PURPOSE: To decrease aerodynamic drag, raise a reliability prformance, make assembling and maintenance easy and make a structure which is so called as a tunnel unnecessary by transmitting a signal by light.

CONSTITUTION: An auto-pilot device 12 situated at a guidance part 1 which is a front fuselage, executes an operation treatment and a generation of an order signal (four axes) and others about a rudder operation of an air frame based on a device information from sensors 14, 14a, 14b. These signals are converted into a time division digital signal at a signal sending treatment part 10, are converted into an optical signal at a signal sending optical part 8 having an optical system and an output is executed. This optical signal is received at a signal receiving optical part 9 of a control part 4 which is a rear fuselage and further by a signal receiving treatment portiion 11, a conversion of each axial rudder operation order signal and the like into an electrical signal is executed and an input into a servo-device 13 is executed. A rudder signal (four axes) and the other signals from the servo-device 13 and other signals are, in like manner, by a composition of a signal sending treatment part 10a, a signal sending optical part 8a, a signal receiving optical part 9a and a signal receiving treatment part 11a, is transmitted to the auto-pilot device 12 of the guidance part 1 which is the front fuselage.