Icing – Good for Cold Drinks, Not for Aircraft: DO-160 Icing Tests at Elite

Ice that clings to the skin of an aircraft is not decorative. It adds weight, it impedes moving parts, and it reduces visibility. An airplane cruising at 35,000 feet is moving through thin air with temperatures below -60⁰ F. If there is moisture, ice is going to form.

The Radio Technical Commission for Aeronautics (RTCA) standard DO-160 prescribes icing tests for aircraft components. Section 24 of DO-160 defines three equipment categories vulnerable to icing.

  • Category A – Equipment installed externally or in an area of the aircraft that is not temperature controlled. The concern is ice or frost forming from condensation when exposed to extremely low temperatures.
  • Category B – Equipment with moving parts that are inhibited in operation from ice buildup.
  • Category C – Equipment or surfaces where water accumulation is a risk and is not temperature controlled. The allowable thickness of ice buildup is determined by the equipment’s performance standards.

Icing Condition Test Procedures

Tests for the three equipment categories have application-specific temperature and moisture cycles. All require thermal chambers to provide the temperature extremes called for in the standard.

  • Category A is intended for equipment exposed on the outside of the aircraft. The device under test (DUT) is fitted with thermocouples and placed in the test chamber alongside a metal test bar that serves as a reference indicator of ice thickness. The chamber is set to the prescribed temperature until the DUT temperature is stabilized at the Ground Survival Low Temperature specified in DO-160. A uniform water spray is applied as the ice thickness is monitored over time. Steps are repeated until the prescribed ice thickness has been reached. After four hours have passed, photos are taken of the DUT before it is removed to check its condition. The DUT is then brought to room ambient temperature and checked for proper operation.
  • Category B applies to equipment to moving parts, requiring temperature and atmospheric pressure to be varied. The chamber’s relative humidity is set at 95% as the temperature and pressure are cycled 25 times. After the final cycle, the DUT is stabilized at -20˚ C and checked that it meets its performance standards.
  • Category C tests equipment that is not operating, stabilized at a temperature allowing clear, hard ice to form with a fine water spray. When the ice is at a thickness required by its performance standard, the DUT is maintained at -20˚ C and checked that it meets its performance standards.

Icing Tests at Elite

Elite’s long experience in aerospace compliance verification extends to DO-160 icing tests. Using state of the art thermal chambers, aerospace components are tested with the precision that aviation safety requires. Icing tests are run in Elite’s thermal chambers on DUTs in a variety of sizes and configurations.

Test Preparation and Procedure

One of Elite’s thermal chambers used in icing tests

Prior to the actual test, preliminary information from the customer’s test plan is reviewed to confirm the DUT’s configuration. The test plan is developed by Elite after careful discussion with the customer on details such as the DUT’s operation, the ice thickness required, and the type of baseline test required to confirm success.

When the test is scheduled, the test chamber and its accompanying chilled water tank are prepared. The DUT is placed in the chamber in the configuration specified in the test plan. The DUT is given an operational checkout to establish a baseline, the temperature in the chamber is verified, and the icing process begins.

Setup inside thermal chambers for an icing test

Ice accumulation is checked periodically. When ice accumulation reaches the appropriate level, the water spray is turned off and the DUT is maintained at subzero temperatures for four hours to allow the ice to harden.

After the prescribed time has passed, photos are taken of the ice buildup and the DUT is examined for damage and excess water ingress. The DUT is later brought to ambient temperature and checked for proper operation as given in the test plan.

Avionic equipment needs to work, ice or no ice. Contact the experts at Elite for more information on the DO-160 icing tests for your avionic device.

More Electric Aircraft (MEA) Systems – Elite Can Test That

A folded paper airplane will fly, at least for a while. But it can’t be steered or stay aloft any longer than the air around it will allow. Even with their breakthrough in 1903, the Wright brothers got their flying machine in the air for only twelve seconds.

Aircraft control systems make it possible to safely stay in the air, and they need reliable electrical power for the devices that make up those control systems. Aircraft have duplicate power sources to operate the devices on board, typically generating 115 VAC, 400 Hz, and 28 VDC.

Power originates from Integrated Drive Generators (IDGs) driven by the aircraft engines. The 400 Hz frequency allows smaller, lighter components to be used than those using 60 Hz power. The AC passes through duplicate Transformer Rectifiers (TRs) to provide 28 VDC for charging on-board batteries and other devices requiring DC.

