 +_____________________________________________________________________
 ] AUTHOR:            ]                             ] SMS: B22567      ]
 ]   R. SAUSER        ]    BFS PROGRAM NOTE         ] DR: 106180       ]
 ]____________________]                             ]__________________]
 ] ORG/PHONE:         ] OPS NOTE ( )  USER NOTE (X) ] DATE:            ]
 ]   922-4164         ]      RELEASE NOTE ( )       ]      2/5/91      ]
 ]____________________]_____________________________]__________________]
 ] OI/FLIGHT EFFECTIVITY:        ]  USER AFFECTED:                     ]
 ]        OI-8C & SUBS           ]  CREW (X)  GROUND (X)  DUMP ONLY ( )]
 ]_______________________________]_____________________________________]
 ]           MAJOR SOFTWARE AREA:            ] OPS MODES AFFECTED:     ]
 ]BSL( ) BSS( ) GNC( ) SEQ(X) SM/SP( ) IPL( )]   GNC 1, 6              ]
 ]_____________________________________________________________________]
 ] SOFTWARE SUB-AREA: SSME HIP                                         ]
 ]_____________________________________________________________________]
 ] PRINCIPAL FUNCTIONS: MG038120/3.3.1.14                              ]
 ]_____________________________________________________________________]
 ] TITLE:  ERRONEOUS SSME COMMAND PATH FAILURE ANNUNCIATION            ]
 ]                                                                     ]
 ]_____________________________________________________________________]
 ] DESCRIPTION:                                                        ]
 ] EVERY 40 MSEC THE GPC'S READ A SIX WORD ENGINE VEHICLE DATA TABLE   ]
 ] (VDT) FROM THE CONTROLLERS TO DETERMINE ENGINE OPERATING STATUS,    ]
 ] CHAMBER PRESSURE, FAILURE PARAMETERS AND COMMAND ACCEPT DATA. EVERY ]
 ] TIME THE GPC SENDS A DIFFERENT COMMAND TO THE ENGINE CONTROLLER THE ]
 ] FLIGHT SOFTWARE PROGRAM EXPECTS AN ACKNOWLEDGEMENT THAT THE PREVIOUS]
 ] ENGINE COMMAND WAS RECEIVED AND DECODED PROPERLY. THIS ACKNOWLEDGE- ]
 ] MENT IS PRESENT IN THE MEC ONLY DURING ONE 40 MSEC INTERVAL.        ]
 ]                                                                     ]
 ] THE GPC TIME BASE OSCILLATOR AND THE MEC TIME BASE OSCILLATOR ARE   ]
 ] NOT SYNCHRONIZED. IF THE GPC "40 MSEC" READ PERIOD IS SLOWER THAN   ]
 ] THE MEC "40 MSEC" READ CYCLE, AN OCCASIONAL VDT FRAME WILL BE       ]
 ] OMITTED.                                                            ]
 ]                                                                     ]
 ] IF THE MISSED FRAME IS THAT ONE FRAME WHICH CONTAINED THE COMMAND   ]
 ] ACKNOWLEDGEMENT THEN A FAILURE IS DECLARED EVEN THOUGH THE ENGINE   ]
 ] RECEIVED THE PROPER COMMAND. THE FAILURE IS ANNUNCIATED BY THE GPC  ]
 ] ON THE COCKPIT DISPLAY MESSAGE LINE AND LIGHTING OF AN AMBER ENGINE ]
 ] STATUS LAMP. THE AMBER LIGHT IS EXTINGUISHED ON THE NEXT GOOD       ]
 ] COMMAND/COMMAND ACKNOWLEDGE CYCLE. THE FAILURE IS ALSO DOWNLISTED.  ]
 ]_____________________________________________________________________]
 ] USER RESPONSE:                                                      ]
 ] BE AWARE OF THE POTENTIAL AMBER LIGHT INDICATIONS AND THE ABOVE SIT-]
 ] SITUATIONS. IF THE FAILURE IS AN ENGINE THROTTLING COMMAND, ENGINE  ]
 ] CHAMBER PRESSURE MAY BE MONITORED FOR FAILURE VALIDATION. TO REMOVE ]
 ] THE MESSAGE ANNUNCIATION FROM THE COCKPIT DISPLAY IT WILL BE NECES- ]
 ] SARY TO PRESS THE MSG RESET BUTTON.                                 ]
 ]_____________________________________________________________________]
 ]CONCURRENCE:                           ]APPROVAL:                    ]
 ]RI: <S> C. PURTELL        DATE 02/06/91]                             ]
 ]    --------------------      ---------]                             ]
 ]FDSD:   W. R. PRUETT      DATE 02/19/91]                             ]
 ]     -------------------      ---------] DARRELL E. STAMPER 02/20/91 ]
 ]PF MGR:  K. O. TODD       DATE 02/20/91]------------------- -------- ]
 ]       -----------------      ---------] CHAIRMAN, SASCB      DATE   ]
 ]_____________________________________________________________________]
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