What does an alternate static system provide during flight?

The alternate static system provides an alternate source of static air during flight. This system is essential, especially if the primary static port becomes blocked or malfunctions, which could affect the accuracy of instruments that rely on static pressure, such as the altimeter, vertical speed indicator, and airspeed indicator.

When activated, the alternate static source typically uses air from within the cabin or another location that is not subject to the same blockage as the main static port. This allows the instruments to continue to function and provide the flight crew with necessary altitude and airspeed information, ultimately enhancing safety and situational awareness during flight operations.

The other options do not accurately reflect the function of the alternate static system. It is not designed for supplying fuel, backing up the flight control systems, or operating in a non-pressurized cabin environment. Instead, its role is specific to ensuring continued access to static pressure for accurate instrumentation during flight.