RTCA / DO-160: aerospace qualification testing
DNB Engineering covers all RTCA/DO-160 standard's sections:
Electromagnetic Compatibility (EMC) and Lightning performances
Environmental simulations
The RTCA/DO-160 standard (Environmental Conditions and Test Procedures for Airborne Equipment), maintained by the Radio Technical Commission for Aeronautics (RTCA), specifies a series of minimum standard environmental test conditions and applicable test procedures for airborne equipment. The standard provides a manufacturer and laboratory means of demonstrating the performance characteristics of airborne equipment in environmental conditions that may experience in the airborne operation of the equipment in aircraft. The testing scope includes electromagnetic compatibility, electrical, climatic, lightning, mechanical, and fire testing of avionics equipment for the entire spectrum of aircraft. RTCA/DO-160 applies to the United States when there is a European equivalent, known as EUROCAE ED-14 (EUROCAE is the non-profit European Organization for Civil Aviation Equipment). The latest revision of RTCA/DO-160 was issued in 2010. The document is identified jointly as RTCA/DO-160G/EUROCAE ED14-G.
The categories defined within each environmental test procedure have proved to be a practical set of boundary conditions between the requirements of real-world installations and the performance of installed equipment. Here at DNB Testing Laboratories, we have the knowledge, expertise, and necessary equipment to help our customers to develop detailed test procedures based on the general test procedures in RTCA/DO-160.
Environmental simulation under RTCA/DO-160
Section 4.0 Temperature & Altitude
The Temperature and Altitude tests define the performance characteristics of equipment at the applicable categories for the temperatures and altitudes. The following categories cover a wide range of environments known to exist in most aircraft types and installation locations.
Section 5.0 Temperature Variation
Temperature Variation test determines the efficiency of the characteristics of the equipment during temperature variations between high and low operating temperature extremes.
Note: The test is not intended to verify the behavior of the equipment in wet or icing conditions. In conducting this test, the test chamber may incorporate the capability of controlling or altering humidity to the extent that condensation is minimized or does not occur.
Temperature Change Rate by category:
- Category A – For equipment external to the aircraft or internal to the aircraft: 10 degrees Celsius minimum per minute;
- Category B – For equipment in a non-temperature-controlled or partially temperature-controlled internal section of the aircraft: 5 degrees Celsius minimum per minute;
- Category C – For equipment in a temperature-controlled internal section of the aircraft: 2 degrees Celsius minimum per minute;
- Category S1 – For equipment external to the aircraft or internal to the aircraft: known rate of change greater than 10 degrees Celsius per minute. The rate of change shall be noted in the Qualification Form;
- Category S2 – For equipment external to the aircraft or internal to the aircraft: unknown rate of change greater than 10 degrees Celsius per minute.
Section 6.0 Humidity
The Humidity test determines the ability of the equipment to withstand either natural or induced humid atmospheres. The main aftereffects to be expected are:
- Corrosion
- Change of equipment characteristics resulting from the absorption of humidity.
Equipment Categories and Test Procedures:
- Category A – Standard Humidity Environment;
- Category B – Severe Humidity Environment;
- Category C – External Humidity Environment.
Section 7.0 Operational Shock and Crash Safety
The Operational Shock Test checks that the equipment will continue to function within standards after exposure to shocks experienced during regular aircraft operations. These shocks may appear during taxiing, landing, or when the aircraft encounters sudden gusts in flight. This test applies to all equipment installed on fixed-wing aircraft and helicopters.
The Crash Safety Test verifies that specific equipment will not detach from its mountings or separate in a manner that presents a hazard during an emergency landing. It applies to equipment installed in compartments and other areas of the aircraft where the hazard to occupants, fuel systems, or emergency evacuation equipment.
Test procedure:
- Alternate Test Procedure
- Crash Safety
- Test Procedure 1 (Impulse)
- Alternate Test Procedure (Impulse)
- Test Procedure Sustained
Section 8.0 Vibration
The Vibration tests demonstrate that the equipment complies with the applicable equipment performance standards (including durability requirements) when subjected to vibration levels specified for the appropriate installation.
The appropriate category (or categories) selected from the groups should be based upon the level of assurance required for the equipment demonstration of performance. For equipment on fixed-wing aircraft, either a standard or a robust vibration test may be performed. The need to do the high-level short duration test is dependent upon the equipment performance requirements. For equipment on helicopters, only a robust test may be performed.
