What occurs if the Control Speed Unit (CSU) fails?

If the Control Speed Unit (CSU) fails, the overspeed governor takes over to maintain the proper operation of the engine. The CSU plays a critical role in regulating engine speed by adjusting the fuel flow to the engine. In the event of its failure, the overspeed governor is designed to act as a backup system to prevent the engine from exceeding safe operational limits.

This safety mechanism is essential because it provides an additional layer of control to ensure that the engine does not reach harmful speeds, which could potentially lead to engine damage or failure. By taking over the control of the fuel flow, the overspeed governor helps stabilize the engine's performance and mitigates risks associated with the CSU malfunction.

Other options, such as an engine shutdown or fuel flow interruption, do not happen as a direct result of CSU failure because the overspeed governor's primary function is to maintain engine safety rather than allow for such critical failures. The aircraft losing altitude is also not a consequence of CSU failure, as the failure does not directly impact the aircraft's aerodynamic capabilities or control surfaces.