A320 Information Systems: ATSU, AOC and FlySmart

The A320's information systems gather the equipment that exchanges and presents operational information rather than flying the aircraft. At their center is the air traffic service unit (ATSU), which runs the datalink: written messages with the airline and with air traffic control, sent over VHF, HF or satellite. Around it sit the crew's interfaces (the MCDU, the datalink control and display units, a printer and ECAM memos), the FlySmart with Airbus electronic flight bag (EFB), and the systems that let passengers use phones, internet and in-seat power.

For a type rating the subject is mainly media and modes, the pages that set them up and the rules for reverting to voice. The figures here are those of the A320 FCOM; datalink and cabin equipment are customized by each operator, so the options fitted and their pages vary. The radios themselves, the RMPs and the DCDU are covered in A320 communications and datalink, the principles in ACARS and aircraft datalink.

The ATSU and its communication media

Datalink traffic falls into two families: AOC applications, for messages with the airline's operations center, and ATC applications, which give communication, navigation and surveillance services for air traffic management. A message from the ground is an uplink, one from the aircraft a downlink, and either can be exchanged automatically or by the crew through the DCDU, the MCDU or the RMP.

The ATSU controls all datalink communication. It hosts the AOC applications, the ATC applications and the router services, and it automatically selects the best available medium among VHF, HF and SATCOM:

VHF 3 data mode is the normal setting. The routers choose the VHF frequency from the aircraft position, following the scan mask: the list of datalink service providers in the airline's order of priority, ARINC and SITA being the two main worldwide networks. The scan mask is compulsory for the router to work; without one the ECAM shows DATALINK ATSU FAULT, ATSU INIT FAULT. VHF 3 can be switched to voice after a failure of VHF 1 or VHF 2, or for specific AOC functions chosen by the operator. Where ACARS is installed, VHF 3 should not be used for voice with ATC unless VHF 1 and VHF 2 are inoperative. The SOP keeps VHF 1 for ATC, as the only VHF available in the emergency electrical configuration, VHF 2 for ATIS and company frequencies and VHF 3 for ACARS. The green VHF 3 VOICE memo means VHF 3 is in voice mode and ACARS communication is interrupted.

The HF Data Link works in the same spirit: in data mode the HFDL frequency is tuned automatically, and the crew can switch the HF to voice and set a voice frequency on the RMP. SATCOM sends voice and data from the aircraft through a satellite to a ground earth station, from where international networks such as ARINC and SITA route them anywhere in the world. Radio principles are in VHF, HF and satellite communications.

ATC applications: FANS A and FANS B

The ATC datalink lets controllers follow the aircraft's navigation and so improves the traffic flow. Two packages exist, each with an enhanced version:

FANS A+ and FANS B+ are evolutions that introduce ATS 623 applications and datalink recording. The optional applications, compatible only with A+ or B+, are departure clearance, oceanic clearance and digital ATIS (D-ATIS), carried over ACARS air traffic services (ATS 623). ADS-C sends surveillance data automatically to connected ATC centers through the ATC datalink. ADS-B is a different application: the Mode S transponder broadcasts position and navigation data to ATC centers and other aircraft, and the ATC datalink does not host it (see ADS-B and controller-pilot data link communications).

On each side, a DCDU displays uplinks and downlinks and lets the crew handle them, and an ATC MSG pushbutton on the glareshield alerts the crew to a new uplink and, when pressed, cancels the alert. For a route clearance the crew press ATC MSG, then select STBY, SEND and LOAD on the DCDU; LOAD must be the selection, as another may prevent loading, and LOAD SEC OK confirms that the route is in the secondary flight plan. If they accept it, they answer WILCO and can activate the secondary. To change it, they modify the loaded clearance in the secondary flight plan on the MCDU, reject it with UNABLE on the DCDU and send ATC a new request with the modified flight plan.

ATC datalink needs the clock within ±1 s of UTC; otherwise messages may be rejected or obsolete ones accepted, so for FANS operations the crew do not set the clock manually during cockpit preparation. If the DCDU shows ATC MSG RECORD NOT RELIABLE at ATSU power-up, it means that two CPDLC messages with the same time stamp were stored before the last power-off; the record has been emptied and new CPDLC messages are not stored, and the crew reset the ATSU manually as the system reset table directs.

AOC applications

AOC applications carry airline operational communications: messages between the crew and the airline's operations center, which the FCOM calls the Airline Operational Control. Each operator customizes them, so the pages depend on the airline's choices and its datalink service provider. Typical functions:

Requests to ATC, such as a departure clearance or a direct routing, are ATC functions, not AOC ones. The two meet in flight plan uplinks. When the MCDU scratchpad shows AOC SEC F-PLN UPLINK, the crew select AOC F-PLN INSERT on the SEC INDEX page, which places the airline's route in the secondary flight plan, review or modify it, and select SEC F-PLN REQ DISPLAY. The DCDU then displays a datalink message, which the crew send to ATC (see A320 FMGS and MCDU).

