New fighter-style autopilot error behind YFQ-42 Dark Merlin crash, Says General Atomics

Berlin, June 12. A software issue in a newly developed high-performance autopilot system caused the crash of the YFQ-42 Dark Merlin prototype in April, according to General Atomics Aeronautical Systems Inc. (GA-ASI) President David Alexander.

Speaking to Aviation Week at the ILA Berlin Air Show, Alexander said the accident involving the Collaborative Combat Aircraft (CCA) prototype on April 6 stemmed from a fault in an advanced autopilot designed specifically for fighter-like manoeuvring. The incident led the US Air Force to suspend flight testing until May 21 while a safety review was conducted.

GA-ASI had earlier disclosed that investigators traced the crash to an “autopilot miscalculation” related to the aircraft’s weight and centre-of-gravity parameters. Alexander provided further details, noting that the company’s traditional autopilot system, used on its medium-altitude long-endurance platforms, has accumulated nearly 700,000 sorties and more than 9.3 million flight hours.

However, the new system developed for the YFQ-42 was designed to support aggressive manoeuvres associated with fighter aircraft, including high-G turns and rapid changes in direction, while preventing structural overstress.

“This is more of a fighter autopilot,” Alexander said, adding that the software had logged only around 43 flights before the mishap occurred.

According to Alexander, engineers quickly identified and corrected the problem, enabling the programme to resume testing.

“There was an issue with it. We found it, we fixed it,” he said, adding that the Air Force wanted the programme to regain momentum as rapidly as possible.

The YFQ-42 features a fly-by-wire control architecture equipped with multiple layers of flight envelope protection. These safeguards are incorporated into a sophisticated non-linear inversion autopilot, which automatically adjusts control commands according to speed and manoeuvring conditions.

Alexander acknowledged the complexity involved in programming those protections, describing the process as particularly challenging because command limits must be continuously scaled to different flight regimes.

Following the completion of the safety review and implementation of corrective measures, the General Atomics contender for the US Air Force’s CCA Increment 1 programme has returned to flight testing.

“It’s unfortunate, but you’ve got to get right back up and get in the saddle and get moving,” Alexander said.