Under what condition should an aircraft be positioned when trimming an engine?

Positioning the aircraft into the wind while trimming an engine is crucial for several reasons. When an aircraft is facing directly into the wind, it allows for optimal airflow over the control surfaces, which can provide better control and stability during engine trimming. This position is especially important as it minimizes the effects of wind on the aircraft, ensuring that any adjustments made to the engine function are accurate and not influenced by lateral winds.

By facing the aircraft into the wind, you also help maintain an appropriate ground speed, which is critical for determining engine performance and alignment. Proper positioning in this way helps to ensure safety and effectiveness during procedures that require careful monitoring of engine operations.