[Federal Register Volume 66, Number 242 (Monday, December 17, 2001)]
[Proposed Rules]
[Pages 64931-64934]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-31042]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2001-SW-39-AD]
RIN 2120-AA64


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

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes superseding an existing airworthiness 
directive (AD) for MD Helicopters Inc. Model MD-900 helicopters. That 
AD currently requires inspecting the main rotor upper hub assembly 
drive plate attachment flange (flange), determining the torque of each 
flange nut (nut), and if a crack is found, before further flight, 
replacing the hub assembly. In addition to the current requirements, 
this action would require visually inspecting the outer surface of the 
flange at specified intervals and removing the drive plate and visually 
inspecting the flange for a crack at specified intervals and replacing 
any unairworthy hub assembly. This proposal is prompted by reports that 
cracks starting at the drive plate attachment holes were found in the 
main rotor hub. The actions specified by the proposed AD are intended 
to detect a crack in the flange and to prevent failure of the hub 
assembly, loss of drive to the main rotor, and subsequent loss of 
control of the helicopter.

DATES: Comments must be received on or before February 15, 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-39-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: Jon Mowery, Aviation Safety Engineer, 
FAA, Los Angeles Aircraft Certification Office, Airframe Branch, 3960 
Paramount Blvd., Lakewood, California 90712, telephone (562) 627-5322, 
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-39-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-39-AD, 2601 Meacham Blvd., Room 
663, Fort Worth, Texas 76137.

Discussion

    On December 17, 1999, the FAA issued Emergency AD 99-26-20 to 
require certain inspections of the hub assembly for a crack, ensuring 
the correct torque of each nut, and replacing any cracked hub assembly 
with an airworthy hub assembly. That action was prompted by three 
occurrences of cracked hub assemblies. The FAA discovered errors after 
issuing Emergency AD 99-26-20 and corrected those errors by superseding 
that Emergency AD with AD 2001-07-09, Amendment 39-12175 (66 FR 19383, 
April 16, 2001). The requirements of that AD were intended to prevent 
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 AD, the FAA has received reports 
indicating that additional cracks have been found in the main rotor hub 
emanating from the drive plate attachment holes.
    This unsafe condition is likely to exist or develop on other MD 
Helicopters Inc. Model MD-900 helicopters of the same type design. 
Therefore, the proposed AD would supersede AD 2001-07-09 to contain the 
current requirements and to also require the following:
     Visually inspect the outer surface of the flange using a 
light and a 10x or higher magnifying glass at intervals not to exceed 
100 hours TIS.
     Remove the drive plate and visually inspect the flange for 
a crack at intervals not to exceed 300 hours TIS.
     Replace any unairworthy hub assembly before further 
flight.
    The FAA estimates 28 helicopters of U.S. registry would be affected 
by this proposed AD. It would 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,

[[Page 64932]]

if necessary. The proposed actions would require approximately 1 work 
hour for a 100-hour TIS inspection, and 3 work hours for a 300-hour TIS 
inspection, at an average labor rate of $60 per work hour. Required 
parts to replace the hub assembly, if necessary, would 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 $159,770 for 
the first year, assuming 5 hub assembly replacements and assuming each 
helicopter has 6 torque verifications, 6 inspections, two 100-hour 
inspections, and one 300-hour inspection.
    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 removing Amendment 39-12175 (66 FR 
19383, April 16, 2001), and by adding a new airworthiness directive 
(AD), to read as follows:

MD Helicopters, Inc.: Docket No. 2001-SW-39-AD. Supersedes AD 2001-
07-09, Amendment 39-12175, Docket No. 2000-SW-15-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 (e) 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/N 900R2101006-107,
    (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 
SB 900-072, 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, accomplish Part II, of the 
Accomplishment Instructions, 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, certain provisions of this AD 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 to correspond with the drive 
plate hole numbers (see Figure 1 of this AD).
    (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 each 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  x  or higher magnifying glass and light, 
inspect the mating surface area and the area around and inside the 
10 boltholes 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.
BILLING CODE 4910-13-P

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[GRAPHIC] [TIFF OMITTED] TP17DE01.000

BILLING CODE 4913-10-C
    (c) Within 100 hours TIS and thereafter at intervals not to 
exceed 100 hours TIS, visually inspect the outer surface of the 
flange for a crack using a light and a 10  x  or higher magnifying 
glass. If a crack is detected, replace the unairworthy hub assembly 
with an airworthy hub assembly before further flight.
    (d) At intervals not to exceed 300 hours TIS, remove the drive 
plate and visually inspect the flange for a crack using a light and 
a 10  x  or higher magnifying glass. If a crack is detected, replace 
the unairworthy hub assembly with an airworthy hub assembly before 
further flight.
    (e) 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.

    (f) If any nut torque is below minimum torque and no hub 
assembly crack is found before disassembly inspection, after 
retorque

[[Page 64934]]

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 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 December 11, 2001.
David A. Downey,
Manager, Rotorcraft Directorate, Aircraft Certification Service.
[FR Doc. 01-31042 Filed 12-14-01; 8:45 am]
BILLING CODE 4910-13-P