From Departure to Arrival

By Björn Syrén, SAS

How datalink supports flight operations today.

A typical ACARS Flight Leg.

The following scenario is based on how SAS uses datalink today (2008) or in the near future. While most applications are already in use, some are being developed or studied. This account is a mix of both. It is intended to give the reader, already familiar with traditional airline procedures, an insight into the possibilities with datalink.

To read about datalink applications that are in service, go to the Applications page.

The applications descibed in the story below are not fiction or fantasy in the sense that they require technology not currently available. They are - if not already in use - realistic and feasible to implement today using existing infrastructure and technology.

Advances in datalink technology in the future are likely to allow much more advanced applications than those described here.

B737-683 SE-DNM at Stockholm Arlanda airport, Sweden, 1998.
Photo by R. Schoenherr Jr.

Preparing for Departure

One of their first tasks in the cockpit preparations for the flight is to select ACARS on the MCDU and press the Init Request button. This sends a short message to SAS' ground datalink system informing it that the flight is now ready to be supported by datalink procedures for the next leg. Basic flight information such as flight number, date, departure station, destination station and estimated time of departure is now retrieved from the Opus system and uplinked automatically into the ACARS unit. This also ensures that all subsequent messages from the flight are correctly identified.

The ACARS Initialization request triggers automatic uplink of a number of messages to the aircraft:

• The ACARS Auto Init uplink response
• An updated Crew List
• A summary of preliminary Loadsheet and Notoc information from the PALCO system
• A Flow message containing departure slot (CTOT) and/or last-minute ATC flight plan routing changes.
• A Maintenance Statement containing information about the aircraft airworthiness status
• New Sigmet information applicable for the flight.
• A Departure Information message consisting of condensed data for the flight: cabin configuration, company route, next+1 leg and STD for the aircraft, any other special information for the pilots eg requests for APU starts, autoland.
• A traffic Irregularity Info update about the flight (if applicable)
• An airport weather update for the departure station from the RODOS system

The pilot requests and receives an ATIS uplink from the airport. This contains information about runway in use, MET conditions and other special information or procedures in use. The pilot request a Departure Clearance. The clearance is uplinked when the ATC system has processed it, and the pilot acknowledges it electronically.

To the cabin datalink terminal in the galley area the following information is sent:

• An updated Crew List
• A Cabin Information List (passenger list, route & destination info)

Using data from the Loadsheet and ATIS, the pilot requests and receives a Takeoff Data Calculation from the TODC system. After 15-20 seconds he receives an uplink with vital information about speeds, flap settings and engine thrust ratings for the takeoff.

The FMC flightplan is uplinked to the Flight Management Computer. The company OFP operational flightplan can be requested and uplinked from the Rodos system or uplinked by dispatchers.

Enroute wind forecast information is uplinked and insterted into the FMC.

If the flight is to be dispatched with a malfunction (according to CAA regulations), a MEL Advisory message is received from central maintenance control.

The pilot may request de-icing. The ground de-icing application will uplink a confirmation and information about the de-icing location and time. After the de-icing has been completed, an uplink message will confirm the type of fluid and hold over time.

If the flight is delayed, the pilot sends a Departure Delay message to the OPUS system including a delay code and a new expected ETD. The delay status is immediately indicated on the traffic displays at the Operations Control Center. If necessary, the FLOW system automatically obtains a new departure slot from the CFMU in Brussels and uplinks it to the cockpit.

Fueling can be requested and confirmed via acars. After fueling is completed the fuel check is performed on the MCDU and a Fuel report is downlinked. This is a required input for the weight and balance calculation (loadsheet) and is also used for reconciliation against fuel invoices.

When passenger boarding, cargo loading and fueling is completed, the doors are closed and the flight is ready for departure. The Final Loadsheet is received from the PALCO system and the centralized load control center that performs load control for all departures. This gives the final load figures. If necessary a new TODC calculation is made based on this.

