What is the pneumatic pressure gauge red line indicating?

The red line on the pneumatic pressure gauge indicates a limit that should not be exceeded to ensure safe operation of the aircraft. In the case of the King Air 350, the correct answer of 20 PSI signifies the maximum permissible pneumatic pressure. Operating beyond this red line could lead to mechanical failures or compromise the system’s integrity, impacting the effectiveness of the aircraft's pressurization and de-icing systems.

Understanding this limitation is crucial for pilots and operators to maintain control over the aircraft systems, ensure safety, and comply with operational regulations. The pneumatic systems are an integral part of flight operations, including air conditioning and cabin pressurization; hence, monitoring the pressure levels and adhering to the specified limits is vital for safe flight operations.