Patent GB-967195-A (GB)
Title: Aircraft navigation system
IPC: B64D45/00
Filed: 1961-01-20
Abstract: 967, 195. Electric analogue computers; navigation. SPERRY RAND CORPORATION. Jan. 20, 1961 [Jan. 25, 1960], No. 2362/61. Heading G4G. [Also in Division B7]. In an aircraft, a computer computes a desired speed or altitude which varies with the distance of the aircraft from its destination, and a signal is produced representing the amount of control required to be applied to a speed or altitude control device to achieve the desired speed or altitude. In the Figure signals from a gyromagnetic compass 10 on a helicopter are fed to the three phase stator of a resolver 11, the other fixed coils deriving signals energizing potentiometers 12 and 13 driven by a servo 15 controlled by an airspeed sensor 14, so that the wipers feed summing circuits 24 and 25 with inputs representing North-South and East- West components of the helicopter airspeed respectively. The airspeed and direction of a base, such as an aircraft carrier, are set manually on knobs 20, 23, respectively, the former driving a potentiometer 21 energizing the stator of a resolver 22, the rotor being driven by knob 23, so that the rotor coils derive signals representing the N-S and E-W components of the base airspeed. These are fed to summing circuits 24 and 25, the outputs of which are the N-S and E-W components of the helicopter speed relative to the base. These outputs are fed to integrators 26 and 27 to derive the helicopterbase distances in N-S and E-W directions. The range and bearing of the helicopter destination or target are set manually on knobs 32, 35, respectively, the former driving a potentiometer 33 energizing a resolver 34 driven by knob 35, to derive N-S and E-W components of the target distance from the base. These signals are fed to summing circuits 36 and 37, as are the helicopter-base distance components from integrators 26 and 27. The outputs of circuits 36 and 37 thus represent the N-S and E-W helicopter-destination distance components. These signals energize the stator windings of a resolver 40, the rotor of which is driven by knob 31 set manually to the on course bearing of the target. The rotor windings thus derive signals D oc  and D cc  being the on course distance from the target, and the lateral deviation from the required course, respectively. The helicopterbase velocity components from circuits 24 and 25 also energize the stator windings of a resolver 30 driven by knob 31, so that the rotor windings derive signals V oc . and V cc , the on course and cross course velocities. The on course distance signal is indicated on a register 41, and fed through a summing circuit 44 to a limiter 45 which limits the signal to one corresponding to a maximum airspeed preset by knob 46. The limited signal is fed to a fore-and-aft cyclic pitch control mechanism, or to a meter movement 62 so that vertical displacement of a bar 53 relatively to a fixed index 55 shows the amount of fore-and-aft cyclic pitch control required. The airspeed is thus controlled manually or automatically, and to "ordered airspeed", which is the preset maximum until the signal D oc  falls below a value corresponding to the preset maximum, when the ordered airspeed falls off proportionally to the target distance. The base airspeed signal from potentiometer 21 may be added as an input to summing circuit 44, so that when D oc  is zero, the helicopter airspeed can be controlled manually or automatically to equal that of the base, whereby the helicopter keeps station over the base. The signal V oc  from resolver 30 controls a pointer 56, or the collective pitch mechanism, so that altitude is or can be held proportional to airspeed. In this way, altitude decreases with airspeed as the target is approached. The target altitude may be supplied as a datum signal in a manner not described. The lateral deviation from course signal D cc  is fed through a limiter 71 to a summing circuit 70 having the cross course velocity V oc  as a second input. The algebraic sum is used to control lateral displacement of a bar 54 showing the lateral cyclic pitch control required, and a pointer 60 showing the yaw control required, or to control the lateral cyclic pitch and yaw control mechanisms. The helicopter, when off course, is thus brought back by a turn coordinated in roll and yaw. Ground speed signals derived by Doppler radar may be used instead of airspeed signals, particularly when the base is fixed, the system being modified appropriately. When flying between fixed points, the wind speed and direction at the destination may be set on knobs 21 and 23. Specification 854, 904 is referred to.