Historically, on-board pneumatic systems draw power from thrust drawn off the engines, typically 4-6% of the propulsive energy. A higher efficiency architecture called More Electric Aircraft (MEA) looks to replace many of the hydraulic and pneumatic systems with electrically driven motors and pumps. The advantages are not just higher efficiency, but also reduced weight and fewer failure-prone mechanical components. Since thrust is not being bled from the engines, this is called a no-bleed system.

Hydraulic aircraft functions replaceable by localized electric motors in an MEA design (

Electrical components in an MEA aircraft have different requirements. Aircraft power systems have long employed a constant-frequency AC power system, typically 400 Hz. Later aircraft designs, such as the Boeing 787 and the Airbus A380, use a variable-frequency system, where the power frequency varies with the engine speed that drives the generator.

As an example, the Boeing 787 uses an electrical system that is a hybrid consisting of 235 VAC, 115 VAC, 28 VDC, and ±270 VDC. The 235 VAC and the ±270 VDC sources are part of the no-bleed design with an expanded electrical system generating twice the electricity of previous airplane models.

Generators directly connected to the engine gearboxes operate at a variable frequency (360 to 800 hertz) proportional to engine speed. It’s a more efficient system because it does not require a complex constant-speed drive. As a result, the generators are more reliable, require less maintenance, and have lower spare costs than the traditional IDGs.

Applicable Standards

The Radio Technical Committee for Aeronautics (RTCA) publishes standard DO-160, covering a wide range of environmental tests required to confirm that airborne equipment will operate safely and reliably. Section 16 of DO-160 covers power input and outlines the limits and test procedures of the power system components.

DO-160 defines equipment categories to determine test levels and procedures.

  • Categories A(CF), A(NF), A(WF) and A: These are equipment used on aircraft electrical systems where primary power is supplied from either a constant or variable frequency AC system, and where the DC system is supplied from TR units.
    • For AC equipment: Category A(CF), A(NF) or A(WF)
      • A(CF) is AC equipment used on aircraft electrical systems where primary power is from constant frequency (400 Hz) AC system.
      • A(NF) is AC equipment used on aircraft electrical systems where primary power is from variable frequency AC between 360 – 650 Hz.
      • A(WF) is AC equipment used on aircraft electrical systems where primary power is from a wider variable frequency AC between 360 – 800 Hz.
    • For DC equipment: Category A
  • Category B: 14 V or 28 V DC equipment used on aircraft electrical systems supplied by engine-driven alternator/rectifiers, or DC generators where a battery is floating on the DC bus.
  • Category D: 270 V DC equipment used on aircraft electrical systems where DC is generated from primary power supplied from either a constant or variable frequency AC system.
  • Category Z: 28 V DC equipment that may be used on all other types of aircraft electrical systems applicable to these

Elite’s Aerospace Testing Experience

Elite’s decades of experience testing aviation and aerospace devices assures timely and authoritative results. Elite’s capabilities include:

The experts at Elite can answer your questions about DO-160 tests and the array of related tests needed for compliance with aviation standards.

Mark Rugg – From Airfone to Air Force Two

Elite Electronic Engineering is a name that’s been identified with avionics testing for decades. When aircraft equipment manufacturers need compliance and reliability testing, Elite is among those at the top of their lists. It’s no surprise that technical professionals with experience around aircraft would be found at Elite.

Electromagnetic compatibility (EMC) engineer Mark Rugg fits that description. An engineer in Elite’s MIL-AERO area, he started his career as an aircraft mechanic with Braniff International, expanding his experience in testing and maintenance on aircraft electronics. With the shift in the airline industry in the 1980s, Mark moved on to Airfone, the flight-to-ground phone service operated by GTE and later by Verizon.

Mark became a manager at Verizon, where he remained for 20 years. “That was where I got experience in EMC, testing and certifying aircraft and ground-based telephones,” he said.

Air Force Two – Mark verified the vice-president’s telephone

One of Mark’s responsibilities was the phone service on Air Force Two, the aircraft designated for the vice-president. “That was interesting, working with the flight crew and vice-president’s staff. The requirements are tighter than commercial standards.”

