✔ 最佳答案
The answer depends on:
1. the weight of the heli;
2. the lift generated by the rotor.
Lift are generated by the rotors. The faster it rotates, the more lift it generates (at the same height). The higher the height, the thinner the air. It affects the power generated to rotate the rotors and the lift (In vacuum, no matter how fast the rotor rotates, there is no lift).
So the answer to your question should be:
The heli cannot fly higher when the rotors cannot produce lift more than its weight.