DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2017-0952; Product Identifier 2017-CE-028-AD]
RIN 2120-AA64

Airworthiness Directives; Stemme AG Gliders

AGENCY: Federal Aviation Administration (FAA), Department of
Transportation (DOT).

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: We propose to supersede Airworthiness Directive (AD) 2017-10-
11 for Stemme AG Model Stemme S10-VT gliders (type certificate
previously held by Stemme GmbH & Co. KG). This proposed AD results from
mandatory continuing airworthiness information (MCAI) originated by an
aviation authority of another country to identify and correct an unsafe
condition on an aviation product. The MCAI describes the unsafe
condition as certain propeller front transmission gear wheels having
insufficient material strength because of improper heat treatment
during manufacturing. We are issuing this proposed AD to require
actions to address the unsafe condition on these products and to add
Stemme AG Model Stemme S 12 to the applicability.

DATES: We must receive comments on this proposed AD by November 24, 2017.

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

Federal eRulemaking Portal: Go to http://www.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: U.S. Department of Transportation, Docket
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New
Jersey Avenue SE., Washington, DC 20590, between 9 a.m. and 5 p.m.,
Monday through Friday, except Federal holidays.

For service information identified in this proposed AD, contact
STEMME AG, Flugplatzstrasse F2, Nr. 6-7, D-15344 Strausberg, Germany;
telephone: +49 (0) 3341 3612-0, fax: +49 (0) 3341 3612-30; Internet:
https://www.stemme.com. You may review copies of the referenced service
information at the FAA, Policy and Innovation Division, 901 Locust,
Kansas City, Missouri 64106. For information on the availability of
this material at the FAA, call (816) 329-4148.

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-2017-0952;
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 proposed AD, the regulatory evaluation, any comments
received, and other information. The street address for the Docket
Office (telephone (800) 647-5527) is in the ADDRESSES section. Comments
will be available in the AD docket shortly after receipt.

FOR FURTHER INFORMATION CONTACT: Jim Rutherford, Aerospace Engineer,
FAA, Small Airplane Standards Branch, 901 Locust, Room 301, Kansas
City, Missouri 64106; telephone: (816) 329-4165; fax: (816) 329-4090;
email: jim.rutherford@faa.gov.

SUPPLEMENTARY INFORMATION:

Comments Invited

We invite you to send any written relevant data, views, or
arguments about this proposed AD. Send your comments to an address
listed under the ADDRESSES section. Include "Docket No. FAA-2017-0952;
Product Identifier 2017-CE-028-AD" at the beginning of your comments.
We specifically invite comments on the overall regulatory, economic,
environmental, and energy aspects of this proposed AD. We will consider
all comments received by the closing date and may amend this proposed
AD because of those comments.

We will post all comments we receive, without change, to http://
regulations.gov, including any personal information you provide. We
will also post a report summarizing each substantive verbal contact we
receive about this proposed AD.

Discussion

We issued AD 2017-10-11, Amendment 39-18885 (82 FR 24239, May 26,
2017) ("AD 2017-10-11") to address an unsafe condition on all Stemme
AG Model Stemme S10-VT gliders (type certificate previously held by
Stemme GmbH & Co. KG) equipped with a certain front gearbox, part
number 11AG, and was based on mandatory continuing airworthiness
information (MCAI) originated by an aviation authority of another
country.

Since we issued AD 2017-10-11, we have type certificated Stemme AG
Model Stemme S 12 gliders in the United States and have determined
those model gliders should also be included in the applicability of AD
2017-10-11. In addition, Stemme AG has issued new service information
with procedures for addressing the unsafe condition.

Related Service Information Under 1 CFR Part 51

Stemme AG has issued STEMME Service Bulletin Dok. Nr.: P062-980010,
Issue: 01, dated June 14, 2017, and STEMME Procedural Specification
Dok. Nr.: P320-900060, dated June 14, 2017. In combination, the service
information describes procedures for replacing the front gearbox. This
service information is reasonably available because the interested
parties have access to it through their normal course of business or by
the means identified in the ADDRESSES section of this NPRM.

FAA's Determination and Requirements of the Proposed AD

This product has been approved by the aviation authority of another
country, and is approved for operation in the United States. Pursuant
to our bilateral agreement with this State of Design Authority, they
have notified us of the unsafe condition described in the MCAI and
service information referenced above. We are proposing this AD because
we evaluated all information and determined the unsafe condition exists
and is likely to exist or develop on other products of the same type
design.

Differences Between This Proposed AD and the Service Information

The service information for this proposed AD allows the owner/
operator to do certain maintenance tasks. Also, the service information
specifies certain maintenance tasks be done by Stemme AG. However, for
this proposed AD, we do not allow the owner/operator to do any
maintenance tasks; all maintenance tasks must be done by an
appropriately certified mechanic or maintenance shop. In addition, we
do not require any maintenance tasks be done specifically by Stemme AG;
any appropriately certified mechanic or maintenance shop may do the
tasks required by this proposed AD.

Costs of Compliance

According to the U.S. registry, we have a total of 51 of both
glider types registered, but there are still only 14 serial numbers of
the part number 11AG front gearbox. Therefore, the most gliders that
could be affected remains 14. According to Stemme AG, there are a total
of 4 of the affected front gearboxes on both glider types of U.S.
registry (2 for each model).

It will take an estimated 19 work-hours per product to comply with
the basic requirements of this proposed AD. The average labor rate is
$85 per work-hour. Required parts would cost about $2,000 per product.

Based on these figures, if we consider the costs for all 14
affected gearboxes, then we estimate the cost of the proposed AD on
U.S. operators to be $50,610, or $3,615 per product.

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.

This AD is issued in accordance with authority delegated by the
Executive Director, Aircraft Certification Service, as authorized by
FAA Order 8000.51C. In accordance with that order, issuance of ADs is
normally a function of the Compliance and Airworthiness Division, but
during this transition period, the Executive Director has delegated the
authority to issue ADs applicable to small airplanes, gliders, and
domestic business jet transport airplanes to the Director of the Policy
and Innovation Division.

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 above, 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, 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.

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 Amendment 39-18885 (82 FR
24239, May 26, 2017), and adding the following new AD: