1.1 Purpose
Use low pressure (altitude) tests to determine if materiel can withstand and/or operate in a low pressure environment and/or withstand rapid pressure changes.
1.2 Application
Use this method to evaluate materiel likely to be:
- a. stored and/or operated at high ground elevation sites.
- b. transported or operated in pressurized or unpressurized areas of aircraft (also consider Method 520.5 for actively-powered materiel operated at altitude).
- c. exposed to a rapid or explosive decompression and, if so, to determine if its failure will damage the aircraft or present a hazard to personnel.
- d. carried externally on aircraft.
1.3 Limitations
This Method is not intended to be used to test materiel to be installed or operated in space vehicles, aircraft or missiles that fly at altitudes above 21,300 m (70,000 ft). Recommend the test be to the maximum altitude (minimum pressure) normally reached by the appropriate mode of transportation.
Procedure IV is not intended to be used for materiel transported in a cargo bay. For example, analysis for a C-5 aircraft indicates that to go from a cabin altitude of 2438 m (8,000 ft) to an ambient altitude of 12192m (40,000 ft) in 1 second would require a hole of approximately 33.4 m² (360 ft²). Instantaneous creation of a hole that large in the side of the airplane would be catastrophic to the airplane. Please note that the 33.4 m² (360 ft²) hole is for a 1-second depressurization. To depressurize in one tenth of a second would require a hole ten times as large.