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PROPOSED AD BELL HELICOPTER TEXTRON INC.: Docket No. FAA-2017-0052; Product Identifier 2016-SW-081-AD.
(a) APPLICABILITY

    This  AD applies  to Model  412 and  412EP helicopters  with a  serial
    number (S/N) 33001 through  33213, 34001 through 34036,  36001 through
    36648, 36650 through 36657, 36660 through 36672, 36674 through  36680,
    36685, 36687,  36689, 36691,  36693, 36695,  and 37002  through 37012,
    certificated in any category,  with a static inverter  (inverter) part
    number (P/N) 412-375-079-101 or 412-375-079-103 installed.

(b) UNSAFE CONDITION

    This AD  defines the  unsafe condition  as the  failure of an inverter
    under  instrument  meteorological  conditions  or  night  flight. This
    condition  could  result  in smoke  in  the  cockpit, increased  pilot
    workload due to  the loss of  primary flight and  navigation displays,
    alternating current  powered engine  and transmission  indicators, and
    autopilot, and subsequent loss of control of the helicopter.

(c) AFFECTED ADS

    This  AD  replaces  AD 2015-04-04,  Amendment  39-18106  (80 FR  9594,
    February 24, 2015).

(d) COMMENTS DUE DATE

    We must receive comments by October 1, 2018.

(e) COMPLIANCE

    You are  responsible for  performing each  action required  by this AD
    within  the  specified  compliance time  unless  it  has already  been
    accomplished prior to that time.

(f) REQUIRED ACTIONS

(1) Within 25 hours time-in-service:

(i) For helicopters  with a S/N 33001 through 33213,  34001 through 34036,
    and  36001 through 36086,  replace the inverter with inverter P/N 412-
    375-079-105.

(ii) For helicopters with a S/N 36087 through 36648,  36650 through 36657,
     36660 through 36672, 36674 through 36680, 36685, 36687, 36689, 36691,
     36693, 36695, and 37002 through  37012, install retrofit kit P/N  412
     -704-058-103 and replace the  inverter with inverter P/N  412-375-079
     -105.

(2) After accomplishing the actions required  by  paragraph (f)(1) of this
    AD,  you  may  remove   the  placard  and  Rotorcraft   Flight  Manual
    limitations, required by  AD 2015-04-04, prohibiting  night operations
    and restricting flights to visual flight rules.

(3) After the effective date of this AD,  do not install  an  inverter P/N
    412-375-079-101 or 412-375-079-103 on any helicopter.

(g) ALTERNATIVE METHODS OF COMPLIANCE (AMOCS)

(1) The Manager, DSCO, FAA, may approve AMOCs for this AD.  Send your pro-
    posal to:  Tim Beauregard, Aviation Safety Engineer, DSCO Branch, AIR-
    7J0, FAA, 10101 Hillwood Pkwy, Fort Worth, TX 76177; telephone 817-222
    -5190; email 9-ASW-190-COS@faa.gov.

(2) For operations conducted under a 14 CFR part 119 operating certificate
    or under 14 CFR  part 91, subpart K,  we suggest that you  notify your
    principal inspector, or lacking a principal inspector, the manager  of
    the  local flight  standards district  office  or  certificate holding
    district office before operating  any aircraft complying with  this AD
    through an AMOC.

(h) ADDITIONAL INFORMATION

    Bell Alert Service Bulletin 412-15-164, dated March 13, 2015, and Bell
    Alert Service Bulletin 412-16-171, dated March 22, 2016, which are not
    incorporated  by  reference,  contain additional information about the
    subject  of  this  AD.  For service information identified in this AD,
    contact  Bell Helicopter Textron, Inc.,  P.O. Box 482,  Fort Worth, TX
    76101; telephone (817) 280-3391; fax (817) 280-6466; or at http://www.
    bellcustomer.com/files/.  You may  review  this service information at
    the FAA, Office of the Regional Counsel, Southwest Region, 10101 Hill-
    wood Pkwy., Room 6N-321, Fort Worth, TX 76177.

(i) SUBJECT

    Joint Aircraft Service Component (JASC) Code: 2422, AC Inverter.

Issued in  Fort Worth,  Texas, on  June 19,  2018. Scott  A. Horn,  Deputy
Director for Regulatory Operations, Compliance and Airworthiness Division,
Aircraft Certification Service.

