of the Presidential Commission on the Space Shuttle Challenger Accident


[79] PART 1


Recommendation IX



[80] Presidential Commission Recommendation IX

Maintenance Safeguards. Installation, test, and maintenance procedures must be especially rigorous for Space Shuttle items designated Criticality 1. NASA should establish a system of analyzing and reporting performance trends of such items.

Maintenance procedures for such items should be specified in the Critical Items List, especially for those such as the liquid-fueled main engines, which require unstinting maintenance and overhaul.

With regard to the Orbiters, NASA should:




[81] NASA has developed an improved integrity assurance program to ensure that the performance of all systems meets the design requirements for each flight.

System integrity assurance includes those configuration, inspection, maintenance, operations, and analysis activities, beginning with initial hardware acceptance tests and continuing through the life of the hardware, that are required to ensure safe and reliable operation of the NSTS. These activities are performed at the launch and landing sites, the design centers, element contractor facilities, off-line repair and maintenance facilities, and during flight operations. Information management systems that provide the appropriate visibility into these activities are part of the overall program.

Development of this capability is being complemented by a program-wide documentation review to rebaseline the NSTS processing requirements and procedures.



NASA has developed and published the System Integrity Assurance Program (SIAP) Plan to ensure that the NSTS Program is supported by an integrated maintenance and logistics program. The SIAP establishes the functional responsibilities and program requirements necessary to provide the proper configuration, operations, inspection, maintenance, logistics, and certified personnel to ensure that the NSTS is ready for flight.

The SIAP includes a management information system that provides the necessary insight into requirements verification, problems, anomalies, and performance trends to verify the status of readiness for the next flight. The Deputy Director, NSTS Program, is responsible for ensuring implementation of the SIAP Plan.

The program compliance assurance and status system (PCASS), a relational data base and reporting system that provides the capability for data and problem communications and control across the program, is the key element of the SIAP. It compiles data from the project elements and provides NSTS management with visibility and access into program critical data, including requirements status, problem data, trends, risk decisions, hazards, critical item history, and failure modes and effects analysis/critical item data. This system provides the information required by the safety, reliability, maintainability, and quality assurance (SRM&QA) organization to perform analysis and report [82] data independently of the NSTS. Figure 41 reflects the major capabilities of the SIAP. The major elements of the PCASS are indicated in Figure 42.

Specific tasks and responsibilities for establishing format and data requirements have been identified for the NSTS Program and each project element, and are being implemented. These data will be collected and reported, using systems currently in place, until the system software can be fully developed. Data acquired will be used to verify that all configurations, operations, and maintenance requirements, structural inspections, problems, or actions have been closed out, or waivers have been written prior to each flight.

The PCASS will provide visibility into the status of mission flow, flight hardware schedules, operational maintenance requirements, and launch constraints, and provide status, assessment results, and closure rationale for Criticality 1 and 1R hardware and software anomalies.

All anomalies occurring during flight vehicle prelaunch processing, flight, and turnaround and maintenance will be incorporated into the data base, as will anomalies occurring in the Shuttle mission simulator, Shuttle Avionics Integration Laboratory, and off-line maintenance facilities. The data repository provides the capability to correlate actual failures with predicted failures and to generate critical item status and history reports.

A risk decision history data base will be included in the system and will be used to assist program management in reviewing deferral actions, waivers, and exceptions. Trend analysis algorithms will be used to perform reliability, performance, and supportability trends and will form the basis for modifying requirements, procedures, and/or spares inventories.


Figure 41. System Integrity Assurance Program Chart.

Figure 41. System Integrity Assurance Program.


Figure 42. PCASS Data Base Elements Chart.

Figure 42. PCASS Data Base Elements.




SRM&QA is responsible for implementing an independent problem reporting and corrective action system for the NSTS Program. The element projects are responsible for providing the data for this system. Utilizing the data compiled by the projects, SRM&QA will monitor the performance of, and perform trend analyses on, selected Criticality 1, 1R, and 2 components.

The NSTS will utilize the PCASS and the problem reporting and corrective action system to analyze the performance of all element hardware and software systems. This analysis will be performed at the system line replaceable unit (LRU) level. Specific "performance change" criteria will be defined which, when exceeded, will result in a detailed review of the affected LRU or system. Performance trend data will be used to extend the design life of the LRU's, when the data indicate such an extension is justified. Adverse performance trends will be used to define a reduced design life validation program.

Performance trend data collection requirements will be defined, and the data collected will be analyzed and used to update such factors as turnaround time, mean time between failures/repairs, and maintenance demand rates. Equipment supportability trend data will be used for establishing logistics requirements, which will ensure that adequate spares and provisions are available to support the projected flight rate. Time/age/ cycle requirements developed from data compiled through the PCASS will be incorporated into the appropriate maintenance and operational documentation.

A design life validation program is being developed which will verify that critical LRU's and systems meet their certified design life requirements. Factors such as time/age/ [84] life cycle, degradation/wear, and performance comparisons with original acceptance test results will be considered in selecting components for teardown analysis. Results of the teardown analyses will be integrated into the processing requirements, design life certification, time/age/cycle limits, logistics requirements, FMEA/CIL's, and hazard analyses, as appropriate.



A prime objective of the SIAP is to ensure a strong logistics (spares) and maintenance function. Logistics support plans are being reviewed, updated, and implemented by the element projects in accordance with requirements contained in the SIAP. These plans will identify the requirements for spares and provisions necessary for supporting flight-to-flight reconfiguration, maintenance operations, and replacement of failed and limited-life LRU's, to preclude the need for using LRU's from other flight vehicle or ground systems.

NASA has alleviated the requirement for routine removal of parts from one vehicle to supply another by expanding and accelerating various aspects of the NSTS logistics program. The SIAP defines the ground rules for such removal of parts, which will be permitted only when approved by the Program Requirements Control Board.

An improved hardware inventory management system is being implemented to track hardware availability and inventory requirements. Spares and repair forecasting techniques are being updated using projected flight rate and trend analysis data. Spares and provisioning requirements to support replacement of failed or limited-life hardware are being addressed.

Additional repair capability is being developed for the Shuttle Services Center to ensure that flight and critical ground hardware can be repaired and maintained within design specification requirements in a timely manner. The center provides the capability to perform local test and repair of components and reduces the need for sending items back to the original equipment manufacturer for repair. Hardware status will be maintained through modification/repair cycles, and data will be recorded to support trend analysis.



Program-wide reviews of the vehicle processing requirements and implementation documents are under way, and are discussed in Part 2 of this report. This review and revision of existing maintenance documentation by each NSTS project has resulted in the identification of new maintenance and inspection requirements, which are being incorporated into the appropriate documentation after review and approval. The operational maintenance instructions are being modified to ensure that all procedures which involve Criticality 1 and 1R items are prominently displayed. These documents must be approved by the appropriate NASA design center prior to use. Any changes that affect critical items or critical processes must receive appropriate design center concurrence.

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