Description

a. Procedure I – Rain and Blowing Rain: The rainfall rate used in Procedure I may be tailored to the
anticipated deployment locale and duration. Although various rainfall intensities have been measured in
areas of heavy rainfall, recommend a minimum rate of 1.7 mm/min (4 in/hr) since it is not an uncommon
occurrence, and would provide a reasonable degree of confidence in the materiel. MIL-HDBK-310
(paragraph 6.1, reference a) contains further information. During the pretest set-up, rain fall measurements
should be taken at a minimum of 5 random locations. The average of these rain rate measurements should
be within 10% or +/- 0.1 mm/min (0.25 in/hr) of the specified value, whichever is less. To ensure a uniform
distribution of simulated rain on the test item each measurement should be within 25% or +/- 0.2 mm/min
(0.5 in/hr) of the specified rain rate whichever is less.
b. Procedure II – Exaggerated: This procedure uses (as a guideline) a 276 kPa (40 psig) nozzle pressure with a
flow rate of 20.8 L/min (5.5 gal/min) that should produce water droplets traveling at approximately 64 km/h
(40 mph) when using a nozzle such as specified in paragraph 4.1.2.
c. Procedure III – Drip: The drip test has a requirement for a volume of water greater than 280 L/m2/hr
(7 gal/ft2/hr) dripping through a pre-determined hole pattern. An alternative requirement is for items exposed
only to 140 L/m2/hr (3.5 gal/ ft2/hr): Appropriately reduce the drip rate as long as the duration of the test is
extended to 30 minutes to ensure the equivalent volume of water falls on the test item