Downloaded from https://www.everyspec.com MIL-HDBK-502: A MIL-HDBK-502: A CQUISITION CQUISITION L OGISTICS OGISTICS Wording the Performance Requirement The specific wording of requirements presents many pitfalls. Emphasize stating the requirements in performance terms. There are two good reasons for this emphasis. First, the requirement needs to be measurable so that all concerned can judge whether a system is functioning as it should. Subjectivity is not useful in this context, and requirements stated in terms that allow subjective interpretation are harmful. Second, the wording of the requirement should not reflect the user’s bias as to the design for the product.
The requirement should state what the user needs, not explain how the requirement is to be met. The goal here is not to stifle initiative or arbitrarily cut off innovative approaches to satisfying the requirement. Poor Examples The following examples of poorly written supportability requirements are followed by notes explaining their deficiencies. 1. The signature-suppressed generator sets (15/30/60 KW) shall demonstrate a maintenance ratio (MR) not to exceed .05 . Note: the term “demonstrate” is ambiguous here. It is more positive to say the maintenance ratio shall not exceed 0.05. The maintenance level (unit or intermediate) should be specified. 2.
The vehicle engine or engine and transmission assembly can be removed and reinstalled in less than 10 man-hours. Note: This measurement should be expressed as a percentile; e.g., perform the function in 10 man-hours 90% of the time. 3. The sniper weapon system bolt assembly must be replaceable within 1 minute, without the use of tools, and without affecting the zero of the weapon. 4. The sniper weapon system must be designed to allow the operator to perform necessary maintenance using standard DoD lubricant/ solvent, without the use of any tools other than the cleaning kit equipment. 5.
The sniper weapon system must have cleaning equipment that is not detrimental to the weapon when used properly and which fits in the M-16 cleaning kit pouch. Note: Requirements 3, 4, and 5 are actually design requirements. They are not expressed in clear measurable terms. To measure the operational capability of the weapon system requires that it takes no more than X minutes Y percent of the time to service (clean/repair) the weapon. 6-13