Aircraft navigation system

Claim 1

A NAVIGATION INSTRUMENT FOR AIRCRAFT BY MEANS OF WHICH SAID AIRCRAFT MAY BE CONTROLLED TO MAINTAIN A FIRST PREDETERMINED SPEED AND ALTITUDE OVER AN INITIAL PORTION OF A DISTANCE TO BE TRAVELLED TO A DESTINATION AND OVER THE REMAINING PORTION OF SAID DISTANCE THE SPEED AND PROVIDING ARE GRADUALLY DECREASED COMPRISING MEANS FOR PROVIDING A SIGNAL REPRESENTATIVE OF THE DISTANCE FROM THE CRAFT TO SAID DESTINATION, MEANS INCLUDING LIMITING MEANS FOR LIMITING THE AMPLITUDE OF SAID DISTANCE-TO-DESTINATION SIGNAL IN EXCESS OF A PREDETERMINED AMPLITUDE AS A FUNCTION OF A PREDETERMINED SPEED OF SAID AIRCRAFT, FIRST SIGNAL RESPONSIVE MEANS RESPONSE TO THE OUTPUT OF SAID LIMITING MEANS FOR PROVIDING A FIRST OUTPUT INDICATIVE OF A REQUIRED CHANGE IN CRAFT CONDITION TO CAUSE SAID AIRCRAFT TO APPROACH AND MAINTAIN SAID FIRST PREDETERMINED SPEED OVER SAID INITIAL PORTION OF SAID DISTANCE AND THEREAFTER MAINTAIN A SPEED IN ACCORDANCE WITH SAID DISTANCE-TO-DESTINATION SIGNAL, MEANS FOR PROVIDING A SIGNAL REPRESENTATIVE THE SPEED OF SAID AIRCRAFT, AND SECOND SIGNAL RESPONSIVE MEANS RESPONSIVE TO SAID SPEED SIGNAL FOR PROVIDING A SECOND OUTPUT INDICATIVE OF THE CHANGE REQUIRED IN CRAFT ALTITUDE TO CAUSE SAID CRAFT TO APPROACH AND MAINTAIN A DESIRED ALTITUDE WHEREBY OVER SAID FIRST PORTION OF SAID DISTANCE THE SPEED AND ALTITUDE MAY BE MAINTAINED SUBSTANTIALLY CONSTANT AND MAXIMUM AND THEREAFTER THEY MAY BE GRADUALLY DECREASED.