Jaap's Psion II Page

Airnav Professional Manual

Also available is what seems to be a slightly earlier version of the Airnav Manual.



The Air Navigator for the Psion Organiser

Software Manual
Versions 1A and up

For use with both two line and four line Organisers


If you are not yet familiar in the way in which the Organiser works, follow the next instructions to install the software and to set up your Organiser.

Note that to select items from the menu, you can EITHER move the cursor onto the item you wish to select, and press EXE, OR press the first letter of the item eg Q for quit. If two items in the menu start with the same letter, the cursor moves to the next item and you must press EXE to select the item you want.

Inserting the AIRNAV datapack:-

  1. With the Organiser OFF, insert the AIRNAV datapack into slot B. (In the back of the Organiser nearest the display). It will not work properly in slot C. The AIRNAV program will run in slot C, but it will look in slot B for the databases.
  2. Press ON TWICE. The first press turns on the Organiser, the second press automatically inserts AIRNAV into the menu.
  3. Press EXE to go into the AIRNAV software.
  4. You now have the first menu of the AIRNAV package.

The use of AIRNAV is simple once you have been through an example, so here is an example which incorporates many of the facilities


Adding a new point to the database:-

Select EDIT_DB. Bournemouth (Hurn) airport is already in the database, but you may wish to be able to enter HURN instead of BOURN to find the entry in the database. Note that it will find a match on any number of letters anywhere in the database. Have to hand the name of your data point (max 15 characters) and its latitude and longitude (degrees and minutes only) and select ADD. When it says NAME TO ADD, type HURN then EXE. Now enter the latitude. It will only accept N or S and then requires FOUR digits. (Note that you do not have to press the shift key to get numbers because the program knows what to expect). The latitude of Hurn is N 5047, so enter it then EXE. Similarly, the longitude must be W or E, and Hurn is W 00150 (note that longitude requires FIVE digits), press EXE. You are now prompted to add more details. If you want to add radio, runway and height information, press Y.

When you have finished, your entry is displayed line by line. Read it carefully and press any key. You now have the choice to accept that entry by pressing Y, not accept it and try again by pressing N, or Q to quit (give up!). If you press Y, the entry is permanently written into the datapack. It will not be lost when you switch off or even if you remove the datapack, but if it is wrong, it can be deleted by selecting DEL from the EDIT_DB menu. Note that entering data on aircraft for the weight and balance calculation is done in a similar manner. It is not recommended to delete entries from the database as the memory taken up by that entry is not re-usable. There is enough room on the datapack for hundreds of more entries. Select QUIT to return to the AIRNAV menu.


From the main menu, select NAVAID to plan a journey from Bournemouth to Oxford. Select VAR'N to enter the magnetic variation. In the south of England it is W, six degrees. Press W 6 EXE. Select FUEL, and add your fuel data. Any choice of units can be used, but be consistent and your answer will be in those units eg galls, litres, pounds etc. FUEL QUANTITY is the total fuel on board including any reserve. You will be asked to enter the consumption per hour and then your reserve quantity. Note that VAR'N and FUEL are optional and do not need to be run.

Select DATA and enter the wind data. Note that all directions are given or asked for in magnetic (M) or true (T). Enter the wind direction (T), and wind speed in Knots.

Your True Air Speed may be entered by pressing T or EXE, or you may want to enter Indicated Airspeed or Mach number.

If IAS is selected, you are prompted for your proposed flight level and IAS. TAS is calculated at standard temperature for that flight level and is displayed. (The IAS to TAS calculation is done at the nearest 1,000 ft below, eg Flt level 245 will be calculated at 24,000 feet, the same as Flt level 240, and will only allow input of up to Flt level 500). If you wish to calculate TAS at another temperature, press Y and enter the new temperature (deg C). When TAS is displayed, press any key to get to the next menu. The calculated value for TAS is used in the navaid calculations.

TAS from Mach number is calculated from the true air temperature and is displayed in a similar way.

If you already know your track and distance, you may select TRACK/DIST and enter data as requested, but we will select POS'N. The program will work out your track and distance FROM one point TO another.

Select FROM. You may choose one of four ways to establish the FROM point.

