Icing Testing

Icing testing is carried out in most cases in a climate chamber and tests the function of a device in situations where ice or frost may occur.  This can happen in situations when temperature, altitude, and humidity vary rapidly.

EMCC's experts can conduct icing testing in accordance with the RTCA DO-160 and MIL-STD 810.

According to the RTCA DO-160 standard, the equipment can be divided into three categories:

  • A: This test is relevant to equipment placed externally or in non-temperature-controlled regions of the aircraft, where ice or frost may form as a result of condensation when the equipment is cold soaked to extremely low temperatures and then exposed to humid air at temperatures above freezing.

    B. This test applies to equipment with moving elements where ice development might prohibit or impede movement, or where forces caused by ice growth could harm structural or functional components. Condensation, freezing, melting, and/or re-freezing can cause ice to develop in or on equipment, which can lead to water or ice accumulation inside non-sealed enclosures.

    C: This test is relevant to objects placed externally or in non-temperature-controlled places where there is a possibility of free water collecting and freezing on the equipment's cold surfaces. The purpose of the test is to see how a representative thickness of ice affects the equipment's performance or to establish the maximum thickness that can be tolerated before de-icing is required. The applicable equipment performance standards describe the needed ice thickness and distribution, as well as any requirements for progressive ice build-up.

Icing Testing

According to the MIL-STD 810 standard, icing testing is performed to evaluate the effect of icing on the operational capability of material.

This procedure can be divided into 9 steps:

Step 1. Stabilize the test item temperature at 0°C (-0/+2°C (32°F (-0/+4°F)).

Step 2. Deliver a uniform, pre-cooled water spray for 1 hour to allow water penetration into the test item crevices/openings (although a water temperature of 0 to 3°C (32 to 37°F) is ideal, a water temperature of 5°C (41°F) and a water delivery rate of 25 mm/h (1 in/h) has proven satisfactory).

Step 3. Adjust the chamber air temperature to -10°C (14°F) or as specified and maintain the water spray rate until the required thickness of ice has accumulated on the appropriate surfaces. Wind or a side spray may be used to assist accumulation of ice on the sides of the test item.

NOTE: If it is difficult to produce a satisfactory layer of glaze ice, vary one or more of the parameters as necessary, i.e., water or test item temperature, spray rate, distance between the nozzles and the test item, etc. Generally an air temperature no warmer than-2 C (28°F) is more likely to produce glaze ice.

NOTE: It may be easier to stop spraying during the temperature reduction to facilitate temperature adjustment and to minimize frosting of test chamber refrigeration coils.

Step 4. Maintain the chamber air temperature for a minimum of 4 hours to allow the ice to harden. Examine for safety hazards and, if appropriate, attempt to operate the test item. Document the results (with photographs if necessary).

Step 5. If Step 4 has resulted in failure, or if the specification requires or allows ice removal, remove the ice. Limit the method of ice removal to that determined in paragraph 3.1b, e.g., built-in ice removal systems, plus expedient means that could be expected to be employed in the field. Note the effectiveness of ice removal techniques used. If the test item fails to operate as intended, follow the guidance in paragraph 4.3.2 for test item failure.

Step 6. Examine for safety hazards and, if appropriate (and possible), attempt to operate the test item at the specified low operating temperature of the materiel. If the test item fails to operate as intended, follow the guidance in paragraph 4.3.2 for test item failure.

Step 7. If required, repeat Steps 3 through 6 to produce other required thicknesses of ice.

Step 8. Stabilize the test item at standard ambient conditions and perform a post-test operational check. See paragraph 5 for analysis of results.

Step 9. Document (with photographs if necessary) the results for comparison with pretest data.

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