 +_____________________________________________________________________
  AUTHOR:                                          DR:  109216      
  J. MAGLEY              PASS PROGRAM NOTE            PAGE 1 OF 2   
 ____________________                             __________________
  ORG/PHONE: USA/PASS OPS NOTE (X)  USER NOTE ( )  DATE:  08/11/1999
  (281)282-4406            RELEASE NOTE( )         REV: B 05/25/2000
 ___________________________________________________________________
  OI/FLIGHT EFFECTIVITY:          USER AFFECTED:                     
  OI-26 THROUGH OI-27, STS-98,    CREW (X)  GROUND (X)  DUMP ONLY ( )
  STS-100, STS-102                                                   
 ____________________________________________________________________
         MAJOR SOFTWARE AREA:        OPS MODES AFFECTED:             
 SSW ( )  GNC (X)  VU ( )  SM/PL ( ) G3, G6                          
 _____________________________________________________________________
  SOFTWARE SUB-AREA: NAVAID, ENTRY                                    
 _____________________________________________________________________
  PRINCIPAL FUNCTIONS: 4.77                                           
 _____________________________________________________________________
  TITLE:                                                              
      TACAN DESELECT/RESELECT DURING SELF-TEST MAY LOCK IN DILEMMA    
 _____________________________________________________________________
  DESCRIPTION:                                                        
  DESELECTION AND THEN RESELECTION OF A TACAN INVOLVED IN A DILEMMA   
  WHILE A TACAN SELF-TEST IS IN PROGRESS MAY RESULT IN LOCKING IN     
  THE DILEMMA.  THIS OCCURS BECAUSE TACAN RM IS DESIGNED TO RETAIN    
  THE SELECTION OF THE TWO LRU'S THAT ARE IN DILEMMA UNTIL THE        
  PROCESSING AT SELF-TEST COMPLETION HAS BEEN PERFORMED, AND THE      
  RESELECTION ZEROES A DILEMMA COUNTER WHICH MUST BE OVER THE DILEMMA 
  COUNTER LIMIT FOR THE COMPLETION PROCESSING TO BE PERFORMED.        
                                                                      
  IF A DESELECT/RESELECT DURING SELF-TEST OCCURS, AND IF THE DILEMMA  
  CONDITION DOES NOT EXIST FOR AT LEAST 9.6 SEC AT SOME TIME AFTER THE
  RESELECTION, THEN THE FSW DILEMMA WILL BE LOCKED IN.  DESELECTION   
  OR RESELECTION OF LRU'S WILL NOT RESOLVE THE DILEMMA.  PROCESSING   
  OF THE MEASUREMENT (BEARING OR RANGE) THAT WAS ORIGINALLY IN        
  DILEMMA WILL CONTINUE, BUT THE PROCESSING OF THE OTHER MEASUREMENT, 
  AS WELL AS CHANNEL AND CONE OF CONFUSION PROCESSING, WILL NOT       
  OCCUR.                                                              
 _____________________________________________________________________
 USER RESPONSE:                                                       
    AVOID EXECUTING THE TACAN DESELECT/RESELECT ITEM ENTRIES ON SPEC  
  50 WHEN THE TACAN "TEST" INDICATION IS DISPLAYED.  IN PARTICULAR, DO
  NOT RESELECT A TACAN IF IT WAS INADVERTENTLY DESELECTED DURING      
  SELF-TEST.                                                          
    IF A TACAN IS RESELECTED DURING SELF-TEST, COMPLETE TACAN DATA    
  PROCESSING BY THE GNC FSW CANNOT BE RESTORED UNLESS THE SAME        
  MEASUREMENT ON THE ORIGINAL TWO LRU'S HAPPENS TO GO INTO DILEMMA    
                  (CONTINUED ON THE NEXT PAGE)                        
 _____________________________________________________________________
 CONCURRENCE:                           APPROVAL:                    
 USA/PASS: JOHN MAGLEY  DATE 06/27/2000                              
           -----------       -----------                             
 CHAIR:    KENNETH HILL DATE 06/27/2000                              
           ------------      -----------DARRELL E. STAMPER 07/05/2000
 PF MGR:    C. SIMMONS DATE  06/07/2000 ------------------ ----------
           -----------       ----------- CHAIRMAN, SASCB      DATE   
 ____________________________________________________________________
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1
 +_____________________________________________________________________
                                                                      
                        SUPPLEMENTAL SHEET                            
                                                                      
 _____________________________________________________________________
  AUTHOR:                                          DR:  109216      
  J. MAGLEY              PASS PROGRAM NOTE            PAGE 2 OF 2   
 ____________________                             __________________
  ORG/PHONE: USA/PASS OPS NOTE (X)  USER NOTE ( )  DATE:  08/11/1999
  (281)282-4406            RELEASE NOTE( )         REV: B 05/25/2000
 ___________________________________________________________________
  TITLE:                                                              
       TACAN DESELECT/RESELECT DURING SELF-TEST MAY LOCK IN DILEMMA   
                                                                      
 _____________________________________________________________________
  DESCRIPTION:                                                        
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
                                                                      
 _____________________________________________________________________
 USER RESPONSE:                                                       
                                                                      
  AGAIN.  A NEW DILEMMA CONDITION MAY BE FORCED, AND THE DILEMMA LOCK 
  CLEARED, BY SWITCHING ONE OF THE TACAN UNITS TO TRANSMIT/RECEIVE    
  (T/R) AND USING THE THUMBWHEELS TO SELECT AN INVALID CHANNEL (SUCH  
  AS 013X OR 013Y) FOR AT LEAST 10 SECONDS.  THEN RESELECT GPC MODE   
  AND DESELECT/RESELECT ONE OF THE UNITS USING THE ITEM ENTRIES ON    
  SPEC 50.  BE AWARE THAT (WHILE IN T/R) BFS PROCESSING OF TACAN DATA 
  WILL BE HALTED WHILE THE TACAN UNITS ARE ON DIFFERENT CHANNELS.     
                                                                      
  IF PASS FSW PROCESSING IS NOT RESTORED, TACAN DATA MAY BE OBTAINED  
  BY USING THE DIGITAL ADI GUIDANCE COMMANDS ON THE BFS TRAJ DISPLAY  
  TO FLY MANUALLY. TACAN DATA FOR MANUAL CONTROL MAY ALSO BE OBTAINED 
  BY SWITCHING THE HSI DATA SOURCE TO TACAN.                          
                                                                      
                                                                      
                                                                      
 _____________________________________________________________________
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