The H-21 had winterization features permitting operation at temperatures as low as −65 °F (−54 °C), and could be routinely maintained in severe cold weather environments.
H-21 memiliki fitur winterization memungkinkan operasi pada temperatur serendah -65 °F (-54 °C), dan dapat dipertahankan secara rutin di lingkungan cuaca dingin yang parah.