Green ECAM memos report AOC events:

• COMPANY MSG: a message has arrived from the ground.
• COMPANY CALL: the ground asks for a voice call on VHF.
• COMPANY ALERT: an uplink alert message, or an AOC condition that needs pilot action on the MCDU; it pulses for 180 s, then stays steady, with a 1 s buzzer.
• COMPANY DATALINK STBY: AOC air-ground communication is temporarily unavailable, but not lost.

The communications chapter of the FCOM also lists an ACARS CALL memo, for a ground request for a VHF voice call, which pulses for 60 s before becoming steady.

MCDU messages and printer

The MCDU manages the AOC and ATC functions and passes data to the DCDU; the RMP tunes frequencies, the ECAM reports abnormal operation and the printer prints datalink messages displayed on the DCDU. The datalink initializes itself once a list of service providers has been scanned and all the required parameters received and validated by the ATSU; if it does not, the crew initialize it manually from the COMM CONFIG or COMM INIT page, which lists those parameters.

The VHF3 SCAN SELECT page holds the scan mask: the crew select service providers in the airline's order of priority and activate the selection, and EMPTY SCAN ACTIVATE loads an empty scan mask to inhibit VHF datalink altogether. A change can lose the air-ground VHF datalink and raise the service provider's charges, so the crew leave the setting alone unless told to change it.

FlySmart with Airbus (EFB)

The A320's standard operating procedures assume that both pilots use an EFB, and Airbus recommends two to reduce the risk of erroneous inputs. FlySmart with Airbus is the Airbus application suite for it. It aims to improve access to operational information, reduce paper, shorten revision and distribution cycles, ease data updates and give accurate, optimized performance computation. It runs on a portable electronic device (PED), which the crew can plug into the 110 VAC, 60 Hz outlets on each lateral console; the 115 VAC, 400 Hz outlets at the rear of the cockpit are for maintenance only.

The performance applications work from the aircraft configuration and the external conditions: runway, surrounding obstacles and weather for takeoff and landing, weather in flight. The Loadsheet application eases the computation of zero fuel weight and its CG, takeoff weight and takeoff CG and, where the airline's authority accepts it, can produce the load and trim sheet itself (load and trim sheet). MEL and CDL items, missing items included, selected in the OLB pass automatically to the Takeoff and Landing applications (technical log, MEL and deferred defects).

Each application has a My Flight page. It shows the version of the installed applications and data, so the crew can check that they are current, starts the Manager application and initializes the applications with the tail number, flight number and city pair. An entry made on one My Flight page is retrieved by the others; on the OLB's page only the aircraft type and registration can be entered. The regulatory side of EFBs is in electronic flight bags.

Cabin connectivity and passenger devices

The cabin connectivity systems let passengers use cell phones for voice and data and, where fitted, a wireless internet connection. Cell phones are prohibited in the cockpit and the lavatories. The GSM onboard system may not be used below 3,000 m (about 10,000 ft) above ground level or in some geographical areas; it identifies these conditions and turns itself off. The In-Seat Power Supply System (ISPSS) feeds the in-seat power supply unit (ISPSU) outlets so that passengers can use PEDs, and it is disconnected automatically in a rapid decompression.

The controls, whose fit depends on the cabin options:

• MOBILE COM (45 VU, overhead): ON activates the cell phone system and the passenger internet. Released, its OFF light comes on in white, but the phone system takes about 4 min to disconnect and stays usable meanwhile; the blue DISC IN PROG light stays on until disconnection is complete, and the memo GSM DISC < 4 MN gives way to NO MOBILE.
• CINS RESET resets all cabin connectivity systems; PAX COM at OFF cuts them off, with a white OFF light.
• PAX SYS at ON or AUTO powers all ISPSUs, the in-flight entertainment (IFE) and cabin connectivity, and at OFF switches them all off together.
• PAX PERSONAL ELEC SPLY at AUTO powers the ISPSUs except during takeoff, landing or a decompression, or when the PED power switch on the forward attendant panel is off; OFF removes power from all of them, and an INOP label means the ISPSS has been deactivated.

The FCOM's list of cabin connectivity controls also names NO PED, which works the signs. On the SIGNS panel, beside SEAT BELTS, the second switch is NO SMOKING, EXIT or NO PORTABLE ELEC DEVICE, depending on the cabin. Each has three positions: ON, OFF and AUTO, which lights the signs when the landing gear or the slats and flaps are extended. If the cabin altitude exceeds 11,300 ft (±350 ft), all cabin signs come on whatever the switch positions, except NO PORTABLE ELEC DEVICE, and the ECAM shows NO PED among its memos when that sign is on (A320 cabin systems and CIDS).

Library articles are written for study and exam preparation. They do not replace your aircraft's approved documentation, your operator's procedures or the regulations themselves.