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[Federal Register Volume 90, Number 8 (Tuesday, January 14, 2025)]
[Proposed Rules]
[Pages 3046-3048]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2025-00588]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2024-2555; Project Identifier AD-2024-00214-R]
RIN 2120-AA64

Airworthiness Directives; Siam Hiller Holdings, Inc, Helicopters

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD) 
for Siam Hiller Holdings, Inc. (Siam Hiller), Model UH-12E (Army OH-23G 
and H-23F) and UH-12E-L helicopters. This proposed AD was prompted by 
reports of cracks found in a main rotor (M/R) transmission drive shaft 
(drive shaft). This proposed AD would require inspecting certain M/R 
drive shafts for a crack, prohibit installing certain M/R drive shafts 
unless the inspection is done, and prohibit using certain paint 
removers. The FAA is proposing this AD to address the unsafe condition 
on these products.

DATES: The FAA must receive comments on this proposed AD by February 
28, 2025.

ADDRESSES: You may send comments, using the procedures found in 14 CFR 
11.43 and 11.45, by any of the following methods:
     Federal eRulemaking Portal: Go to regulations.gov. Follow 
the instructions for submitting comments.
     Fax: 202-493-2251.
     Mail: U.S. Department of Transportation, Docket 
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New 
Jersey Avenue SE, Washington, DC 20590.
     Hand Delivery: Deliver to Mail address above between 9 
a.m. and 5 p.m., Monday through Friday, except Federal holidays.
    AD Docket: You may examine the AD docket at regulations.gov under 
Docket No. FAA-2024-2555; or in person at Docket Operations between 9 
a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD 
docket contains this NPRM, any comments received, and other 
information. The street address for Docket Operations is listed above.
    Other Related Material: For Hiller Aircraft Corporation material 
identified in this proposed AD, contact Hiller Aircraft Corporation, 
925 M Street, Firebaugh, CA 93622; phone: (559) 659-5959; or website: 
hilleraircraftcorporation.com/.

[[Page 3047]]

FOR FURTHER INFORMATION CONTACT: Calvin L. Hang, Aviation Safety 
Engineer, FAA, 3960 Paramount Boulevard, Lakewood, CA 90712; phone: 
(562) 627-5254; email: [email protected].

SUPPLEMENTARY INFORMATION:

Comments Invited

    The FAA invites you to send any written relevant data, views, or 
arguments about this proposal. Send your comments to an address listed 
under the ADDRESSES section. Include ``Docket No. FAA-2024-2555; 
Project Identifier AD-2024-00214-R'' at the beginning of your comments. 
The most helpful comments reference a specific portion of the proposal, 
explain the reason for any recommended change, and include supporting 
data. The FAA will consider all comments received by the closing date 
and may revise this proposal because of those comments.
    Except for Confidential Business Information (CBI) as described in 
the following paragraph, and other information as described in 14 CFR 
11.35, the FAA will post all comments received, without change, to 
regulations.gov, including any personal information you provide. The 
agency will also post a report summarizing each substantive verbal 
contact received about this NPRM.

Confidential Business Information

    CBI is commercial or financial information that is both customarily 
and actually treated as private by its owner. Under the Freedom of 
Information Act (FOIA) (5 U.S.C. 552), CBI is exempt from public 
disclosure. If your comments responsive to this NPRM contain commercial 
or financial information that is customarily treated as private, that 
you actually treat as private, and that is relevant or responsive to 
this NPRM, it is important that you clearly designate the submitted 
comments as CBI. Please mark each page of your submission containing 
CBI as ``PROPIN.'' The FAA will treat such marked submissions as 
confidential under the FOIA, and they will not be placed in the public 
docket of this NPRM. Submissions containing CBI should be sent to 
Calvin L. Hang, Aviation Safety Engineer, FAA, 3960 Paramount 
Boulevard, Lakewood, CA 90712; phone: (562) 627-5254; email: 
[email protected]. Any commentary that the FAA receives which is 
not specifically designated as CBI will be placed in the public docket 
for this rulemaking.

