12-2] USES OF DISPLAY INFORMATION 611 



having established a set of tasks within the ken of the human operator, 

 one can begin to devise and evaluate various clever and aesthetically 

 pleasing means for coding the information. 



Control. The purpose of many displays is to allow the operator to 

 function as an element in a control loop. For example, the operator may 

 be required to position the antenna or the range gate so that it brackets 

 the target preparatory to initiating automatic lock-on. In such cases a 

 marker (or strobe) is provided on the display which provides an indication 

 of the actual position of the antenna or range gate — or both. The operator 

 is provided with a control handle, button, or wheel and is required to 

 manipulate the control to put the strobe on the target. This sounds very 

 simple; however, experience has shown that operators are so sensitive to 

 the coding of the strobes and the configuration of the control that the mean 

 time to position the range and angle strobes of an AI radar can vary by 

 5 : 1 or more depending upon the configuration employed. The time 

 required has a direct effect upon either the tactical utility of the weapons 

 system or the detection requirements of the radar system. For example, 

 in Chapter 2 the AI radar detection requirements were based on mean 

 lock-on times of 6 to 12 seconds. At the maximum closing speed of 2000 fps, 

 every additional 3 seconds spent fumbling with the control will increase the 

 detection range requirements by 1 mile. 



The AI radar example provides a second important example of the 

 control function: weapon aiming control. As explained in Chapter 2, the 

 radar information is combined with aircraft flight data and stored weapon 

 information to produce an aiming error signal. This signal is presented to 

 the pilot, who then attempts to fly the aircraft in such a manner that the 

 error becomes less than 2° by the time missile launching range is reached. 

 The display also may present an indication of when the missile can be 

 launched and when the pilot should break off the attack to avoid collision 

 with the target. 



This operation (data interpretation and subsequent control) requires a 

 great deal from both the operator and the display. First of all, the basic 

 steering task itself is most difficult and normally requires additional 

 information to produce a stable steering loop (see Paragraph 12-7). Second, 

 in addition to the steering and firing information, various tactical situation 

 indications such as range, range rate, and bearing angle must be presented. 

 (With respect to these, the previous remarks on tactical situation displays 

 apply.) 



Flight control and navigation functions form another important area for 

 the utilization of radar display information for control purposes. These 

 functions may require a radar map which allows the pilot to navigate m 

 the same manner as if visual contact were maintained. 



