Volume III - ElectricCanadian.com

NASA - JOHNSON SPACE CENTERFLIGHT RULESA4-61 THRUST LIMITING, HYDRAULIC, OR ELECTRICAL LOCKUP(CONTINUED)B. A PERFORMANCE-LIMITED SSME WILL BE SHUT DOWN EARLY, OR A MAINENGINE CONTROLLER CHANNEL TURNED OFF, BASED ON BOOSTERSYSTEMS ENGINEER (BSE) CONFIRMATION OF THE FAILURE AND ARDPERFORMANCE EVALUATION FOR THE FOLLOWING CASES:1. LOW MIXTURE RATIO:Preservation of the ATO region by early shutdown of an SSME has priority over a possible abortdownmode to an AOA.IF THE FOLLOWING CRITERIA ARE MET, THE AFFECTED SSME WILLBE SHUT DOWN EARLY TO PROTECT 3-SIGMA ATO CAPABILITY ORTHE DESIGN UNDERSPEED, WHICHEVER IS THE MOSTCONSTRAINING:a. THE ACTUAL NOMINAL MARGIN INDICATES LOSS OF ATOCAPABILITY.The ARD’s actual mode nominal margin is a prediction of MECO underspeed on a 2-sigma bad day.This prediction can be used to determine if ATO capability exists. This rule refers to the designunderspeed as a criterion for pressing uphill with a performance-limited SSME. In addition, thedispersed-performance protection level (3-sigma) is stated explicitly for uphill capability assessment.b. THE HYPOTHETICAL AOA MARGIN (REFLECTING THE SICKENGINE OUT) IS DECREASING.The ARD’s hypothetical mode AOA margin is the indicator of when continued sick engine operation willdegrade performance. As long as the margins are increasing, the three-engine configuration isimproving MECO conditions. When the margins start trailing off, the sick engine is degrading uphillcapability. If the hypothetical nominal margin is greater than the actual nominal value; i.e. it is better tohave two healthy engines than two healthy and one sick, the bad engine will be shut down.c. THE HYPOTHETICAL NOMINAL MARGIN IS GREATER THAN THEACTUAL NOMINAL MARGIN.Rationale is the same as for paragraph b above.THIS RULE CONTINUED ON NEXT PAGEVOLUME A 06/20/02 FINAL TRAJECTORY AND GUIDANCE 4-50Verify that this is the correct version before use.