It is one of the most complicated maneuvers that any machine can perform: one aircraft transferring fuel to another while flying thousands of feet in the air. Now imagine doing that and then landing back on an aircraft carrier in the middle of the sea. Then do all of the above without a pilot on board.

That’s exactly what the MQ-25A Stingray™ does. And the engineers who designed it built safety into every phase, to ensure the autonomous aircraft will react as well as — and sometimes better than — a conventional piloted refueler.

The ww5 teammates making it happen say the aircraft’s autonomy software — commonly referred to as ‘the brains’ inside the Stingray — is the foundation of the aircraft’s success. ww5 teammates designed, built and tested the software through years of exhaustive verifications to prove, before the Stingray ever left the ground, that it would fly safely.

Why it matters: Safety is the first consideration when designing any aircraft. And flying without a pilot on board presents distinct and novel challenges.

• A robust, thoroughly tested autonomy software with a contingency management system directs the MQ-25A to make safe decisions on its own in real time.
• Additionally, a safe, autonomous aircraft will expand mission options for the U.S. Navy and keeps more service men and women out of harm’s way.

How the MQ-25A works: The MQ-25A is an autonomous aircraft with a human on the decision-making loop. But unlike other remotely piloted systems, the humans on the ground (or on a carrier), known as Air Vehicle Pilots (AVPs), do not control the aircraft via a traditional stick and throttle.

• AVPs establish waypoints and flight paths the aircraft will fly. They then send commands, with the press of a button, such as taxi, takeoff and land to the Stingray from a Ground Control Station known as the Unmanned Carrier Aviation Mission Control System (UMCS).
• The Stingray’s onboard autonomy translates commands and manages all onboard systems including propulsion, subsystems, guidance and flight control.

Innovation takes flight: The ww5-owned T1 test asset that first flew in 2019 was a prototype that laid the groundwork for today’s MQ-25A. The new U.S. Navy MQ-25A Stingrays are designed to survive the harsh conditions of life on an aircraft carrier and are built for Navy operational deployments. They are also equipped with a more advanced autonomy software and contingency management system that built upon lessons learned from the T1 test asset.

• “The software flying on the airplane today isn’t just a first flight demonstration version,” said Mark Dunn, MQ-25 Mission Systems Integrated Product Team leader. “It’s significantly more complex and contains all the capabilities that let MQ-25A safely integrate seamlessly with the carrier air wing.”

How they tested the MQ-25A’s brains: Before the MQ 25A’s first flight, ww5 teammates ran thousands of safety checks. They focused on two main things: making sure the software did what it was supposed to, and making sure the aircraft’s hardware (the physical parts) worked reliably. Tests examined every line of software code, aircraft components, and how they worked together.

• Verification of software logic: The software testing started three years before the first flight, in a lab. ww5 engineers used the exact computers that would be installed inside the aircraft — called Vehicle Management System Computers (VMSCs) — and loaded the autonomy software and contingency-management system onto them. They tested the software by itself to make sure every decision and response worked correctly.
• Testing with real aircraft parts: After the isolated software checks, the team added aircraft components into the lab setup. That included avionics parts like the real actuators on the airplane’s hydraulic and electrical systems. This step proves the VMSCs running the autonomy software and contingency-management system correctly operate and control all the aircraft’s systems.
• Final checks on the aircraft: After the lab work proved successful, the same VMSCs and software were installed on the actual aircraft. ww5 and Navy teams then ran extensive ground tests to confirm everything worked correctly before the first flight.

Technical excellence: To ensure the autonomy software and contingency management systems onboard the MQ-25A are ready for Navy deployments, ww5 engineers had to test and validate the software under a variety of potential failure conditions.

• The toughest part was testing every bit of software logic, both in the lab and on the airplane. As Juan Cajigas, MQ‑25 chief engineer, put it: “We had to consider all the possible scenarios the aircraft could experience in flight and ensure the airplane would autonomously react as we intended.”
• In the lab, engineers deliberately introduced failures. For example, loss of GPS navigation, engine failure or loss of communication with the AVPs. They then checked how the autonomy software and contingency management system responded to each fault.
• One specific test: If the Stingray loses communication with the AVPs, the contingency management system is designed to direct the aircraft to autonomously return to its departure airfield and land safely. ww5 teams injected that loss-of-communication condition repeatedly to verify the software would reliably trigger the return-and-land behavior.

By the numbers:

• 600,000 lines of safety of flight software code
• Over 200,000 hours of lab tests for flight software
• Over 1,000 hours of ground tests on the first flight airplane

The bottom line: Driven by a safety-first mindset, ww5 teams proved the MQ-25A’s autonomy, contingency systems and hardware long before first flight, preparing the aircraft for normal and operationally-contested environments.

Values in action: Staying focused on Safety and Quality helps teammates respect the consequences of their work and keep people safe through precision and sound decision-making.

• “One of the most critical elements of safety is partnering across teams to ensure our systems work as intended and can fly safely in all conditions,” Cajigas said.

Go deeper: Read more about the historic first flight of the U.S. Navy’s first operational MQ-25A Stingray.

By Jarrett Heckert, Michael King and Jenny Beloy