Environmental Conditions and Test Procedures for Airborne Equipment

Ensuring that airborne equipment can withstand a numerous environmental challenge is the core focus of the DO-160 standard.

Published by the Radio Technical Commission for Aeronautics (RTCA), DO-160 serves as a benchmark for the environmental testing of avionics hardware. This blog explains the purpose of DO-160 and explores its various sections, each designed to evaluate airborne equipment under specific environmental conditions.

Purpose of DO-160

The essence of DO-160 lies in providing a standardized framework for testing the performance characteristics of airborne equipment across the entire spectrum of aircraft. From light general aviation planes and helicopters to massive jumbo jets and high-speed supersonic transport, DO-160 aims to create a controlled laboratory environment that mimics the challenges faced during actual airborne operations. The standard outlines a set of minimal environmental test conditions and corresponding test procedures, which can be used in conjunction with applicable equipment performance standards. This ensures a minimum specification under environmental conditions, instilling confidence in the performance of airborne equipment aboard diverse air vehicles.

Sections of DO-160

DO-160 is organized into various sections, each dedicated to scrutinizing different environmental factors and their impact on airborne equipment. Let’s explore sections:

  • Temperature (Section 4.0): This section assesses the effects of temperature on the system, including considerations for condensation resulting from cold temperatures.
  • Altitude (Section 5.0): Tests under this section evaluate the impact of altitude, including the loss of cabin pressure, dielectric strength, cooling under low pressure, and resilience to rapid changes in air pressure.
  • Temperature Variation (Section 5.0): These tests subject the assemblies to extreme temperature changes and assess the effects of differing coefficients of thermal expansion.
  • Humidity (Section 6.0): Testing under humidity checks the effects of high humidity concentrations and the equipment’s ability to withstand moisture-induced issues such as corrosion.
  • Shock & Crash Safety (Section 7.0): Aircraft type-dependent tests checking the effects of mechanical shock. Crash safety tests ensure that items do not become projectiles in a crash.
  • Vibration (Section 8.0): Aircraft type-dependent tests checking the effects of vibration and the equipment’s ability to operate during all vibration scenarios.
  • Explosion Proofness (Section 9.0): These tests subject the test article to an environment under vacuum, with a gaseous mixture of combustibles, ensuring it operates without igniting the environment.
  • Water Proofness (Section 10.0): These tests subject the test article to various scenarios of dripping water or pooled water to verify that the unit will fully operate in the given condition.
  • Fluids Susceptibility (Section 11.0): This section includes tests for aviation-related fluids susceptibility, ranging from carbonated sugared beverages to various cleaners and solvents.
  • Sand & Dust (Section 12.0): This test subjects the unit to an environment of blowing sand and dust of specific particle sizes in which the unit must operate at the end of exposures.
  • Fungus Resistance (Section 13.0): These tests determine whether equipment material is adversely affected by fungi under conditions favorable for their development, such as high humidity, a warm atmosphere, and the presence of inorganic salts.
  • Salt & Fog (Section 14.0): This test verifies the test article’s ability to survive multiple exposures of salt fog and drying and assesses the environment’s ability to cause accelerated corrosion.
  • Magnetic Effect (Section 15.0): This test determines the magnetic effect of the equipment, ensuring it can operate properly without interference, particularly affecting the nearby aircraft’s compass.
  • Power Input (Section 16.0): This includes tests for input power conducted emissions and susceptibility, transients, drop-outs, and hold-up. These simulate conditions of aircraft power from before engine start to after landing, including emergencies.
  • Voltage Spike (Section 17.0): This test determines whether equipment can withstand the effects of voltage spikes arriving at the equipment on its power leads, either AC or DC.
  • Audio Frequency Conducted Susceptibility (Section 18.0): This test determines whether the equipment will accept frequency components of a magnitude normally expected when the equipment is installed in the aircraft.
  • Induced Signal Susceptibility (Section 19.0): This test determines whether the equipment interconnect circuit configuration will accept a level of induced voltages caused by the installation environment.
  • RF Emission and Susceptibility (Sections 20.0 and 21.0): These sections address radio frequency energy, covering radiated emissions and susceptibility via an electromagnetic reverberation chamber.
  • Lightning Susceptibility (Sections 22.0 and 23.0): Covering direct and indirect effects depending on mounting location, this section includes induced transients into the airframe or wire bundle.
  • Icing (Section 24.0): This test determines performance characteristics for equipment that must operate when exposed to icing conditions encountered during rapid changes in temperature, altitude, and humidity.
  • ESD (Section 25.0): This test checks for resilience against Electrostatic Discharge (ESD) in handling and operation.
  • Flammability (Section 26.0): This section involves an analysis and test to verify that the assembly will not provide a source for fire.

In conclusion, DO-160 stands as a guide for environmental testing in the aviation industry. By addressing a wide range of environmental conditions and providing corresponding test procedures, DO-160 ensures that airborne equipment meets stringent performance requirements. As the aviation landscape evolves, DO-160 continues to adapt, playing a crucial role in maintaining the safety, reliability, and resilience of avionics systems soaring through the skies.