Future Air Navigation Systems (FANS) — Page 322, Lesson 381

Let's pick up with the data link messages themselves. We've got the FANS concept in place, so now I want to walk you through the actual content that flows over that link between the aircraft and the Air Traffic Services Unit, the ATSU. There are many different types of message that can be sent by data link to or from an ATSU. Let's look at the more important ones, starting with the Departure Clearance. Here's a real example of a PDC, a Pre-Departure Clearance. Read it with me: "PDC 130044, CPA065, B742, VHHH, 0100. CLEARED TO OMDB VIA 07R, LAKE1A DEPARTURE V1. ROUTE: FLIGHT PLAN ROUTE. MAINTAIN: 5000FT. EXPECT: F330. SQUAWK A5156. -END." Let me decode that line by line, because every field matters. "PDC 130044" — that's the message type and a serial number. "CPA065" is the callsign. "B742" is the aircraft type, a Boeing 747-200. "VHHH" is the departure airport, Hong Kong. "0100" is the time. Then the clearance itself: cleared to OMDB, Dubai, via runway 07R, using the LAKE1A departure, transition V1. "ROUTE: FLIGHT PLAN ROUTE" means the routing is exactly as filed. "MAINTAIN: 5000FT" — that's your initial altitude to hold. "EXPECT: F330" — that's the flight level you can expect later, flight level 330. "SQUAWK A5156" is your transponder code. And "-END" terminates the message. Now the Oceanic Clearance. This one's used over the oceans where there's no radar. Here's the example: "CLRNCE 123, SAS911, CLRD TO KEWR VIA 57N010W, RANDOM ROUTE, 58N020W, 58N030W, 57N040W, 55N050W, OYSTR, STEAM. FM 57N010W/1034, MNTN F310, M082. ATC/ENTRY POINT CHANGE. ROUTE CHANGE AT 58N 20W. END OF MESSAGE." So "CLRNCE 123" is the message type and number. "SAS911" is the callsign. "CLRD TO KEWR" — cleared to Newark. Then you get a series of waypoints: 57N010W, 58N020W, 58N030W, 57N040W, 55N050W, then OYSTR and STEAM, which are named fixes. This is a "RANDOM ROUTE" — not a standard airway, but a track defined by these coordinates. "FM 57N010W/1034" means from that waypoint at time 1034. "MNTN F310, M082" — maintain flight level 310, and M082 is the Mach number, Mach 0.82. Then "ATC/ENTRY POINT CHANGE, ROUTE CHANGE AT 58N 20W" — that's a revision to the routing. And it ends with "END OF MESSAGE." Next is the Digital ATIS — the Automatic Terminal Information Service delivered by data link. Here's an example: "/HKGATYA.TI2/VHHH ARR ATIS Z, 2205Z. HONG KONG ATIS. RWY IN USE 07R. EXPECT ILS DME APCH. WIND LIGHT AND VARIABLE. VIS 10 KM. CLOUD FEW 1600FT. TEMP 28, DP 22, QNH 1007. ACK Z ON FREQ 119.1 FOR ARR AND 129.9 FOR DEP." So the header tells you it's the arrival ATIS for VHHH, information Zulu, issued at 2205 Zulu. Then the actual weather and airport info: runway in use 07R, expect an ILS DME approach, wind light and variable, visibility 10 kilometres, few clouds at 1600 feet, temperature 28, dew point 22, QNH 1007. And critically, the acknowledgement instruction: "ACK Z ON FREQ 119.1 FOR ARR AND 129.9 FOR DEP" — you must acknowledge receiving information Zulu on the appropriate frequency, 119.1 for arrivals, 129.9 for departures. Now let's shift to the AOC messages — Airline Operational Control. The aircraft operator, the airline or company, needs to know where their aircraft are at any time to ensure an efficient and cost-effective operation. So a data link is set up to pass messages to and from the aircraft. The important types are the OOOI messages. That's four letters: Out of Gate, Off Ground, On Ground, In the Gate. These are the four key phases of a flight from the operator's perspective. Out of Gate: "OUTRP 1065/31 EGLL/KJFK .G-BOAC/OUT 0850." So OUTRP is the message type, 1065/31 is a sequence number, EGLL/KJFK is the route, London Heathrow to New York Kennedy, G-BOAC is the aircraft registration, and OUT 0850 is the time you left the gate. Off Ground: "OFFRP 1247/31 EGLL/KJFK .G-BOAC/OUT 0850/OFF 0900/ETA 1525." Now you've got OUT 0850, OFF 0900 — the time you became airborne — and ETA 1525, the estimated time of arrival. On Ground: "ONRP 1499/31 KJFK .G-BOAC/ON 1540." ON 1540 is the time you touched down. In the Gate: "INRP 1803/31 KJFK .G-BOAC/ON 1540/IN 1550." IN 1550 is the time you arrived at the gate. So the full sequence is OUT, OFF, ON, IN — and each message builds on the previous one, giving the operator a complete picture of where the aircraft is and when. Finally, the Load Sheet. This is the mass and balance document sent by data link. Let me walk you through the fields: "LOADSHEET FINAL 9999 EDN 01. SK9999/01 31SEP01. ARN OSL ACREG 9901S 2/4. ZFW 49764 MAX 59874 L. TOF 6100. TOW 55864 MAX 70760. TIF 2100. LAW 53764 MAX 64410. UNDLD 10110. PAX CM 60/17 TTL 77. DOI 59. DLI 56. LIZFW 31. MAC-ZFW 7. MAC-TOW 10. TRIM BY CABIN AREA – SECTION SI. BOARDING PAX WEIGHTS USED: -OSL ADULT 84 CHILD 35 INF 00. BOARDING BAG WEIGHTS USED: -OSL 13/PIECE. TOTAL EET: 00:28. AIRB TIME: 00:43. ENDURANCE: 02:20. ALTN: ENTO." Let me decode the key ones. ZFW is Zero Fuel Weight, 49764, with a maximum of 59874. TOF is Take-Off Fuel, 6100. TOW is Take-Off Weight, 55864, maximum 70760. TIF is Trip Fuel, 2100. LAW is Landing Weight, 53764, maximum 64410. UNDLD is the undelivered or unused load, 10110. PAX is passengers: 60 in cabin class, 17 in another, 77 total. DOI and DLI are the take-off and landing trim indices. MAC-ZFW and MAC-TWO are the mean aerodynamic chord positions for zero fuel and take-off weight. Then you have the trim by cabin area, the boarding weights used — adults 84 kilos, children 35, infants 0 — and bag weights at 13 kilos per piece. And at the bottom: total estimated elapsed time 00:28, airborne time 00:43, endurance 02:20, and the alternate airport, ENTO. So that's the full picture of what actually travels over the data link — clearances, ATIS, operational position reports, and the load sheet. Each one is a structured message with defined fields, and as a pilot you need to read them precisely because every number and code carries operational meaning.