AFTN Flight Planning

Flying was a very tangible freedom. In those days, it was beauty, adventure, discovery, new worlds.

(Anne Morrow Lindbergh, 1929)

Not any more.   The International Civil Aviation Organization (ICAO) was formed in 1947. And today flying is very a regulated and planned activity.  Pilots strictly follow ICAO FPL flight plans.  All Dash 7 flights in and out of Rothera require the submission of an ICAO FPL flight plan to the global Aeronautical Fixed Telecommunications Network (AFTN) cloud.

One of the computers in the tower at Rothera has been connected to the UK AFTN Parent node located at the CAA London Control Centre in Swanwick .  This computer is running an AFTN Terminal Application that can send and receive flight planning and meteorology messages to the AFTN cloud(via Swanwick).

To prepare for a Dash 7 flight we will need to send an FPL flight planning message (based on a template) to the AFTN and record the AFTN message number onto the flight following log sheet.  When the flight departs we will send a DEP message to the AFTN and record the message number on the log sheet.  Once the aircraft arrives at the destination an ARR message will be sent and logged.  We will also be able to use the AFTN terminal to report delays (DLA),  send progress report messages, request METAR meteorology reports or if necessary cancel (CNL) a flight plan.   If the AFTN terminal fails the backup procedure is to print the FPL form (CA48) and fax the form to Swanwick.  We will also receive AFTN messages such as METARs and flight plans and progress updates sent by other stations regarding aircraft in the vicinity.

I will be trained in the specific processes for managing the Dash 7 plans when I arrive on the base, however this week I have been learning generally about  UK Flight Planning procedures. Yesterday we visited the operations tower at Duxford Airport and learned about the systems and procedures to submit, activate and progress FPL flight plans via an AFTN terminal.  Colin also usefully suggested that I read the CAA UK Flight Planning Guide CAA CAP694.

Nowadays flight plans will almost always be submitted electronically either via an AFTN terminal like they do at Rothera or online via the flight planning webpage .   But I found that initially attempting to understand how to complete the paper form and read the raw text FPL messages was a good way to start gaining an understanding of the layout and coding requirements of flight planning AFTN messages.

FPL Form Source
FPL message
Example ICAO FPL message

 At first sight the form  and message seems quite impenetrable.  But of course once you learn the message format and all the codes by heart the form magically transforms from a wad of meaningless gobbledygook-gook  into a gloriously concise and precise presentation of a large amount of information.

The remainder of this story will discuss in some detail the individual fields on an FPL message, if that’s not of interest to you then you might want to leave it here.  Otherwise,  grab a hot drink (you will need it) and let me talk you through the format and coding of a ICAO FPL flight plan message.

The Aircraft Identification code  (Callsign) is the first question in the FPL message section of the form.  I will need to have the BAS aircraft callsigns at the tip of my tongue when I am working in the tower.  The bathroom wall is kindly helping me learn these.


 The Flight Rules codes are relatively simple:
I = Exclusively IFR (Instrument)
V= Exclusively VFR (Visual)
Y= Initially IFR but will change to visual during the flight
Z= Initially VFR but will change to instruments during the flight

The Type of Flight codes are straight forward and almost guessable:
S = Scheduled Service
N  = Non-scheduled Operation
G  =  General Aviation.
M =  Military
X  =  Other than any of the defined categories above.

The Number of Aircraft field is left blank unless it is more than one. No codes to learn.

The Type of Aircraft code is the ICAO Aircraft Type Designator which can be looked up in the ICAO DOC 8643.  I will need to know the BAS aircraft designator codes without needing to look them up and hence am learning these with the help of the fridge.

ICAO Aircraft Type Designator Codes
ICAO Aircraft Type Designator Codes

The Wake Turbulence Category codes are relatively simple:
H = Heavy > 136,000 kg
M =  Medium > 7,000 kg (eg Dash 7)
L =  Light < 7,000 kg (eg Twin Otter)

The Equipment field has two parts with a / used as a field separator.  On the left side of the /  the  Radio, Navigation AND Approach Instruments are coded. The letter S can be used to note that the  standard equipment including VHF RTF, VOR and ILS is fitted.  On the right side of the / SSR transpoder and other surveillance capabilities are noted.

So for example -S/C indicates standard equipment and a mode Charlie transponder.

The Departure Aerodrome code is entered as an ICAO airport code.  I unquestionably need to learn these by heart for the  airports in the vicinity of Rothera so they get prized position at the kitchen sink.

ICAO Codes
ICAO airport codes on the wall behind the kitchen sink

If the airfield hasn’t been assigned an ICAO code then ZZZZ can be entered and the name entered manually in the Other Information field preceded by DEP/
And if the aircraft is already in flight then AFIL can be entered.

The Time of Departure is always entered as Z-Zulu time which is UTC.
This time is referred to as the estimated off-block time (EOBT)

The Cruising Speed entered is the cruising True Air Speed and can be entered as :
Knots (e.g. N0215)
or Kilometres (e.g. K0400)
or Mach number, to the nearest hundredth of a mach (e.g. M033)

The Crusing Level can be entered in one of the following formats:
Flight Level(e.g. F230 for Flight Level 230)
Altitude in hundreds of feet (e.g. A230 for 23,000 ft)
Tens of metres on standard atmosphere (e.g. S0700 7000m on 1013)
Altitude in tens of metres,  (e.g. M0700 7000m above msl)
or the letters VFR if a cruising level is not planned for the flight

The planned Route section of the form is where the details of planned changes to speed, levels and flight rules will be entered.  For us this information will be provided by the Flight Operations Manager and we will enter the details into this section.  I might write another post about the format of these plans. It is too much to go into here.

