Nick Chitterdon, 46, landed next to a golf course near Polzeath in October 2015, and escaped uninjured.
He was the only person on the Aeronca C3, a light plane built in the US in 1936.
The Air Accidents Investigation Branch (AAIB) said problems with part of that model were first recognised in 1939.
The pilot, who was unnamed in the report, made a distress call to Newquay Airport before finding a landing strip.
There was "a loud bang" and then "the pilot saw the propeller falling away", the AAIB report said.
Examination of the propeller - which was recovered from a building site - found that the detachment was caused by a fatigue crack on the mechanical part on which the propeller was mounted.
The AAIB said the issue with the crankshaft of this type of aircraft was noted almost 80 years ago, but had not resulted in any mandatory regulations.
The Light Aircraft Association has issued information leaflets to the known owners of planes with this engine, requiring them to inspect the mechanics involved with the propeller before they can fly again.
A pilot was forced to make an emergency landing when a propeller fell from his 80-year-old plane at 2,500ft (762m), an accident report has found.