What is a secondary function of the APU during flight?

The APU, or Auxiliary Power Unit, serves several essential functions, particularly when the aircraft is on the ground and during flight. One of its important secondary functions during flight is providing backup electrical power. This capability is critical in ensuring that essential systems remain operational in the event of an engine failure or other power loss scenarios. The APU can generate electricity, which helps maintain the operation of avionics and other necessary equipment, securing the safety and functionality of the flight.

While enhanced fuel consumption, navigation assistance, and emergency landing gear deployment are important aspects of aircraft operation, they do not pertain to the APU's role while in flight. The primary design of the APU focuses on auxiliary power generation, which significantly increases operational reliability and safety in flight.