Hybrid Power Could Help Drone Delivery Take Off

Google, Amazon, and DHL are working on drones that could someday deliver packages straight to your doorstep. Unfortunately, most drones would struggle to carry something as heavy as a textbook more than a dozen kilometers on battery power.

A new hybrid gas-electric aircraft could make drone delivery more practical. Developed by a startup called Top Flight Technologies, the six-rotor drone can fly for more than two-and-a-half hours—or 160 kilometers—carrying a payload weighing nine kilograms.

The aircraft’s range is many times that of any quadcopter on the market—the most popular type of drone for its maneuverability. Almost all quadcopters run on batteries, and can fly for only about 40 minutes between charges with a payload weighing just a couple of kilograms. The new drone can also fly more than twice as far as a radio-controlled, gasoline-powered helicopter of similar size.

Top Flight’s technology is distinct from what’s being developed by Google. The Google aircraft takes off vertically but then reorients itself and flies like an airplane. But the company isn’t saying much about how far the prototype drones can travel or how much they can carry. And demonstrations of the aircraft in Australia involved delivering relatively lightweight packages, such as dog treats, vaccines, and a first-aid kit.

The efficiency of Top Flight’s drone is made possible by using batteries to supplement the gasoline engine. Power can come from the batteries, from a gasoline generator, or from both at once. And because the gasoline engine doesn’t have to supply all of the power, it’s possible to use a much smaller and more efficient one. Unlike a hybrid car, however, Top Flight’s drone doesn’t capture energy from braking.

Top Flight isn’t the first to try hybrid technology with drones. The U.S. Army and Air Force, together with an Oregon-based company called Northwest UAV, have experimented with hybrid airplanes. A representative of Northwest UAV says the company is also working on a hybrid system for use with multi-rotor craft such as quadcopters.

Top Flight was founded and is advised by researchers from Draper Laboratories and MIT. It has selected a relatively simple type of hybrid engine, known as a series hybrid, in which there is no mechanical connection between the gasoline engine and the rotors. The engine serves only as a generator that charges the battery or supplies electricity to the electric motors. Long Phan, cofounder and CEO of Top Flight, says “future vehicles will fly well over three hours—we already have the new engine to do it.” The company is also developing object-avoidance technology and other safety features—which likely will be required for drones, at least in the United States (see “FAA’s Caution Not the Only Obstacle for Drone Delivery”). Phan says the company hopes to start selling its hybrid drones by the end of the year.