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PROPOSED AD STEMME AG: Docket No. FAA-2021-1010; Project Identifier MCAI-2020-00807-G.
(a) COMMENTS DUE DATE

    The FAA must receive comments on this airworthiness directive (AD)  by
    January 6, 2022.

(b) AFFECTED ADS

    None.

(c) APPLICABILITY

    This AD applies  to Stemme AG  TSA-M Model S6  and S6-RT gliders,  all
    serial numbers, certificated in any category, with a propeller gearbox
    tooth belt marked "Synchroforce Carbon" installed.

(d) SUBJECT

    Joint Aircraft System Component (JASC) Code 6100, Propeller System.

(e) UNSAFE CONDITION

    This AD was prompted by mandatory continuing airworthiness information
    (MCAI) issued by the aviation authority of another country to identify
    and  correct an  unsafe condition  on an  aviation product.  The  MCAI
    describes  the  unsafe  condition as  a new  version of  the propeller
    gearbox tooth belt with a reduced life limit. The FAA is issuing  this
    AD to  prevent a  propeller gearbox  tooth belt  remaining in  service
    beyond its fatigue life. The unsafe condition, if not addressed, could
    result in  failure of  the propeller  gearbox tooth  belt and  reduced
    control of the glider.

(f) COMPLIANCE

    Comply with this AD within the compliance times specified,  unless al-
    ready done.

(g) REQUIRED ACTIONS

    Before  the propeller  gearbox tooth  belt accumulates  5 years  since
    installation on a glider or within 30 days after the effective date of
    this AD, whichever  occurs later, and  thereafter at intervals  not to
    exceed 5 years, remove the  propeller gearbox tooth belt from  service
    and install  a propeller  gearbox tooth  belt with  zero hours time-in
    -service.

(h) ALTERNATIVE METHODS OF COMPLIANCE (AMOCS)

(1) The Manager, International Validation 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
    certification  office,  send  it  to  the  attention  of  the   person
    identified in paragraph (i)(1) of this AD or email: 9-AVS-AIR-730-AMOC
    @faa.gov.

(2) Before using any approved AMOC,  notify your appropriate principal in-
    spector, or lacking  a principal inspector,  the manager of  the local
    flight standards district office/certificate holding district office.

(i) RELATED INFORMATION

(1) For more information about this AD,  contact Jim Rutherford,  Aviation
    Safety Engineer,  General Aviation & Rotorcraft Section, International
    Validation Branch, FAA,  901 Locust,  Room 301, Kansas City, MO 64106;
    phone: (816) 329-4165; fax: (816) 329-4090; email: jim.rutherford@faa.
    gov.

(2) Refer  to  European Union Aviation Safety Agency  (EASA) AD 2020-0140,
    dated June 23, 2020, for more information. You may examine the EASA AD
    in the AD docket  at https://www.regulations.gov  by searching for and
    locating it in Docket No. FAA-2021-1010.

Issued on November 15, 2021. Lance T Gant, Director, Compliance & Airworth
-iness Division, Aircraft Certification Service.

DATES: The FAA must receive comments  on  this  proposed AD  by January 6,
2022.
PREAMBLE 

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2021-1010; Project Identifier MCAI-2020-00807-G]
RIN 2120-AA64

Airworthiness Directives; Stemme AG Gliders

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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

SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD)
for certain Stemme AG TSA-M Model S6 and S6-RT gliders. This proposed
AD was prompted by mandatory continuing airworthiness information
(MCAI) issued by the aviation authority of another country to identify
and correct an unsafe condition on an aviation product. The MCAI
describes the unsafe condition as a new version of the propeller
gearbox tooth belt with a reduced life limit. This proposed AD would
require establishing a life limit of 5 years for certain propeller
gearbox tooth belts. 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 January 6,
2022.

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 https://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: Deliver to Mail address above between 9
a.m. and 5 p.m., Monday through Friday, except Federal holidays.
For service information identified in this NPRM, contact STEMME AG,
Flugplatzstrasse F2, Nr. 6-7, D-15344 Strausberg, Germany; phone: +49
(0) 3341 3612-0; fax: +49 (0) 3341 3612-30; email:
airworthiness@stemme.de; website: https://www.stemme.com. You may view
this service information at the FAA, Airworthiness Products Section,
Operational Safety Branch, 901 Locust, Kansas City, MO 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 at https://www.regulations.gov by
searching for and locating Docket No. FAA-2021-1010; 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, the MCAI,
any comments received, and other information. The street address for
Docket Operations is listed above.

FOR FURTHER INFORMATION CONTACT: Jim Rutherford, Aviation Safety
Engineer, General Aviation & Rotorcraft Section, International
Validation Branch, FAA, 901 Locust, Room 301, Kansas City, MO 64106;
phone: (816) 329-4165; fax: (816) 329-4090; email:
jim.rutherford@faa.gov.

