 +_____________________________________________________________________
 ] AUTHOR:            ]                             ] DR:              ]
 ] CHUAN              ]    PASS PROGRAM NOTE        ]       39417      ]
 ]____________________]                             ]__________________]
 ] ORG/PHONE:         ] OPS NOTE ( )  USER NOTE (X) ] DATE: JULY 1987  ]
 ] VER/282-8937       ]      RELEASE NOTE( )        ] REV A: 06/06/89  ]
 ]____________________]_____________________________]__________________]
 ] OI/FLIGHT EFFECTIVITY:        ]  USER AFFECTED:                     ]
 ] REL 19 AND SUBS               ]  CREW (X)  GROUND ( )  DUMP ONLY ( )]
 ]_______________________________]_____________________________________]
 ]        MAJOR SOFTWARE AREA:       ] OPS MODES AFFECTED:             ]
 ]SSW ( )  GNC (X)  VU ( )  SM/PL ( )] G3, G6                          ]
 ]_____________________________________________________________________]
 ] SOFTWARE SUB-AREA:  ENTRY, GUID                                     ]
 ]_____________________________________________________________________]
 ] PRINCIPAL FUNCTIONS: 4.144                                          ]
 ]_____________________________________________________________________]
 ] TITLE: HAC ROLL OSCILLATIONS                                        ]
 ]_____________________________________________________________________]
 ] DESCRIPTION:                                                        ]
 ]                                                                     ]
 ] DURING AN ENTRY HAVING A SIGNIFICANTLY DEGRADED NAV STATE, AILERON  ]
 ] AND RUDDER OSCILLATIONS MAY BE EXPERIENCED THROUGHOUT THE HEADING   ]
 ] ALIGNMENT INTERVAL OF TAEM GUIDANCE (AS VEHICLE ROLLS TO FOLLOW     ]
 ] HEADING ALIGNMENT CYLINDER ARC). OSCILLATIONS BECOME PERCEIVABLE    ]
 ] FOR 1 DEGREE TACAN ERRORS OR EQUIVALENT. THE FREQUENCY OF THE       ]
 ] INDUCED ROLL OSCILLATION WILL BE 0.25 HZ; THE PEAK RUDDER DEFLECTION]
 ] COMMAND COULD REACH +/- 1 DEGREE; THE PEAK AILERON DEFLECTION COM-  ]
 ] MAND COULD REACH +/-0.5 DEGREES; AND THE MAXIMUM ROLL EXCURSION     ]
 ] COULD REACH APPROX. 0.6 DEGREES PEAK-TO-PEAK AMPLITUDE FOR 3 DEGREES]
 ] TACAN ERRORS OR EQUIVALENT.                                         ]
 ]                                                                     ]
 ] THE OSCILLATIONS ARE DRIVEN BY NAV UPDATES TO THE ORBITER STATE, THE]
 ] ERRORS IN THE LATTER RESULTING FROM DISPERSIONS DUE TO DEGRADED     ]
 ] IMU'S, TACAN FAILURES, ETC. THESE OSCILLATIONS CEASE ONCE "GOOD"    ]
 ] MSBLS MEASUREMENTS ARE INCORPORATED.                                ]
 ]                                                                     ]
 ]_____________________________________________________________________]
 ] USER RESPONSE:                                                      ]
 ]                                                                     ]
 ] THESE ROLL CHANNEL OSCILLATIONS ARE EXPERIENCED DURING THE HEADING  ]
 ] ALIGNMENT CIRCLE (HAC) ROLL PERIOD IN THE AUTO ROLL/YAW FC MODE     ]
 ] ONLY. IF CREW PROCEDURES CALL FOR THIS FLIGHT INTERVAL TO BE FLOWN  ]
 ] IN THE AUTO MODE AND OSCILLATIONS DUE TO THIS SITUATION ARE EXPER-  ]
 ] IENCED, IT SHOULD BE RECOGNIZED THAT THESE OSCILLATIONS CAN BE      ]
 ] ELIMINATED BY MODING FC TO CSS IN ROLL/YAW.                         ]
 ]                                                                     ]
 ]_____________________________________________________________________]
 ]CONCURRENCE:                           ]APPROVAL:                    ]
 ]IBM: WYATT COOPER         DATE 06/29/89]                             ]
 ]    --------------------      ---------]                             ]
 ]SSD: SAM ANKNEY           DATE 07/14/89]                             ]
 ]    --------------------      ---------] M.C. GREMILLION    08/20/89 ]
 ]PF MGR: L.B. MC WHORTER   DATE 07/27/89]------------------- -------- ]
 ]       -----------------      ---------] CHAIRMAN, SASCB      DATE   ]
 ]_______________________________________]_____________________________]
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