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Stingray Testing Forging Ahead

 - November 15, 2021, 4:00 AM
MQ-25 T1 refuels a VX-23 F-35C on September 13. The Aerial Refueling Store is the same as that currently employed by the Super Hornet for carrierborne tanker duties. (Photo: Boeing)

Boeing (Stand 1200) has been undertaking a busy test campaign with its MQ-25 Stingray unmanned aerial refueler prototype with the aim of ironing out any “bugs” prior to the launch of production. The company-owned test vehicle—known as T1—undertook its first flight on September 19, 2019, at the company’s test facility at MidAmerica St. Louis airport in Mascoutah, Illinois, 40 miles from the Boeing factory at Lambert Field, St. Louis, and has since kept busy clearing a large number of test points.

 “We’ve modified the normal ‘buy-build-test’ acquisition development model,” said Dave Bujold, MQ-25 program director. “Instead of testing last, we’re testing first. The result is an enormous amount of data that informs our production of the Navy’s MQ-25.” As Boeing puts it, the company is employing T1 to “strengthen the digital thread connecting aircraft design to production to test to operations and sustainment.”

Boeing has also invested heavily in model-based engineering, allowing engineers to predict how each system will perform under certain conditions. It then uses data from the test flights to validate the predictions, or to inform changes required if real-world results differ from those generated in the digital model. “The flights follow on many hours in the lab using the models to simulate flight and aircraft performance,” said Jim Young, MQ-25 chief engineer. “Digital modeling is also being used to support MQ-25 production, and to model sustainment planning and growth for the future.”

Following initial vehicle system flight trials, T1 was fitted with the intended Cobham Air Refueling Store (ARS) in 2020, allowing the start of tanking trials. Initially, the tests focused on the behavior of the MQ-25 while carrying the ARS before wake trials with receivers began, eventually clearing the way for contacts to be undertaken.

On June 4, on T1’s 26th flight, it successfully refueled an F/A-18F Super Hornet from Navy test squadron VX-23. The history-making contact came after the receiver flew in close proximity to the MQ-25—at times as close as 20 feet—to assess wake patterns behind the tanker. On August 18 the Stingray then refueled a Northrop Grumman E-2D Hawkeye airborne early earning aircraft from VX-20.

Most recently, T1 successfully refueled a Lockheed Martin F-35C. During the September 13 flight, the F-35C from VX-23 undertook a preliminary wake survey prior to making contact with the drogue and receiving fuel from the MQ-25. That completed the tanking demonstrations for the principal types of aircraft that the Stingray would refuel in service.

By the time of the F-35C refueling, T1 had flown more than 120 flight hours in the two years since its first flight, and had expanded the envelope considerably. Earlier in the year it had flown for more than six hours, and had reached an altitude of 30,000 feet. “The aircraft is performing well across the flight envelope, and we’re hitting our stride with the processes and procedures for flying this aircraft on a routine basis," said Boeing test pilot Ty “Grouch” Frautschi. “We’ve had Navy testers with us every step of the way taking advantage of the early learning this aircraft provides.”

The Stingray emerged from a long-running program to place a stealthy unmanned ISR/strike aircraft aboard the U.S. Navy’s carriers, but subsequently evolved into the Carrier-Based Air Refueling System (CBARS), the new program being adopted in 2016. The concept of CBARS centers on providing a tanker with some low-observable features that can download the burden of inflight refueling from the Boeing Super Hornet fleet, in turn freeing more F/A-18s for combat missions.

In August 2018 the Navy selected Boeing’s design over competition from General Atomics and Lockheed Martin, awarding an initial $805 million contract for development and production of four Engineering Development Model (EDM) aircraft. In April 2020 it added three System Demonstration and Test Article (SDTA) aircraft to the order. Boeing elected to build T1 at its own expense in order to expedite the development and procurement process.

Boeing has the first two EDM aircraft now in build. The Navy plans to acquire 72 MQ-25s for deployment across the carrier air wings. Initial operating capability is slated for 2024. In the meantime, Boeing will continue to use T1 to refine the design, and plans to undertake deck handling trials aboard a carrier to test elements of the vessel integration. For that it will be transported to Norfolk, Virginia, before being craned aboard a carrier.