DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2021-1015; Project Identifier 2019-CE-014-AD]
Airworthiness Directives; DG Flugzeugbau GmbH and Schempp-Hirth
Flugzeugbau GmbH Gliders
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Notice of proposed rulemaking (NPRM).
SUMMARY: The FAA proposes to adopt a new airworthiness directive
for DG Flugzeugbau GmbH Model DG-1000T gliders and Schempp-Hirth
Flugzeugbau GmbH Model Duo Discus T gliders with a Solo Kleinmotoren
GmbH Solo Model 2350C or 2350D engine installed. 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 failure of the bearing of the upper pulley of
the belt driven reduction gear resulting in separation of the propeller
from the engine. This proposed AD would require replacing a certain
hex-nut and would establish a lift limit for the ball bearing assembly.
The FAA is proposing this AD to address the unsafe condition on these
DATES: The FAA must receive comments on this proposed AD by January
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
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 Solo
Kleinmotoren GmbH, Postfach 600152, D71050 Sindelfingen, Germany;
phone: +49 703 1301-0; fax: +49 703 1301-136; email: firstname.lastname@example.org;
website: http://aircraft.solo-online.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-2021-1015; 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-2021-1015; Project Identifier
2019-CE-014-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, FAA, 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 Aviation Safety Agency (EASA), which is the Technical
Agent for the Member States of the European Union, has issued EASA AD
2019-0029, dated February 8, 2019 (referred to after this as ``the
MCAI''), to address an unsafe condition on Solo Kleinmotoren GmbH Solo
Model 2350B, 2350BS, 2350C, and 2350D engines. The MCAI states:
An occurrence was reported of failure of the bearing of the
upper pulley of the belt driven reduction gear, resulting in
separation of the propeller from the engine.
This condition, if not corrected, could lead to similar
occurrences, with possible reduced control of, and damage to, the
To address this potential unsafe condition, Solo redesigned the
nut securing the pulley bearing on the axle and introduced a life
time limit of 15 years for the reduction gear bearings.
For the reason stated above, this [EASA] AD requires replacement
of affected parts with serviceable parts, and introduces a life
limit for the affected ball bearings.
You may examine the MCAI in the AD docket at https://www.regulations.gov
by searching for and locating Docket No. FAA-2021-1015.
Related Service Information Under 1 CFR Part 51
The FAA reviewed Solo Kleinmotoren GmbH Service Bulletin 4603-18,
dated January 22, 2019. The service information contains procedures for
replacing the hex-nut at the excentric axle and the ball bearing
assemblies at the bearing block of the reduction gear. 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 removing the affected hex-nut from
service and replacing it with a flange-nut. This proposed AD would also
establish a lift limit of 15 years for the affected ball bearing
Differences Between This Proposed AD and the MCAI or Service
The MCAI applies to Solo Kleinmotoren GmbH Solo Model 2350B,
2350BS, 2350C, and 2350D engines. None of these model engines have an
FAA engine type certificate. However, Model 2350C and Model 2350D
engines are certificated by the FAA with the type certificate for
certain gliders. This proposed AD would not apply to Solo Kleinmotoren
GmbH Solo Model 2350B and 2350BS engines because they are not part of
an FAA glider type design.
The MCAI requires replacing an affected ball bearing assembly
before it accumulates 15 years since first installation on an engine.
This proposed AD would require replacing both ball bearing assemblies
simultaneously before either accumulates 15 years since first
installation on an engine.
Costs of Compliance
The FAA estimates that this AD, if adopted as proposed, would
affect 10 gliders of U.S. registry. The FAA estimates that for gliders
with an affected hex-nut, replacement would take about 0.5 work-hour
and require a part costing $95. The average labor rate is $85 per work-hour.
Based on these figures, the FAA estimates the cost to replace the hex-nut
U.S. operators to be $1,380 (assuming all 10 gliders have this
configuration) or $138 per glider.
In addition, the FAA estimates that for gliders with the affected
ball bearing assemblies, replacement would take about 4 work-hours for
both ball bearing assemblies and require ball bearing assemblies
costing $118 (2 units). The average labor rate is $85 per work-hour.
Based on these figures, the FAA estimates the cost of the ball bearing
assembly replacement on U.S. operators to be $4,580 (assuming all 10
gliders have this configuration) or $458 per glider.
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