Background

    The FAA received a report of two cracks in an M/R drive shaft that 
were found during an inspection involving a Siam Hiller Model UH-12E 
helicopter. These cracks resulted from hydrogen embrittlement, possibly 
due to improper baking after the electroplating process, and certain 
paint strippers exploiting galvanic potential between the steel and 
cadmium. Since the affected part may also be installed on Model UH-12E-
L helicopters, this model helicopter is also affected by this unsafe 
condition.
    Accordingly, this proposed AD would require inspecting certain M/R 
drive shafts for a crack, prohibit installing certain M/R drive shafts 
unless the inspection is done, and prohibit using certain paint 
removers. This condition, if not addressed, could result in could 
result in loss of the M/R drive shaft and subsequent loss of control of 
the helicopter.

FAA's Determination

    The FAA is issuing this NPRM after determining that the unsafe 
condition described previously is likely to exist or develop on other 
products of the same type design.

Other Related Material

    The FAA reviewed Hiller Aircraft Corporation UH-12E Series 
Helicopters, Main Rotor Transmission Assembly, Overhaul Manual 63-20, 
dated June 01, 2015. This material specifies overhaul procedures for 
the M/R transmission assemblies.

Proposed AD Requirements in This NPRM

    This proposed AD would require, with the M/R drive shaft removed, 
removing the coatings from all surfaces of the M/R drive shaft by using 
certain paint strippers, hydrogen embrittlement relief baking the M/R 
drive shaft, and performing a magnetic particle inspection of the M/R 
drive shaft for a crack. Depending on the results of the magnetic 
particle inspection, this proposed AD would require removing the M/R 
drive shaft from service and installing an airworthy part. This 
proposed AD would also prohibit installing an affected M/R drive shaft 
on any helicopter unless the actions required by this proposed AD have 
been accomplished and prohibit using certain paint removers on the M/R 
drive shaft.

Costs of Compliance

    The FAA estimates that this AD, if adopted as proposed, would 
affect 110 helicopters of U.S. registry. Labor costs are estimated at 
$85 per work-hour. Based on these numbers, the FAA estimates the 
following costs to comply with this proposed AD.
    Removing the coatings, hydrogen embrittlement relief baking, and 
magnetic particle inspecting the M/R drive shaft would take 5 work-
hours and parts would cost $500 for an estimated cost of $925 per 
helicopter and $101,750 for the U.S. fleet. If required, replacing the 
M/R drive shaft would take 5 work-hours and parts would cost $15,000 
for an estimated cost of $15,425 per helicopter.

Authority for This Rulemaking

    Title 49 of the United States Code specifies the FAA's authority to 
issue rules on aviation safety. Subtitle I, section 106, describes the 
authority of the FAA Administrator. Subtitle VII: Aviation Programs, 
describes in more detail the scope of the Agency's authority.
    The FAA is issuing this rulemaking under the authority described in 
Subtitle VII, Part A, Subpart III, Section 44701: General requirements. 
Under that section, Congress charges the FAA with promoting safe flight 
of civil aircraft in air commerce by prescribing regulations for 
practices, methods, and procedures the Administrator finds necessary 
for safety in air commerce. This regulation is within the scope of that 
authority because it addresses an unsafe condition that is likely to 
exist or develop on products identified in this rulemaking action.

Regulatory Findings

    The FAA determined that this proposed AD would not have federalism 
implications under Executive Order 13132. This proposed AD 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.
    For the reasons discussed above, I certify this proposed 
regulation:
    (1) Is not a ``significant regulatory action'' under Executive 
Order 12866,
    (2) Would not affect intrastate aviation in Alaska, and
    (3) Would not have a significant economic impact, positive or 
negative, on a substantial number of small entities under the criteria 
of the Regulatory Flexibility Act.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

[[Page 3048]]

The Proposed Amendment

    Accordingly, under the authority delegated to me by the 
Administrator, the FAA proposes to amend 14 CFR part 39 as follows:

PART 39--AIRWORTHINESS DIRECTIVES

0
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]

0
2. The FAA amends Sec.  39.13 by adding the following new airworthiness 
directive:

Siam Hiller Holdings, Inc.: Docket No. FAA-2024-2555; Project 
Identifier AD-2024-00214-R.

 (a) Comments Due Date

    The FAA must receive comments on this airworthiness directive 
(AD) by February 28, 2025.

 (b) Affected ADs

    None.

 (c) Applicability

    This AD Applies to Siam Hiller Holdings, Inc., Model UH-12E 
(Army OH-23G and H-23F) and UH-12E-L helicopters, certificated in 
any category, with a main rotor (M/R) transmission drive shaft 
(drive shaft) having part number (P/N) 23600, installed.

