Tuesday, April 13, 2021

The Quadshot: An aerobatic blend of an R/C helicopter and airplane

Santa Cruz, CA: Piotr Esden-Tempski, Chris Forrette, Jeff Gibboney and Pranay Sinha are excited to announce the Quadshot, a remote-controlled aircraft that melds advanced Open-Source hardware and software with a unique airframe design.

“The Quadshot represents a breakthrough in the area of remote-controlled aircraft in that it can both fly forward like an airplane and hover like a helicopter – but without the usual complicated, expensive, and fragile moving parts,” says Pranay Sinha, the aerospace engineer responsible for aerodynamics and controls.

The Quadshot differs from a typical remote-controlled airplane or helicopter in that it contains an advanced flight computer system that assists in stabilizing the aircraft in flight. The system, dubbed “Lisa,” is equipped with a sensor suite called an Inertial Measurement Unit (IMU), which includes solid-state accelerometers and gyroscopes that measure the aircraft’s orientation and rotation rates in three dimensions.

Hundreds of times per second, Lisa’s STM32 microprocessor combines sensor data from the IMU with the pilot’s commands to determine the correct speed for each of its four motors. This allows the pilot to command the Quadshot to hover like a helicopter, fly slowly and steadily like a trainer airplane, or unlock full control for aerobatics – all at the flip of a switch.

Thanks to the computer assistance, the Quadshot does not need a traditional tail for stabilization. It consists of a one-meter (39 inch) wing and four pylons – two above the wing and two below. Each pylon supports an individually-controlled brushless motor and propeller, which work with two elevons driven by servos to control the aircraft.

“I wanted the Quadshot airframe to be lightweight, yet durable,” says Jeff Gibboney, the mechanical engineer that designed the airframe. The wing is made from expanded polypropylene (EPP) foam, with a carbon-fiber spar for strength. The pylons are plastic-reinforced EPP foam which act as landing gear, motor mounts, and tailfins.

Inset into the wing’s center is an electronics enclosure, which houses the flight computer and IMU, R/C receivers, lithium-polymer battery, and a standard threaded mount suitable for carrying a small camera slung under the wing. There are also mounts for an optional wireless communication module, which can stream flight data between the Quadshot and a computer on the ground.

“The Quadshot appeals to me as an RC modeler because it solves many of the problems airplanes typically have when designed with vertical takeoff and landing in mind, such as having to transition into forward flight and how to easily control it,” says Chris Forrette, the Quadshot test pilot and prototype builder. “It is also super responsive thanks to its differential thrust, more so than many aerobatic planes of the same size that I have flown. Besides, most people crash helicopters while learning, where as the Quadshot has a really easy learning curve.”

The Quadshot project embraces the Open-Source philosophy: the flight computer and IMU electronics are Open-Hardware, and the flight software is based on the Open-Source Paparazzi project. “We really encourage people to experiment with and hack their Quadshots – we can’t wait to see all the things people do with them!” says Piotr Esden-Tempski, the electrical and software engineer responsible for the Quadshot’s avionics and embedded software.

The Quadshot developers have built several working prototypes, and are raising funds on Kickstarter to allow them to get into production. Pledging $300 secures a pre-order for a complete ready-to-fly model, which has an anticipated retail price of $400. There are also kits and other models available for pledges ranging from $50 to $1500.

Gary Mortimer
Gary Mortimer
Founder and Editor of sUAS News | Gary Mortimer has been a commercial balloon pilot for 25 years and also flies full-size helicopters. Prior to that, he made tea and coffee in air traffic control towers across the UK as a member of the Royal Air Force.