The basic concept behind tiltrotor aircraft is rather ingenious in its simplicity. Rather than a single, stationary rotor, as you’d see on a typical helicopter, tiltrotors use a pair of rotors mounted on both sides of the vehicle, both of which are placed on a swiveling joint. While on the ground and taking off, the rotors are positioned vertically to generate the necessary upward lift.
Once the vehicle is safely in the sky and moving forward, the rotors then swivel down to their horizontal configuration, switching from vertical lift to horizontal torque. In other words, the rotors tilt — it’s all right there in the name. Think of it as a helicopter transforming into a biplane, shifting its energy generation from pushing it off the ground to propelling it forward.
By carefully adjusting the tilting rotors, operators of this kind of vehicle could use it for all kinds of practical purposes, including transporting cargo, search-and-rescue, and troop transport. That’s one of the reasons it’s so attractive to military organizations — if all aircraft could land without the use of a runway, it would greatly increase operational possibilities and save space.