AD Amdt-39-10989

[Federal Register Volume 64, Number 11 (Tuesday, January 19, 1999)]
[Rules and Regulations]
[Pages 2810-2813]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 99-683]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-SW-24-AD; Amendment 39-10989; AD 98-12-30]
RIN 2120-AA64


Airworthiness Directives; McDonnell Douglas Helicopter Systems 
Model MD-900 Helicopters

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This document publishes in the Federal Register an amendment 
adopting Airworthiness Directive (AD) 98-12-30 which was sent 
previously to all known U.S. owners and operators of McDonnell Douglas 
Helicopter Systems (MDHS) Model MD-900 helicopters by individual 
letters. This AD requires inspecting the main rotor upper hub assembly 
(hub assembly) for cracks, and if a crack is found, replacing the hub 
assembly. The AD also requires verifying attachment nut torque values 
and a repetitive inspection at intervals not to exceed 150 hours time-
in-service. This amendment is prompted by the discovery of cracks in 6 
main rotor upper hub assemblies. This 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.

DATES: Effective February 3, 1999, to all persons except those persons 
to whom it was made immediately effective by priority letter AD 98-12-
30, issued on June 4, 1998, which contained the requirements of this 
amendment.
    Comments for inclusion in the Rules Docket must be received on or 
before March 22, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Office of the Regional Counsel, Southwest Region, 
Attention: Rules Docket No. 98-SW-24-AD, 2601 Meacham Blvd., Room 663, 
Fort Worth, Texas 76137.

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

SUPPLEMENTARY INFORMATION: On June 4, 1998, the FAA issued priority 
letter AD 98-12-30, applicable to MDHS Model MD-900 helicopters, which 
requires inspecting the hub assembly, part number 900R2101006-101 or -
103, for cracks, and if a crack is found, replacing the hub assembly. 
The AD also requires verifying attachment nut torque values and a 
repetitive inspection at intervals not to exceed 150 hours time-in-
service. That action was prompted by the discovery of cracks in 6 hub 
assemblies. This 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 unsafe condition described is likely to exist or develop 
on other MDHS Model MD-900 helicopters of the same type design, the FAA 
issued priority letter AD 98-12-30 to prevent failure of the hub 
assembly, loss of drive to the main rotor, and subsequent loss of 
control of the helicopter. The AD requires inspecting the hub assembly, 
part number 900R2101006-101 or -103, for cracks, and if a crack is 
found, replacing the hub assembly. The AD

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also requires verifying attachment nut torque values and a repetitive 
inspection at intervals not to exceed 150 hours time-in-service. Due to 
the criticality of the hub assembly, the short compliance time is 
required. The previously described unsafe condition can adversely 
affect the controllability of the helicopter and this AD must be issued 
immediately.
    Since it was found that immediate corrective action was required, 
notice and opportunity for prior public comment thereon were 
impracticable and contrary to the public interest, and good cause 
existed to make the AD effective immediately by individual letters 
issued on June 4, 1998 to all known U.S. owners and operators of MDHS 
Model MD-900 helicopters. These conditions still exist, and the AD is 
hereby published in the Federal Register as an amendment to Sec. 39.13 
of the Federal Aviation Regulations (14 CFR 39.13) to make it effective 
to all persons.
    The FAA estimates that 26 helicopters of U.S. registry will be 
affected by this AD, that it will take approximately 14 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 
$21,610 per helicopter. Based on these figures, the total cost impact 
of the AD on U.S. operators is estimated to be $583,700 to accomplish 
the required actions and replace the hub assemblies on all the fleet, 
if necessary.

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 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. 98-SW-24-AD.'' The postcard will be date stamped and 
returned to the commenter.
    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.
    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, 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 98-12-30  McDonnell Douglas Helicopter Systems: Amendment 39-
10989. Docket No. 98-SW-24-AD.

    Applicability: Model MD-900 helicopters, with main rotor upper 
hub assembly (hub assembly), part number (P/N) 900R2101006-101 or -
103, 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 
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 (f) 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 as indicated, unless accomplished 
previously.
    To prevent failure of the hub assembly, loss of drive to the 
main rotor assembly, and subsequent loss of control of the 
helicopter, accomplish the following:
    (a) For a hub assembly that has accumulated 300 or more hours 
time-in-service (TIS), accomplish the inspection procedures in 
paragraph (b) of this AD before further flight. For a hub assembly 
that has accumulated less than 300 hours TIS, accomplish the 
inspection procedures in paragraph (b) of this AD within the next 25 
hours TIS.
    (b) Inspect and reassemble the hub assembly as follows:
    (1) If present, remove sealant from the drive plate attachment 
to the main rotor assembly.
    (2) Using an indelible marker, number the main rotor drive plate 
attachment fastener torque sequence on the drive plate (Figure 1).

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    (3) Remove the main rotor drive plate assembly (drive plate 
assembly) and fretting buffer. Discard the 10 bolts and nuts and 20 
washers.
    (4) Using paint stripper (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.
    (5) Using a 10-power or higher magnifying glass, inspect the 
area around the 10 bolt holes of the hub assembly for cracks. If a 
crack is found, replace the hub assembly with an airworthy hub 
assembly.
    (6) Remove any fretting from the mating surfaces of the hub 
assembly and the drive plate assembly.

    Note 2: Boeing McDonnell Douglas Helicopter Systems Service 
Letter SL900-039, dated May 20, 1998, pertains to the subject of 
this AD.

    (7) Reinstall the main rotor drive plate using 10 new sets of 
replacement attachment hardware. Torque the nuts to 160-180 in.-lbs. 
above locknut locking/run-on torque in the sequence shown (Figure 
1). Record in the rotorcraft log book the locknut locking/run-on 
torque for each nut.
    (c) After the next flight, verify that the torque on each of the 
10 nuts is at least 160 in.-lbs. above the locknut locking/run-on 
torque (minimum torque). Re-torque as required without loosening 
nuts. Fillet surface seal main rotor drive plate to fretting buffer 
to hub assembly mating lines, and seal all exposed unpainted upper 
surfaces of the hub assembly.
    (d) 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. Re-torque as required without loosening 
nuts. This torque verification is no longer required after the 
torque on each of the 10 nuts has stabilized at the minimum torque 
for each nut during two successive torque verifications.
    (e) Repeat the requirements specified in this AD at intervals 
not to exceed 150 hours TIS.

    Note 3: Rotorcraft Maintenance Manual, CSP-900RMM-2, Section 62-
20-00 and 63-10-00, pertain to the subject of this AD.

    (f) 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 4: 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.

    (g) 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.
    (h) This amendment becomes effective on February 3, 1999, to all 
persons except those persons to whom it was made immediately 
effective by priority letter AD 98-12-30, issued June 4, 1998, which 
contained the requirements of this amendment.

    Issued in Fort Worth, Texas, on January 4, 1999.
Henry A. Armstrong,
Manager, Rotorcraft Directorate, Aircraft Certification Service.
[FR Doc. 99-683 Filed 1-15-99; 8:45 am]
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