[Federal Register Volume 66, Number 248 (Thursday, December 27, 2001)]
[Proposed Rules]
[Pages 66821-66823]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-31556]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2001-SW-40-AD]
RIN 2120-AA64


Airworthiness Directives; MD Helicopters, Inc. Model 369D, 369E, 
369F, and 369FF Helicopters

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the adoption of a new airworthiness 
directive (AD) for MD Helicopters, Inc. Model 369D, 369E, 369F, and 
369FF helicopters with a tailboom modified according to Aerometals 
supplemental type certificate (STC) SH5055NM or SH4801NM. The AD would 
require an inspection to identify the part number (P/N) of the bolts 
that attach the tail rotor gearbox to the tailboom and replacing any 
bolt of inadequate grip length with an airworthy bolt. This AD would 
also require determining the number of bolt threads protruding from 
each nutplate and adding an additional washer if more than four threads 
protrude. This proposal is prompted by the discovery that bolts of 
inadequate grip length were specified to attach the tail rotor gearbox 
to the tailboom. The actions specified by the proposed AD are intended 
to prevent loss of a tail rotor gearbox due to bolts of inadequate

[[Page 66822]]

grip length and subsequent loss of control of the helicopter.

DATES: Comments must be received on or before February 25, 2002.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Office of the Regional Counsel, Southwest Region, 
Attention: Rules Docket No. 2001-SW-40-AD, 2601 Meacham Blvd., Room 
663, Fort Worth, Texas 76137. You may also send comments electronically 
to the Rules Docket at the following address: [email protected]. 
Comments may be inspected at the Office of the Regional Counsel between 
9 a.m. and 3 p.m., Monday through Friday, except Federal holidays.

FOR FURTHER INFORMATION CONTACT: John Cecil, Aviation Safety Engineer, 
FAA, Los Angeles Aircraft Certification Office, Airframe Branch, 3960 
Paramount Blvd., Lakewood, California 90712-4137, telephone (562) 627-
5228, fax (562) 627-5210.

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed rule by submitting such written data, views, or arguments as 
they may desire. Communications should identify the Rules Docket number 
and be submitted in triplicate to the address specified above. All 
communications received on or before the closing date for comments will 
be considered before taking action on the proposed rule. The proposals 
contained in this document may be changed in light of the comments 
received.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed rule. All 
comments submitted will be available, both before and after the closing 
date for comments, in the Rules Docket for examination by interested 
persons. A report summarizing each FAA-public contact concerned with 
the substance of this proposal will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their mailed 
comments submitted in response to this proposal must submit a self-
addressed, stamped postcard on which the following statement is made: 
``Comments to Docket No. 2001-SW-40-AD.'' The postcard will be date 
stamped and returned to the commenter.

Availability of NPRMs

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, Office of the Regional Counsel, Southwest Region, 
Attention: Rules Docket No. 2001-SW-40-AD, 2601 Meacham Blvd., Room 
663, Fort Worth, Texas 76137.

