[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 [www.gpo.gov]
[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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