Thoughts on the Bell 360 Invictus army helicopter: return of the Comanche?

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The poem Invictus is about survival and stoicism. It was read by US prisoners of war in North Vietnamese prisons, sometimes written with rat droppings on toilet paper. The 360 Invictus is Bell Helicopter’s proposal for the US Army requirement for an armed scout helicopter. We asked Ron Smith, former Head of FuturProjects at Westland Helicopters, for his thoughts on the return of a futuristic, yet familiar, shape. 

“Bell has released imagery representing its proposition for the US Army FARA (Future Armed Reconnaissance Aircraft) requirement. Details of the requirement are a little sketchy, but a recent summary in Vertiflite (members’ magazine of the Vertical Flight Society) highlights the specific characteristics, which can be seen at the bottom of this page. 

From a general point of view, there is a general similarity to the schemes shown in the past for Comanche. Indeed, the early 1980s work at Westlands, featuring shaped fuselage, internal weapons carriage and close attention to IR signature anticipates some of these features. The Bell version of a canted Fenestron (they will wince at the name), or ‘fan-in-fin’, will be designed with minimisation of external noise in mind. Of equal importance will be preventing the visibility of rotating tail rotor elements to threat radars, at least from a frontal aspect.
The latter consideration also applies to the closely faired rotor head assembly shown in the Bell artist’s impression. One can expect minimisation of corner reflectors, screening of sensors, metallised transparencies and choice of materials and treatments in rotor blade construction. Bell state “This design is based on Bell’s 525 Relentless rotor system which has been tested and proven at speeds in excess of 200 Knots True Air Speed (KTAS).”
The only comment made by Bell that can be related to an optionally manned capability is that “Fly-by-wire flight control system—synthesises technologies, reduces pilot workload and provides a path to autonomous flight”
In terms of the impression, the weapon bay shown looks slightly small – one cannot envisage more than four weapons being carried internally on an aircraft of this size. Bell commented that it could be “Armed with a 20-mm cannon, integrated munitions launcher with ability to integrate air-launched effects, and future weapons, as well as current inventory of munitions”.
The nacelle fairings suggest that the front face of the engines will be shielded from view, but that extreme measures have not been taken in respect of infra-red suppression. This makes me wonder if a variable area nozzle / variable cycle engine approach might be under consideration to provide the required dash speed. Bell talk in terms of a supplemental power unit without defining this further.
Bell claim a speed >185kt (without saying whether this is continuous or a dash capability). For maximum compliance, they would be looking for this as a sustained capability. In terms of mission performance, they state a combat radius: 135nm with >90 minutes of time on station and the ability to hover out of ground effect at 4,000 ft and 95F, which is a pretty standard US Army requirement.
The clean wing surface (devoid of weapons and weapon mounts) is consistent with a degree of unloading the rotor at speed. Bell’s press release confirms this. This also avoids the typical clutter of corner reflectors that would have an adverse impact on radar cross section.
The sketch also leaves one wondering about target acquisition and identification. There is a relatively small nose-mounted sensor, which is low-set and would result in exposing the helicopter above the skyline if it is used for target acquisition. Also, a desire to reach out farther (than Hellfire) implies (to me) non-line of sight operations, or at least third-party targeting and networked operations. The same target acquisition question also surely arises if the aircraft is to be used in an optionally un-manned mode. The Bell statement “Provisioned for enhanced situational awareness and sensor technologies” leaves open the possibility that these are deliberately not shown in the current artist’s impression.
Among Bell’s final statements is that “Bell is committed to providing the U.S. Army with the most affordable, most sustainable, least complex, and lowest risk solution among the potential FARA configurations, while meeting all requirements,” said Keith Flail, vice president of Advanced Vertical Lift Systems at Bell.  More questions than answers, but it looks like a very interesting and credible project with strong resonances with work that I was involved in twenty-five years ago. That credibility is consistent with a relatively straightforward approach to addressing the FARA requirements.

 

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“FARA is one element of FVL (Future Vertical Lift), which seeks to break out of a cycle of military rotorcraft development by incremental upgrade, in particular by focusing on advanced rotorcraft configurations.”

