Overview

The Triad is an experimental Vertical Take-Off and Landing (VTOL) aircraft. In simple terms, this means it can hover like a helicopter and also transition into forward flight like a plane. Control is achieved with three thrust-vectoring flaps arranged around a central thrust axis. These flaps redirect the thrust to control pitch, roll, and yaw. In forward flight, the Triad uses three symmetrically placed wings to generate lift. This configuration ensures balanced lift across the roll axis at all times regardless of the aircraft’s orientation. As a result, the aircraft can sustain flight along any point along the thrust line. These sets of three, the flaps and wings, are what give the project its name: Triad, meaning a group of three elements. See below for a flight demonstration.

Flight Demonstration

Design

The Triad is not a forgiving platform. Still, the system began to work after I learned a few key lessons. One challenge was that I developed everything in parallel—airframe, controls, electronics, software and tuning—without knowing if any individual part was fully functional. Most of the time, I could only tell which parts weren’t behaving as expected; I was never completely sure what was working. The following sections outline the major challenges I encountered and what I learned throughout the project.

With the Triad, my goal was to build a kinematically efficient VTOL aircraft. I wanted every motor and actuator to contribute meaningfully in both hover and forward flight, avoiding idle components in either mode. The aircraft was designed so that each degree of freedom—pitch, roll, yaw, and linear movement along the thrust axis—would have a corresponding actuator. This reduces the cost and weight of the finished aircraft. I also wanted the Triad to support omni-axis flight around its thrust vector—flying upright, inverted, sideways, or in any orientation in between.

Control mixing was one of the first challenges to solve. In this configuration, only the central motor responds directly to linear input. All other controls are handled via a custom mixing matrix, which maps flight inputs (pitch, roll, yaw) to actuator outputs. I wrote custom scripts to define and tune these mappings, allowing the Triad to achieve stable hover and controlled transitions. Unlike many other VTOL platforms, like the quad plane, there is no transition state. This means the mixing script does not change in forward flight or hover, only the angle of attack changes to achieve a different flight format.

Balancing stability, control authority, and simplicity proved especially difficult for a first-time layout. Multiple iterations were required to find a geometry that supported both hover and forward flight without excessive structural complexity.

Correctly sizing the wings and flaps was essential to building a flyable aircraft. I tested a variety of configurations in simulation and in real-world flight to find a balance between lift, responsiveness, and stability.

In-flight vibration was the most persistent issue. As I reduced weight and increased control-loop tuning rates, the airframe became more sensitive to mechanical vibration and feedback-loop instability. By version 3.3, I introduced foam board supports to stiffen the structure. In version 4.0, I redesigned the frame with carbon fiber tubes for increased stiffness and reduced flex. Other improvements included:

Early versions of the Triad (up to v3.3) failed to maintain heading in forward flight. The aircraft would pitch forward or backward but wouldn’t stay on course. Upon reviewing flight footage, I realized the aircraft was weathervaning—rotating to align with the direction of airflow, either from wind or its own motion. The root issue was that the center of pressure did not align with the center of gravity. To correct this, I modeled one-third of the aircraft (a wing + flap section) in CAD and calculated the center of gravity of the resulting 2D shape. This gave a close approximation of the aircraft’s center of pressure, which I then aligned with the CG along the Z-axis.

If I were to redesign the Triad, I would keep the core configuration but improve the airframe’s stiffness and efficiency. Here are a few areas of potential improvement: