Use Environment per MIL HDBK-217F (Naval):
Naval, Sheltered: Includes sheltered or below deck conditions on surface ships and equipment installed in submarines.
Naval, Unsheltered: Unprotected surface shipborne equipment exposed to weather conditions and equipment immersed in salt water. Includes sonar equipment and equipment installed on hydrofoil vessels.
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Ground Environments, Airborne Environments
Back to the Mean Time Between Failure Definition, or the Military Specifications page.
MIL-STD-1399 Specification
Electronic Key Words: Failure Mode Analysis, Reliability Prediction, MIL-HDBK-217, Ship, Sea, Navy, Bellcore / Telcordia, IEC 62380
