Purpose This standard specifies reliability demonstration guidelines and practices for liquid rocket engines. Application This standard provides methodology for conducting reliability demonstration programs suitable for use with liquid rocket engines. To be most meaningful and statistically correct@a demonstration program should be conducted at the highest practical level of assembly and under conditions representative of those experienced in the use environment. Program limitations in conjunction with need for data at early dates in the program force certain compromises which historically have proven acceptable. The first of these compromises is that it is necessary to utilize static test results. Second@ design and development configuration engines which closely approximate the planned flight engines may be included in the demonstration sample. Finally@certain programs may not provide for sufficient complete engine tests and subsystem test results may be combined with tests of the complete engine to produce a sufficient sample for reliability demonstration. Validity of the reliability demonstration program is adversely affected as the samples depart from the use configuration and environment. The extent to which subsystem data is combined with data obtained from tests of the complete engine system shall be mutually agreed to between the contractor and procuring activity. General requirements and the reliability demonstration criteria described in the detailed requirements (Section 5 ) will be the principal basis for assessment of liquid rocket engine reliability. Specific demonstration plans will be prepared by the contractor in keeping with customer requirements@ as part of the overall reliability program plan. This standard applies primarily to large liquid rocket engines but may be adapted for other liquid rocket engine applications as an option of the contractor and procuring activity.