Mark with communications for Air Force Two (left image). Mark checking out Air Force Two’s office space (right image)

He later worked at Row 44, a broadband supplier to commercial aircraft, and later continued in avionics with Telefonix, an aerospace telecommunications company. Telefonix products required a lot of regulatory testing, and since Elite’s Downers Grove campus was conveniently between Mark’s home and Telefonix’s office, he spent long hours at Elite overseeing tests.

In 2020, Mark was ready to spend all his time running EMC tests and joined Elite’s staff of expert compliance engineers. He is one of the go-to members of the MIL-AERO group that customers rely on for MIL-STD, DO-160, and other specialized regulatory tests.

Being at Elite at this point in his career is a natural fit. “It works since my commute is reasonable and I was familiar with Elite’s lab from the time I spent with Telefonix’s gear,” he explained. If you have aerospace equipment that needs compliance tests, Mark is one of the engineers with the background and experience that has made Elite the Midwest’s premiere test laboratory.

A HIRF can Hurt Your Aircraft Gear – Testing High Intensity Radiated Field Immunity

Air travel is the safest form of travel, by far. Data from the International Air Transport Association (IATA) showed that the risk is so low that that on average, a person would need to fly every day for 461 years before experiencing an accident with at least one fatality.

The aviation industry has held its impressive record through careful attention to detail. That attention is focused on the aircraft itself, of course, but also on understanding the aircraft’s environment. Besides the obvious atmospheric concerns like wind, rain, and lightning, the presence of radiofrequency (RF) fields can disrupt the aircraft’s electronics.

RF fields are everywhere, and most are at low enough levels that they pose little threat to safe operation. But high intensity radiated fields (HIRFs) can overwhelm guidance devices. Airports are rich with HIRFs from radar, guidance, and communications systems that rely on high-powered transmitters. Elite Electronic Engineering’s Pat Hall and Tom Klouda have been performing HIRF tests on aircraft components for decades and explain how the test is done.

Standards and Test Planning

Aviation HIRF testing is specified in the Radio Technical Commission for Aeronautics (RTCA) standard DO-160, Section 20. The standard identifies susceptibility categories set at different RF levels. The table below shows the categories in the columns and the frequency ranges in the rows. The cells of the table give the test levels in Volts/meter.

Testing is normally done in one of Elite’s mode-stirred chambers, which are shielded rooms equipped with rotating stirrers. Different forms of the RF field are applied, such as pulsed or continuous wave, depending on the application.

As an example, Elite’s lab often tests aircraft display hardware, which is composed of the display panel itself and the electronics that drive it. In those cases, Category G is the level most often called for when testing those devices. The specified field levels are highlighted below, taken from Table 20-3 of the DO-160 standard. The field at those levels is applied to the equipment under test (EUT) while its operation is monitored for responses.

Those fields are generated most often in a mode-stirred chamber, shown in the illustration below. An RF amplifier feeds an antenna inside a shielded enclosure to create the field, and the modes of the field are stirred by a rotating metal tuner/stirrer. The effect is to provide a consistent average field level to the the EUT from the combination of reflections from the metal surfaces and the paddle’s rotation. The wide variety of angles and levels seen by the EUT during the test assures that specified overall level over time will be applied.

Stirred-mode test chamber setup, showing the EUT within the calibrated test volume and the tuner/stirrer that provides an overall average field level

The test chamber calibration establishes the power levels needed to generate the field across the frequency range. The dashed-line box in the illustration below shows the chamber’s test volume. An isotropic RF probe measures the field level at each frequency in the specified range. The probe is set up at nine points in the test volume, one at each corner and one in the center. The power-level numbers collected in calibration are programmed into the amplifier controller, which can then provide consistent field levels during the test.

Stirred-mode test chamber setup, showing the EUT within the calibrated test volume and the tuner/stirrer that provides an overall average field level

The EUT is set up according to its test plan and monitored for any response as the radiated field is applied across the frequency range. The positioning of enclosures, cables, connectors, and other components of the EUT are specified in the test plan so that its actual environment is simulated. The EUT’s function and form and its proximity to other equipment and the aircraft’s body are fundamental to determining how to position it during the test. The EUT’s pass/fail criteria also need to be understood so that meaningful evaluations can be made if responses are seen during the test.

