Which static wick dischargers must be intact for the aircraft to be airworthy?

The condition of the static wick dischargers is essential for ensuring that the aircraft can safely manage static electricity, which can accumulate during flight and potentially interfere with avionics or create a spark hazard. The requirement for airworthiness is typically focused on dischargers that are critical in preventing the build-up of static charge during operation.

In the case of the static wick dischargers on the Endeavor Air CRJ 900, the top two dischargers on each winglet are specifically designed to be effective in managing the static charges that may develop. Since the winglets play a significant role in airflow and aerodynamics, the integrity of these top dischargers is crucial to maintain the aircraft's airworthiness. Ensuring these components are intact helps to facilitate the safe transfer of any accumulated static electricity from the aircraft structure to the atmosphere, therefore mitigating risk during flight operations.

Other options, such as specific dischargers on the trailing edges or the bottom winglet dischargers, may also be important but do not hold the same level of criticality for airworthiness as the top dischargers on each winglet. Thus, for the aircraft to meet airworthiness standards, having the top two dischargers on each winglet is paramount.