From where is fuel supplied to the APU?

The auxiliary power unit (APU) on the Canadair Regional Jet (CRJ) is supplied fuel from the left collector tank. This tank is designed to provide an adequate flow of fuel to ensure that the APU operates effectively during ground operations or when the main engines are not running.

Utilizing the left collector tank as the primary fuel source minimizes the risk of fuel starvation during operations, as it allows for reliable fuel delivery in different operational scenarios. The APU's requirements for fuel are carefully integrated into the jet's fuel system design, ensuring that it remains functional regardless of any supply from the main fuel tanks.

The main fuel tanks and the right collector tank play different roles in the overall fuel management system of the aircraft, primarily serving the engines rather than the APU. The option concerning an external fuel source doesn't apply here, as the APU relies on internal fuel supplies for operation.