What is the minimum air temperature in flight set at?

The minimum air temperature in flight is critically important for maintaining aircraft performance and safety. The value set for the CRJ550 is -70 degrees Celsius. This threshold is established based on operational limits that account for various factors, including engine performance, structural integrity, and freezing point considerations of fuel and other systems.

Setting the minimum air temperature at -70 degrees Celsius ensures that the aircraft can operate safely in colder climates without the risk of ice formation or other adverse effects that might occur if the temperature drop too low. The selection of this specific temperature reflects the balance between safety margins and the operational capabilities of the aircraft systems under extreme conditions.

The other temperatures presented as options are outside the operational limits, and using any of those would not adequately address the safety and performance requirements for the aircraft. Therefore, -70 degrees Celsius is the proper minimum air temperature for flight as it ensures the aircraft remains within its designed operational safety margins.