Maybe you have wondered about the file names of the IGC log files that are generated by your flight recorder. For example, "15KC3WK1.IGC". It looks like a strange random combination of letters and numbers, but each character does have a meaning. In the example above it means, "1st Flight on May 20th, 2011* using a Cambridge flight recorder serial number 3WK". Simple? Not so much.

Here is what each digit means in the IGC filename;
Format: YMDCXXXF.IGC

• Y=Last digit of year
• M=Month of year (1-9, A-C)**
• D=Day of month (1-9, A-V)**
• C=Manufacturer of logger
• XXX=Serial number of logger (3 alpha-numeric digits)
• F=Flight number of day (1-9, A-Z)**
• IGC=File extension name

To ease the decoding of the convoluted IGC file name, I created a "simple" spreadsheet to decode these file names and as a teaching aid so that after a while you can figure the dates yourself just by looking at them. You might find this useful if you are sorting through a bunch of old log files.

WARNING: I suggest that you do not rename your IGC files. There have been reports of renamed IGC files causing scoring problems at contests and for badges. If you want to keep a renamed file, only rename a copy of the original, and keep the original "pristine".

*NOTE: Due to limitations of the IGC file naming standard (DOS 8.3) and the IGC standard only one character is available to represent the year of the flight**. Therefore, flights during years ending in the same digit will be listed in the spreadsheet as occurring in the closest year within the current decade.

For example, the years 2024, 2014, 2014 will all use the same year digit - in this case "4". That is, any flight during those years will all seem to be in the same year. and have the same first "Y" digit in the IGC filename ("4"). Because the spreadsheet cannot tell the difference, all flights will indicate a flight year within the current decade.

The actual date and time of the flight is shown within the text of the IGC log file (so you can't cheat!). Sorry folks, but there is no way around this in my spreadsheet without reading the contents of the file, which Excel cannot directly do (if you know how, let me know).

See the table below for date examples to help illustrate this issue;

Other information can be found at the International Air Sports Federation (FAI) Gliding (IGC) web site.

• Cambridge Aero Explorer
• IGC Flight Replay- for viewing in Goole Earth
• Charlie Thaeler 3D Rendering

For example, if the day of the month is the "5th", this is represented by a "5". Easy. But the "11th" is above 9 so it is represented by the letter "B". Say the month is December (12th month). This is represented by the letter "C". More than 9 flights in a day? Got you covered but only up to 35 flights ("Z"). Let me know if you had 35 flights in one day - that has to be a record of some sort!

The alignment of the single IGC filename characters to their true meanings are shown in the table below and in the spreadsheet.