There are many other systems in the aircraft, some are just in case of emergency. For the sake of brevity, we just mention some of them providing a brief description. Notice also that this taxonomy is not standard and thus the reader might encounter it in a different way in other textbooks.
Pneumatic system: Pursues the same function as hydraulic systems, actuating also in control surfaces, landing gears, doors, etc. The only difference is that the fluid is air.
Oxygen system: Emergency system in case the cabin is depressurized.
Ice and rain protection system: In certain atmospheric conditions, ice can be formed rapidly with influence in aerodynamic surfaces. There exist preventive systems which heat determined zones, and also corrective systems that meld ice once formed.
Fire protection system: Detection and extinction system in case of fire.
Information and communication system: Provides information and permits both internal communication with the passengers (musical wire), and external communication (radio, radar, etc). External communication includes VHF and HF communication equipment. Also, flight-deck audio systems might be included. Information system refers also to data- link communications, including all kind of data broadcasted from the ATM units, but also all aircraft performance data (speed, pressure, altitude, etc.) that can be recorded using Flight Data Recorder (FDR), Automatic Dependent Surveillance Broadcast (ADSB), and track-radar. Please, refer to Chapter 11.
Air navigation system: It includes all equipment needed for safe navigation. All navigation instruments and electronic displays already described in Section 5.1 might be seen as part of this system. Inertial navigation systems (IMUs) can also be categorized as air navigation equipment. The Traffic Alert and Collision Avoidance System (TCAS) can be also included in this system. Please, refer to Chapter 11.
Avionics system: This term is somehow confuse, since avionics refers to the electronics on board the aircraft. As it has been exposed throughout the chapter, electronics is becoming more and more important in modern aircraft. Practically every single system in an aircraft has electronic elements (digital signals, displays, controllers, etc.) to some extent. Therefore, is not clear whether avionics should be a system by itself, but is becoming more and more popular to use the term avionics systems to embrace all electronics on board the aircraft (and sometimes also the earth-based equipment that interrogates the aircraft). Characteristic elements of avionics are microelectronic devices (microcontrollers), data buses, fibre optic buses, etc. It is also important to pay attention to system design and integration since the discipline is transversal to all elements in the aircraft.