If the flight is delayed due to an ATC slot time restriction, the pilot can send an "All doors closed" message to Flow Control indicating that the flight is ready for departure and can accept an earlier slot time if offered.

Pushback, Engine Start and Taxi out

A pushback, startup and taxi clearance is requested and obtained from ATC. As soon as the parking brake is released the ACARS automatically sends an Out Report to the OPUS system. This also gives a visual indication on the displays at the OCC that the flight is now "off-block".

During taxiing ATC may offer or order a different runway or takeoff position than originally planned. The TODC application allows the pilot to quickly decide if a takeoff from that runway is possible and obtain the new takeoff data.

If there is a delay during taxi, eg due to de-icing or heavy traffic, the pilot sends a Takeoff Delay message to OPUS, including a delay code and an expected takeoff time. This is visually flagged at the OCC. If the flight must return to the gate, this is also automatically reported to OPUS and OCC.

B737-683 SE-DNM, SAS' first B737-600. Seen departing Boeing Field, Seattle on its non-stop delivery flight to
Stockholm, Sweden.
Photo by Boeing.

Takeoff and Climb

The moment the aircraft lifts off the runway, ACARS automatically sends an Off Report to OPUS. It contains the Out and Off time and also an initial estimated time of arrival, ETA.

The ACMS system sends an Engine Takeoff Report to the Flight Data Analysis system. This gives information on the condition of the engines for long-term health monitoring.

From the departure station comes information to passengers in case there was connecting baggage which did not make it onboard due to a short connection. If the departure and takeoff was significantly delayed, the stations system also sends a preliminary update about passengers which have missed their original connections and therefore have already been re-booked at this stage.

Cruise

On the way to the destination, the pilot can request TAF and METAR weather information and ATIS for the destination and for other airports along the route to keep him updated. If it is an oceanic flight he will receive the Oceanic Clearance message over datalink. New Sigmets that affect the flight are automatically uplinked. NOTAMS are available for uplink on request.

ATS waypoint position reports are sent automatically. Company position reporting can be activated by the pilot or ground for use by the OCC operations control center and Dispatch Department, where the aircraft position is then plotted on a map display.

Information about the expected runway and arrival procedure (STAR) is uplinked. This allows the FMC to re-calculate a more precise ETA. Information about the latest descent winds is also uplinked, further enhancing the ETA calculation.

If there is a change in the calculated arrival time, an ETA change report is sent to OPUS and to ATC. If there is a significant delay (eg a holding) he sends an Enroute Delay including estimated approach time, ETA and delay code to OPUS. The ETA change reports can be sent manually by the pilot or triggered automatically by the FMS (progress reports).

ATC may uplink an RTA required time of arrival overhead a particular waypoint, eg the STAR entry point, or at the actual runway threshold. This allows the FMS to control the flight to meet this time constraint, avoiding wasteful congestion (holding, radar vectoring) at the destination and saving fuel.

The OCC has instant access to up-to-date information about the progress of each flight: position, latest ETA, delay status, snags, downlink message logs etc. It is possible to view the traffic situation from a stations-oriented perspective. For example: all inbound aircraft to CPH with an ETA within 30 minutes, all aircraft currently taxiing in, all aircraft parked at gate, all aircraft taxiing out. The same type of focusing can be made from geographical airspace-oriented perspectrive. The OCC can also do broadcast-type uplink of information to selected SAS aircraft.

Throughout the flight the pilot has the option to use several types of freetext telexes for ad-hoc communication with various functions in SAS: Ops Control, Dispatch, Stations, Maintenance, Crew services, Flight Ops. It is also possible to send air-to-air telexes to other aircraft.

The aircraft periodically downlinks AMDAR MET observations from the climb, cruise and descent flight phases. The ACMS system downlinks engine stable cruise trend data and systems' performance for processing by the Flight Data Analysis department.

During the flight the pilot can access data from various ground EDP systems eg:

• Flight progress information, any flight
• Aircraft disposition, any aircraft
• MEL/Technical status any aircraft
• Irregularity Info, any flight or station

Changes to crew schedules can be uplinked by the crew scheduling department.

