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Aircraft utilize electrical power for many functions ranging from simple devices such as resistive heaters to highly advanced and complex systems responsible for communications, situational awareness, electronic warfare and fly-by-wire flight controls. The operational states of these electronic systems affect safety, mission success and the overall economic expense of operation and maintenance. These electronic systems rely on electrical power within established limits of power quality. In recent years, electrical power quality is becoming excessively degraded due to increased usage of nonlinear and dynamic loads coupled to aircraft power systems that were neither designed nor tested for these loads. Legacy power generation systems were designed for electrical loads with resistive and inductive properties, which previously represented the majority of actual aircraft electrical loads.

Aircraft electrical power quality effects the operation and life of avionics equipment. The military interface document that defines aircraft electrical power at the input to utilization equipment is MIL-STD-704. Testing is required to demonstrate compatibility of avionics with aircraft electrical power. This paper summarizes the aircraft electrical operating conditions and power groups of MIL-STD-704. The paper also gives an overview of the test guidance for 28 volt DC aircraft utilization equipment provided in the recently published handbook MIL-HDBK-704, “Guidance for Test Procedures for Demonstration of Utilization Equipment Compliance to Aircraft Electrical Power Characteristics”. Common causes of power quality parameters and the effects on avionics are given.