Final answer:
A lightning hole in a sheet metal wing rib serves two main purposes: reducing weight and improving aerodynamics.
Step-by-step explanation:
A lightning hole in a sheet metal wing rib serves two main purposes:
To reduce weight: By removing material from the rib in a strategic manner, the overall weight of the aircraft can be reduced while maintaining its structural integrity.
To improve aerodynamics: The lightning hole allows air to flow through the rib, reducing drag and improving the overall performance of the aircraft.