Which component is used for external starting of a helicopter?

The component used for external starting of a helicopter is the external air source. This setup provides the necessary high-pressure air to start the helicopter's engines, which is especially important for turbine engines that rely on this air supply for ignition and operation.

In helicopter operations, an external air source typically refers to a dedicated pneumatic system that delivers compressed air, allowing the engine to reach the required speed for starting. It is critical for ensuring reliable engine startups, particularly in various environmental conditions or when onboard systems are not sufficient.

While other options like a pneumatic cart and ground power unit play roles in supporting the helicopter's other functions, they are not specifically designed for starting the engine in the same way that an external air source is. A backup battery serves to provide electrical power but does not supply the necessary air pressure for engine ignition. Understanding these functions helps ensure proper aircraft operations and maintenance.