  1. Select POINT and enter the name of a point in the database. A match will be found, press Y to accept that point or N to search for another match. All the entries in the database contain the lat and long.
  2. Select CO-ORDS to enter the latitude and longitude of your FROM point.
  3. Select FIX. You will now have to enter FIX1 and FIX2 and the bearings to those points. If you want to take a fix on an NDB, choose NDB and enter the aircraft heading and the relative bearing of the beacon from the aeroplane. AIRNAV will calculate the absolute bearing. When both FIXs are entered, select CALC. AIRNAV will calculate your lat and long. This is now your FROM point.
  4. Select VOR/DME if you want to calculate your FROM point from a VOR with DME. You will have to select your VOR from the database in the usual way, enter the radial that you are on and finally the distance from the VOR/DME. AIRNAV will calculate your lat and long. This is now your FROM point. If you use the reciprocal radial, your position will be wrong! Also note that as VORs are aligned to magnetic north, if you do not use VAR'N, there will be an error in your calculated position.

The TO coordinate CAN NOT be obtained by a FIX or VOR/DME, but may be a point in the database or its lat and long entered.

To enter your FROM point, select POINT and enter BOUR (for example) followed by EXE. Note that it finds a match anywhere in the database, so it finds BOURN first. Press N or EXE to get the next match which is BOURNEMOUTH. Press Y. Note that you could enter EGHH to find Bournemouth as wherever possible the EGxx code has been included in with the airport name.

Select TO then POINT and enter your TO point. Enter OXF then EXE and answer Y to OXFORD.

Having entered both the FROM and TO points, select CALC. The track and distance of your journey will be calculated and displayed. (Note that this facility can be used to offset a VOR to an airfield.)

Press any key to obtain your heading (true and mag).

Press any key to obtain your ground speed and journey time.

Press any key to obtain fuel information (only if you entered FUEL data). Note that it gives REServe plus the amount of fuel left. If your journey uses enough fuel to go into the reserve, it will display a message and beep twice. Press any key, and if you have any fuel left, you have the option to update the amount of fuel in the program memory. Press Y. This can be done as many times as you run CALC from this menu, each time reducing the amount of fuel left in the program memory.

If, at the top level menu, you selected TARIFF and entered a cost per hour, the cost of this journey will be displayed. You are given the option of clearing the previous accumulated cost before you update it with the new cost. In this way, the accumulated cost of a journey with many legs can be found.

By selecting SWAP, the FROM and TO points are swapped over. For example, FROM BOURNEMOUTH, TO OXFORD becomes FROM OXFORD, TO BOURNEMOUTH. If you intend going on to a different destination, you then only need to enter a new TO point.

If you wish to find your FROM position from two bearings on VORs or QDM from an airport, select FROM and FIX. You may now take FIX1 and FIX2 and CALC your position. (Note that in taking a fix, you CAN enter the reciprocal bearing, it does not affect the calculation). The option of NDB is given because bearings from an NDB are relative bearings.

If you choose this option, you will be asked for the aircraft heading (Magnetic) and the relative bearing to the NDB. The program will calculate the absolute bearing. After you have entered FIX1 and FIX2, select CALC and it will calculate your latitude and longitude. Press Q to QUIT this part of the program. This position is now your FROM point, and if you enter your TO point, you can calculate your new heading and time to the TO point. If you had previously entered your TO point, there is no need to enter it again, just select CALC.


If you selected LOG and CREATE at the top level menu, a logfile was created and each time that you CALCulate a journey, you are asked if you wish to log that part of your journey. If you answer Y, the heading, time and ground speed are saved in the logfile. After all the journey legs have been calculated, you can view the logfile from the top level menu by selecting LOG and VIEW. When you have finished with the information, you should delete the logfile. The logfile is stored in RAM in the Organiser, not in the datapack, so the use of logfile does not use up the datapack. When the logfile is deleted, the memory that was used by the logfile is available for use again. This information is retained even if you leave AIRNAV and can be VIEWed on return to the program (unless the battery has been removed in the meantime).


The first time you run this part of the program, you will need to ADD data on your aircraft and its fuel.

Select BALANCE from the top level menu to get the weight and balance menu. You will have the choice of DATA, LIST, ADD, DEL or QUIT. (If you are unsure of the state of your battery, it is worth using a new one, or using the Psion power supply to enter this important data into the database. If you should get the message "Battery Too Low", replace the battery, delete the entry and re-enter the data.)

