hollow steel propeller

例句：

1. 1. The new aircraft uses a hollow steel propeller to reduce weight and increase efficiency.
   新型飞机使用空心钢螺旋桨以减轻重量并提高效率。
2. 2.The helicopter's main rotor is made of hollow steel, which makes it more durable and efficient.
   直升机的主旋翼由空心钢制成，使其更耐用且效率更高。
3. 3.The hollow steel propeller was designed to improve the aircraft's performance in low-altitude flight.
   空心钢螺旋桨的设计旨在提高飞机在低空飞行时的性能。