Updates regarding enroute winds and temperatures are uplinked to the FMC. Company flight plan updates or inflight replanning can be requested from RODOS.

If the aircraft operates in FANS-airspace, the aircraft will send automatic ADS position reports and the pilot will communicate with the ATC center using CPDLC-messages for routing re-clearances, altitude changes etc. Traffic capacity in such airspace is greater and more fuel efficient routings are possible.

In higher-density airspace, the pilot communicates with the ATC controllers using Link2000 CPDLC procedures over the VDL Mode-2 ATN network.

A landing data calculation can be obtained from TODC.

Passenger medical problems can be reported and advice obtained.

If there are malfunctioning equipment this is reported by the pilot tomaintenance control using the Snag Report. The maintenance department can request additional information either through freetext or by interrogating the ACMS system. Cabin crew log and send cabin log remarks from their terminal. Further, the onboard central maintenance computer automatically logs defects and sends the information to the ground. When the aircraft lands, the spares will be at hand and the technicians will be waiting for the aircraft, well briefed about the problem.

If the pilot needs to talk directly with ground personnel he sends a Voice Contact report advising the ground to call the aircraft on CUT or SATCOM phone. This contact can also be initiated by the ground. Voice often remains the best medium for communication in complicated and non-normal situations.

Descent, Approach and Landing

At 20 minutes before ETA (depends on aircraft type) the ACARS sends an Inrange Report. This is used by Hermes to retrieve and uplink various information needed in connection with arrival:

• Irregularity Information
• Arrival information: terminal, gate, baggage handling etc from the stations system
• Connecting flight information for the passengers from the stations system
• Passenger re-bookings
• Next leg data for the aircraft itself from OPUS

General arrival, connection, rebooking and traffic irregularity information is displayed on the cabin monitors of the Airshow system. Messages to individual passengers are printed and delivered by hand.

The Airshow system will also graphically display the airport layout, parking gate and gates for connecting flights.

The pilot requests updates to ATIS for the destination airport.

In the event of a diversion, the pilots sends a Diversion Report to OPUS containing new destination and ETA. The diversion event is immediately indicated at the OCC. This information is also provided to the original destination and new destination. The pilot has instant access to weather info and ATIS for alternate airports. The OCC uplinks additional information. Thus the pilot has access to all important information to help him make the best decisions.

When the aircraft is established on approach another automatic downlink is sent to advise the airport systems and stations personnel that the aircraft will shortly be landing. Gate personnel and technicians will be dispatched to meet the aircraft at the gate on time.

On touchdown the ACARS automatically sends an On Report to OPUS.

Taxi in and Parking

Shortly after landing a Crew Next Duty uplink is received from CRU80. This lists the next duty details for each crewmember: flight, acreg, version, STD, ETD, slot time. Each crew member knows where to go and what to do immedately after landing. CRU80 also sends a Next Crew List for the Captain and Purser respectively to help the gather their crew for their next leg.

Taxi instructions are uplinked by ATC. If there is a delay during taxi in, eg the gate is occupied or unmanned, the pilot sends a Gate Delay report to OPUS.

A last minute update regarding passenger connections and rebookings may be uplinked and displayed on the cabin monitiors. The passengers step off the plane well informed about airport procedures, layout and their connecting flights.

After parking the ACARS automatically sends an In Report to OPUS and shortly thereafter a Flight Summary report.

Groundstop

When the aircraft has a groundstop at one of SAS' main hubs CPH, ARN and OSL the opportunity is taken to download ACMS and QAR bulk data for FOQA and maintenance analysis using a broadband datalink (gatelink). Onboard maintenance computer data, inflight sales and stock figures are also downloaded. Updates to onboard navigation database and onboard electronic manuals are uploaded. Inflight entertainment system updates are uploaded.

MD-87 LN-RMA Hasting Viking at Gate 40, OSL Airport 01JAN2000.
Photo: Per Ø. Bøe, SAS Data

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