Aerial spraying of soil or crops thereon

Claim 1

AN AIRCRAFT INCLUDING MEANS FOR SPRAYING THE GROUND BENEATH IT COMPRISING A HOLLOW APRAY BAR, SPRAYING NOZZLES ON SAID SPRAY BAR MEANS, SUSPENDING SAID SPRAY BAR FROM THE AIRCRAFT AT A POSITION BELOW THE AIRCRAFT AND TRANSVERSELY OF THE AIRCRAFT''S HEADING, SAID MEANS COMPRISING AT LEAST ONE LINEAR ACTUATOR, BY WHICH THE SPRAY BAR CAN BE RAISED AND LOWERED RELATIVELY TO THE AIRCRAFT, ELECTRICAL MEANS CONTROLLING THE EXTENSION OF SAID ACTUATOR, A DEVICE FOR ACCURATELY MEASURING AND SIGNALLING THE INTANTANEOUS HEIGHT ABOVE GROUND OF THE AIRCRAFT, AT LEAST ONE DEVICE MOUNTED ON THE SPRAY BAR AT A DEFINE POINT THEREOF FOR ACCURATELY MEASURING SAID SIGNALLING THE INTANTANEOUS HEIGHT ABOVE GROUND OF SAID POINT, MEANS RECEIVING DEMAND SIGNALS FOR HEIGHT ABOVE GROUND OF THE AIRCRAFT AND OF THE SPRAY BAR RESPECTIVELY, MEANS TRANSMITTING TO SAID EXTENSION-CONTROLLING MEANS SAID DEMAND SIGNALS AND THE SIGNALS OF SAID HEIGHT MEASURING DEVICES SAID EXTENSIONCONTROLLING MEANS INCLUDING MEANS FOR ALGEBRICALLY SUMMING THE SIGNALS IT RECEIVES TO PRDUCE, AND TRANSMIT TO THE ACTUATOR AN OUTPUT SIGNAL REPRESENTING THE ERROR OF ACTUATOR EXTENSION, THE ACTUATOR HAVING CONTROL MEANS RESPONSIVE TO SAID ERROR SIGNAL FOR CORRECTING THE SIGNALLED ERROR.