Document ID: FAA-2017-0141-0054
Agency: faa
Document Type: Rule
Title: Airworthiness Directives: The Enstrom Helicopter Corporation Helicopters
Posted Date: 2018-01-17T05:00Z

[Federal Register Volume 83, Number 11 (Wednesday, January 17, 2018)]
[Rules and Regulations]
[Pages 2366-2369]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2018-00659]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2017-0141; Product Identifier 2016-SW-067-AD; Amendment 
39-19154; AD 2018-02-01]
RIN 2120-AA64

Airworthiness Directives; The Enstrom Helicopter Corporation 
Helicopters

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: We are superseding Airworthiness Directive (AD) 2015-08-51 for 
the Enstrom Helicopter Corporation (Enstrom) Model F-28A, 280, F-28C, 
F-28C-2, F-28C-2R, 280C, F-28F, F-28F-R, 280F, 280FX, and 480 
helicopters. AD 2015-08-51 required an inspection of the main rotor 
spindle (spindle) and reporting the inspection results to the FAA. This 
new AD was prompted by additional reports of cracked spindles and 
requires establishing a life limit and a recurring inspection. The 
actions of this AD are intended to prevent the unsafe condition on 
these products.

DATES: This AD is effective February 21, 2018.

ADDRESSES: For service information identified in this final rule, 
contact Enstrom Helicopter Corporation, 2209 22nd Street, Menominee, 
MI; telephone (906) 863-1200; fax (906) 863-6821; or at 
www.enstromhelicopter.com. You may view this referenced service 
information at the FAA, Office of the Regional Counsel, Southwest 
Region, 10101 Hillwood Pkwy., Room 6N-321, Fort Worth, TX 76177.

Examining the AD Docket

    You may examine the AD docket on the internet at http://www.regulations.gov in Docket No. FAA-2017-0141; or in person at the 
Docket Management Facility between 9 a.m. and 5 p.m., Monday through 
Friday, except Federal holidays. The AD docket contains this AD, the 
economic evaluation, any comments received, and other information. The 
address for the Docket Office (phone: 800-647-5527) is Document 
Management Facility, U.S. Department of Transportation, Docket 
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New 
Jersey Avenue SE, Washington, DC 20590.

FOR FURTHER INFORMATION CONTACT: Manzoor Javed, Senior Aerospace 
Engineer, Chicago ACO Branch, Compliance and Airworthiness Division, 
FAA, 2300 East Devon Ave., Des Plaines, IL 60018; telephone (847) 294-
8112; email [email protected].

SUPPLEMENTARY INFORMATION: 

Discussion

    We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR 
part 39 to remove AD 2015-08-51, Amendment 39-18160 (80 FR 28172, May 
18, 2015) (AD 2015-08-51) and add a new AD. AD 2015-08-51 applied to 
Enstrom Model F-28A, 280, F-28C, F-28C-2, F-28C-2R, 280C, F-28F, F-28F-
R, 280F, 280FX, and 480 helicopters with a spindle part number (P/N) 
28-14282-11 or 28-14282-13 installed. AD 2015-08-51 required conducting 
a one-time magnetic particle inspection (MPI) of the spindle for cracks 
and reporting the inspection results to the FAA. AD 2015-08-51 was 
prompted by a fatal accident and reports of spindles with cracks. AD 
2015-08-51 was issued as an interim action and was intended to detect a 
crack in a spindle and prevent loss of a main rotor blade and 
subsequent loss of control of the helicopter.
    The NPRM published in the Federal Register on March 2, 2017 (82 FR 
12308). The NPRM was prompted by additional reports of cracked 
spindles. Based on review of in-service data and a fatigue analysis, 
the FAA determined a life limit and recurring MPIs are necessary to 
reduce the risk of a crack developing in a spindle. We also determined 
the reporting requirement in AD 2015-08-51 is no longer necessary. 
Accordingly, the NPRM proposed to require an MPI of the spindle every 
500 hours time-in-service (TIS) until the spindle reaches its new life 
limit of 1,500 hours TIS.
    Since the NPRM was issued, the FAA's Aircraft Certification Service 
has changed its organizational structure. The new structure replaces 
product directorates with functional divisions. We have revised some of 
the office titles and nomenclature throughout this Final rule to 
reflect the new organizational changes. Additional information about 
the new structure can be found in the Notice published on July 25, 2017 
(82 FR 34564).

