[Federal Register Volume 66, Number 73 (Monday, April 16, 2001)]
[Rules and Regulations]
[Pages 19383-19387]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-8619]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2000-SW-15-AD; Amendment 39-12175; AD 2001-07-09]
RIN 2120-AA64


Airworthiness Directives; MD Helicopters Inc. Model MD-900 
Helicopters

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This amendment supersedes an existing emergency airworthiness 
directive (AD) that applies to MD Helicopters Inc. (MDHI) Model MD-900 
helicopters. That emergency AD requires, within 6 hours time-in-service 
(TIS), or before further flight after January 31, 2000, whichever 
occurs first, inspecting the main rotor upper hub assembly drive plate 
attachment flange (flange) and determining the torque of each flange 
nut (nut). If a crack is found, the hub assembly must be replaced 
before further flight. The emergency AD also requires, within 25 hours 
TIS or before further flight after January 31, 2000, whichever occurs 
first, inspecting the hub assembly and verifying that the torque on the 
nuts is correct. Replacing a cracked hub assembly with an airworthy hub 
assembly is required before further flight. This amendment requires the 
same actions as the existing emergency AD but removes the January 
compliance dates and corrects errors in the existing emergency AD. This 
amendment is prompted by the discovery that there are several errors in 
the emergency AD. The actions specified by this AD are intended to 
prevent failure of the hub assembly, loss of drive to the main rotor, 
and subsequent loss of control of the helicopter.

DATES: Effective May 1, 2001. The incorporation by reference of certain 
publications listed in the regulations is approved by the Director of 
the Federal Register as of May 1, 2001.
    Comments for inclusion in the Rules Docket must be received on or 
before June 15, 2001.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Office of the Regional Counsel, Southwest Region, 
Attention: Rules Docket No. 2000-SW-15-AD, 2601 Meacham Blvd., Room 
663, Fort Worth, Texas 76137. You may also send comments electronically 
to

[[Page 19384]]

the Rules Docket at the following address: [email protected].
    The service information referenced in this AD may be obtained from 
MD Helicopters Inc., Attn: Customer Support Division, 5000 E. McDowell 
Rd., Mail Stop M615-GO48, Mesa, Arizona 85215-9797, telephone 1-800-
388-3378 or 480-891-6342, fax 480-891-6782. This information may be 
examined at the FAA, Office of the Regional Counsel, Southwest Region, 
2601 Meacham Blvd., Room 663, Fort Worth, Texas; or at the Office of 
the Federal Register, 800 North Capitol Street, NW., suite 700, 
Washington, DC.

FOR FURTHER INFORMATION CONTACT: Greg DiLibero, Aviation Safety 
Engineer, FAA, Los Angeles Aircraft Certification Office, 3960 
Paramount Blvd., Lakewood, California 90712, telephone (562) 627-5231, 
fax (562) 627-5210.

SUPPLEMENTARY INFORMATION: On December 17, 1999, the FAA issued 
Emergency AD 99-26-20 that applies to MDHI Model MD-900 helicopters and 
requires, within 6 hours TIS or before further flight after January 31, 
2000, whichever occurs first, inspecting the hub assembly for a crack 
and verifying the nut torque. If a crack is found, replacing the hub 
assembly with an airworthy hub assembly is required before further 
flight. That action was prompted by the discovery of three cracked hub 
assemblies. Inspections of one hub assembly revealed cracks from all 10 
holes in the flange and, in another hub assembly, from one of the 10 
holes. That condition, if not corrected, could result in failure of the 
hub assembly, loss of drive to the main rotor, and subsequent loss of 
control of the helicopter.
    Since the issuance of that emergency AD, the FAA has discovered 
several errors. Paragraph (b)(2) of the emergency AD incorrectly refers 
to paragraph (b)(4) rather than (b)(3). There is no paragraph (b)(4) in 
the emergency AD. That error is corrected in this superseding AD. 
Paragraphs (b)(2), (b)(3), (b)(3)(vii) and (b)(3)(x) are revised to 
more clearly state the compliance procedures and the torque stability 
requirements necessary for accomplishing the AD actions. We have also 
removed the January compliance dates from this superseding AD as those 
dates have already passed.
    Since an unsafe condition has been identified that is likely to 
exist or develop on other MDHI Model MD-900 helicopters of the same 
type design, this AD supersedes emergency AD 99-26-20 to require, 
within 6 hours TIS, inspecting the hub assembly, part number 
900R2101006-105 or 900R2101006-107, for a cracked flange and 
determining the torque of each nut. If a crack is found, the hub 
assembly must be replaced before further flight. This AD also requires, 
within 25 hours TIS, inspecting the hub assembly and verifying the nut 
torque. Replacing a cracked hub assembly with an airworthy hub assembly 
is required before further flight. The actions must be accomplished in 
accordance with the service bulletin described previously. The short 
compliance time involved is required because the previously described 
critical unsafe condition can adversely affect the structural integrity 
and controllability of the helicopter. Therefore, since the initial 
actions are required within 6 hours TIS, this AD must be issued 
immediately.
    Since a situation exists that requires the immediate adoption of 
this regulation, it is found that notice and opportunity for prior 
public comment hereon are impracticable, and that good cause exists for 
making this amendment effective in less than 30 days.
    The FAA estimates that 28 helicopters of U.S. registry will be 
affected by this AD, that it will take approximately 1 work hour per 
helicopter to verify the torque, 3 work hours per helicopter to perform 
the inspection, and 10 work hours per helicopter to replace the hub 
assembly, if necessary. The average labor rate is $60 per work hour. 
Required parts to replace the hub assembly, if necessary, will cost 
approximately $21,610 per helicopter. Based on these figures, the total 
cost impact of the AD on U.S. operators is estimated to be $151,370, 
assuming 6 torque verifications per helicopter, per year; 6 inspections 
per helicopter, per year; and 5 hub assembly replacements.

