AD NUMBER: 2009-04-08
MANUFACTURER: Burkhart Grob
SUBJECT: Airworthiness Directive 2009-04-08
SUMMARY: We are adopting a new airworthiness directive (AD) for the products listed above. This AD results from mandatory continuing airworthiness information (MCAI) issued 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: The Luftfahrt-Bundesamt received a report from the Grob Company that a bolt in the air brake control was found failed during a pre-flight inspection on a G 103C TWIN III ACRO. During an extensive investigation (metallurgical investigation) a double sided fatigue crack was found as root cause. As the bolt is insignificantly stressed by cyclic bending the crack was probably caused by mean stress supported by a bolt torque exceeding the limit. The actions specified by this airworthiness directive are intended to prevent further bolt cracking which can result in air brake as well as elevator failure (elevator control is on the same pedestal) and reduced controllability of the power glider. We are issuing this AD to require actions to correct the unsafe condition on these products

FMI: www.faa.gov/regulations_policies/airworthiness_directives/