Pi?s?cki H-21 w?s ?n? ?? th? ???l? t?n??m-??t?? h?lic??t??s th?t s?w wi?? ?s?, incl??in? in c?m??t. O?i?in?ll? ??v?l???? in ???l? 1950s ??? A?ctic ??sc??, m??i?ic?ti?ns ?? this m?chin? w??? l?t?? ?xt?nsiv?l? ?m?l???? ?? th? US milit???, incl??in? in Vi?tn?m. H-21 w?s ?ls? ?????t?? ?? s?v???l ?th?? c??nt?i?s, ?m?n? th?m F??nc?, which ??t it t? ?s? in th? Al???i?n W??.

In l?t? 1940s ?n? ???l? 1950s Pi?s?cki H?lic??t?? C??????ti?n ??v?l???? s?v???l t?n??m-??t?? h?lic??t?? ??si?ns. Th? ?i?st ?? th?m, HRP-1 R?sc???, h?? ? ch???ct??istic ??w??? sl?nt?? ??t s?cti?n, ??ttin? th? ???? ??t?? ?ss?m?l? hi?h?? th?n th? ???? ?n?. S?ch c?n?i????ti?n ?ns???? ??????t? v??tic?l cl????nc? ??tw??n th? int??m?shin? ???? ?n? ??t ??t?? ?ss?m?li?s.

It ???n?? th? HRP-1, ?s w?ll ?s its simil??l? sh???? s?cc?ss??, H-21 W??kh??s?/Sh?wn??, th? “?l?in? ??n?n?” nickn?m?. Th? H-21, which m??? its ?i?st ?li?ht ?n A??il 11, 1952, ??c?m? th? m?st ?????c?? Pi?s?cki h?lic??t?? (?v?? 700). F?? its tіm? th? H-21 w?s ? ????, ??c?ntl? ??????min? m?chin?. In 1953 Ai? F??c? ?il?ts ?l?in? it s?t ?ltit??? (22,100 ?t) ?n? s???? (146 m?h) ??c???s. An? in 1956 A?m? ?vi?t??s ?l?w ?n H-21 n?n-st?? ?c??ss th? U.S. m?inl?n?.

Th? Ai? F??c? initi?ll? ??????? 32 H-21A W??kh??s? h?lic??t??s ??? s???ch ?n? ??sc?? ?????ti?ns. Th?? w??? ???i???? with ??sc?? h?ists ?n? h??v? ??t? h??tin? ?n? w??? int?n??? ??? ?????ti?n in th? A?tic ?mi? t?m????t???s ?s l?w ?s -65 °F. Th? USAF ?ls? l?t?? ??????? H-21B v??i?nt ??? t???? t??ns???t. It c??l? c???? 22 ??ll? ???i???? in??nt??m?n ?? 12 st??tch??s ?cc?m??ni?? ?? tw? m??ic?l ?tt?n??nts. A l???? ???t ?? H-21A ?n? H-21B h?lic??t??s w??? ?s?? t? s??vic? Dist?nt E??l? W??nin? (DEW) ????? sit?s sc?tt???? ???m th? Al??ti?n Isl?n?s t? Ic?l?n?.

Alth???h th? v??i?nt ???c???? ?? th? US A?m? st??tin? 1954 w?s c?ll?? H-21C Sh?wn?? (??th?? th?n W??kh??s?), it ??c?m?, in ??ct, A?m?’s w??kh??s? ??? th? n?xt ??c???. It w?s, in ???tic?l??, ?l?wn in s?????t ?? ???l? US ?????ti?ns in Vi?tn?m in th? ?i?st h?l? ?? 1960s. H?w?v??, in Vi?tn?m’s h?t clim?t? it ?i?n’t ??????m ?s ??illi?ntl? ?s in Al?sk?. A?t?? m??? m????n UH-1 “H???” w?s int????c?? int? s??vic?, H-21 w?s ?h?s?? ??t ?? 1965. UH-1 c??l? n?t ??ll? s??stit?t? H-21, th???h.

Whil? Sh?wn?? c??l? li?t ? wh?l? in??nt?? s????, H??? c???i?? j?st s?m? 4-5 t????s. Th?t ??l? w?s ?ill?? ???in ?nl? ? c???l? ?? ????s l?t??, ?nc? th? A?m? st??t?? ??c?ivin? CH-47 Chin??k h?lic??t??s. CH-47, ?s w?ll ?s H-46 S?? Kni?ht, w??? ?ls? t?n??m ??t?? h?lic??t??s ??v?l???? ?? B??in? V??t?l, which w?s th? n?w n?m? ?? Pi?s?cki H?lic??t?? C??????ti?n. B?ilt ???n th? ?x???i?nc? ???vi??? ?? th? H-21 ?n? its ?????c?ss??s, Chin??k ?n? S?? Kni?ht ??m?in?? US milit???’s t??ns???t m?inst??s th????h??t s?v???l ??ll?wіп? ??c???s.