Discussion

    This document proposes adopting a new AD for MD Helicopters, Inc. 
Model 369D, 369E, 369F, and 369FF helicopters with a tailboom modified 
according to either Aerometals STC SH5055NM or SH4801NM. Yehnert 
Helicopters, Inc. formerly owned both STCs. This proposal is prompted 
by the discovery that the maintenance instructions supplied to 
installers of STCs SH5055NM and SH4801NM incorrectly specified the tail 
rotor gearbox attaching bolt as P/N NAS6204-25, which has an inadequate 
grip length. This condition, if not corrected, could result in loss of 
a tail rotor gearbox and subsequent loss of control of the helicopter.
    The FAA has reviewed Aerometals Service Bulletin SB-001, dated 
August 3, 2000, which describes procedures for verifying that the 
proper attaching bolts are used to install the tail rotor gearbox to 
the tailboom.
    We have identified an unsafe condition that is likely to exist or 
develop on other MD Helicopters, Inc. Model 369D, 369E, 369F, and 369FF 
helicopters of the same type design modified by STC SH5055NM or 
SH4801NM. Therefore, the proposed AD would require the following:
     Inspect the tail rotor gearbox attach bolts to determine 
the P/N. Replace any bolt for which a P/N cannot be determined and any 
bolt that is not P/N NAS1304-26 before further flight. After replacing 
a bolt, inspect for loosening of the bolt torque at a specified 
interval. Retorque the bolt, reapply the slippage mark, and reinspect 
the torque between 2 and 10 hours TIS thereafter.
     Remove the tailboom control rod and determine the number 
of bolt threads protruding from each nutplate on the internal surface 
of the aft tailboom frame casting. At least one thread must protrude. 
If more than four threads protrude, add an additional washer under the 
bolt head.
    The FAA estimates that this proposed AD would affect 500 
helicopters of U.S. registry. The FAA estimates approximately \1/2\ 
work hour would be required to determine whether either STC has been 
installed. For the estimated 40 helicopters that have been modified by 
either STC, approximately 1 work hour per helicopter will be required 
to inspect and replace the bolts. The average labor rate is 
approximately $60 per work hour. Required parts would cost 
approximately $40 per helicopter. Based on these figures, the total 
cost impact of the proposed AD on U.S. operators is estimated to be 
$19,000.
    The regulations proposed herein would not have a substantial direct 
effect 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, it 
is determined that this proposal would not have federalism implications 
under Executive Order 13132.
    For the reasons discussed above, I certify that this proposed 
regulation (1) is not a ``significant regulatory action'' under 
Executive Order 12866; (2) is not a ``significant rule'' under the DOT 
Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); 
and (3) if promulgated, 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 copy of the draft 
regulatory evaluation prepared for this action is contained in the 
Rules Docket. A copy of it may be obtained by contacting 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.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
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:

MD Helicopters, Inc.: Docket No. 2001-SW-40-AD.
    Applicability: Model 369D, 369E, 369F, and 369FF helicopters, 
modified in accordance with Aerometals Supplemental Type Certificate 
(STC) SH5055NM or SH4801NM, certificated in any category.

    Note 1: This AD applies to each helicopter 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

[[Page 66823]]

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 request approval for an alternative method of 
compliance in accordance with paragraph (c) 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 loss of the tail rotor gearbox due to attaching bolts 
of inadequate grip length and subsequent loss of control of the 
helicopter, accomplish the following:
    (a) Within 25 hours time-in-service (TIS), conduct the following 
inspections:
    (1) For each tail rotor gearbox attaching bolt (bolt):
    (i) Determine the part number (P/N).
    (ii) If the P/N cannot be determined or if the bolt is not P/N 
NAS1304-26, before further flight, replace the bolt with bolt, P/N 
NAS1304-26.
    (iii) Torque the bolt to 100-110 in-lbs and apply a slippage 
mark.
    (2) Remove the tailboom control rod and determine the number of 
bolt threads protruding from each nutplate on the internal surface 
of the aft tailboom frame casting, P/N 369D23503, as shown in Figure 
1. At least one thread must protrude. If more than four threads 
protrude, add an additional washer, P/N AN960D416, under the bolt 
head. Torque the bolt to 100-110 in-lbs., and reapply a slippage 
mark.
    (b) Between 2 and 10 hours TIS after accomplishing the 
requirements of paragraph (a) of this AD, inspect the torque on each 
bolt by applying 100 in-lbs. If any bolt movement occurs, retorque 
the bolt to 100-110 in-lbs. and reapply a slippage mark. Reinspect 
the torque between 2 and 10 hours TIS thereafter until no bolt 
movement occurs.

    Note 2: Aerometals Service Bulletin SB-001, dated August 3, 
2000, pertains to the subject of this AD.

[GRAPHIC] [TIFF OMITTED] TP27DE01.000

    (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 (LAACO), FAA. Operators shall submit their requests through 
an FAA Principal Maintenance Inspector, who may concur or comment 
and then send it to the Manager, LAACO.

    Note 3: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the LAACO.

    (d) Special flight permits will not be issued.

    Issued in Fort Worth, Texas, on December 14, 2001.
David A. Downey,
Manager, Rotorcraft Directorate, Aircraft Certification Service.
[FR Doc. 01-31556 Filed 12-26-01; 8:45 am]
BILLING CODE 4910-13-U