Metrology is the science of measurement. Metrology is required to ensure that Air Force systems are accurate and can reliably perform their designated missions. Every system in the Air Force inventory requires some type of accurate and reliable measurement to be made in development or operation. For example, when landing a plane, the pilot counts on the Instrument Landing System to tell him if he's centered on the runway and making his approach at the proper angle. A laser-guided bomb requires both the target designator and the guidance sensor on the bomb to operate at the proper wavelength and at correct power levels for the successful munitions delivery. Finally, the weight of aircraft must be known to ensure that they are not overloaded and that they have the proper amount of fuel for safe flights. The accuracy and reliability of all of these systems can be directly traced to measurements made here at the Air Force Primary Standards Laboratory (AFPSL).
One element of Metrology is calibration. Calibration is the comparison of an instrument of unconfirmed accuracy to another instrument of known and even greater accuracy. The instrument of unconfirmed accuracy is referred to as the unit under test and the instrument of known accuracy is known as a measurement standard. Calibrations are performed to ensure Air Force instruments are accurate enough to meet the performance requirements of Air Force systems. Instruments requiring calibration range from weighing scales and tire pressure gages to laser targeting devices and complex communication systems.
Prior to the early 50's, the Air Force had no formal, centralized calibration program. However, during this period of rapidly expanding technology, operational and testing accident rates increased dramatically and contractor conformance deteriorated. In addition, the emerging space program and some launch failures at caused a rethinking of calibration requirements for systems. An accuracy audit of the failed launch's equipment revealed many errors such as pressure gages that were off by 100 percent. Incorporation of improved calibration processes and a successful launch convinced HQ Air Force of the need for a centralized, formal calibration program. This was implemented in January 1958 as project "Test Shop" and directed that test equipment repair and calibration activities be established at Air Force bases worldwide.
With the publication in early 1958 of AF Regulation 74-2 (which outlined policies and assigned responsibilities for managing the Air Force Metrology and Calibration (AFMETCAL) Program), the Precision Measurement Equipment Laboratory (or PMEL) was officially recognized. PMELs calibrate Test, Measurement, and Diagnostic Equipment (TMDE) for organizations using Air Force systems on their base. Each of the PMELs is responsible for the accuracy of approximately 4500 pieces of test equipment that amounts to about 700,000 pieces of equipment total. AFMETCAL is responsible for ensuring that those PMELs have the policies, procedures, environment, equipment, and training necessary to do the job. Implementing instructions for the AFMETCAL Program are detailed in AFI 21-113.
The Air Force recognized the need for a centralized organization to serve as the single control point for the technical aspects of the Air Force Calibration system. The Directorate of Metrology was established to serve as the manager of the AFMETCAL program. With the closure of Newark Air Force Base in 1996, the Directorate of Metrology became Air Force Metrology and Calibration (AFMETCAL).