Comments Invited

    Although this action is in the form of a final rule that involves 
requirements affecting flight safety and, thus, was not preceded by 
notice and an opportunity for public comment, comments are invited on 
this rule. Interested persons are invited to comment on this 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 under the caption ADDRESSES. All 
communications received on or before the closing date for comments will 
be considered, and this rule may be amended in light of the comments 
received. Factual information that supports the commenter's ideas and 
suggestions is extremely helpful in evaluating the effectiveness of the 
AD action and determining whether additional rulemaking action would be 
needed.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the rule that might 
suggest a need to modify the 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 that 
summarizes each FAA-public contact concerned with the substance of this 
AD will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their mailed 
comments submitted in response to this rule must submit a self-
addressed, stamped postcard on which the following statement is made: 
``Comments to Docket No. 2000-SW-15-AD.'' The postcard will be date 
stamped and returned to the commenter.
    The regulations adopted herein will 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 final rule does not have federalism 
implications under Executive Order 13132.
    The FAA has determined that this regulation is an emergency 
regulation that must be issued immediately to correct an unsafe 
condition in aircraft, and that it is not a ``significant regulatory 
action'' under Executive Order 12866. It has been determined further 
that this action involves an emergency regulation under DOT Regulatory 
Policies and Procedures (44 FR 11034, February 26, 1979). If it is 
determined that this emergency regulation otherwise would be 
significant under DOT Regulatory Policies and Procedures, a final 
regulatory evaluation will be prepared and placed in the Rules Docket. 
A copy of it, if filed, 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:

[[Page 19385]]

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:

2001-07-09  MD Helicopters Inc: Amendment 39-12175. Docket No. 2000-
SW-15-AD. Supersedes Emergency AD 99-26-20, Docket No. 99-SW-89-AD.
    Applicability: Model MD-900 helicopters, with main rotor upper 
hub (hub) assembly, part number (P/N) 900R2101006-105 or 
900R2101006-107, installed, 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 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 failure of the hub assembly, loss of drive to the 
main rotor, and subsequent loss of control of the helicopter, 
accomplish the following:
    (a) For the hub assembly, P/N900R2101006-107,
    (1) Within 6 hours time-in-service (TIS), visually inspect the 
main rotor upper hub assembly drive plate attach flange (flange) for 
a crack and determine the torque of each flange attach nut (nut) in 
accordance with the Accomplishment Instructions, Part I, paragraph 
2.A., steps (1) through (7) of MD Helicopter Inc. Service Bulletin 
SB900-072, dated December 10, 1999 (SB). If a crack is found, before 
further flight, remove and replace the hub assembly with an 
airworthy hub assembly.
    (2) Within 25 hours TIS, conduct the Accomplishment 
Instructions, Part II, paragraph 2.B., steps (1) through (6), (8), 
and (9) of the SB. If a crack is found, before further flight, 
remove and replace the hub assembly with an airworthy hub assembly.
    (b) For the hub assembly, P/N 900R2101006-105,
    (1) Within 6 hours TIS, visually inspect the flange for a crack 
and determine the torque of each nut in accordance with the 
Accomplishment Instructions, Part I, paragraph 2.A., steps (1) 
through (7) of the SB.

