Assertion: airfoil's lift | /r/HasProperty | lost
Facets:
value: during the down stroke
type: TEMPORAL
Source sentences:
text: This is because the inherent mechanism of flapping consists of phases when lift and thrust are lost (during the down stroke) and the thrust generated is not constant over the flapping cycle.
text: Lift is lost due to shock-induced flow separation on the upper surface near the trailing edge .