Choose ADD and follow the prompts to enter the following data.
  Aircraft data required:-
     Aircraft type (eg C172)
     Fuel weight per volume (eg lbs/US Gall, Kgs/Lt etc)
     Unit of volume used (eg US GALLS)
     Unloaded aircraft weight (without fuel)
     Unit of weight (eg LBS, KGS)
     Maximum take-off weight
     Unit of length (eg INS)
     Unloaded aircraft datum to C of G.
     Minimum distance of C of G behind datum
     Maximum distance of C of G behind datum
     Distance of fuel tank behind datum
     The number of stations you wish to use
     Station 1's name eg FRONT SEATS
     Station 1's distance behind the datum
     Station 2 ... etc for all stations up to a max of 8 stations

If your aircraft has more than one fuel tank, you can either enter the main tank as normal, and other tanks as stations BUT you will have to enter the weight of fuel in these tanks. OR you can calculate the effective datum to tank distance of all the tanks as though they were one. This approach assumes an even distribution of fuel in all the tanks.

It can not be stressed too highly that this information must be accurate and that the program is only a C of G calculator. The program calculates where the C of G is from the weight and lever information. The program can not take into consideration any "aircraft specific" information that may be available from the aircraft operating manual.

Note that if the station is in front of the datum, it must be entered as a negative number.

You are prompted to press any key to check the data, after which you can accept the data by pressing Y, and it will be stored in the datapack. If you have made a mistake, press N and try again.

Also note that you are prompted to enter units of volume, weight and length in the aircraft data. These are used only as a prompt when data is entered. The program will not automatically do conversions and will give you the wrong answer if you use the wrong units.

When Balance is run by selecting DATA, you enter the aircraft type. The program looks up the information on that aircraft in the database. (If a match is not found in the database, you may use LIST to view the entries in the database). You are then prompted to enter the weight at each station and the results of the calculation are shown.

Entries in the database may be deleted by selecting DEL.


In addition, you may write your own programs and use them from AIRNAV. To do this, your first program must be called MYPROG. For example:-



All these GLOBAL Variables are declared in the first procedure used when AIRNAV is run, but will not necessarily contain real data until the program has been used.

WDWind Direction
WSWind speed
TASTrue Air Speed
GALFuel Quantity
GPHFuel consumption per hour
RESFuel Reserve
VARMagnetic variation (west +ve, east -ve)
NS$(5)Current point latitude (format eg. N5132)
EW$(6)Current point longitude (formal eg. W00145)
X(n)Decimal value of longitude - see below
Y(n)Decimal value of latitude - see below
TRKCurrent track
DSDistance of current journey (nautical miles)
TITime (mins) of current journey
CHCost of flying per hour
TCHTotal cost of journey

X and Y are both 1 dimensional arrays with 4 values. X(1) and Y(1) are the decimal values of the latitude and longitude of your FROM point, X(2) and Y(2) are of your TO point, X(3), Y(3) and X(4), Y(4) are your two FIX points. Northern hemisphere is positive, and east of 0 degrees is positive.

In AIRNAV PROFESSIONAL, beacon and airfield data is included in the database. This can be viewed by selecting EDlT_DB from the top level menu, then select FIND. Subsequent pressing of any key will display lat and long, beacon or airfield frequencies, runway numbers and height AMSL. Note that for long entries, the screen will scroll until any key is pressed. Usually, the frequencies are displayed for approach and tower, but where only one frequency is shown, it is usually the main air to ground frequency. If a name is in brackets, it is the name of the station controlling that airspace.

From the top level menu, you may LIST all the entries in the database. Use the up and down cursor keys to scroll up or down the list of entries.

Also provided in AIRNAV PROFESSIONAL is the conversions. Select CONVERSION from the top level menu. You can select the conversion from the list in the usual way. If you wanted to convert from US gallons to Imperial gallons, select IMP/US-GALLS. The display shows the conversion requested and prompts you for Y or N. If IMP to US gallons was required, press Y. As we will convert US to IMP, press N and you are prompted to enter the number of US GALLS to convert and the answer is displayed after EXE is pressed.

When you have completed your conversions, return to the top level menu by pressing Q(uit) or ON/CLEAR.


