 
coupling assembly is replaced in all 82 helicopters.
    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

[[Page 7499]]

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 FAA, Office of the 
Regional Counsel, Southwest Region, Attention: Rules Docket No. 97-SW-
61-AD, 2601 Meacham Blvd., Room 663, Fort Worth, Texas 76137.

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 adding a new airworthiness directive 
to read as follows:

AD 99-04-12  McDonnell Douglas Helicopter Systems: Amendment 39-
11036. Docket No. 97-SW-61-AD.

    Applicability: Model 369D, 369E, 369FF, 369H, MD500N, and MD600N 
helicopters, with input shaft coupling assemblies, part number (P/N) 
369F5133-1, serial number 
(S/N) 030829-0126 through 030829-0207, installed on main 
transmission, P/N 369F5100-503, and on overrunning clutch, P/N 
369F5450, certificated in any category.

    Note 1: This AD applies to each helicopter 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 helicopters that have been modified, 
altered, or repaired so that the performance of the requirements of 
this AD is affected, the owner/operator must use the authority 
provided in paragraph (c) to request approval from the FAA. This 
approval may address either no action, if the current configuration 
eliminates the unsafe condition, or different actions necessary to 
address the unsafe condition described in this AD. Such a request 
should include an assessment of the effect of the changed 
configuration on the unsafe condition addressed by this AD. In no 
case does the presence of any modification, alteration, or repair 
remove any helicopter from the applicability of this AD.

    Compliance: Required within 100 hours time-in-service after the 
effective date of this AD, unless accomplished previously.
    To prevent failure of the spline teeth in each input shaft 
coupling assembly (coupling assembly), loss of drive to the main 
rotor system, and subsequent loss of control of the helicopter, 
accomplish the following:
    (a) Visually inspect the coupling assemblies, P/N 369F5133-1, 
installed on main transmission, P/N 369F5100-503, and on overrunning 
clutch, P/N 369F5450, for pitting under the solid film lubricant in 
the spline area of the coupling.
    (b) If there is pitting in the splines, replace the coupling 
assembly with an airworthy coupling assembly, P/N 369F5133-1, that 
has been inspected as required by paragraph (a) of this AD.
    Note 2: Boeing Service Bulletin SB369H-240, SB369E-085, SB500N-
013, SB369D-192, SB369F-072, SB600N-003, dated September 26, 1997, 
pertains to this AD.

    (c) 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, FAA. Operators shall submit their requests through an FAA 
Principal Maintenance Inspector, who may concur or comment and then 
send it to the Manager, Los Angeles Aircraft Certification Office.

    Note 3: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Los Angeles Aircraft Certification Office.

    (d) 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 helicopter to a location where 
the requirements of this AD can be accomplished.

    Issued in Fort Worth, Texas, on February 5, 1999.
Eric Bries,
Acting Manager, Rotorcraft Directorate, Aircraft Certification Service.
[FR Doc. 99-3591 Filed 2-12-99; 8:45 am]
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