John Schtroumpf
Posting as a curiosity, I saw this video posted on a German woodworking site:

https://www.youtube.com/watch?v=c0N5pV8N1H0&app=desktop

It is an older film showing the action of a plane blade (good and bad). Around 4:15 the action of the Doppelhobel (double iron) is shown.

Edit to add:

The film shows:

Plane with the grain, against the grain causes tear out.
Close the mouth on a single iron plane.
A close set chip breaker reduces tear out.
Open the mouth on a double iron plane to prevent clogging.