Originally Posted by Lodesman
Are you talking about Kort nozzles? They are used to vector the thrust in a specific direction ...
A Kort nozzle is simply a shrouded, or ducted propeller
assembly; which may be either fixed
, or vectored (pivoting) steering
Kort’s breakthrough (1930s) was to shape the shroud
like an aerofoil rather than a simple ring.
➥ Kort Propulsion Co Ltd
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"