Assertion: zeppelin's airship | /r/HasProperty | held at low altitude
Facets:
value: by dynamic downforce
type: CAUSE
Source sentences:
text: At this point the airship was flying light due to the heat of the sun having caused the hydrogen to expand, and was being held at a low altitude by dynamic downforce generated by flying in a nose-down attitude: with the loss of the power of one engine, it rose to an altitude of 820 m (2,690 ft), venting gas from the relief valves as it did so.