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 ADDRESSES. Include ``Docket No. FAA-2021-1010; Project Identifier
MCAI-2020-00807-G'' 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 amend
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
https://www.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 Jim
Rutherford, Aviation Safety Engineer, General Aviation & Rotorcraft
Section, International Validation Branch, FAA, 901 Locust, Room 301,
Kansas City, MO 64106. 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 European Union Aviation Safety Agency (EASA), which is the
Technical Agent for the Member States of the European Union, has issued
EASA AD 2020-0140, dated June 23, 2020 (referred to after this as ``the
MCAI''), to address an unsafe condition on Stemme AG (Stemme) TSA-M
Model S6 and S6-RT powered sailplanes (gliders) and ASP S15-1
airplanes. The MCAI states:

The airworthiness limitations for Stemme TSA-M powered
sailplanes and Stemme ASP aeroplanes, which are approved by EASA,
are currently defined and published in Chapter 4 of the applicable
AMM [aircraft maintenance manual]. These instructions have been
identified as mandatory for continued airworthiness.
Failure to accomplish these instructions could result in an
unsafe condition.
During a regular incoming part inspection at Stemme, the
supplier delivered a new version of the tooth belts used in the
propeller gearbox. The new part (with marking ``Carbon'') deviates
from the previously used part (with marking ``Extreme'') by its
layer build up. The new tooth belt has been found airworthy,
although with a reduced life limit.
Before Stemme identified the issue, new tooth belts were
delivered, identified as Part Number (P/N) 830.185, the same as the
previous part. These parts have to be identified by inspection,
changed to P/N 832.502, and the reduced life limit implemented.
Consequently, Stemme issued the applicable ALS [airworthiness
limitations section] introducing the new life limit for the new
part. Stemme also issued the SB [service bulletin] providing
additional instructions on relevant inspections and corrective
actions.
For the reasons described above, this [EASA] AD requires a one-
time inspection of the propeller gearbox tooth belts, and, depending
on findings, re-identification. This [EASA] AD also requires
implementation of the reduced life limit by accomplishment of the
actions specified in the applicable ALS.

After issuance of the MCAI, EASA approved extending the life limit
of the new ``Synchroforce Carbon'' belt to 5 years, the same as the
original ``Extreme'' belt, as documented by Stemme in Revision 15 to
the AMM Chapter 04 ALS.
You may examine the MCAI in the AD docket at https://www.regulations.gov
by searching for and locating Docket No. FAA-2021-1010.

Related Service Information

The FAA reviewed Stemme Service Bulletin (SB) Doc. No. P062-980049,
Revision 00, dated May 27, 2020. This SB specifies identifying the
front propeller gearbox tooth belt, revising the AMM and illustrated
parts catalogue, and introducing a life limit for the propeller gearbox
tooth belt marked ``Synchroforce Carbon.''

FAA's Determination

This product has been approved by the aviation authority of another
country and is approved for operation in the United States. Pursuant to
the FAA's bilateral agreement with this State of Design Authority, it
has notified the FAA of the unsafe condition described in the MCAI and
service information referenced above. The FAA is issuing this NPRM
after determining the unsafe condition described previously is likely
to exist or develop on other products of the same type design.

Proposed AD Requirements


This proposed AD would establish a life limit of 5 years for the
affected propeller gearbox tooth belt.

Differences Between This Proposed AD and the MCAI or Service
Information


The MCAI applies to Stemme AG Model ASP S15-1 airplanes, and this
proposed AD would not because that model does not have an FAA type
certificate.
The MCAI requires an inspection to determine whether the propeller
gearbox tooth belts are ``Synchroforce Carbon'' or ``Extreme.'' This
proposed AD would not require this inspection because instead, it would
apply only to gliders with a ``Synchroforce Carbon'' propeller gearbox
tooth belt installed.
The MCAI requires revising the existing aircraft maintenance
program (AMP) to introduce the reduced life limit for the affected
propeller gearbox tooth belt, as well as other life limits, as
specified in the Temporary Revision to the aircraft maintenance manual
airworthiness limitations section (ALS). After the AMP is revised, the
MCAI does not require recording AD compliance on a continued basis each
time a task in the revised AMP is performed. Because the AMP is not
required for U.S. operators and the ALS specified in the MCAI includes
additional tasks that do not address the unsafe condition, this
proposed AD would establish a life limit for the affected propeller
gearbox tooth belt by requiring that it be removed from service after 5
years. Operators would be required to record AD compliance each time an
affected propeller gearbox tooth belt reaches its life limit and is
replaced.
Stemme SB Doc. No. P062-980049, Revision 00, dated May 27, 2020,
requires reporting information to Stemme AG, and this proposed AD would
not.

Costs of Compliance

The FAA estimates that this AD, if adopted as proposed, would
affect 3 gliders of U.S. registry. The FAA estimates that it would take
4 work hours to replace the propeller gearbox tooth belt and require a
part costing $300. The average labor rate is $85 per work hour. Based
on these figures, the FAA estimates the cost to replace the propeller
gearbox tooth belt on U.S. operators to be $1,920 or $640 per glider,
every 5 years.

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.

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 adding the following new airworthiness
directive: