What is the main purpose of speed brakes in aviation?

The main purpose of speed brakes in aviation is indeed to reduce the overall speed of an aircraft. These devices are typically deployed during flight to create increased aerodynamic drag, which helps to quickly decrease the aircraft's speed without needing to pitch down or change the angle of descent significantly. Speed brakes are particularly useful during the approach phase of landing, as they allow pilots to manage their airspeed effectively while maintaining control of the aircraft. Additionally, speed brakes can help to achieve a steeper descent angle in cases where a quicker descent is required.

This function contrasts with other options, like increasing lift during takeoff, which isn't associated with speed brakes, as they are primarily designed to slow the aircraft down. Maintaining altitude during turbulence would require different aerodynamic considerations and control techniques, rather than simply deploying speed brakes. Similarly, while speed brakes can affect aircraft control during landing, they do not directly assist in the deployment of landing gear, which serves a separate function in the landing process.