Category Definitions:
- Standard Vibration Test (Category S)
- Robust Vibration Test (Categories R, U, U2)
- High-Level, Short Duration Vibration Test (Categories H, Z)
Section 9.0 Explosion Atmosphere
The Explosive Atmosphere test specifies requirements and procedures for aircraft equipment that may come into contact with flammable fluids and vapors such as those specified herein. It also refers to normal and faults conditions that could occur in areas that are or may be subjected to flammable fluids and vapors during flight operations.
The flammable test fluids, vapors, or gases referred to in this section simulate those normally used in conventional aircraft, and that require oxygen for combustion (e.g., mono-fuels are not included).
Section 10.0 Waterproofness
Waterproofness tests discover whether the equipment can resist the effects of liquid water being sprayed or falling on the equipment or the effects of condensation. These tests are not intended to verify the performance of hermetically sealed equipment. Therefore, hermetically sealed equipment may be considered to have met all waterproofness requirements without further testing. Equipment shall be considered hermetically sealed when the seal is permanent and airtight.
Test Procedures:
- Condensing Waterproof Test
- Drip Proof Test
- Spray proof Test
- Continuous Proof Test
Section 11.0 Fluids Susceptibility
Fluids Susceptibility tests determine whether the materials used in the construction of the equipment can withstand the deleterious effects of fluid contaminants. Fluid susceptibility tests should only be performed when the equipment will be installed in areas where fluid contamination could be commonly encountered. The fluids are representative of those commonly used fluids encountered in airborne and ground operations. Fluids not listed herein and for which susceptibility tests are indicated shall be included in the relevant equipment specification.
Test Procedures:
- Spray Test
- Immersion Test
Section 12.0 Sand and Dust
This test determines the resistance of the equipment to the effects of blowing sand and dust were carried by air movement at moderate speeds. The main adverse effects to be anticipated are:
- Penetration into cracks, crevices, bearings, and joints, causing fouling and/or clogging of moving parts, relays, filters, etc.
- Formation of electrically conductive bridges.
- Action as a nucleus for the collection of water vapor, including secondary effects of possible corrosion.
- Pollution of fluids.
Section 13.0 Fungus Resistance
These tests determine whether equipment material is adversely affected by fungi under conditions favorable for their development, namely, high humidity, warm atmosphere, and presence of inorganic salts.
Test Procedures:
- Preparation of Mineral-Salts Solution
- Purity of Reagents
- Purity of Water
- Preparation of Mixed Spore Suspension
- Viability of Inoculum Control
- Control Items
- Inoculation of Test Control
- Incubation
- Inspection
- Analysis of Results
- Precautions
Section 14.0 Salt Spray
This test determines the effects on the equipment of prolonged exposure to a salt atmosphere or to salt fog experienced in normal operations. The main adverse effects to be anticipated are:
- Corrosion of metals.
- Clogging or binding of moving parts as a result of salt deposits.
- Insulation fault.
- Damage to contacts and uncoated wiring.
Test Procedures:
- Temperature
- Atomization
- Placement of Salt Fog Collection Receptacles
- Measurement of Salt Solution
- Preparation of Test Item
- Performance of Normal Salt Fog Test (Category S)
- Performance of Normal Salt Fog Test (Category T)
- Failure Considerations
Section 24.0 Icing
These tests determine performance characteristics for equipment that must operate when exposed to icing conditions that would be encountered under conditions of rapid changes in temperature, altitude, and humidity. Three icing test procedures are specified according to the category for which the equipment is designed to be used and installed in the aircraft.
These procedures specify test methods for evaluating the effects of various icing conditions on the performance or aircraft equipment, namely:
- The effects of external ice or frost adhering to it
- The effects of ice caused by freezing of water condensation or by re-freezing of melted ice
- The effects of ice build-up caused by direct water exposure
Section 26.0 Fire, Flammability
Flammability and fire tests apply to equipment installed on fixed-wing propeller-driven aircraft, fixed-wing turbojet aircraft, turbofan aircraft, prop fan aircraft, and helicopters.
These tests are applicable for equipment:
- Mounted in pressurized zones
- Mounted in fire zones
- Installed in non-pressurized, non-fire zones
There are three Equipment Categories
- Category A: Fireproof
- Category B: Fire Resistant
- Category C: Flammability
Electromagnetic Compatibility (EMC) Testing under RTCA/DO-160
Section 15.0 Magnetic Effect
Magnetic Effect test determines the magnetic effect of the equipment and is mainly intended for finding or proving the closest distance to compasses or compass sensors (flux gates) at which that unit is allowed to be installed. This test ensures that equipment can operate properly without interference, which may affect the nearby computer, determining equipment compliance with the applicable equipment performance standard or assisting the installer in choosing the proper location of the equipment in the aircraft.
