[3] An embargo enforced by the First World War made access to goods problematic, and the firm had to improvise.
They changed production to rifle flasks, while also delivering lumber to companies that produced plane propellers.
Hartzell started doing this, and received an order from the US Navy for propellers for Liberty engines, the most common plane motor of the time.
However, Hartzell found it problematic to compete against his own customers, and to combine production of propellers with aircraft.
At the same time, the company received orders from the Navy for propellers for the airships Macon and Shenandoah.