DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2021-0716; Project Identifier 2019-CE-023-AD]
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
for all Stemme AG Model Stemme S 12 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 an airspeed indicator (ASI) with speed markings
inconsistent with the approved and published values. This proposed AD
would require inspecting the ASI markings and, depending on findings,
either replacing the ASI or amending the existing aircraft flight
manual (AFM) until the ASI is replaced. 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 October
ADDRESSES: You may send comments, using the procedures found in
11.43 and 11.45, by any of the following methods:
Federal eRulemaking Portal: Go to https://www.regulations.gov. Follow
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:
email@example.com; 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)
Examining the AD Docket
You may examine the AD docket at https://www.regulations.gov by
searching for and locating Docket No. FAA-2021-0716; 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:
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-2021-0716; Project Identifier
2019-CE-023-AD" 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.
The European Union Aviation Safety Agency (EASA), which is the
Technical Agent for the Member States of the European Union, has issued
EASA AD 2019-0082, dated April 12, 2019 (referred to after this as
"the MCAI"), to address an unsafe condition on Stemme AG Model Stemme
S 12 gliders. The MCAI states:
During a production inspection of a new powered sailplane, an
ASI was found with speed markings inconsistent with the approved and
published values (begin[ning] of the white and green arc).
Subsequent investigation of the production records for delivered
Stemme S 12 powered sailplanes does not exclude that a similar, non-
conforming ASI was installed during production.
This condition, if not corrected, could lead to erroneous
information being provided to the pilot, particularly at the lower
speed operation limits, possibly resulting in reduced control of the
To address this unsafe condition, Stemme AG issued the SB
[service bulletin] to provide inspections instructions.
For the reason described above, this [EASA] AD requires a one-
time inspection of the markings of the affected part and, depending
on findings, amending the Aircraft Flight Manual (AFM) and replacing
the affected part. This [EASA] AD also prohibits installation of
You may examine the MCAI in the AD docket at https://www.regulations.gov
by searching for and locating Docket No. FAA-2021-0716.
Related Service Information Under 1 CFR Part 51
The FAA reviewed Stemme Service Bulletin No. P062-980027, Revision
00, dated December 17, 2018. The service information specifies checking
the ASI markings and provides illustrations of correct markings. The
service information specifies the procedure to replace an affected ASI
with an ASI with correct markings. The service information also
includes a temporary page to insert into the AFM until the ASI is
replaced. 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 ADDRESSES.
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 in This NPRM
This proposed AD would require a one-time inspection of the ASI
markings and, depending on findings, either replacing the ASI before
further flight or amending the existing AFM until the ASI is replaced
within 3 months.
Costs of Compliance
The FAA estimates that this AD, if adopted as proposed, would
affect 20 gliders of U.S. registry. The FAA estimates that it would
take about 0.5 work-hour per glider to comply with the inspection
requirements of this AD. The average labor rate is $85 per work-hour.
Based on these figures, the FAA estimates the cost of this AD on
U.S. operators to be $850 or $42.50 per glider.
The FAA estimates that amending the AFM to insert and then remove
the temporary page as a result of the inspection would take about 1
work-hour per glider for a total cost of $85 per glider. The FAA
estimates that replacing the ASI would take about 3.5 work-hours and
require parts costing $603, for a total cost of $900.50 per glider. The
FAA has no way of determining the number of gliders that may need these
The FAA has included all known costs in its cost estimate.
According to the manufacturer, however, some of the costs of this AD
may be covered under warranty, thereby reducing the cost impact on
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.
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
(1) Is not a "significant regulatory action" under Executive
(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
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