Comments

    After our NPRM was published, we received comments from 50 
commenters.

A. Support for the NPRM

    One commenter supported the 500-hour repetitive inspection proposed 
by the NPRM.

B. Comments Regarding the FAA's Justification of the Unsafe Condition

    Many commenters, including Enstrom, disagreed with the FAA's 
determination that an unsafe condition exists and requested the FAA 
provide more information about the additional cracks that prompted this 
AD.
    Request: A few commenters noted the entire fleet has been inspected 
in accordance with AD 2015-08-51 and no additional cracks were found. 
Other commenters stated no additional cracks have been found in the 
area of a spindle where a failure could cause a catastrophic accident. 
A few commenters, including Enstrom, stated no additional cracking has 
been reported in the same location as that of the accident spindle.
    Other commenters requested the FAA provide information about the 
number of additional reported cracks and whether there is any 
correlation between cracks and manufacturing dates or suppliers. 
Enstrom stated the cracked spindles discovered after the accident were 
manufactured between 1975 to 1980 by two specific suppliers.
    FAA Response: We agree to provide information about the cracks that 
prompted this AD. Contrary to the public comments stating there were no 
additional cracks found by the inspections required by AD 2015-08-51, 
those inspection results revealed 34 cracked spindle assemblies. The 
commenters are correct that the additional cracking was not in the same 
location as that of the accident spindle. The location of the 
additional 34 spindle cracks was at the hole for the cotter pin 
securing the lamiflex bearing nut. However, we disagree that the 
additional cracks were not in an area where a failure could cause a 
catastrophic accident. A spindle assembly is a primary structural 
element and a critical part. Flight with any known crack is prohibited 
in primary

[[Page 2367]]

structural elements including spindle assemblies. Regardless of the 
location of the crack, failure of a spindle assembly could result in 
loss of a main rotor blade.
    We agree with Enstrom's comment that the cracked spindles 
discovered after the accident were manufactured between 1975 to 1980 by 
two specific suppliers. However, the accident helicopter had two 
cracked and one failed spindle that were manufactured in 1984 by a 
third manufacturer. The identities of the manufacturers are unknown. 
The parts were marked differently with a letter designation at the end 
depending on the manufacturer, but no manufacturing records exist to 
indicate which letter corresponds to which manufacturer. Therefore, no 
investigation could be conducted as to what manufacturing processes or 
specifications used by these suppliers may have resulted in the 
cracking. Accordingly, we cannot draw a conclusion as to whether the 
manufacturer and date range are causal factors in the accident.
    Request: One commenter questioned whether the FAA investigated the 
possibility that the cracked spindle resulted from improper maintenance 
action or procedures.
    FAA's Response: As part of the accident investigation, the NTSB lab 
inspected the three spindles from the accident aircraft for any tool 
marks that might indicate an initiation point that was maintenance 
related. They were unable to find such marks. Based on the number of 
cracks found in the field and the fact that they were not all 
maintained by the same organization, there is no data to suggest that 
this resulted from improper maintenance.

C. Comments Regarding the Required Actions

    Request: Thirty-eight commenters, including Enstrom, requested the 
AD not require the 1,500-hour life limit because it would be burdensome 
and unnecessary. Most of these commenters also stated that the 
repetitive inspections specified by Enstrom would be effective in 
identifying cracks and removing any cracked spindles from service. Four 
commenters requested the life limit be higher than 1,500 hours, and 
proposed alternative life limits of 4,000 hours, 6,750 hours, between 
8,000 and 9,000 hours, and 15,000 hours.
    FAA Response: We disagree. The corrective action outlined in the 
Enstrom service information did not reduce the risk to an acceptable 
level. Consequently, we used the crack data to conduct a risk 
assessment in accordance with the FAA's Rotorcraft Risk Analysis 
Handbook, Revision 3, dated September 10, 2014. The accident 
investigation and inspection results from AD 2015-08-51 show cracked 
spindles from 1,800 hours up to 9,300 hours (on the accident 
helicopter). A Weibull analysis identified a life limit of 
approximately 800 hours. But the goodness of fit was not high as the 
times on these parts historically have not been tracked, so we assumed 
the part time to be the time on the airframe, which may not be 
accurate. We therefore applied an additional method to determine an 
appropriate life limit. We used inspection results as baseline data to 
conduct a fatigue analysis using standard fatigue methodology and 
scatter factors found in Advisory Circular (AC) 23-13A, ``Fatigue, 
Fail-Safe, and Damage Tolerance Evaluation of Metallic Structure For 
Normal, Utility, Acrobatic, and Commuter Category Airplanes.'' While 
this AC was written for small aircraft, its approach for establishing a 
life limit is conventional and was the most computationally valid 
method considered. This analysis resulted in a life limit of 1,500 
hours. We also reviewed the potential for higher life limits, but these 
resulted in unacceptably short inspection intervals. For example, a 
retirement age of 10,000 hours with an initial inspection at 1,500 
hours would require repetitive inspections every 75 hours to maintain 
an acceptable level of risk. We rejected these short inspection 
frequencies because of the potential for increased maintenance errors. 
Additionally, we considered the life limit of 1,500 hours is similar to 
those for spindles used in other rotorcraft.
    Request: Twenty-three commenters, including Enstrom, disagreed with 
the compliance time for the 500-hour initial inspection. To support 
this disagreement, most of these commenters stated no cracks have been 
reported on spindles with less than 1,800 hours TIS. The commenters 
requested that the AD require the initial inspection within 1,500 hours 
as specified in Enstrom's service information.
    FAA Response: We disagree. While the commenters are correct that no 
cracks have been reported on spindles with less than 1,800 hours TIS, 
this factor is less significant than those discussed above. Standard 
practice in addressing fatigue and life limits require inspection 
intervals that provide two inspection opportunities to detect a crack 
before a life limit is reached. Because the FAA determined a life limit 
of 1,500 hours TIS is required for the spindles, it follows that at a 
minimum initial and repetitive inspections every 500 hours TIS are 
necessary.
    Request: One commenter requested the AD require the spindle life 
limit of 7,500 cycles instead of 1,500 flight hours.
    FAA Response: We disagree. All data considered and analysis 
conducted for this AD has been determined using flight hours. The 
commenter states he used figure AC 27 MG 11-9 from AC 27-1B, 
``Certification of Normal Category Rotorcraft,'' for his conversion. 
The spectrum in that figure is an example and therefore we do not find 
the commenter's conversion the most appropriate in this case.
    Request: Two commenters disagreed with the AD because of the 
service history of their helicopters and Enstrom's history in general.
    FAA Response: The fact that the individual helicopters owned or 
operated by some commenters have not experienced cracking does not 
negate the existence of an unsafe condition. The risk analysis used to 
support the requirements of this AD was based on in-service data 
reported as a result of AD 2015-04-51. This data represents the actual 
service state of the current Enstrom fleet, which is more accurate than 
the factors mentioned by the commenters.

D. Requests To Allow Alternative Actions

    Request: Many commenters, including Airwolf Aerospace (Airwolf), 
requested the AD allow installing an Airwolf tension-torsion strap 
assembly (TT strap) as a means of complying with or terminating the AD. 
In support of this request, Airwolf stated that TT strap installation 
completely removes the threaded area of the spindle, leaving nothing 
left to inspect.
    FAA Response: We disagree. The commenter's request is unnecessary. 
The Airwolf TT strap installation modifies the helicopter and the 
spindle, changing the P/N of the spindle, such that the AD would no 
longer apply.
    Request: One commenter requested that instead of a life limit, the 
AD require a visual inspection of the cotter pin hole at each 100-hour 
or annual inspection. No technical data supporting this request was 
provided by the commenter.
    FAA Response: We disagree. As explained above, the FAA has 
determined a life limit is required to correct the unsafe condition. 
Inspection programs alone are not sufficient to lower the risk to an 
acceptable level.
    Request: Four commenters stated they have already inspected the 
spindles in accordance with AD 2015-08-51. One

[[Page 2368]]

commenter requested the AD allow a 300-hour grace period for spindles 
that have already been inspected.
    FAA Response: We disagree. Providing a grace period within which to 
comply with a life limit essentially extends the life limit and would 
not be appropriate.

