Halos

Interesting phenomenon.

They might perhaps be bare-metal blades in zero-thrust condition i.e. essentially edge on to the airflow so they could run the engines up without jumping the chocks?

Propeller companies were, by 1945, producing propellers capable of going into reverse thrust to shorten the landing roll of large aircraft. This aircraft could be fitted with those with the prop pitch lever not set fully to reverse to enable high-rpm runs without thrust.

They also appear to be Curtiss props, which were electrically operated and which were used on the B-50.

Anon.