What is the function of the holdback chain during high-power operations?

The function of the holdback chain during high-power operations is to keep the aircraft stationary. This is crucial during engine runs, especially during high-power checks, which involve testing the aircraft's engines at various power settings. The holdback chain prevents the aircraft from moving forward due to the thrust generated by the engines, ensuring both safety and control during these operations.

Understanding the holdback chain's purpose helps emphasize the importance of maintaining proper aircraft positioning and control while the engines are at high power. Keeping the aircraft stationary allows for safe checks and inspections without the risk of unintended movement, which could be dangerous to crew and equipment nearby.

In contrast, other options do not accurately represent the role of the holdback chain. It does not provide power to the aircraft, secure the main landing gear, or connect to the ground in a way that would be relevant to its primary purpose during high-power operations.