E. Comments Regarding Costs of Compliance With This AD

    Request: Many commenters stated that the cost to comply with this 
AD is underestimated or inaccurate. These commenters stated the cost 
should include the costs associated with loss of utility; should 
reflect a replacement cost of $24,492 for three spindles; and should 
increase the labor rate.
    FAA's Response: We disagree. The cost analysis in AD rulemaking 
actions typically includes only the costs associated with complying 
with the AD, which does not include indirect costs such as down-time 
and loss of revenue.
    The parts costs for this AD were provided by the manufacturer. We 
do not control any price differences or retail pricing.
    The labor rate of $85 per hour is provided by the FAA Office of 
Aviation Policy and Plans for the FAA to use when estimating the labor 
costs of complying with AD requirements.
    Request: Several commenters requested the FAA not issue the AD 
because the extremely high cost will cause small operators to cease 
operations.
    FAA's Response: We disagree. Although the FAA sympathizes with 
owners and the economic impact this AD may have, it does not negate the 
need to correct the identified unsafe condition. The applicable 
spindles in this design are critical for safe flight.

FAA's Determination

    We have reviewed the relevant information and determined that an 
unsafe condition exists and is likely to exist or develop on other 
helicopters of these same type designs and that air safety and the 
public interest require adopting the AD requirements as proposed.

Related Service Information

    We reviewed Enstrom Service Directive Bulletin No. 0119, Revision 
3, dated June 24, 2016, for Model F-28A, F-28C, F-28F, 280, 280C, 280F, 
and 280FX helicopters with a spindle P/N 28-14282-11 or 28-14282-13. We 
also reviewed Enstrom Service Directive Bulletin No. T-050, Revision 3, 
dated June 24, 2016, for Model 480 helicopters, serial numbers 5001 
through 5004 and 5006, and with a spindle P/N 28-14282-13, except those 
aircraft modified with tension-torsion straps. Both service directive 
bulletins specify sending the spindle to Enstrom for an MPI before the 
spindle reaches 1,500 hours TIS, or within 5 hours TIS for those 
spindles with 1,500 or more hours TIS. Thereafter, the service 
directive bulletins specify returning the spindle to Enstrom for an MPI 
every 500 hours.

Differences Between This AD and the Service Information

    This AD requires establishing a spindle life limit of 1,500 hours 
TIS. The service information does not specify a life limit.
    This AD requires that the MPI be conducted by a Level II or Level 
III inspector or equivalent. The service information specifies sending 
the spindle to Enstrom for an MPI.
    This AD requires an initial MPI before further flight for a spindle 
with 500 or more hours TIS, unless an MPI has been done within the last 
500 hours TIS. The service information specifies an initial MPI 
compliance time of within 5 hours TIS for a spindle with 1,500 or more 
hours TIS.

Costs of Compliance

    We estimate that this AD affects 323 helicopters of U.S. Registry. 
We estimate that operators may incur the following costs in order to 
comply with this AD. Labor costs are estimated at $85 per work-hour. 
Inspecting the spindles takes about 15 work-hours for an estimated cost 
of $1,275 per helicopter and $411,825 for the U.S. fleet per inspection 
cycle. Replacing a cracked spindle costs $8,164 for parts and no 
additional work-hours. Replacing a set of three spindles that have 
reached their life limit takes about 14 work-hours and parts will cost 
$17,500 for a total cost of $18,690 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.
    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 have determined that this AD will not have federalism 
implications under Executive Order 13132. This AD will 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 that this AD:
    (1) Is not a ``significant regulatory action'' under Executive 
Order 12866;
    (2) Is not a ``significant rule'' under DOT Regulatory Policies and 
Procedures (44 FR 11034, February 26, 1979);
    (3) Will not affect intrastate aviation in Alaska to the extent 
that a regulatory distinction is required; 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.

