I'll give you an example.
Working schedules: {there are three that come to mind} 1. Two day shifts; two swing shifts; two mid shifts; and two days off (48 hours max). This normally is done with four crews, and usually is augmented with a floater crew
that is mostly trainees and trainers, to expedite training.
2. Two day shifts; two swing shifts; 2 days off (48 hours); two mid shifts; and three days off (72 hours). This takes five crews and is best for the body to adjust to the rotation.
It is also augmented with a floater crew of trainees and trainers.
3. One swing shift (6 hours); a 12 hour break; one afternoon shift (6 hours; a 12 hour break; one morning shift (6 hours); a 12 hour break; one mid shift (6 hours); and a 60 hour break (the rest of that day, all day the next day, and 18 hours of the third day. This takes five crews, and this rotation is hardest on the body, but a favorite of the FAA due to the time off.
Also, this rotation can have the hours adjusted from 6 hours on some shifts to 8 hours {mostly on the morning and afternoon shifts} and 5 hours on the other shifts to allow some overlap.
Part Time Second Jobs: The FAA can authorize controllers to get a second job, through filling out a form and getting signed permission from management.
This is why most FAA controllers (the Union) like the rapid rotation of the 3rd example of the work schedule.
My first question of these "FAA Incidents/Accidents" would be Was the working controller involved, ... authorized to work a second job?
Did he truly have an undisturbed eight hours of rest before his Air Traffic Control Shift?
These second-job considerations, I believe, will be one of the contributing factors to most these problems.