1+_____________________________________________________________________
 ] AUTHOR:            ]                             ] DR:              ]
 ] R. DOBSON          ]    PASS PROGRAM NOTE        ]       37594      ]
 ]____________________]                             ]__________________]
 ] ORG/PHONE:         ] OPS NOTE ( )  USER NOTE (X) ] DATE: SEPT. 1987 ]
 ] IBM/282-7330       ]      RELEASE NOTE( )        ] REV B: 01/27/94  ]
 ]____________________]_____________________________]__________________]
 ] OI/FLIGHT EFFECTIVITY:        ]  USER AFFECTED:                     ]
 ] REL 19 AND SUBS               ]  CREW (X)  GROUND (X)  DUMP ONLY ( )]
 ]_______________________________]_____________________________________]
 ]        MAJOR SOFTWARE AREA:       ] OPS MODES AFFECTED:             ]
 ]SSW ( )  GNC (X)  VU ( )  SM/PL ( )] G1, G6                          ]
 ]_____________________________________________________________________]
 ] SOFTWARE SUB-AREA:  SSME                                            ]
 ]_____________________________________________________________________]
 ] PRINCIPAL FUNCTIONS: 4.222                                          ]
 ]_____________________________________________________________________]
 ] TITLE:      ERRONEOUS 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 ACKNOWLEDGMENT THAT THE PREVIOUS ]
 ] ENGINE COMMAND WAS RECEIVED AND DECODED PROPERLY.  THIS             ]
 ] ACKNOWLEDGEMENT IS PRESENT IN THE MEC ONLY DURING ONE 40 MSEC       ]
 ] INTERVAL.                                                           ]
 ]                                                                     ]
 ] 1) 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.                                        ]
 ]                                                                     ]
 ] 2) IF AN EIU POWER ON RESET (POR) OCCURS ON A SINGLE POWER SUPPLY   ]
 ] FOR AN EIU, IT IS POSSIBLE THAT A FALSE "COMMAND REJECTED" INDICATOR]
 ] MAY BE SET FOR FEEDBACK TO THE FSW FOR ONE 40 MSEC PERIOD.  THIS    ]
 ] MAY OCCUR EVEN IF NO NEW COMMAND HAS BEEN SENT OUT TO THE EIU       ]
 ] WITHIN THE PAST THREE CYCLES.  A "COMMAND REJECTED" INDICATION      ]
 ] RESULTS IN A COMMAND PATH FAILURE FOR THE EIU.                      ]
 ]                                                                     ]
 ]                     -- CONTINUED ON SUPPLEMENT PAGE --              ]
 ]_____________________________________________________________________]
 ]CONCURRENCE:                           ]APPROVAL:                    ]
 ]IBM:   JEAN L. ZOPHY      DATE 02/15/94]                             ]
 ]    --------------------      ---------]                             ]
 ]FDSD:ELIZABETH A. FOUNTAINDATE 02/15/94]                             ]
 ]     ---------------------    ---------] DARRELL E. STAMPER  02/15/94]
 ]PF MGR:   DON PREVETT     DATE 02/15/94]------------------- -------- ]
 ]       -----------------      ---------] CHAIRMAN, SASCB      DATE   ]
 ]_______________________________________]_____________________________]
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1+_____________________________________________________________________
 ]                                                                     ]
 ]                       SUPPLEMENTAL SHEET                            ]
 ]                                                                     ]
 ]_____________________________________________________________________]
 ] AUTHOR:            ]                             ] DR:              ]
 ] R. DOBSON          ]    PASS PROGRAM NOTE        ]       37594      ]
 ]____________________]                             ]__________________]
 ] ORG/PHONE:         ] OPS NOTE ( )  USER NOTE (X) ] DATE: SEPT. 1987 ]
 ] ENG/282-7330       ]      RELEASE NOTE( )        ] REV B: 01/27/94  ]
 ]____________________]_____________________________]__________________]
 ] TITLE: ERRONEOUS COMMAND PATH FAILURE ANNUNCIATION                  ]
 ]                                                                     ]
 ]                                                                     ]
 ]_____________________________________________________________________]
 ] DESCRIPTION:                                                        ]
 ]                                                                     ]
 ] FOR BOTH 1) AND 2) ABOVE, A COMMAND PATH 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 SUBSEQUENT  ]
 ] COMMAND AND ACKNOWLEDGEMENT THE COMMAND WAS RECEIVED AND DECODED    ]
 ] PROPERLY.  THE MESSAGE LINE ANNUNCIATION MAY NOT OCCUR IF A SUB-    ]
 ] SEQUENT COMMAND IS PROCESSED WITHIN 1.92 SECONDS.  THE FAILURE IS   ]
 ] ALSO DOWNLISTED.                                                    ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]_____________________________________________________________________]
 ] USER RESPONSE:                                                      ]
 ]                                                                     ]
 ] BE AWARE OF THE POTENTIAL AMBER LIGHT INDICATIONS AND THE ABOVE     ]
 ] SITUATIONS.  IF THE FAILURE IS AN ENGINE THROTTLING COMMAND, ENGINE ]
 ] CHAMBER PRESSURE MAY BE MONITORED FOR FAILURE VALIDATION.           ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]                                                                     ]
 ]_____________________________________________________________________]
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