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Federal Register / Vol. 86, No. 228 / Wednesday, December 1, 2021 / Proposed Rules Fax: 202 4932251.
Mail: U.S. Department of Transportation, Docket Operations, M
30, West Building Ground Floor, Room W12140, 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
13010; fax: +49 703 1301136; email:
aircraft@solo-germany.com; 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 3294148.
Examining the AD Docket You may examine the AD docket at https www.regulations.gov by searching for and locating Docket No.
FAA20211015; 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 3294165; fax: 816
3294090; email: jim.rutherford@
faa.gov.
SUPPLEMENTARY INFORMATION:

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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.
FAA20211015; Project Identifier 2019CE014AD 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

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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.
Background The European Aviation Safety Agency EASA, which is the Technical Agent for the Member States of the European Union, has issued EASA AD 20190029, 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 aircraft.
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. FAA2021
1015.

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Related Service Information Under 1
CFR Part 51
The FAA reviewed Solo Kleinmotoren GmbH Service Bulletin 460318, 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.
FAAs 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 FAAs 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 flangenut. This proposed AD would also establish a lift limit of 15 years for the affected ball bearing assemblies.
Differences Between This Proposed AD
and the MCAI or Service Information 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
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