“平稳地”的英语可以翻译为：on an even keel，placidly，reposefully ...

缓慢、平稳地加油。Add the oil in a slow, steady stream.他拉起机头,平稳地降落下来.He brought the aircraft's nose up and made a perfect landing.这辆汽车平稳地以每小时100公里的速度行驶.The car was cruising along at 100 kilometres an hour....