Bell XH-40 US ArmyThese are 1 72 scale decals for the Bell XH 40, the prototype that started it all the direct ancestor of the most produced military helicopter in history. The XH 40 was Bell's response to the U. S. Army's 1955 requirement for a turbine powered utility helicopter to replace the piston engined designs then in service. First flown on October 22, 1956, the XH 40 demonstrated the transformative potential of the Lycoming T53 turboshaft engine lighter, more