FARA itself is intended to be optionally manned. To me, this is a slightly debatable philosophy. If the vehicle is to be manned at all, it will be constrained by various requirements that would not arise for a purely unmanned platform. These might include:
• Space, volume and protection provision for the crew (when present)
• Provision of external fields of view for human operation
• Design for human crash survival protection
• On-board information display and control systems arranged to suit human anthropometry
• Levels of redundancy to meet acceptable safety (probability of failure) criteria when a human crew is present (and therefore at risk) (whether from accident, or enemy action)
These considerations are likely to be significant cost and weight drivers and will generally have a negative impact on vehicle shape, size and detectable signatures compare with a fully unmanned system.
Similarly, if a vehicle that can fly with human crew is also required to operate unmanned, it will have additional complexity associated with on-board and off-board decision making, particularly in respect of deploying weapons and protecting third parties, be they members of the public, innocent civilians, coalition partners or members of one’s own forces.
Various elements of hardware and software that might not be regarded as safety critical in a manned aircraft may become a concern in unmanned operations.
By being ‘optionally manned’ the system is burdened with two (possibly conflicting) sets of constraints, simply as a result of being neither one thing, nor the other (or both at once, if you prefer).

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1980s Westland study 

Moving on to other FARA requirements:
• Ability to leverage deep interoperability across intel, fire and manoeuvre elements (thoroughly sensible, but probably requires doctrinal developments if it is to be effective)
• Able to avoid radar detection
• Ability to operate in tight urban canyons (implies 40ft maximum rotor diameter, but likely also to have comms, datalink and target acquisition / tracking challenges)
• Open avionics systems architecture – pretty much a given nowadays; current terminology is MOSA modular open systems architecture. Bell comment that their MOSA solution is being provided by Collins. There will probably be some emphasis on use of Artificial Intelligence for crew decision support (whether operating manned, or unmanned).
• Able to exercise some level of interoperability with unmanned systems – interesting to speculate whether this means data sharing for mutual situation awareness, or directing unmanned systems to engage targets, or being directed based on information gathered by unmanned systems …
• FVL anticipates air launched effects from platforms such as FARA to degrade or destroy “Area Access and Aerial Denial” structures (which I take to mean (at least) layered air defence systems). Support to ground troops is also mentioned, in conjunction with longer stand-off ranges than are available with Hellfire. (RVS – Target acquisition and positive identification is likely to be a challenge for such non-line of sight systems and will presumably rely on networked intelligence from a range of assets).
• General Rugen, Army Director of FVL is quoted as saying flying should start in November 2022 (to support government-sponsored flight test and evaluation in fiscal year 2023).
• Cruise at 180 kt or more; dash at up to 200 kt or more
• 20mm cannon and integrated munitions launcher
• Gross weight around 14,000lb (RVS comment: similar to Westland Wildcat)
• Single or twin engine
Note: Optionally manned and available turboshaft engine powers probably favour a twin-engine solution. (RVS)

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— Ron Smith
October 2019

Dr Ron Smith joined the British helicopter company Westland in 1975, working in Research Aerodynamics, remotely piloted helicopters, before becoming Head of Future Projects. He had a strong influence on the design of the NH90, and was involved in the assessment of the Apache for Britain. 

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2 comments

  1. Vulcan

    “Optionally manned” is the stupidest thing anyone has come up with so far, bringing the worst of all worlds to the table.

    By making allowances for a crew, you take up large amounts of space and weight in the aircraft that could be better used for fuel, weapons, or sensors if the unmanned control systems are used. By requiring the unmanned systems be fully developed you add years of extra work and system complexity – not to mention vastly higher cost – to a vehicle designed to be flow by a crew.

    No, this is silly. Go fully unmanned, or don’t bother with autonomous control systems for unmanned flight.

    • Ron Smith

      I couldn’t agree more, although my comments in the article avoided actually saying it was stupid. If you can do unmanned you will free up space and have a range of new design options. But there are all sorts of challenges … rules of engagement, deconfliction, safety of own troops, coalition partners, etc. A manned solution will definitely work and an ‘optionally manned’ system will be harder than either a manned, or an unmanned, solution. Superficially attractive, but actually nonsensical. Don’t go there.

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