MQ-25 Stingray: Boeing's unmanned tanker flies with a refuelling store for the first time

The 9 December flight has brought the US Navy a big step closer to its programme for a forward-deployable "filling-station drone". For the first time, Boeing's T1 prototype of the unmanned MQ-25 Stingray carried a Cobham hose-drum refuelling store – a 31-301 Model Buddy Store mounted under the left wing.

Two and a half hours of flight testing, controlled from the ground

For more than two and a half hours, a Boeing test pilot flew the aircraft from a ground station at MidAmerica St. Louis Airport in Mascoutah, Illinois. The trials are to clarify whether the hose and drogue need to extend or retract further. The system holds 1,136 litres internally. It delivers fuel to a receiving aircraft at 833 litres per minute, at a drogue pressure of either 30 or 60 psi.

The current design stems from a 2018 contract: the US Navy chose Boeing to develop a tanker drone for carrier operations, while General Atomics and Lockheed Martin, also interested, came away empty-handed. The idea: in the medium term, the Stingrays are to replace the F-18E/F in the carrier air wings that currently fly the so-called "buddy-buddy" tanker role – freeing both aircraft and crews for combat missions. Dave Bujold, Boeing's MQ-25 programme director, said: "Seeing T1 fly as a tanker today, with the hardware and above all the software behind it, is a visible sign of the new capabilities we are bringing to the carrier decks."

MQ-25 Stingray: up to 70 tankers planned from 2024

The system first flew only in September 2019 and has since logged around 30 flight hours. In parallel, the US Navy had already gained valuable experience with (deck) operations of large unmanned systems in 2013 – with the X-47B, which successfully took off from and landed on carriers dozens of times. Thanks to electro-optical sensors, the type should also be able to perform intelligence, surveillance and reconnaissance (ISR). The Navy leadership hopes to distribute up to 70 of these filling stations across the various carrier air wings from 2024; so far, however, only an initial test batch of seven is under contract. The drone is to relieve the existing fleet on the flight decks and significantly extend the combat radius of the "Carrier Wings".

Given the military rivalry between the US and China, for example in the South China Sea, this matters – and the rivalry is likely to continue under a Biden administration. On the other hand, large unmanned aircraft systems (UAS) flying their figure-of-eight patterns on the "racetrack" are relatively defenceless, even more so than the crewed "multipliers" (tankers, AWACS, SIGINT platforms). They would then need protection from combat aircraft, which in turn tie up tanking resources.