Caption reads: "...FIRST SUCCESSFUL FLIGHT OF THE TWIN-TURBINE...CHINOOK...."
U.S. Department of the Army
1962
<a rel="nofollow" class="external text" href="https://babel.hathitrust.org/cgi/pt?id=umn.31951d00831253j;view=1up;seq=594">Annual Report of the Secretary of the Army for Fiscal Year 1962</a>, Page 148, Figure 14