Elite has two mode-stirred chambers with different test volumes. The larger of the two can test from 100 MHz – 18 GHz up to 2kV/m, and the smaller can test from 400 MHz – 18 GHz up to 5kV/m. The photo below shows Elite HIRF expert Tom Klouda setting up a test in the larger chamber, with the tuner/stirrer visible in the background.

Elite’s Tom Klouda (center) reviews chamber setup with Mark Rugg (left) and Fred Rub. The mode-stirring paddle is at the upper rear of the chamber.

Preparation takes up the bulk of time for a test. EUTs can be any size, with a wide variety of ancillary equipment and cables that collectively make up the overall EUT. The test plan will specify how the EUT is to be configured, how the cables are to be exposed, and what modes of operation the EUT needs to run. With those factors in place and the EUT in position, the actual test is run across the specified range while the EUT is monitored.

Contact the experts at Elite with any questions on HIRF testing, the applicable standard, and the steps required to prepare. Trust Elite put its decades of experience to work for you.

Employee Spotlight — Adam Grant: From Martial Arts to Outer Space

Aerospace technology operates at environmental far edges. Equipment installed on spacecraft and in military applications deal with temperature extremes, direct lightning strikes, and earth-shaking vibration. Devices need to prove their ability to keep working when they’re hit by those shocks.

Adam Grant is among the expert staff at Elite who understands the need for reliable aerospace operation.  In 19 years as an engineer in Elite’s Miltary and Aerospace EMC Testing lab, he’s run tests on the devices that keep planes and rockets in the air.

Adam’s interest in aerospace began at an early age. Fascinated with space travel and rocketry as a high school freshman, he attended the Space Academy at the Marshall Space Flight Center in Huntsville, Alabama. The planned launch of NASA’s Artemis 1 moon mission brings Adam’s background into sharp focus.

The week-long experience opened his eyes to the aerospace world. “We did simulations as flight crews. That showed us how difficult it can be to pilot a spacecraft,” Adam said. “The ground crew simulations came after that, so we saw both ends of a mission.”

Adam’s Space Academy certificate

He started working at Elite a year or so after graduation from DeVry University. “When I was getting into aerospace when I was in high school, I never thought I’d be testing that same equipment as a career.” Adam has done lightning and electromagnetic compatibility (EMC) testing for the military-aerospace industry, along with automotive EMC, areas that are critical to public safety. “It’s been interesting,” he said. “It’s a good environment at Elite that really is operated as a family.”

The work requires mental discipline, something Adam developed while rising to the level of third degree Black Belt in Taekwondo. He started training in high school, and for a few years was an instructor in his off hours. “I still do the occasional training and stay with it to keep in shape.” The physical benefits are real and has made him appreciate the value of focus and ongoing study.

Adam describes his twelve-year-old son and eight-year-old daughter as bright stars. “They could easily go into engineering – I sometimes ask them when I have technical questions.” They take an interest in the kind of work he does, which he understands. At their age he was fascinated by the tools of space travel and aviation.

Adam’s expertise and curiosity led to his most recent move into Elite’s sales and marketing group. “I wanted to try another part of the business,” he explained. The chance to describe the testing process to customers when they call was attractive to Adam. When you call to ask about getting a quote and planning tests of your aerospace or automotive device, you’re likely to talk to Adam. He’s seen it all and can explain the standards and how they apply to your product.

Adam is another reason Elite is your first choice for trusted, timely testing. If you talk with him, he can arrange the right test at the right price on your schedule. And he might tell you how to operate a spacecraft, too.

10 Tips to Faster and Smoother Aerospace and Military EMC Tests

Elite Electronic Engineering is renowned for its industry-leading Aerospace EMC and Military EMC test expertise. The trusted results and timeliness are products of decades of experience in performing those tests and helping to write the standards.

Elite’s Senior EMC Engineer Steve Framarin (right) is part of that legacy of experience and has outlined ten tips to make a military or aerospace EMC test series run more smoothly. The testing process can appear daunting when reviewing applicable standards and a customer faces choices in setup, operation, and the range of device parameters.