AIRNAV-entry point into Airnav program.
QUIT-quit will always return you to the previous menu or will exit you from Airnav if you are at the top menu.
OFF-at various menus, you have the ability to turn off the Organiser. Turn it back on by pressing ON/CLEAR and you will return to the same point in the program where you left.
NAVAID-entry point into the main navigational calculator.
DATA-entry point into next level of program and data entry.
EDIT_DB-entry point into database editing facility.
MORSE-entry point into morse sounder program, to escape from this program, press ON/CLEAR or EXE instead of a letter or number. Use the SHIFT key to get numbers.
TARIFF-enter the hourly cost of flying.
BALANCE-Entry point into the weight and balance schedule program.
XWIND-calculates the runway crosswind component.
MYPROG-the program will try to find an OPL program called MYPROG to run.
LIST-list all of the database entries. Use the cursor keys to scroll up and down the list. Press any other key to return to the menu.
FIND-find a particular entry in the database. Avoid finding a single letter because it will find every occurrence of that letter in the database.
ADD-add a point in the database.
DEL-delete a point in the database.
VAR'N-enter the local magnetic variation. (up to 45 degrees E or W).
FUEL-enter your fuel data (total fuel on board, quantity used per hour, and reserve).
TRK/DIST-if you know your intended track and distance, this part of the program will calculate your heading, ground speed etc.
FROM/TO-entry point into the part of the program that lets you input your FROM point and your TO point, it will then calculate your track and distance.
FROM-enter your FROM point.
TO-enter your TO point.
CALC-calculate your track and distance, heading, ground speed etc.
SWAP-swap your FROM and TO points. Use this either for your return journey, or if you want to go on to another waypoint, use swap and then enter a new TO point.
FIX-entry point into the part of the program that enables you to calculate your FROM position from two fixes on suitable beacons or other entries in the database.
POINT-choose a point from the database. You only need to enter a few characters eg BOUR for Bournemouth, a match will be found on any entry with BOUR in it which you may press Y(es) to use it, or N(o) to find another. If a match is not found, END OF FILE is displayed and you are returned to the previous menu.
NDB-Similar to POINT, but intended to find a point from the database that will be used as an NDB. You will then be asked for your heading and the relative bearing of the NDB. It will calculate the true bearing of the beacon and use it in the FIX CALCulation. It does not matter if you use the reciprocal bearing by mistake.
VOR/DME-calculate your FROM point from a radial and distance from a VOR/DME. You can not use the reciprocal radial.
CO-ORDS-you may enter the latitude and longitude of your FROM point or TO point.
FIX1-enter your first fix details.
FIX2-enter your second fix details.
CALC-calculates your current position and enters it as your FROM point.
LOG-allows you to CREATE a logfile, DELETE a logfile or VIEW a logfile.
CONVERSION-entry point into the conversion part of the program.

NOTE ..... if you intend to add a large number of points into the database, it is wise to use the Psion power supply as adding data will reduce your battery life.

The world of AIRNAV goes from dateline to dateline but will not cross the dateline or the poles. If you wish to cross the dateline with AIRNAV, place a way point on the dateline at a convenient place. If this is not done, AIRNAV will take you the long way round!

AIRNAV has been designed as an aid to route planning and has been thoroughly tested. The designer reserves the right to make improvements without notice and takes no responsibility for the owner's use of AIRNAV. It is always wise to double check your results. The accuracy of the calculations is generally within one degree, one nautical mile or one Knot. AIRNAV will allow you to get a fix on bearings down to two degrees apart or up to 178 degrees apart.

If you have any comments or queries on AIRNAV, please make note of the version of the software that you have (the first thing to be displayed on the screen when you run AIRNAV) and contact Interair Flight Centre, Interair Aviation, Bournemouth International Airport, Dorset, BH23 6HA. Telephone (0202)581300. Fax (0202)581984. Telex 417123.

Weight and Balance Data Checklist

Aircraft type
Fuel density
Unit of volume
Unloaded aircraft weight
Unit of weight
Maximum take-off weight
Unit of length
Unloaded aircraft datum to C of G
Minimum C of G from datum
Maximum C of G from datum
Distance of fuel tank from datum
Station 1 name
Station 1 from datum
Station 2 name
Station 2 from datum
Station 3 name
Station 3 from datum
Station 4 name
Station 4 from datum
Station 5 name
Station 5 from datum
Station 6 name
Station 6 from datum
Station 7 name
Station 7 from datum
Station 8 name
Station 8 from datum