8-32] ACCURACY REQUIREMENTS ON ANGLE TRACK STABILIZATION 457 



accurate, with low drift rates, but they are expensive and require tempera- 

 ture-compensating circuits to maintain the preset value of damping torque. 

 Generally, this accuracy is not needed to provide antenna stabilization, but 

 is needed for the fire-control computer which uses the gyro signals to 

 provide accurate information about the line-of-sight motion. 



Aircraft Gyro Stabilization Loops. Another of the many methods 

 of providing antenna stabilization is shown in Fig. 8-37c. Because the 

 aircraft with a fire control system and tracking antenna frequently has 

 autopilot gyroscopes, it is possible to use them to provide the antennas with 

 stabilization signals. This reduces the total number of rate gyros needed 

 in the system, but other components must be added as shown in the 

 simplified figure. ^^ 



The other components are tachometer and position indicators on the 

 azimuth and elevation antenna actuators and a converter to change the 

 space rate signals from three aircraft coordinates to two antenna coor- 

 dinates. Although the converter is not complex, the conversions must be 

 made accurately, and the three aircraft gyros should be mounted near the 

 antenna base to prevent discrepancies from occurring in the rate measure- 

 ments which are different in various parts of the aircraft owing to structural 

 flexing. 



From this discussion it is evident that several methods of providing 

 antenna stabilization are available. Although the integrating gyro may 

 have slight advantages over the other systems, the ultimate choice of a 

 system configuration will depend upon the required accuracy, the allowable 

 expense, and the permitted complexity of the application. 



8-32 ACCURACY REQUIREMENTS ON THE ANGLE TRACK 

 STABILIZATION LOOP 



The stabilization accuracy requirements for the angle track stabilization 

 loop are determined from the basic functions of the stabilization loops 

 (Paragraphs 8-25 and 8-30) and from different criteria depending on 

 whether a pilot or autopilot is used, a lead collision course or pursuit course 

 is being flown, or a ballistic or target-seeking missile is being fired. The 

 significance of these factors is discussed in the following paragraphs. 



Stabilization Accuracy Required to Reduce Aircraft Rate Signal 

 Errors. The magnitude of the error in the antenna rate signal caused by 

 own-ship's motion must be reduced to an acceptable value. This value 

 depends on the nature of the system. If an autopilot is used, it must be 



^^Note that there are three aircraft gyros which do not measure the desired antenna rates 

 In azimuth and elevation. Therefore the information in three channels must be converted to 

 two channels using the relative rates and angles of the antenna with respect to aircraft in two 

 dimensions. For simplicity the figure depicts a one-channel conversion. 



