引用・参考資料等 https://airandspace.si.edu/collection-objects/helmet-flying-protective-type-p-1a-united-states-air-force/nasm_A19800071000https://cfhelmets.com/wp-content/uploads/2025/03/A_History_of_US_Aircrew_Flight_Helmets_and_collecting_flightgear.pdf
http://www.nicovideo.jp/watch/sm45669424
