Boeing has announced that it’s Hummingbird drone has has successfully changed the final drive ratio of its transmission in flight, which will allow two rotor speed settings, one being about ½ of the other.

It turns out that slower rotational speeds work better at hover and low speeds, but limit forward speed, because of retreating blade stall, and most helos therefore operate as a compromise. (The A160T set its record in slow rotor mode).

All in all, this program is moving along at a blindingly fast pace, with US special forces already making purchases of the diminutive helicopter.

Boeing’s PR is here.