Steve offers these tips to minimize delays and provide the results you need when you need them:

  1. Have a current test plan that spells out the device under test (DUT), its configuration, and the tests to be performed. Elite can help develop a plan specific to your DUT and its intended operation.
  2. Be sure to have current operating instructions for projects that are sent to Elite when the manufacturer’s staff cannot be on-site for the test.
  3. Whenever possible, have spare DUTs for projects that are sent to Elite.
  4. Verify operation of ALL equipment (the DUT, the support equipment, cables, etc.) before it arrives at Elite.
  5. Make sure the latest software/firmware versions are installed on the DUT and its support equipment.
  6. Have equipment sent in or dropped off at Elite the day before testing begins, if possible.
  7. Provide clear equipment-return instructions to minimize delay and assure the best care of the DUT.
  8. Define the response criteria/status/class – what is a failure condition, what is successful operation, etc.
  9. Define ALL testing parameters, e.g., limits, severity levels, generator impedances, etc. Many standards allow for a range, which is often defined by the customer.
  10. Double-check Elite’s quote to make sure it aligns with the latest test plan revision or scope of testing.

Steve and his colleagues at Elite will work through these steps with your team so that you can get the results you need in the least amount of time.

Contact the experts at Elite to find out how to identify these steps for your aerospace or military EMC testing project.

MIL-STD testing in Elite’s EMC lab

Ka-Boom! Lightning is More Than a Bright Flash

An aircraft’s environment is everything. It needs air to provide lift, it needs to stay aloft in the rain and heavy winds, and it needs to endure lightning strikes. Designed for that environment, its outer form minimizes drag and its conductive surface offers a diversion for lightning currents.

Lightning strikes are common on aircraft. How could they not be? Lightning is going to happen when a large conductive object appears within range of a thundercloud. Fortunately, lightning energy travels over the surface of the metal body and continues its discharge path to meet the ground.

Among the risks to the aircraft is the energy that can be induced into cabling routed under the outer skin. The enormous voltages of a lightning strike will couple some energy into nearby conductors, posing a risk to the aircraft’s electrical system. The conductors are wired directly into the electronics on board and carry their induced voltages into those devices.

Applicable Standards – RTCA DO-160

The Radio Technical Commission for Aeronautics (RTCA) is the industry organization publishing aviation technical standards. DO-160 is RTCA’s standard covering airborne equipment environmental conditions and their tests, which includes those for lightning susceptibility. Lightning-induced cable transients on unshielded cables, however brief, can be of exceedingly high voltage and current. Shielded cables offer protection by carrying the bulk of the induced energy on the cable shield where it can be dissipated.

Section 22 of DO-160 addresses lightning-induced susceptibility.

There are various waveforms defined that reflect the complexity of induced currents from lightning strikes. The waveforms are intended to demonstrate compliance for aircraft protection and the protection of its systems against the lightning environment.

The basic waveforms of the induced current and voltage in the aircraft cabling is shown below. Note the sharp rise time of the induced voltage and the slower rise time of the induced current.

Induced voltage waveform
Induced current waveform

The resonance of the cables naturally brings about a damped sinusoidal wave as the energy dissipates, as shown below.

Damped sinusoidal waveform resulting from lightning-induced transient

Lightning normally occurs in multiple strokes, with waveform behavior as illustrated in the figure below.

Illustration of the transient peaks resulting from multiple lightning strokes.

The subsequent strokes result in damped sinusoidal waves and gradually diminishing peak voltage and current peaks. To simulate these conditions, DO-160 Section 22 defines test steps and levels.

Indirect Lightning Test Process 

Five power levels are defined in DO-160 and are chosen based on how critical the connected device is for flight operation.

  • Level 1, the lowest, is intended for equipment and wiring installed in a well-protected environment
  • Level 2 is intended for equipment and wiring installed in a partially protected environment
  • Level 3 is intended for equipment and wiring in a moderate electromagnetic environment
  • Levels 4 and 5, the highest, are intended for equipment and wiring exposed in severe electromagnetic environments

The test specification is indicated in the test plan describing the pins to receive injection and the cable-test waveform sets and the levels to be applied. These choices are made depending on how critical the equipment is to the aircraft’s safe operation.

Section 22 defines two test methods:

  • Pin Injection – Selected waveforms are injected directly into the pins or cables of the equipment under test (EUT). The EUT is normally powered and operational during the test so that its immunity to the injected transient can be monitored.
  • Cable Induction – In this test, the selected waveform is applied through a coupling clamp around the targeted cables, or the waveform is injected into the test-table ground plane so that it can be induced into the cable.

