When just applying an engine to an aircraft (here called "bothEngines") without a nacelle, TiGL-opens an error dialog box in the GUI:

After clicking on "close", TiGL proceeds and shows the rest of the geometry - but from my perspective it should be fine to have an aircraft with engine but without nacelle (e.g. engine buried in the fuselage).
When just applying an engine to an aircraft (here called "bothEngines") without a nacelle, TiGL-opens an error dialog box in the GUI:

After clicking on "close", TiGL proceeds and shows the rest of the geometry - but from my perspective it should be fine to have an aircraft with engine but without nacelle (e.g. engine buried in the fuselage).