The Destination Aerodrome is entered as an ICAO airport code.  I have already discussed ICAO airport codes in the departure aerodrome section so I won’t repeat it.

The Total EET Time is the  total estimated elapsed time. It is worth emphasising that this is NOT the estimated time of arrival. This is the total  estimated time required between take-off and arriving over the destination aerodrome. The EET is expressed in hours and minute as a 4 digit number.  For example a flight with and EOBT of 0900 and an EET of 0130 would have an ETA of 1030 and only the 0900 and 0130 values are included on the form.

The Alternate Aerodrome  is entered as the ICAO airport code for the airfield where the pilot will take the aircraft if the destination airfield cannot be reached.  For example SCRM (Marsh Airport on King George Island) might be an alternative airfield for a flight to SCCI (Punta Arenas).  The FPL plan will appear in the AFTN terminal of the Alternate AIrfield so that they are aware of the information within the  plan and can monitor the flight progress updates.  Again use ZZZZ and manually enter the name preceded by ALTN/ in the other information field if the alternate airfield has not been assigned a ICAO airport code.

In the Other Information field you can enter a 0 (Zero) if there is no other information.    But that will not be the case as a minimum the date of the flight (DOF/) in YYMMDD format will be entered into this section.

It’s also very likely that some information about the IFR instruments and capabilities of the aircraft(PBN/ and NAV/) will be included.   These information included in this section will be very specific to the aircraft equipment and routes. I will learn more about what information is included in this section . When I arrive in Rothera.  It is perhaps worth mentioning that the coding of this information changed in 2012.

The Supplemental Information is not included in the main FPL message, it is kept at the location where the FPL is filed.

In the Endurance (E/) field enter the fuel endurance in hours and minutes format.

In the Persons On Board ( P/) field enter the total number of passengers and crew if this is not known at the time the plan is submitted you can enter TBN.

The three Emergency Radio (R/)  check-boxes should be reviewed and crossed out with a large X if the aircraft is not equipped with the relevant radio.  If the aircraft does not have UHF on frequency 243.00 MHz then put a cross through the U box. If the aircraft does not have VHF on frequency 121.500 MHz  then put a cross through V box (but this is very unlikely).  If the aircraft does not have an emergency location transmitter (ELT) then put a cross through the E box.

The four Survival Equipment (S/) checkboxes should also be reviewed.   Put an X through the P if polar survival equipment is not carried.  Put an X through D if desert survival equipment is not carried. Put an X through M if maritime survival equipment is not carried.
And put an X through J if jungle survival equipment is not carried.

The three Jackets (J/ ) checkboxes should be reviewed.
Put an X through L if life jackets are not equipped with lights.
Put an X through F if life jackets are not equipped with fluorescein.
Put an X through U and/or V; as in R/ (above) to indicate radio capability of
jackets, if any.

In the Dinghies (D/) section  put an X through both  D and C if no dinghies are carried.  If Dinghies are carried enter the number of dinghies carried and total capacity, in persons, of all dinghies together.  Put an X through the C if the dinghies are not covered and enter the colour of the dinghies.

In the Aircraft Colour and Markings (A/) enter the colour of aircraft and any significant markings.

If you don’t need to enter any special Remarks (N/ ) Simply put a X through the N .  You may however use this field to make remarks regarding survival equipment on the aircraft.

In the Pilot field  (C/) enter the  name of the pilot-in-command.

The Message Header

The FF header section at the top of the paper form isn’t strictly a part of the FPL message.  A header would be needed for any message (eg ARR DEP).  This informs the routing of the message that follows, much like the header in an email.

In the header you need to specify the message recipients (destinations),  sender (originator) and the filing time in the header section of the

The Message Header Destination Addresses are AFTN addresses.  These are eight characters long  made up of:
– A four-letter ICAO Location Indicator (on the kitchen sink wall)

– A three-letter-group identifying a specific service area . I have not yet found a definitive list of these code but below are the examples cited on wikipedia:

YFY =  AFTN Office
ZTZ = Control Tower
ZPZ = ATS Reporting Office
ZQZ = Area Control Centre
YNY = Notam Office
YDY = Airport Manager
YZY = Met Data Bank
YMY = Local Met Office
ZRZA = Radar Approach

–  The 8th character is an additional letter to identify a department or process within the service area . The letter X is used if the department is not needed.

So for example the destination address for the Tower at Mount Pleasant Airport in the Faulkland Islands might be EGYPZTZX. Another example could be SCRMZQZX for Area Control at Marsh Airport.

The Filing Time is format is DDHHMM(Zulu). So for example 190836 means that the message was filed on the 19th day of month at 08:36 UTC time.

The Originator Address will use the same format as I just talked about for the recipient but obviously this will be the address of the message sender.

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