What is the critical temperature threshold for L9 oil preheat?

The critical temperature threshold for L9 oil preheat is -15°F/-26°C. This threshold is established to ensure that the oil remains sufficiently fluid to enable proper lubrication and functioning of the APU (Auxiliary Power Unit) components. Preheating the oil to this specified temperature helps to mitigate issues related to viscosity, which can increase if the oil is too cold.

If the oil temperature is below this threshold, it may not adequately lubricate internal parts, potentially leading to increased friction or wear during operation and affecting overall performance and reliability of the APU. Understanding this critical temperature ensures proper operational procedures are followed, thereby enhancing the longevity and effectiveness of the APU system.