Test Description
The magnetic effect of the equipment shall be determined in terms of the equivalent deflection of a free magnet in a uniform magnetic field (as produced by the earth) having a horizontal intensity of 14.4 A/m ±10% when the equipment under test is positioned on the east-west line through the pivot of a magnet.
This measurement may be performed with either an uncompensated compass or an equivalent magnetic sensor.
- Category Y: D = 0.0 m. The deflection of the compass is ≤1˚ when measured immediately adjacent to the equipment. This category should be used for equipment whose installation is placed between 0.0 m and 0.3 m from the magnetic compasses or flux gates.
- Category Z: 0< D ≤ 0.3 m. The deflection of the compass is equal to 1˚ when measured >0.0 m to ≤0.3 m to the equipment. This category should be used for equipment whose installation is ≥ 0.3m to magnetic compasses or flux gates.
- Category A: 0.3< D ≤ 1 m. The deflection of the compass is equal to 1˚ when measured >0.3 m to ≤1.0 m to the equipment. This category should be used for equipment whose installation is ≥ 1 m to magnetic compasses or flux gates.
- Category B: 1 m < D ≤ 3 m The deflection of the compass is equal to 1˚ when measured >1.0 m to ≤3.0 m to the equipment. This category should be used for equipment whose installation is ≥3 m to magnetic compasses or flux gates.
- Category C: The deflection of the compass is equal to 1˚ when measured >3.0 m to the equipment. This category should be used for equipment whose installation is >3 m to magnetic compasses or flux gates. Minimum distance for deviation of 1˚ shall be reported in the test form; the equipment location onboard will be selected accordingly.
Section 16.0 Power Input
This section defines test conditions and procedures for ac and dc electrical power applied to the terminals of the equipment under test. It covers the following electrical power supplies:
- 14 V dc, 28 V dc, and 270 V dc
- 115 Vrms ac and 230 Vrms ac at either a nominal 400 Hz frequency or over a variable frequency range which includes 400 Hz
Equipment categories and frequency classes, test conditions, and procedures for equipment using other electrical power supplies must be defined in applicable equipment performance standards.
Section 17.0 Voltage Spike
The Voltage Spike test determines whether the equipment can withstand the effects of voltage spikes arriving at the equipment on its power leads, either ac or dc. The main adverse effects to be anticipated are:
- Permanent damage, component failure, insulation breakdown.
- Susceptibility degradation, or changes in equipment performance.
Section 18.0 Audio Frequency Conducted Susceptibility – Power Inputs
This test determines whether the equipment will accept frequency components of a magnitude normally expected when the equipment is installed in the aircraft. These frequency components are normally harmonically related to the power source fundamental frequency. This section of DO-160 is intended to provide test procedures and test levels that can be used to test equipment for audio frequency conducted susceptibility of power input lines. It is the responsibility of the installer to make sure the test results satisfy the certification requirements of the proposed installation.
Section 19.0 Induced Signal Susceptibility
This test determines whether the equipment interconnect circuit configuration will accept a level of induced voltages caused by the installation environment. This section relates specifically to interfering signals related to the power frequency and its harmonics, audio frequency signals, and electrical transients that are generated by other on-board equipment or systems and coupled to sensitive circuits within the EUT through its interconnecting wiring.
Section 20.0 Radio Frequency Susceptibility (Radiated and Conducted)
These tests determine whether the equipment will operate within performance specifications when the equipment and its interconnecting wiring are exposed to a level of RF modulated power, either by a radiated RF field or by injection probe induction onto the power lines and interface circuit wiring.
Two test procedures are used: 1) From 10 kHz to 400 MHz, the equipment under test (EUT) is subjected to RF signals coupled by means of injection probes into its cable bundles, and 2) for frequencies between 100 MHz and the upper-frequency limit, the EUT is subjected to radiated RF fields. There is an intentional overlap of the tests from 100 to 400 MHz.
Radiated susceptibility tests from 100 MHz to 18 GHz may be conducted using the Anechoic Chamber Method or Reverberation (Modetuned) Chamber Method. The choice of methods is at the discretion of the applicant.
Equipment with special signal, frequency, modulation or bandpass characteristics may require test variations as specified by the applicable performance standards.
