Assertion: aircraft's engine | /r/HasProperty | developed
Facets:
Source sentences:
text: The introduction of the internal combustion engine at the end of the 19th century became the watershed for helicopter development as engines began to be developed and produced that were powerful enough to allow for helicopters able to lift humans.[citation needed]
text: When the compact, flat engine was developed, the helicopter industry found a lighter-weight powerplant easily adapted to small helicopters, although radial engines continued to be used for larger helicopters.[citation needed]
text: Even so, heavier payloads were obviously in the offing; more powerful engines had to be developed.