Creating a custom Airport Beacon in FSDS


I'm posting this on behalf of someone else, and he's having problems trying to create an Airport Beacon within FSDS.

We're trying to create a light that flashes as the sequence below, and if you know how to achieve this, I would appreciate your help.

Colour = Green

Flash sequence = 3 Flashes (NOT Very fast flashes, they should be flashes that are clearly visible during flight), break/pause for 10 seconds, 4 flashes, break (lets say 5 seconds).

The other option is to edit an FX file in some way to achieve this, but I haven't got a clue how to do it, having never done it before. lol