DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2021-0716; Project Identifier 2019-CE-023-AD; Amendment
39-21799; AD 2021-23-01]
Airworthiness Directives; Stemme AG Gliders
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final rule.
SUMMARY: The FAA is adopting a new airworthiness directive (AD) for all
Stemme AG Model Stemme S 12 gliders. 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 an airspeed indicator (ASI) with speed markings
inconsistent with the approved and published values. This AD requires
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 issuing this AD to address the
unsafe condition on these products.
DATES: This AD is effective January 27, 2022.
The Director of the Federal Register approved the incorporation by
reference of a certain publication listed in this AD as of January 27, 2022.
ADDRESSES: For service information identified in this final rule,
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)
329-4148. It is also available at https://www.regulations.gov by
searching for and locating Docket No. FAA-2021-0716.
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 final rule, the MCAI, any
comments received, and other information. The address for Docket
Operations is 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: 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 issued a notice of proposed rulemaking (NPRM) to amend 14
CFR part 39 by adding an AD that would apply to all Stemme AG Model
Stemme S 12 gliders. The NPRM published in the Federal Register on
August 27, 2021 (86 FR 48065). The NPRM was prompted by MCAI originated
by the European Union Aviation Safety Agency (EASA), which is the
Technical Agent for the Member States of the European Union. EASA
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.
Discussion of Final Airworthiness Directive
The FAA received no comments on the NPRM or on the determination of
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 reviewed the relevant
data and determined that air safety requires adopting this AD as
proposed. Accordingly, the FAA is issuing this AD to address the unsafe
condition on these products. This AD is adopted as proposed in the NPRM.
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.
Costs of Compliance
The FAA estimates that this AD affects 20 gliders of U.S. registry.
The FAA estimates 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.
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. For the reasons discussed above, I certify this AD:
(1) Is not a "significant regulatory action" under Executive Order 12866,
(2) Will not affect intrastate aviation in Alaska, and
(3) 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
Accordingly, under the authority delegated to me by the
Administrator, the FAA amends 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