{HEAD ~ Each propulsor} is driven and configured by {TAIL ~ computer controlled actuators} so that the control surface undulates in various wave forms 
is driven by
{ HEAD ~ Each propulsor } is driven and configured by { TAIL ~ computer controlled actuators } so that the control surface undulates in various wave forms
HEAD HEAD HEAD HEAD HEAD HEAD REL REL OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH