Hermeus has completed the ground portion of the flight test campaign for Quarterhorse Mk 1, including the successful integrated testing of all vehicle subsystems as well as the software and hardware in Hermeus’ custom Flight Deck from which Quarterhorse will be remotely piloted.

This comprehensive ground test campaign at Edwards Air Force Base was completed in just 21 days.

"Hermeus is redefining the pace at which aircraft can be developed, tested, and fielded,” says AJ Piplica, co-founder and CEO of Hermeus. “With Quarterhorse Mk 1, we’ve proven our ability to design and build a clean-sheet aircraft in just 204 days. Now, through this test campaign, we are demonstrating how rapidly and rigorously our team can validate the aircraft for flight – safely and comprehensively."

Ground testing culminated in 130-knot (150 mph) taxi tests with full afterburner on Edwards' iconic dry lakebed, offering a valuable opportunity to validate aerodynamic model assumptions, assess the aircraft's directional control, and evaluate the performance of control surfaces, among other things.

Prior to reaching these taxi speeds, end-to-end testing between the Flight Deck and the aircraft validated redundant RF links and addressed potential electromagnetic interference (EMI) problems.

The team also conducted extensive human-machine interface (HMI) testing to optimise pilot inputs for Quarterhorse. Ensuring pilots receive the precise information needed for effective remote operation presented a unique challenge, requiring meticulous refinement of inputs to enhance situational awareness and decision-making.

With ground testing complete, Hermeus is finalising the administrative efforts to obtain flight approval from the U.S. Air Force 412th Test Wing and the FAA.

The first flight of Quarterhorse will mark a pivotal milestone for Hermeus and offer insights to inform the development of future aircraft. Quarterhorse Mk 1 was purpose-built for a single mission: takeoff and landing. Its high-speed aerodynamic design introduces unique challenges, including a low aspect ratio wing, high wing loading, and a low thrust-to-weight ratio. The data collected from this initial flight, simply by achieving liftoff and sustaining flight, will provide critical learnings.

Key areas of focus for Hermeus include evaluating the effectiveness of control surfaces in flight, assessing performance and handling at high angles of attack, testing manoeuverability under high wing loading, and validating control gains and filters within the flight software.

“One year ago, we hadn’t yet completed testing of Quarterhorse Mk 0, and this aircraft, Mk 1, was just a single structural frame,” says Skyler Shuford, Co-Founder and President of Hermeus. “While this timeline is already unprecedented in modern aerospace development, we also discovered many places where our execution was extremely slow, which gives me and the team confidence that we can go even faster and take on more scope and challenges to stay on pace for developing roughly one new aircraft per year.”

The next iteration of Quarterhorse, Mk 2, is actively being built in Hermeus’ Atlanta factory. This aircraft features a much larger engine, the Pratt & Whitney F100, and will fly at supersonic speeds.