Learn more about HIRF Testing Capabilities at DNB Engineering, Inc.
Section 21.0 Emission of Radio Frequency Energy
These tests determine that the equipment does not emit undesired RF noise in excess of the levels specified below. The notches specified in the radiated emissions limits are included to protect aircraft RF sensors operating frequencies.
Categories are defined in terms of location and separation between the equipment and aircraft radio antennas. As these parameters are widely linked to aircraft type and size, some examples are given with each category definition.
General Requirements
This section does not measure or control spurious signals conducted out of the antenna terminals of receivers or transmitters. That control should be specified in the equipment performance standard for that receiver or transmitter. Radio transmitters or receiver/transmitters must meet specified emissions requirements (including the selected frequency ±50% of the band of frequencies between adjacent channels) while in a non-transmitting or receive mode.
Note: Do not measure radiation emanating from antennas or, in the case of transmitters, any radiation on the selected frequency ±50% of the band of frequencies between adjacent channels while the transmitter is keyed and supplying RF to the load.
Section 25.0 Electrostatic Discharge
The Electrostatic Discharge (ESD) test relates to airborne equipment which may be involved in static electricity discharges from human contact. Some factors contributing to an ESD event may be: low relative humidity, temperature, use of low conductivity (artificial fiber) carpets, vinyl seats and plastic structures which may exist in all locations within an aircraft. This test is applicable for all equipment and surfaces which are accessible during normal operation and/or maintenance of the aircraft. This test is not applicable to connector pins.
Purpose of the Test
The ESD test is designed to determine the immunity or the ability of equipment to perform its intended function without permanent degradation of performance as a result of an air discharged electrostatic pulse.
Test Description
The immunity to electrostatic discharge shall be determined by the ability of the equipment under test (EUT) to withstand a series of electrostatic discharge pulses at a test level of 15,000 volts, directed at specific human contact locations on the EUT. The number of pulses shall be ten (10) in each of the selected locations and in both positive and negative voltage polarities (10 positive and 10 negative).
Lightning simulation under RTCA/DO-160
Section 22.0 Lightning Induced Transient Susceptibility
These test methods and procedures are provided to verify the capability of the equipment to withstand a selection of test transients defined in this section which are intended to represent the induced effects of lightning. The wave-forms and levels, and the pass/fail criteria for equipment performance during the test shall be listed in the applicable equipment specification.
Two groups of tests may be used for equipment qualification. The first is a damage tolerance test performed using pin injection. The second group evaluates the functional upset tolerance of equipment when transients are applied to interconnecting cable bundles. Cable bundle tests include single stroke, multiple stroke, and multiple burst, response tests (hereafter referred to as a single stroke, multiple stroke and multiple burst. Cable bundle tests can also provide an indication of damage tolerance.
Section 23.0 Lightning Direct Effects
The Lightning Direct Effect tests intended to determine the ability of externally mounted equipment to withstand the direct effects of a lightning strike. The term “externally mounted equipment” refers to all equipment mounted externally to the main skin of the aircraft and includes all such equipment that is covered only by a dielectric skin or fairing that is an integral part of the equipment. It also includes connecting cables and associated terminal equipment furnished by the equipment manufacturer as a part of the equipment.
Examples of equipment covered by this section are antennae, exterior lights, air data probes, external sensors, and anti-ice and de-ice equipment which is mounted external to the structure (i.e. electrically heated anti-ice boots), magnetic fluid level indicators, fuel filler caps, and drain valves.
They are two types of direct effects tests:
- High voltage strike attachment tests. It is used to determine likely lightning attachment locations on the test object.
- High current physical damage tests. It is used to determine the damage that may occur to the test object during a lightning channel attachment to or near the test object. The high current physical damage test can be used to assess:
- Arc root damage
- Hot spot formation
- Melt-through behavior
- Adequacy of protection
- The behavior of joints (sparking and damage)
- Level of voltage and current induced on electrical conductors interfacing with the test object
Typically, high voltage strike attachment tests are performed first to determine the likely lightning attachment locations on the test object. The high current physical damage test is then applied to an attachment location identified during the high voltage testing. Test objects that do not have a dielectric covering may not require high strike voltage attachment tests prior to the high current testing if the likely lightning attachment points can be identified. In such cases, the test plan shall define the location on the test object where the high current is to be applied.
Find out more about Direct Effect Lightning Testing at DNB Engineering, Inc.