What is the minimum hydraulic reservoir temperature for engine start?

The minimum hydraulic reservoir temperature for engine start is crucial to ensure the proper functioning of the hydraulic systems during the aircraft's operation. In the case of the Skywest ERJ, the specified minimum hydraulic reservoir temperature is set at -18 °C. This temperature threshold is necessary to prevent the hydraulic fluid from becoming too viscous, which can interfere with the hydraulic system's performance upon engine start. If the hydraulic fluid is too cold, it may not adequately flow through the system, leading to potential issues with critical systems such as control surfaces and landing gear. Therefore, maintaining a hydraulic reservoir temperature above -18 °C ensures that the hydraulic components can operate effectively, supporting the safe commencement of engine operations.