AD 2021-26-25 Requires Replacing Certain Air Brake End Stop Bushings

The FAA is adopting a new airworthiness directive (AD) for certain Schempp-Hirth Flugzeugbau GmbH Model Duo Discus and Duo Discus T gliders.

This AD was prompted by mandatory continuing airworthiness information (MCAI) originated by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI describes the unsafe condition as jerky extension of the air brakes at very high air speeds, including cases where the air brake blades interlock. This AD requires replacing certain air brake end stop bushings, inspecting certain other air brake end stops, and repairing if necessary. The FAA is issuing this AD to address the unsafe condition on these products. This AD is effective February 24, 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 serial-numbered (S/N) Schempp-Hirth Flugzeugbau GmbH Model Duo Discus and Duo Discus T gliders. The NPRM published in the Federal Register on October 21, 2021 (86 FR 58228). 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 AD 2020-0233, dated October 27, 2020 (referred to after this as “the MCAI”), to address the unsafe condition on certain S/N Schempp-Hirth Flugzeugbau GmbH Model Duo Discus, Duo Discus C, and Duo Discus T gliders.

The MCAI states:

• Occurrences were reported of experiencing jerky extension of the airbrakes at very high air speeds, in some cases of which the airbrake blades interlocked. An increasing number of age-related damage was observed on a specific version (22 mm plastic bushes) of the airbrake end-stops.
• This condition, if not corrected, could lead to blockage of the airbrakes, possibly resulting in reduced control of the (powered) sailplane.
• To address this potential unsafe condition, Schempp-Hirth issued the applicable [technical note] TN (original issue) to provide instructions to replace the affected parts with a new version bushing, made of better material.
• Since [EASA planned AD] PAD 20-119 was issued, it was discovered that early s/n sailplanes were equipped with a single metal end stop per airbrake. The applicable TN was revised accordingly. The PAD was revised to include those metal end stops in the definition of ‘affected part' to ensure these are inspected.
• For the reasons described above, this [EASA] AD requires replacement of certain affected parts with serviceable parts. For other affected parts, this [EASA] AD requires a one-time inspection for sufficient overlap and, depending on findings, accomplishment of applicable corrective action(s). This [EASA] AD also prohibits (re)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-2021-0878.

FMI: www.regulations.gov