A self-taught engineer, he joined Douglas Aircraft as a draftsman in 1926, but was laid off within a year.

In 1962 he joined General Dynamics as Corporate Vice President of Engineering.

The airplane designer Burt Rutan listed Heinemann as among the leading pioneers in aviation who had inspired him to become an aerospace engineer.

[citation needed] During his long career at Douglas, Heinemann designed more than 20 combat aircraft, primarily for the U.S. Navy, including many that became legends in aviation history.

Due to the 1929 recession only a small number were sold before the company ceased trading in 1933.