The chosen waveforms can be applied as Single Stroke, Multiple Stroke, or Multiple Burst. The single stroke test replicates the wiring’s response to the most severe lightning strike outside the aircraft. Multiple stroke tests replicate the induced effects to the internal wiring after a lightning strike made up of a single stroke followed by a burst of multiple return strokes.

Lightning Tests at Elite

Cable Induction

Lightning tests performed at Elite rely on a lightning waveform generator and a coupling network to induce the transient voltage into the cable identified in the test plan. The EUT is powered and operational as specified in the test plan. The appropriate waveform and level are chosen for each test and applied through the coupling network into the cable, which is connected to the EUT. During the test, the EUT is monitored for proper operation.

Lightning test setup showing waveform generator and cable-coupling network

Pin Injection

The EUT is not powered during the pin injection test, as this is potentially destructive. The waveform generator is set for the waveform and test level prescribed in the test plan. Connections are made from the waveform generator to the cable conductors or connector pins identified in the test plan. The transient is applied as specified in the test plan, and the EUT is examined at the completion of each test for any component damage and for proper operation.

Lightning waveform generator showing connection point for pin-injection tests

Trusted Test Results

The EUT’s test report provides the detail: which pins received which waveforms at which levels; what waveform and levels were induced on which cable-bundle combination; and the status of the EUT before and after the tests. 

Few things are as critical as aircraft safety. Elite’s has unmatched experience with lightning tests is equipped with more test systems covering all 5 waveform levels than any other lab. Contact the experts at Elite for information on testing your device for DO-160 compliance.

The Pilot’s Best Friend — Airfield Lighting Photometry

Anyone visiting an airport has seen the constellation of lights on the airfield. Runway and taxiway lights, obstruction lights, approach lights, beacons, and more. They look like holiday decorations from a distance, but they’re a vital part of aviation safety.

The critical role these lights play in the safety of aircraft landings and takeoffs requires that rigorous standards be met. In the US, the Federal Aviation Administration (FAA) accepts third-party certification under the Airport Lighting Equipment Certification Program (ALECP).

Elite is one of two test labs accepted under ALECP. Elite’s FAA Program Administrator Brad DeGrave leads the FAA Airport Lighting Certification Team and explains the tests along with Elite’s role.

Elite’s Brad DeGrave setting an amplified detector in the photometric lab

Elite has been accepted by the FAA as a Third-Party Certification Body, which means Elite can determine compliance to the FAA’s Advisory Circulars (AC) through testing, and if the equipment meets the standard, Elite can issue the Certificate of Conformance that is submitted to the manufacturer and the FAA.”

Elite’s certification activities aren’t limited to its own lab, Brad explained. “We can also witness testing that requires special equipment and is performed at the manufacturer’s site, and if requirements are met, we can then issue the Certificate of Conformance. As a certification body, we are also responsible for conducting the required audits and inspections of the manufacturer’s facility.”

FAA AC 150/5345-53D is the ALECP’s guiding document. Each piece of equipment has an AC to outline the design and test requirements, which include photometry, environmental, and electrical testing. All of this is in the service of assuring that aircraft can see consistent airfield lights in all conditions.

Another piece of equipment that is certified but not on the airfield is obstruction lighting. This equipment must operate at up to 95% relative humidity, and survive winds of 150 mph, wind-blown rain, salt fog, and sunshine exposure. Covers must meet specific color requirements. The control equipment for the lights needs to meet similarly harsh requirements.

Elite’s Brad DeGrave and Jessica Kramer setting up a power supply for an airfield lighting test

Elite’s photometry lab measures light intensity levels, flash rates, color, and beam spread, characterized by both daytime and nighttime levels. Each type of light has specific photometric requirements depending on its intended use. These types of lights include runway threshold lights, runway end identifiers, and in-pavement lights for runways and taxiways. Similarly, airfield signs must meet FAA specs for visibility and environmental durability.

As one of only two test labs accepted by the FAA to issue airfield lighting equipment certifications, Brad and his team are critical links in aviation safety.

For more information, contact Elite to ask about photometry lab capability and put Brad’s team’s experience and expertise to work for you.