    Note 2: The SB effectivity does not include hub assembly, P/N 
900R2101006-105; however, for the requirements of this AD, certain 
provisions of the SB do apply to this P/N.

    (2) If any nut has less than 180 inch pounds (20.34 Nm) of 
torque, before further flight, remove the drive plate and fretting 
buffer and inspect the flange in accordance with the procedures in 
paragraph (b)(3) of this AD. If a crack is detected, before further 
flight, remove and replace the hub assembly with an airworthy hub 
assembly. Reassemble in accordance with the procedures in paragraph 
(b)(3) of this AD.
    (3) Within 25 hours TIS, remove the main rotor drive plate 
assembly and anti-fretting ring and visually inspect the main rotor 
hub assembly as follows:
    (i) If present, remove sealant from the drive plate attachment 
to the hub assembly.
    (ii) Mark the main rotor hub holes, bolts, and nuts to 
correspond with the drive plate hole numbers (see Figure 1).
    (iii) Remove the main rotor drive plate (drive plate) assembly 
and anti-fretting ring (fretting buffer).
    (iv) Inspect drive plate to rotor hub assembly mating surfaces 
and the fretting buffer for fretting.
    (v) Using paint stripper (Consumable Item List C313 or 
equivalent) and cleaning solvent (C420 or equivalent), remove the 
paint from the upper mating surface of the hub assembly to enable an 
accurate visual inspection of the drive plate attachment bolt hole 
(bolt hole) area for cracking (Figure 1). Ensure the paint stripper 
and solvent DO NOT contaminate the upper bearing and upper grease 
seal areas.
    (vi) Using a 10-power or higher magnifying glass and bright 
light, inspect the mating surface area and the area around and 
inside the 10 bolt holes of the hub assembly for a crack. If a crack 
is found, prior to further flight, replace the hub assembly with an 
airworthy hub assembly.
    (vii) If no crack is found, remove fretting debris from the 
mating surfaces of the hub assembly and the drive plate assembly, 
reassemble, fillet seal (C211 or equivalent) the surface of the 
drive plate to fretting buffer to hub assembly mating lines, and 
seal all exposed unpainted upper surfaces of the hub assembly.
    (viii) Reinstall the main rotor drive plate using 10 new sets of 
replacement attachment hardware. Torque the nuts to 160 inch pounds 
above locknut locking/run-on torque in the sequence shown (Figure 
1). Record in the rotorcraft logbook, or equivalent record, the 
locknut locking/run-on torque for each nut.
    (ix) After the next flight, verify that the torque on each of 
the 10 nuts is at least 160 inch pounds above the locknut locking/
run-on torque (minimum torque). Retorque as required without 
loosening nuts.
    (x) Thereafter, at intervals of at least 4 hours TIS, not to 
exceed 6 hours TIS, verify that the torque of each of the 10 nuts is 
at least the minimum torque. Retorque as required without loosening 
nuts. This torque verification is no longer required after the 
torque on each of the 10 nuts has stabilized at a torque value of 
160 or more inch pounds for each nut during two successive torque 
verifications.

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

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

    (d) If any nut torque is below minimum torque and no hub 
assembly crack is found before disassembly inspection, after 
retorque in accordance with the applicable Maintenance Manual, a 
special flight permit for one flight below 100 knots indicated 
airspeed 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.
    (e) The flange and torque inspections shall be done in 
accordance with the Accomplishment Instructions, Part I, paragraph 
2.A., steps (1) through (7) and Part II, paragraph 2.B., steps (1) 
through (6), (8), and (9) of MD Helicopters Inc. Service Bulletin 
SB900-072, dated December 10, 1999. 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 
MD Helicopters Inc., Attn: Customer Support Division, 5000 E. 
McDowell Rd., Mail Stop M615-GO48, Mesa, Arizona 85215-9797, 
telephone 1-800-388-3378 or 480-891-6342, fax 480-891-6782. Copies 
may be inspected at the FAA, Office of the Regional Counsel, 
Southwest Region, 2601 Meacham Blvd., Room 663, Fort Worth, Texas; 
or at the Office of the Federal Register, 800 North Capitol Street, 
NW., suite 700, Washington, DC.
    (f) This amendment becomes effective on May 1, 2001.

    Issued in Fort Worth, Texas, on April 2, 2001.
Eric Bries,
Acting Manager, Rotorcraft Directorate, Aircraft Certification Service.
[FR Doc. 01-8619 Filed 4-13-01; 8:45 am]
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