Assertion: kite's type | /r/HasProperty | towed behind german u-boats
Facets:
value: as an aerial observation platform
type: PURPOSE
Source sentences:
text: Research into rotor kites or gyrokites was deepened during World War II, and one type in particular, the Focke Achgelis Fa 330, reached active service, being towed behind German U-boats as an aerial observation platform.