AD 2021-23-01 Requires Inspecting The ASI Markings...

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. This AD is effective January 27, 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 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 powered sailplane.
• 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 affected parts.

You may examine the MCAI in the AD docket at https://www.regulations.gov by searching for and locating Docket No. FAA-2021-0716.

FMI: www.regulations.gov