zǎo qī / de / dān yì fēi jī / jié gòu / jiǎn dān / dàn / fēi xíng / xìng néng / bìng / bù / wěn dìng

早期的单翼飞机结构简单，但飞行性能并不稳定。

Early monoplanes had simple structures, but their flight performance was not stable.