flight engineer vs aircrewman

flight engineer and aircrewman both are nouns.

Word	Noun	Adjective	Verb	Adverb
flight engineer	Yes	No	No	No
aircrewman	Yes	No	No	No

As nouns, aircrewman is a hypernym of flight engineer; that is, aircrewman is a word with a broader meaning than flight engineer:

flight engineer: the flight crewman responsible for mechanical operation while in flight
aircrewman: a member of an aircrew

flight engineer (noun)	aircrewman (noun)
the flight crewman responsible for mechanical operation while in flight	a member of an aircrew