scope:

Purpose

The purpose of this 'Allied Environmental Conditions and Test Publication' is to guide project managers, programme engineers, and environmental engineering specialists in the planning and implementation of environmental tasks. An important function of AECTP-100 is to provide guidance to project managers on the application of AECTP-200 to 250 'Environmental Conditions', AECTP-300 'Climatic Environmental Tests', AECTP-400 'Mechanical Environmental Tests' and AECTP-500 'Electrical / Electromagnetic Environmental Tests.'

Application

The guidance provided in AECTP-100 is applicable to joint NATO defence materiel projects. It may also be applied to defence materiel (multi-) national projects and is compatible with NATO publication AAP-20, 'NATO Programme Management Framework (NATO Life Cycle Model).' AECTP-100 should be useful to environmental engineering specialists during the procurement cycle.

Limitations

There are two ways of subjecting an item to environmental conditions. These are laboratory testing and field exposure. This document discusses laboratory testing and is not intended to address field exposure. For details on field exposure refer to the appropriate national documentation. The following section discusses the relative merits and issues associated with each approach.

Laboratory testing (e.g. climatic chambers or electrical shakers) should be fully and creatively exploited, to determine if any basic problems exist, before testing is conducted in field environments, unless such testing is impractical. Testing in a controlled environment such as a laboratory is economical, reduces test times and serves as a screening procedure to identify design defects early in the acquisition process. Laboratory testing will:

a. Be used to determine if a system satisfies the performance requirements as stated in the requirements documents or system specifications.

b. Provide data for assessing the risk associated with not conducting testing in the natural environment.

c. Limit the need to expose personnel to hazardous materiel prior to qualification.

Systems that fail simulated environmental testing should not be subjected to field exposure until causes for the failure(s) are resolved and corrections have been applied. Laboratory testing has the advantage that it allows the simulation to be undertaken in defined and controlled conditions. It is also useful for gathering data on the difference made by mitigation factors, but cannot wholly simulate real conditions.

Laboratory equipment like climatic chambers and shakers do not properly simulate the actual field environment because they cannot concurrently reproduce all of the synergistic effects associated with that natural environment. However it is possible to test with combined environments to more closely replicate the naturally occurring environment.

Field exposure should not commence on an item until the risks from the materiel have been fully identified, corrected and verified through the use of laboratory testing, on either the item or its sub-components. Field exposure may be more convenient for large and awkward objects, and may be essential where the object interacts significantly with the (combined) conditions of the environment. Field exposure reflects real situations but can only be 'snapshots' of the final environment. Seasonality and the limited duration of exposure must be considered when determining the total affect on materiel. Field exposure trials should be conducted when the environment is expected to be at its most extreme. Caution is advised in the interpretation of data obtained during natural environment testing as there is no way to ensure that the test item encounters events such as storms, local differences or climatic extremes. Field exposure trials will:

a. Allow the item to be incorporated into its full system for testing.

b. Ensure that all personnel and the item are in their correct relative positions; consequently, field trials can be expected to expose materiel to relevant failure mechanisms.

c. Allow for measurement of the environment to validate and/or update appropriate laboratory test severities.

AECTP-100 through 600 were not developed specifically to cover the following applications, but in some cases they may be applied:

Weapon effects other than electromagnetic pulse (EMP);

Munitions safety tests;

Suitability of clothing or fabric items intended for military use;

Environmental stress screening (ESS) methods and procedures.

The test methods as mentioned in AECTP 300, 400 and 500 are also applicable to materiel in its packaged condition or to assess the durability of the packaging itself. These tests however do not assess the way the packaging protects the materiel. Refer to Stanag 4340 [ref. 1] for assessing compliance of the packaging against NATO standard requirements. Refer to Stanag 4434 [ref. 2] for packaged materiel that can be susceptible to electro static discharge.

Test Instrumentation

Ensure the sensors, instrumentation used for measuring environmental conditions and recording responses of test items are suitable for the intended circumstances. The various test conditions may unintentionally affect the accuracy or reliability of the test. For example;

a. Accelerometers used in a combined high temperature/vibration test could give erroneous readings if not designed for high temperature use;

b. A large specimen in/on a relative small test apparatus will affect the accuracy of the controlled parameters within the required tolerances;

c. Direct radiant heat or excessive airflow can give an unrealistic response of a test item during a climatic test.

The ability of test facilities to simulate environmental conditions within the specified tolerances and the accuracy of the instrumentation shall be verified to the satisfaction of the procuring activity. All instruments and test equipment used in conducting the tests must:

a. be calibrated to laboratory standards, traceable to the National Standards via primary standards;

b. meet the calibration interval guidelines of ANSI/NCSL Z540 [ref. 3], ISO 10012 [ref. 4] or equivalent National Standards;

c. have an accuracy at least equal to 1/3 the tolerance of the variable to be measured. In the event of conflict between this accuracy and guidelines for accuracy in any one of the test methods of this standard, the latter governs.

For critical tests, it is recommended to verify the accuracy of instruments and test equipment prior to and following the test.

Test interruption

Test interruptions can result from multiple situations. The following items are possible causes for test interruptions. More specifics and recommended paths forward can be found in each of the test methods as presented in AECTP 300 and 400.

a. Interruption due to laboratory equipment malfunction.

b. Interruption due to test item operation failure.

c. Interruption due to a scheduled event.

d. Interruption due to exceeding test tolerances.