Avionics bay, also known as E&E bay or electronic equipment bay in aerospace engineering is known as compartment in an aircraft that houses the avionics and other electronic equipment, such as flight control computers, navigation systems, communication systems, and other electronic equipment essential for the operation. It is designed to be modular with individual components that can be easily removed and replaced in case of failure and is designed to be highly reliable and fault-tolerant with various backup systems.^[1][2]

In larger commercial airplanes, the main avionics compartment is typically located in the forward section of the aircraft under the cockpit.^[3] Purpose of its location is to provide easy access to the avionics and other electronic equipment for maintenance and repair.

For example, on larger aircraft such as the Boeing 747-400, the avionics bays are divided into 3 parts - the main equipment center (MEC), the center equipment center (CEC) and the aft equipment center (AEC).^[4]

Typically avionics bay contain plug-in modules for:

• Flight Control Computer (FCC)
• Autopilot
• Automatic flight director system (AFDS)
  • Autothrottle system (A/T)
  • Mode control panel (MCP)
  • Flight management computer (FMC)
• Primary flight computers (PFC)
• Actuator control electronics (ACE)
• Flight data recorder
• Cockpit voice recorder
• Battery and battery charger

The avionics bay also contains the oxygen tanks for the pilots in case of a cabin depressurization

The avionics bay of a 747-200 was used as a way to deploy the military into an aircraft in the movie Executive Decision