I have heard of a way of unblocking these vacuum toilets.
1: Take a large diameter pipe (similar OD to the toilet bowl waste pipe).
2: Place one end down the blocked toilet, a nice tight fit!
3: Place the other end down a serviceable toilet, again ensure a nice tight fit!
4: Flush the serviceable toilet and stand back.
Apparently the blockage flies through the pipe at 90 MPH (and probably blocks the serviceable toilet). Imagine trying this technique to unblock a fwd bog using a serviceable rear one.
