4.1 Test Facility
- a. The required apparatus consists of a chamber or cabinet together with auxiliary instrumentation capable of maintaining and monitoring (see Part One, paragraph 5.18) the required environmental condition(s).
- b. Record chamber pressure and, if required, temperature and/or humidity at a sufficient rate to capture data necessary for post-test analysis (see Part One, paragraph 5.18).
4.2 Controls
For standardization purposes:
- a. Altitude change rate. Unless otherwise specified (as in the explosive decompression procedure), do not use an altitude change rate in excess of 10 m/s (32.8 ft/sec.). (See paragraph 2.3.2.)
- b. Charts. When using a chart recorder, ensure charts can be read with a resolution within two percent of full scale.
4.3 Test Interruption
Test interruptions can result from two or more situations, one being from failure or malfunction of test chambers or associated test laboratory equipment. The second type of test interruption results from failure or malfunction of the test item itself during operational checks.
4.3.1 Interruption Due to Chamber Malfunction
MIL-STD-810H
METHOD 500.6
- a. General. See Part One, paragraph 5.11, of this Standard.
- b. Specific to this Method. To achieve the desired effects, subject the test item to the full duration of the low pressure test without interruption; i.e., for either overtest or undertest interruptions, restart the test from the beginning. See paragraph 4.3.2 for test item operational failure guidance.
4.3.2 Interruption Due to Test Item Operation Failure
Failure of the test item(s) to function as required during operational checks presents a situation with several possible options.
- a. The preferable option is to replace the test item with a “new” one and restart from step 1.
- b. A second option is to replace / repair the failed or non-functioning component or assembly with one that functions as intended, and restart the entire test from step 1.
NOTE: When evaluating failure interruptions, consider prior testing on the same test item and consequences of such.
4.4 Test Setup
See Part One, paragraph 5.8.
4.5 Test Execution
The following steps, alone or in combination, provide the basis for collecting necessary information concerning the materiel in a low pressure environment. Unless otherwise specified, maintain the chamber temperature at standard ambient.
4.5.1 Preparation for test
4.5.1.1 Preliminary steps
Before starting the test, review pretest information in the test plan to determine test details (e.g., procedures, test item configuration, test altitude, altitude change rate, duration, parameter levels for storage/operation, etc.).
4.5.1.2 Pretest standard ambient checkout
All test items require a pretest standard ambient checkout to provide baseline data. Conduct the checkout as follows:
- Step 1 Conduct a visual examination of the test item with special attention to stress areas, such as corners of molded cases, and document the results.
- Step 2 If required, install temperature sensors in or on the test item as described in the test plan. If required, install humidity sensor(s) in the chamber.
- Step 3 Conduct an operational checkout (Part One, paragraph 5.8.2) at standard ambient conditions (Part One, paragraph 5.1) and as described in the test plan, and record the results.
- Step 4 If the test item operates satisfactorily, proceed to the appropriate test procedure. If not, resolve the problems and repeat Steps 3 and 4. If resolution requires replacement of the item or removal of sensors in order to repair, then repeat Steps 1 through 3 above.
4.5.2 Procedure I - Storage/Air Transport
- Step 1 Adjust the test item to its storage or transport configuration and install it in the test chamber.
- Step 2 If required, stabilize the test item to the required temperature and humidity (see paragraph 2.3.1). Ensure the temperature rate of change does not exceed 3°C/min (5°F/min).
- Step 3 Adjust the chamber air pressure to that which corresponds to the required test altitude, at an altitude change rate as specified in the test plan.
- Step 4 Maintain the conditions for a minimum of one hour unless otherwise specified in the test plan.
MIL-STD-810H
METHOD 500.6
Step 5 If required, adjust the chamber air to standard ambient conditions at a rate not to exceed 3°C/min (5°F/min).
Step 6 Visually examine the test item to the extent possible and conduct an operational check. Document the results, and see paragraph 5 for further guidance.
4.5.3 Procedure II - Operation/Air Carriage
Step 1 With the test item in its operational configuration, install it in the chamber and adjust the chamber air pressure (and temperature, if required – see paragraph 2.3.1) to that which corresponds to the required operational altitude at a rate not to exceed that specified in the test plan.
Step 2 With the test item operating, maintain the conditions until the equipment reaches thermal stabilization (in accordance with Part One paragraph 5.4.1) unless otherwise specified in the test plan.
- Step 3 Conduct an operational check of the test item in accordance with the requirements documents, and document the results. If the test item does not operate satisfactorily, follow the guidance in paragraph 4.3.2 for test item failure.
Step 4 If required, adjust the chamber air to standard ambient conditions at a rate not to exceed 3°C/min (5°F/min).
- Step 5 Visually examine the test item to the extent possible and conduct an operational check. Document the results, and see paragraph 5 for further guidance.
4.5.4 Procedure III - Rapid Decompression
- Step 1 With the test item in the storage or transit configuration, install it in the chamber and adjust the chamber air pressure (and temperature if appropriate – see paragraph 2.3.1) at a rate not to exceed 3°C/min (5°F/min) or as otherwise specified in the test plan, to the cabin altitude (2,438 m (8,000 ft)) (see paragraph 2.3.1b).
Step 2 Reduce the chamber air pressure to that which corresponds to the required test altitude of 12,192 m (40,000 ft) (18.8 kPa (2.73 psi)), or as otherwise specified in the test plan for the maximum flight altitude, in not more than 15 seconds. Maintain this stabilized reduced pressure for at least 10 minutes.
- Step 3 Adjust the chamber air to standard ambient conditions using a pressure change rate not greater than 10 m/s (32.8 ft/sec.), and if required a temperature change rate not to exceed 3°C/min (5°F/min).
- Step 4 Visually examine the test item to the extent possible. Document the results. Be alert for potential safety problems (see paragraph 5).
4.5.5 Procedure IV - Explosive Decompression
- Step 1 With the test item in the configuration in which it is intended to function when installed, install it in the chamber and adjust the chamber air pressure (and temperature if required–see paragraph 2.3.1) at the rate specified in the test plan to the cabin altitude of 2,438 m (8,000 ft) (see paragraph 2.3.1b).
- Step 2 Reduce the chamber air pressure to that which corresponds to the required test altitude of 12,192 m (40,000 ft) or as otherwise specified in the test program, in not more than 0.1 seconds. Maintain this stabilized reduced pressure for at least 10 minutes.
- Step 3 Adjust the chamber air to standard ambient conditions using a pressure change rate not greater than 10 m/s (32.8 ft/sec.), and a temperature change rate not to exceed 3°C/min (5°F/min) if controlled.
- Step 4 Visually examine the test item to the extent possible. Document the results, and be alert for potential safety problems (see paragraph 5)