 +_____________________________________________________________________
 ] AUTHOR:            ]                             ] SMS: B22587      ]
 ]  RENE SAUSER       ]    BFS PROGRAM NOTE         ] DR: 106266       ]
 ]____________________]                             ]__________________]
 ] ORG/PHONE:         ] OPS NOTE ( )  USER NOTE (X) ] DATE: 17 MAR 1992]
 ]  (310)922-4164     ]      RELEASE NOTE ( )       ] REV A: 4 APR 1992]
 ]____________________]_____________________________]__________________]
 ] OI/FLIGHT EFFECTIVITY:        ]  USER AFFECTED:                     ]
 ]OI-21/STS-49,STS-50,STS-46 ONLY]  CREW (X)  GROUND (X)  DUMP ONLY ( )]
 ]_______________________________]_____________________________________]
 ]           MAJOR SOFTWARE AREA:            ] OPS MODES AFFECTED:     ]
 ]BSL( ) BSS( ) GNC( ) SEQ(X) SM/SP( ) IPL( )]          1              ]
 ]_____________________________________________________________________]
 ] SOFTWARE SUB-AREA: ASCENT, ABORT, OMS, BEC                          ]
 ]_____________________________________________________________________]
 ] PRINCIPAL FUNCTIONS: MG038120/3.3.1.15 BEC                          ]
 ]_____________________________________________________________________]
 ] TITLE: 3 ENGINE-ON ATO ABORT ENGAGEMENT                             ]
 ]_____________________________________________________________________]
 ] DESCRIPTION:                                                        ]
 ]IN ATO ABORTS, TWO WINDOWS MAY EXIST, ONE AT THE START OF THE PRE-   ]
 ] MECO OMS DUMP AND ONE AT THE END OF THE PRE-MECO OMS DUMP. IF BFS IS]
 ] ENGAGED IN EITHER OF THESE WINDOWS, BFS MAY EITHER CYCLE THE OMS    ]
 ] ENGINES OR ALLOW A PASS INITIATED PURGE TO CONTINUE TO NITROGEN DE- ]
 ] PLETION. CYCLING OF OMS ENGINES WITHOUT A MINIMUM 30 SECONDS OF WAIT]
 ] TIME CAN RESULT IN UNCONTAINED OMS ENGINE EXPLOSIONS.               ]
 ]FOR 3-ENGINE ATO'S THE TWO WINDOWS ARE 5.6 SECONDS MAXIMUM IN SIZE.  ]
 ] FOR ENGINE-OUT ATO'S THE TWO WINDOWS ARE 1.7 SECONDS MAXIMUM.       ]
 ]THE WINDOW AT DUMP START BEGINS IMMEDIATELY AFTER PASS ISSUES THE    ]
 ] OMS IGNITION COMMANDS AND EXTENDS FOR THE FIRST 5.6 SECONDS OF DUMP ]
 ] FOR 3-ENGINE ATO'S.                                                 ]
 ]THE WINDOW AT THE END OF THE PRE-MECO OMS DUMP BEGINS IMMEDIATELY    ]
 ] AFTER PASS TERMINATES THE OMS IGNITION COMMANDS AND EXTENDS FOR 5.6 ]
 ] SECONDS BEYOND IGNITION TERMINATION FOR 3-ENGINE ATO'S.             ]
 ] ( ADDITIONAL DETAILED INFO IS PROVIDED ON THE SUPPLEMENTAL SHEET.)  ]
 ]_____________________________________________________________________]
 ] USER RESPONSE:                                                      ]
 ]WINDOW AT DUMP START FOR PRE-MECO OMS DUMPS IN ATO'S:                ]
 ] IN 3-ENGINE ATO ABORTS, BE AWARE THAT IF BFS IS ENGAGED AFTER PASS  ]
 ] HAS STARTED THE PRE-MECO OMS DUMP BUT BEFORE 5.6 SECONDS OF DUMP HAS]
 ] OCCURRED, BFS MAY CYCLE THE OMS ENGINES.                            ]
 ]WINDOW AT THE END OF A PRE-MECO OMS DUMP IN ATO'S:                   ]
 ] IN 3-ENGINE ATO ABORTS, BE AWARE THAT IF BFS IS ENGAGED AFTER PASS  ]
 ] HAS TERMINATED THE OMS IGNITION COMMANDS BUT BEFORE 5.6 SECONDS HAVE]
 ] ELAPSED SINCE TERMINATION, BFS MAY CYCLE THE OMS ENGINES OR ALLOW A ]
 ] PASS INITIATED PURGE TO CONTINUE UNTIL MECO PREP.                   ]
 ]FOR ENGINE-OUT ATO'S THE WINDOWS ARE CONSIDERABLY SMALLER AT 1.7 SEC.]
 ]RE-START OF OMS ENGINES WITHOUT A 30 SEC WAIT CAN CAUSE EXPLOSIONS.  ]
 ]   (ADDITIONAL USER RESPONSE INFO EXISTS ON THE SUPPLEMENTAL SHEET)  ]
 ]_____________________________________________________________________]
 ]CONCURRENCE:                           ]APPROVAL:                    ]
 ]RI: <S> G. ALBRIGHT /JA   DATE 04/21/92]                             ]
 ]    --------------------      ---------]                             ]
 ]FDSD: ROBERT N. HINSON    DATE 04/22/92]                             ]
 ]     -------------------      ---------]WILLIAM J. MOON FOR 04/22/92 ]
 ]PF MGR:GENE MCSWAIN FOR   DATE 04/22/92]------------------- -------- ]
 ]           K. TODD            ---------] CHAIRMAN, SASCB      DATE   ]
 ]_____________________________________________________________________]


 +_____________________________________________________________________
 ]                                                                     ]
 ]                       SUPPLEMENTAL SHEET                            ]
 ]                                                                     ]
 ]_____________________________________________________________________]
 ] AUTHOR:            ]                             ] SMS: B22587      ]
 ] RENE SAUSER        ]    BFS PROGRAM NOTE         ] DR: 106266       ]
 ]____________________]                             ]__________________]
 ] ORG/PHONE:         ] OPS NOTE ( )  USER NOTE (X) ] DATE: 17 MAR 1992]
 ] (310)922-4164      ]      RELEASE NOTE ( )       ] REV A: 4 APR 1992]
 ]____________________]_____________________________]__________________]
 ] TITLE: 3 ENGINE-ON ATO ABORT ENGAGEMENT                             ]
 ]                                                                     ]
 ]_____________________________________________________________________]
 ] DESCRIPTION:                                                        ]
 ]                                                                     ]
 ] WINDOW 1: THIS WINDOW STARTS WHEN PASS COMMANDS THE OMS ENGINES ON  ]
 ] FOR A PRE-MECO OMS DUMP IN AN ATO ABORT. THE SIZE OF THE WINDOW IS  ]
 ] DEPENDENT ON THE TYPE OF ATO DECLARED (3-ENGINE VERSUS ENGINE-OUT), ]
 ] PHASING BETWEEN PASS AND BFS GUIDANCE CYCLES AND PHASING BETWEEN    ]
 ] SEQUENCING MODULES. IF PASS FAILS ANYWHERE IN THIS WINDOW AND BFS IS]
 ] SUBSEQUENTLY ENGAGED IN THE LAST 160 MS OF THIS WINDOW, BFS WILL    ]
 ] TURNOFF AND PURGE THE OMS ENGINES AND 2.36 SECONDS LATER COMMANDS   ]
 ] THE OMS ENGINES BACK ON.                                            ]
 ]                                                                     ]
 ] WINDOW 2: THIS WINDOW IS THE SAME SIZE AS WINDOW 1 BUT CAN BE BROKEN]
 ] INTO 3 DIFFERENT ZONES WHERE PASS CAN FAIL. IN ALL CASES, THE WINDOW]
 ] STARTS AT THE POINT WHERE PASS HAS ISSUED THE TURNOFF COMMANDS TO   ]
 ] THE OMS ENGINES AT THE END OF THE PRE-MECO OMS DUMP IN AN ATO ABORT.]
 ]                                                                     ]
 ] ZONE 1 IS FROM PASS TERMINATION OF THE OMS FIRE COMMANDS TO PASS    ]
 ] START OF THE PURGE (300 MS). ZONE 2 IS FROM PASS START OF THE PURGE ]
 ] TO PASS COMPLETION OF THE PURGE (2.36 SECONDS). ZONE 3 IS FROM THE  ]
 ] POINT AFTER PASS HAS COMPLETED THE PURGE TO THE END OF THE WINDOW.  ]
 ]                                                                     ]
 ] IF PASS FAILS IN ZONE 1 AND BFS IS ENGAGED WITHIN THE SECOND WINDOW,]
 ] BFS WILL RE-START THE OMS ENGINES WITHOUT A MINIMUM WAIT TIME -     ]
 ] POSSIBLE OMS EXPLOSION.                                             ]
 ]                                                                     ]
 ] IF PASS FAILS IN ZONE 2 AND BFS IS ENGAGED WITHIN THE SECOND WINDOW,]
 ] BFS WILL NOT BE ABLE TO STOP THE PURGE THAT PASS STARTED UNTIL MECO ]
 ] PREP - POSSIBLE NITROGEN DEPLETION.                                 ]
 ]                                                                     ]
 ] IF PASS FAILS IN ZONE 3 AND BFS IS ENGAGED WITHIN THE REMAINDER OF  ]
 ] THE SECOND WINDOW, BFS WILL RE-START THE OMS ENGINES WITHOUT A MINI-]
 ] MUM WAIT TIME - POSSIBLE OMS EXPLOSION.                             ]
 ]                                                                     ]
 ] IN 3-ENGINE ATO'S WINDOWS 1 AND 2 MAY EACH BE AS LARGE AS 5.6 SEC OR]
 ] AS SMALL AS 3.6 SEC. IN ENGINE-OUT ATO'S WINDOWS 1 AND 2 MAY EACH BE]
 ] AS LARGE AS 1.7 SECONDS OR AS SMALL AS 0.0 SECONDS.                 ]
 ]_____________________________________________________________________]
 ] USER RESPONSE:                                                      ]
 ] IF PASS FAILS IN ZONE 1 DESCRIBED ABOVE, AND BFS IS ENGAGED AFTER   ]
 ] WINDOW 2 HAS PASSED, NEITHER PASS NOR BFS WILL PERFORM A PURGE.     ]
 ] BE AWARE THAT OMS EXPLOSION COULD OCCUR IF OMS ENGINES ARE          ]
 ] RE-STARTED FOR THE OMS 1 BURN WITHOUT A MINIMUM WAIT TIME OF 10     ]
 ] MINUTES WHEN NO PURGE HAS OCCURRED AT THE END OF THE PRE-MECO DUMP. ]
 ]_____________________________________________________________________]
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