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Design of Boeing’s loyal wingman gives clues about performance and roles

Posted By on November 18, 2021 @ 14:30

If Boeing’s Airpower Teaming System proves to be viable, the Royal Australian Air Force of the future is likely to have scores, maybe hundreds, of fast drones.

The concept of the ATS is to provide large numbers of semi-autonomous helpers, called loyal wingmen, that can move towards an enemy alongside crewed aircraft and also perform missions independently.

Boeing is developing the ATS as a product for the global market. It’s doing this in Australia because the RAAF is using the program to explore potential use of loyal wingmen. The engineering is hard, and prospective application presents major challenges, so even the US Air Force hasn’t yet committed to fielding aircraft like the ATS.

But Boeing is notably building ATS prototypes with volume-manufacturing equipment and said last year that series production could begin in the middle of the decade. Flight testing is underway. If Australia goes for the loyal wingman concept, it is very likely to choose the ATS.

What the ATS might do depends on technical design details. Boeing has said little about this, but much can be observed and deduced. This article offers a preliminary technical assessment of the design; a second piece will discuss what that means in application.

Let’s begin with the major issue that we know least about: the degree of autonomy, which will surely start at some threshold level and improve over time. In the likely concept, people in other aircraft would tell ATSs what to do but, as far as possible, not how to do it.

The viability of the loyal-wingman concept depends fundamentally on providing an adequate level of autonomy. BAE Systems is deeply involved in this aspect of the project, working on the navigation, guidance and flight-control systems.

As for flight performance, the ATS’s cruise speed is easy to guess: it must be near the speed of sound for the drones to keep up with fighters flying to and from their mission stations. This makes the ATS much faster than drones designed for long missions, such as the RQ-4 Global Hawk, which can stay aloft for 34 hours. The other side of the coin is that the endurance of the ATS might not be much more than four hours.

Unlike a fighter, the ATS can’t accelerate to supersonic speed in level flight. We can see that from the combination of the wing’s sweep (only about 30° on the leading edge) and its thickness relative to chord (about 7.6% on a mock-up displayed in 2019). Also, thrust is nowhere near enough for level supersonic fight.

The ATS’s aerodynamics might allow it to go supersonic in an operationally useful dive, however, and Boeing has further provided for such speed by shaping the fuselage sides to form diverterless supersonic inlets for the engine. Such inlets are also stealth features, supplementing such standard stealth shaping as the chines that run down the sides of the forward fuselage.

The degree of stealth depends on many details that can’t be assessed by just looking at the aircraft, but we can at least say that ATSs should be undetectable enough to operate alongside F-35 Lightnings without revealing the presence of the force package.

The ATS’s structural design looks conventional, with carbon-fibre-reinforced plastic over an aluminium substructure. Each ATS is likely to have a short flying life, so Boeing should be able to make many parts lighter than usual. The empty weight of the aircraft is likely to be less than 3 tonnes. (An F-35A weighs 13.3 tonnes empty.)

Every effort will have been made to cut manufacturing costs, a factor at least as important as anything else discussed in this article. ATSs are intended to be attritable, meaning they will be cheap enough to be exposed to high risk and often lost. An air force such as Australia’s could indeed buy hundreds of them.

The ATS is 11.6 metres long, which reveals the dispersal mode: it will fit in a standard 40-foot (12.2-metre) shipping container. The wing is a single piece with a span of 7.3 metres, clearly designed to lift off and lay in the same container.

The landing gear is of the normal, light and compact type usable only on hard, smooth surfaces. So the ATS will be able to fly from runways or roads; rough fields will be unavailable to it.

Boeing has said that the powerplant is a VLJ engine, meaning it was developed for very light personal jets. Only two Western engines strictly meet that definition: the Pratt & Whitney Canada PW600 (generating thrust of 7.2 kilonewtons, or 1,600 pounds, in its most powerful off-the-shelf version) and the Williams FJ33 (6.7 kilonewtons). In military service, engines could be pushed harder at the cost of shorter times between overhauls, a possibly unimportant sacrifice for attritable drones.

Back-of-the-envelope calculations suggest such an engine would indeed be enough for an ATS to cruise at subsonic speeds to keep up with a crewed aircraft that it was working with.

The thrust levels discussed here will dismay people who admire the ATS’s shape, see something that looks a lot like a fighter and imagine fighter-like performance. But such performance is absolutely not affordable in attritable aircraft.

In one respect the ATS will fly like a fighter, briefly. Boeing has put the engine intakes in the usual fighter positions on the sides of the fuselage, where they can gulp in air even when, because of a hard turn, it’s coming from below. If designers didn’t want the ATS to turn hard, they would have fed air to the engine from above the fuselage, a stealthier choice. So, the ATS will be able to turn hard.

Why? Most obviously, to dodge missiles. But hard-turning aircraft lose energy—they slow down, lose height or both—and an ATS will not have abundant engine power to quickly replenish that energy. After one or two dodging turns, an ATS may find that its game is up.

An ability to slip into supersonic speed in a shallow dive would be helpful when working close to enemy fighters. The higher speed will make the enemy cover more ground before taking a shot, which may indeed be unachievable.

Unlike the engine of a high-powered fighter, the ATS’s little turbofan will be working hard even in cruise, a good condition for fuel efficiency. A small engine also leaves more space and mass available for fuel. So does omitting the human pilot and the associated seat, cockpit and other paraphernalia needed to keep a person alive in the stratosphere. The airframe is slippery too, lacking the draggy external pylons and stores of fighters.

All this helps explain the eye-catching range of 3,700 kilometres that Boeing quotes. We can assume that that’s the ferry range—flying from one airfield to another.

The ATS is certain to be designed for prolonged storage, like a missile, and that’s how most aircraft of the type will spend most of their lives. At any time, an operator will keep a few flying so pilots can practice working with them. For ease of storage, electric, not hydraulic, drive for mechanical systems is likely to have been preferred.

Its missions will depend on what operators put in the ATS. The forward bulkhead is in effect a hardpoint and the nose is in effect a store. The nose is an aircraft’s most electromagnetically valuable real estate, with the best lines of sight. The ATS’s nose volume is 1.5 cubic metres and entirely available to payloads. Operators will be able to fit different noses to different ATSs or even switch noses between them.

There’s also space for two weapon bays in the lower corners of the fuselage, ahead of the main landing gear, probably sized for stores about 1.8 metres long. Weapons are not likely to appear in early service, however.



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