DATES: We must receive comments on this proposed AD by October 1, 2018.
PREAMBLE 

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2017-0052; Product Identifier 2016-SW-081-AD]
RIN 2120-AA64

Airworthiness Directives; Bell Helicopter Textron Inc.
Helicopters

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

-----------------------------------------------------------------------

SUMMARY: We propose to supersede airworthiness directive (AD) 2015-04-
04 for Bell Helicopter Textron Inc. (Bell) Model 412 and 412EP
helicopters. AD 2015-04-04 requires revising the Rotorcraft Flight
Manual (RFM) and installing a placard to limit flights to visual flight
rules (VFR) and prohibiting night operations because of failing
inverters. This proposed AD would require replacing the inverters with
a new inverter. The actions in this proposed AD are intended to correct
an unsafe condition on these products.

DATES: We must receive comments on this proposed AD by October 1, 2018.

ADDRESSES: You may send comments by any of the following methods:

Federal eRulemaking Docket: Go to http://www.regulations.gov. Follow the
online instructions for sending your comments electronically.

Fax: 202-493-2251.

Mail: Send comments to the U.S. Department of
Transportation, Docket Operations, M-30, West Building Ground Floor,
Room W12-140, 1200 New Jersey Avenue SE, Washington, DC 20590-0001.

Hand Delivery: Deliver to the "Mail" address between 9
a.m. and 5 p.m., Monday through Friday, except Federal holidays.

Examining the AD Docket

You may examine the AD docket on the internet at http://www.regulations.
gov by searching for and locating Docket No. FAA-2017-
0052; 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 proposed AD, the economic evaluation, any comments received and
other information. The street address for Docket Operations (telephone
800-647-5527) is in the ADDRESSES section. Comments will be available
in the AD docket shortly after receipt.

For service information identified in this proposed rule, contact
Bell Helicopter Textron, Inc., P.O. Box 482, Fort Worth, TX 76101;
telephone (817) 280-3391; fax (817) 280-6466; or at http://www.
bellcustomer.com/files/. You may review service information at the
FAA, Office of the Regional Counsel, Southwest Region, 10101 Hillwood
Pkwy, Room 6N-321, Fort Worth, TX 76177.

FOR FURTHER INFORMATION CONTACT: Tim Beauregard, Aviation Safety
Engineer, DSCO Branch, AIR-7J0, FAA, 10101 Hillwood Pkwy, Fort Worth,
TX 76177; telephone (817) 222-4357; email timothy.beauregard@faa.gov.

SUPPLEMENTARY INFORMATION:

Comments Invited

We invite you to participate in this rulemaking by submitting
written comments, data, or views. We also invite comments relating to
the economic, environmental, energy, or federalism impacts that might
result from adopting the proposals in this document. The most helpful
comments reference a specific portion of the proposal, explain the
reason for any recommended change, and include supporting data. To
ensure the docket does not contain duplicate comments, commenters
should send only one copy of written comments, or if comments are filed
electronically, commenters should submit only one time.

We will file in the docket all comments that we receive, as well as
a report summarizing each substantive public contact with FAA personnel
concerning this proposed rulemaking. Before acting on this proposal, we
will consider all comments we receive on or before the closing date for
comments. We will consider comments filed after the comment period has
closed if it is possible to do so without incurring expense or delay.
We may change this proposal in light of the comments we receive.

Discussion

We issued AD 2015-04-04, Amendment 39-18106 (80 FR 9594, February
24, 2015), for Bell Model 412 and 412EP helicopters with an inverter
part number (P/N) 412-375-079-101 or 412-375-079-103 with a serial
number 29145 or higher. AD 2015-04-04 was prompted by numerous failures
of inverters. The failure of one inverter can result in smoke in the
cockpit, making landing at night and during instrument meteorological
conditions difficult. If two inverters fail, then the pilot will lose
primary flight and navigation displays, autopilot, and alternate
current powered engine and transmission indicators.

To address this condition, Bell issued Alert Service Bulletin (ASB)
412-13-156, dated April 25, 2013, which specifies inspecting inverter
part number (P/N) 412-375-079-101 and either repairing it or replacing
it with inverter P/N 412-375-079-103 to prevent failure. Because the
specific cause of the inverter failures had not been verified, and
since inverter failures continued after Bell issued the ASB, we
determined the actions specified in the ASB did not correct the unsafe
condition. Therefore, AD 2015-04-04 requires revising the RFM and
installing a placard in full view of the pilot to limit flights to VFR
only and prohibit night operations.