    Note 1 to paragraph (c):  Hiller Aircraft Corporation material 
refers to an M/R drive shaft as a transmission M/R mast and M/R 
drive shaft, interchangeably.

 (d) Subject

    Joint Aircraft System Component (JASC) Code 6230, Main Rotor 
Mast/Swashplate.

 (e) Unsafe Condition

    This AD was prompted by reports of cracks in the M/R drive 
shaft. The FAA is issuing this AD to address non-conforming parts 
and the use of improper paint stripper; and detect cracking of the 
M/R drive shaft. The unsafe condition, if not addressed, could 
result in separation of the M/R drive shaft and M/R blades from the 
helicopter and subsequent loss of control of the helicopter.

 (f) Compliance

    Comply with this AD within the compliance times specified, 
unless already done.

 (g) Required Actions

    For an M/R drive shaft that has accumulated 1,200 or more total 
hours time-in-service (TIS) or 4 or more years since new, or at the 
next overhaul of the M/R transmission assembly after the effective 
date of this AD, whichever occurs first, with the M/R drive shaft 
removed, inspect the M/R drive shaft by accomplishing the actions 
required by paragraphs (g)(1) through (3) of this AD.
    (1) Remove all coatings from all surfaces of the M/R drive shaft 
by using paint stripper TT-R-248B or TT-R-2918A Type I.
    (2) Hydrogen embrittlement relief bake the M/R drive shaft for 
24 hours minimum at 375 [deg]F  25 [deg]F.
    (3) Magnetic particle inspect all surfaces of the M/R drive 
shaft for a crack. This magnetic particle inspection must be 
accomplished by a Level II or Level III inspector certified in the 
FAA-acceptable standards for nondestructive inspection personnel. If 
there is a crack, before further flight, remove the M/R drive shaft 
from service and install an airworthy M/R drive shaft.

    Note 2 to paragraph (g)(3):  Advisory Circular 65-31B contains 
examples of FAA-acceptable Level II and Level III qualification 
standards criteria for inspection personnel doing nondestructive 
test inspections.

    Note 3 to paragraph (g):  Hiller Aircraft Corporation Main Rotor 
Transmission Assembly Overhaul Manual, Manual 63-20, for UH-12E 
Series Helicopters, accepted May 6, 2015, contains additional 
information pertaining to inspecting the M/R drive shaft.

 (h) Parts Installation Limitations

    (1) As of the effective date of this AD, do not install an M/R 
drive shaft having P/N 23600 on any helicopter unless the actions 
required by paragraphs (g)(1) through (3) of this AD have been 
accomplished.
    (2) As of the effective date of this AD, do not use any other 
paint stripper other than TT-R-248B or TT-R-2918A Type I to remove 
coatings from all areas of the M/R drive shaft.

 (i) Alternative Methods of Compliance (AMOCs)

    (1) The Manager, West Certification Branch, FAA, has the 
authority to approve AMOCs for this AD, if requested using the 
procedures found in 14 CFR 39.19. In accordance with 14 CFR 39.19, 
send your request to your principal inspector or local Flight 
Standards District Office, as appropriate. If sending information 
directly to the manager of the West Certification Branch, send it to 
the attention of the person identified in paragraph (j)(1) of this 
AD. Information may be emailed to: [email protected].
    (2) Before using any approved AMOC, notify your appropriate 
principal inspector, or lacking a principal inspector, the manager 
of the local flight standards district office/certificate holding 
district office.

 (j) Additional Information

    (1) For more information about this AD, contact Calvin L. Hang, 
Aviation Safety Engineer, FAA, 3960 Paramount Boulevard, Lakewood, 
CA 90712; phone: (562) 627-5254; email: [email protected].
    (2) For Hiller Aircraft Corporation material identified in this 
AD that is not incorporated by reference, contact Hiller Aircraft 
Corporation, 925 M Street, Firebaugh, CA 93622; phone: (559) 659-
5959; or website: hilleraircraftcorporation.com/.
    (3) For advisory circular material identified in this AD that is 
not incorporated by reference, go to faa.gov/regulations_policies/advisory_circulars/index.cfm/go/document.information/documentID/1023552.

 (k) Material Incorporated by Reference

    None.

    Issued on December 9, 2024.
Victor Wicklund,
Deputy Director, Compliance & Airworthiness Division, Aircraft 
Certification Service.
[FR Doc. 2025-00588 Filed 1-13-25; 8:45 am]
BILLING CODE 4910-13-P
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