  _____________________________________________________________________
 ] AUTHOR:            ]                             ] SMS:B27583       ]
 ] C.E. PRICE         ]    BFS PROGRAM NOTE         ] DR: 105429       ]
 ]____________________]                             ]__________________]
 ] ORG/PHONE:         ] OPS NOTE ( )  USER NOTE (X) ] DATE:  6/30/89   ]
 ] RI/922-5196        ]      RELEASE NOTE ( )       ] REV C 10/26/94   ]
 ]____________________]_____________________________]__________________]
 ] OI/FLIGHT EFFECTIVITY:        ]  USER AFFECTED:                     ]
 ]   OI20 AND SUBS               ]  CREW (X)  GROUND (X)  DUMP ONLY ( )]
 ]_______________________________]_____________________________________]
 ]           MAJOR SOFTWARE AREA:            ] OPS MODES AFFECTED:     ]
 ]BSL( ) BSS( ) GNC(X) SEQ( ) SM/SP( ) IPL( )] OPS 6                   ]
 ]_____________________________________________________________________]
 ] SOFTWARE SUB-AREA:  GUID                                            ]
 ]_____________________________________________________________________]
 ] PRINCIPAL FUNCTIONS: MG038104/3.2.3.1.10.5.9                        ]
 ]_____________________________________________________________________]
 ] TITLE: BFS DELAY IN CONVERGENCE AFTER RTLS SELECTION                ]
 ]                                                                     ]
 ]_____________________________________________________________________]
 ] DESCRIPTION: FOLLOWING SELECTION OF AN RTLS, BFS MAY NOT TRACK      ]
 ] PFS IN TERMS OF CONVERGENCE. THIS IS DUE TO COMPUTING THE OUT-OF-   ]
 ] PLANE COMPONENT OF THE THRUST TURNING RATE VECTOR (LAMDY)           ]
 ] USING THE TANGENT OF AN ANGLE THAT GOES THROUGH 90 DEGREES.         ]
 ] THIS CAN INTRODUCE A LARGE TRANSIENT INTO THE PREDICTION PROCESS    ]
 ] AND DELAY CONVERGENCE. THIS COMPUTATION IS PER REQUIREMENTS         ]
 ] AND PFS HAS THE SAME REQUIREMENTS AND THUS COULD EXPERIENCE A       ]
 ] SIMILAR TRANSIENT. IN THE REFERENCED DR, THE TRANSIENT MISTRACKING  ]
 ] LASTED FOR 12.4 SECONDS.                                            ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]_____________________________________________________________________]
 ] USER RESPONSE:                                                      ]
 ]  BE AWARE THAT TRANSIENT MISTRACKING BETWEEN PFS AND BFS CAN BE     ]
 ]  EXPECTED DURING THIS FLIGHT PHASE.                                 ]
 ]                                                                     ]
 ]  THE DIFFERENCES IN CONVERGENCE BETWEEN PASS AND BFS WILL           ]
 ]  BE NOTICEABLE TO THE CREW VIA THE ASCENT TRAJECTORY DISPLAYS.      ]
 ]  IF THE BFS CONVERGES LATER THAN THE PASS, THE GUIDANCE PPA         ]
 ]  PARAMETER WILL INDICATE 'INHB' UNTIL THE BFS ALSO CONVERGES.       ]
 ]  NO CREW ACTIONS ARE NECESSARY.                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]_____________________________________________________________________]
 ]CONCURRENCE:                           ]APPROVAL:                    ]
 ]RI: <S> G. ALBRIGHT       DATE 10/31/94]                             ]
 ]    --------------------      ---------]                             ]
 ]ASD:   ERIC C. BINGHAM    DATE 12/06/94]                             ]
 ]     -------------------      ---------] DARRELL E. STAMPER 12/16/94 ]
 ]PF MGR:JOHN W. CRAFT, JR. DATE 12/15/94]------------------- -------- ]
 ]       ------------------     ---------] CHAIRMAN, SASCB      DATE   ]
 ]_____________________________________________________________________]

