AD 2022-03-07 Requires Establishing A Life Limit Of 5 Years For Certain Propeller Gearbox Tooth Belts

The FAA is adopting a new airworthiness directive (AD) for certain Stemme AG TSA-M Model S6 and S6-RT 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 a new version of the propeller gearbox tooth belt with a reduced life limit. This AD requires establishing a life limit of 5 years for certain propeller gearbox tooth belts. The FAA is issuing this AD to address the unsafe condition on these products. This AD is effective March 2, 2022.

Supplementary Information: The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to certain Stemme AG TSA-M Model S6 and S6-RT gliders. The NPRM published in the Federal Register on November 22, 2021 (86 FR 66229). 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 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.

FMI: www.regulations.gov