The picture below shows the 4 different channels (nominally called Anti-Collision, Navigation, Beacon and Landing) and the flash patterns available. The various patterns are selected by varying the ATV (travel) of the input channel into the controller. The 4 channel controller is not 'programmable' in the traditional sense; you can only vary the flash pattern to one of those in the picture. You can therefore see that there isn't a flash pattern that will flash 2 different channels, at the same time, in the way that you want.
The 2 options available to achieve your desired result are to either Y both lights into one channel (with either the Unilight Y-lead or by making one up yourself) or by using the 8-channel controller, which is fully programmable with a PC.
