What temperature should GPUs be recommended for starting an aircraft?

The recommended temperature for starting an aircraft's gas turbine engines is correlated with the operational capability of the engine's components, particularly the GPU (Ground Power Unit) used to supply power when the aircraft is on the ground. The choice of -18 degrees Celsius as a starting temperature is based on the balance between engine efficiency and the risk of mechanical failure or inefficient combustion.

At -18 degrees Celsius, the GPU can generally provide adequate starting capability without significant concerns regarding the viscosity of lubricants or the performance of the ignition system. This temperature is often seen as a standard benchmark in various aviation guidelines, as it minimizes the potential for cold weather impacts on the engine's startup sequence while maintaining reliability.

Using a higher temperature may risk a more challenging start, while lower temperatures may create even more complications with engine components. Hence, -18 degrees Celsius is specifically chosen for operational safety and efficiency in the context of aircraft operations. This temperature allows the GPU to function effectively, ensuring that ground support operations remain within optimal parameters for engine performance.