List of Subjects in 14 CFR Part 39

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

Adoption of the Amendment

    Accordingly, under the authority delegated to me by the 
Administrator, the FAA amends 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 removing Airworthiness Directive (AD) 
2015-08-51, Amendment 39-18160 (80 FR 28172, May 18, 2015), and adding 
the following new AD:

2018-02-01 The Enstrom Helicopter Corporation (Enstrom): Amendment 
39-19154; Docket No. FAA-2017-0141; Product Identifier 2016-SW-067-
AD.

(a) Applicability

    This AD applies to Enstrom Model F-28A, 280, F-28C, F-28C-2, F-
28C-2R, 280C, F-28F, F-28F-R, 280F, and 280FX helicopters, all 
serial numbers; and Enstrom Model 480 helicopters, serial numbers 
5001 through 5006; with a main rotor spindle (spindle) part number 
(P/N) 28-14282-11 or 28-14282-13, installed, certificated in any 
category.

[[Page 2369]]

(b) Unsafe Condition

    This AD defines the unsafe condition as a crack in a spindle, 
which, if not detected, could result in loss of a main rotor blade 
and subsequent loss of control of the helicopter.

(c) Affected ADs

    This AD supersedes AD 2015-08-51, Amendment 39-18160 (80 FR 
28172, May 18, 2015).

(d) Effective Date

    This AD becomes effective February 21, 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) Before further flight, remove from service any spindle P/N 
28-14282-11 or 28-14282-13 that has 1,500 or more hours time-in-
service (TIS). If the hours TIS of a spindle is unknown, use the TIS 
of the helicopter. Thereafter, remove from service any spindle P/N 
28-14282-11 or 28-14282-13 before accumulating 1,500 hours TIS.
    (2) For each spindle with 500 or more hours TIS, using the hours 
TIS of the helicopter if the hours TIS of the spindle is unknown:
    (i) Before further flight, unless already done within the last 
500 hours TIS, conduct a magnetic particle inspection (MPI) of the 
spindle for a crack, paying particular attention to the threaded 
portion of the spindle. The MPI of the spindle must be conducted by 
a Level II or Level III inspector qualified in the MPI in the 
Aeronautics Sector according to the EN4179 or NAS410 standard or 
equivalent. If there is a crack in the spindle, replace it with an 
airworthy spindle before further flight.
    (ii) Thereafter at intervals not to exceed 500 hours TIS, repeat 
the MPI specified in paragraph (f)(2)(i) of this AD.

(g) Alternative Methods of Compliance (AMOCs)

    (1) The Manager, Chicago ACO Branch, FAA, may approve AMOCs for 
this AD. Send your proposal to: Manzoor Javed, Senior Aerospace 
Engineer, Chicago ACO Branch, Compliance and Airworthiness Division, 
FAA, 2300 East Devon Ave., Des Plaines, IL 60018; telephone (847) 
294-8112; email [email protected].
    (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

    Enstrom Service Directive Bulletin Nos. 0119 and T-050, both 
Revision 3 and both dated June 24, 2016, which are not incorporated 
by reference, contain additional information about the subject of 
this AD. For service information identified in this AD, contact 
Enstrom Helicopter Corporation, 2209 22nd Street, Menominee, MI; 
telephone (906) 863-1200; fax (906) 863-6821; or at 
www.enstromhelicopter.com. You may review a copy of the service 
information at the FAA, Office of the Regional Counsel, Southwest 
Region, 10101 Hillwood Pkwy., Room 6N-321, Fort Worth, TX 76177.

(i) Subject

    Joint Aircraft Service Component (JASC) Code: 6220, Main Rotor 
Head.

    Issued in Fort Worth, Texas, on January 8, 2018.
James A. Grigg,
Acting Director, Compliance & Airworthiness Division, Aircraft 
Certification Service.
[FR Doc. 2018-00659 Filed 1-16-18; 8:45 am]
 BILLING CODE 4910-13-P