Assertion: feather's velocity | /r/HasProperty | low
Facets:
value: by careful control of pitch
type: CAUSE
value: to allow
type: PURPOSE
Source sentences:
text: The maximum relative velocity is kept as low as possible by careful control of pitch to allow the blades to have large helix angles; thin blade sections are used and the blades are swept back in a scimitar shape (Scimitar propeller); a large number of blades are used to reduce work per blade and so circulation strength; contra-rotation is used.