Actions Since AD 2015-04-04 Was Issued

Since we issued AD 2015-04-04, Bell determined the root causes of
the failures were an external connector that caused a short circuit
inside inverter P/N 412-375-079-101 and components chafing because of
variations in the assembly process and packaging tolerances for
inverter P/N 412-375-079-103. Bell introduced an improved inverter, P/N
412-375-079-105, and retrofit kits to replace inverter P/N 412-375-079-
101 or 412-375-079-103 on helicopters with serial numbers 33001 or
higher. These replacements and repairs correct the unsafe condition by
providing 250 voltage amperes (VA) of total power instead of 500 VA,
thereby reducing the input power to the inverter.

FAA's Determination

We are proposing this AD because we evaluated all the relevant
information and determined the unsafe condition described previously is
likely to exist or develop in other products of these same type
designs.

Related Service Information

We reviewed Bell Alert Service Bulletin (ASB) 412-15-164, dated
March 13, 2015 (ASB 412-15-164), which specifies an alternate means of
compliance (AMOC) approved by the FAA for AD 2015-04-04 (80 FR 9594,
February 24, 2015). Instead of the flight limitations mandated by AD
2015-04-04, ASB 412-15-164 limits allow operation under instrument
flight rules (IFR) and night operations with two pilots.

We also reviewed Bell ASB 412-16-171, dated March 22, 2016 (ASB
412-16-171), which specifies replacing certain serial-numbered
inverters P/N 412-375-079-101 and 412-375-079-103 with inverter P/N
412-375-079-105 as a direct replacement or with a retrofit kit. Bell
specifies that completing the actions specified by the ASB constitute
terminating action for Bell ASB 412-15-164.

Lastly, we reviewed Bell Service Instruction for Inverter Retrofit
Kit BHT-412-SI-93, dated February 15, 2016, which provides instructions
for installing retrofit kit P/N 412-704-058-103.

Proposed AD Requirements

The proposed AD would require, within 25 hours time-in-service
(TIS), replacing the inverter with inverter P/N 412-375-079-105 and,
for some helicopters, installing retrofit kit P/N 412-704-058-103.

After accomplishing the previous actions, the proposed AD would
allow removing the placard and Rotorcraft Flight Manual limitations
that prohibit night operations and restrict flights to visual flight
rules.

After the effective date of this AD, this proposed AD would
prohibit installing an inverter P/N 412-375-079-101 or 412-375-079-103
on any helicopter.

Differences Between This Proposed AD and the Service Information

Bell ASB 412-16-171 requires compliance no later than January 1,
2017, while this proposed AD would require compliance within 25 hours
TIS. Bell ASB 412-16-171 makes an electrical load analysis a
determining factor for corrective actions. This proposed AD would make
no such requirement. Bell ASB 412-16-171 provides instructions for
helicopters with serial numbers 36649, 36658, 36659, 36673, 36681
through 36684, 36686, 36688, 36690, 36692, 36694, and 36696 through
36704, and this proposed AD would not. Bell has notified us of errors
in the S/Ns listed for Part B of ASB 412-16-171. Accordingly, this
proposed AD would only be applicable to those serial-numbered
helicopters subject to the unsafe condition.

Costs of Compliance

We estimate that this proposed AD would affect 73 helicopters of
U.S. Registry and that labor costs average $85 per work-hour. Based on
these estimates, we expect that installing a new inverter or retrofit
kit would require about 3 work-hours and a parts cost of $15,749, for a
total cost of $16,004 per helicopter and $1,168,292 for the U.S. fleet.

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.

We are 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

We 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, I certify 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);

3. Will not affect intrastate aviation in Alaska to the extent that
it justifies making a regulatory distinction; and

4. 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.

We prepared an economic evaluation of the estimated costs to comply
with this proposed AD and placed it in the AD docket.

List of Subjects in 14 CFR Part 39

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

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

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. The FAA amends Sec. 39.13 by removing Airworthiness Directive (AD)
2015-04-04, Amendment 39-18106 (80 FR 9594, February 24, 2015), and
adding the following new AD: