Following on the heels of its four competitors, Boeing has released artworks of its candidate for the U.S. Army’s Future Attack Reconnaissance Aircraft (FARA) programme. Equipped with a hingeless rotor and pusher propeller the design is reminiscent of Lockheed’s failed AH-56 Cheyenne first flown in 1967. We asked We asked Ron Smith, former Head of Future Projects at Westland Helicopters, for his thoughts on the return of a yet another futuristic, yet familiar, configuration.  

 

“All FARA contenders are constrained as follows (this information via Vertiflite, magazine of the Vertical Flight Society):

40 ft (12m) maximum rotor diameter
Maximum length 46.5 ft (17.2m)
Max gross weight 14,000 lb (6,350 kg)
180 kt cruise speed
3,000 shp GE T901 Improved Turbine Engine
Hover out of ground effect at 4,000ft, 95F
20mm Cannon and ability to integrate ‘current and future weapons’ (therefore presumably meaning Hellfire, possibly in both RF and laser guided forms).
Capability for “air-launched effects”
Modular Open Systems Architecture.
One can assume that other capabilities such as crashworthiness, the ability to operate in sand, dust, snow, etc. will also be incorporated, along with wire strike protection and so on. Operation in built environments (the so-called urban canyons) may throw up a number of challenges – not least co-ordination within and between units operating in the same areas.
The Boing aircraft has tandem seats (with a large expanse of cockpit glazing). It features a shaped fuselage and a rotorhead fairing, both reducing radar cross-section and (for the hub) parasite drag. A retractable undercarriage and internal weapons carriage is featured.

[Thus far, there is little that was not anticipated by Westland 45 and 47 some 35 years ago, which had a very similar gross weight]

There is an electro-optic sensor under the nose, and a 20mm cannon. There is a canted tail rotor to the rear and the tail of the aircraft has a pusher propeller. This latter has three potential advantages:

1. By providing propulsive thrust, less main rotor cyclic and collective pitch range is required, and the rotor flight envelope will be improved (delaying the point at which stall flutter is encountered).

2. The ability to provide forward and reverse thrust will enable acceleration with only limited fuselage attitude change and increased deceleration capability, without encountering rotor overspeed in autorotation, where pitch attitude limits restrict the maximum deceleration that can be achieved.

3.  It may well be that limiting the amount of fuselage pitch attitude change with speed and acceleration / deceleration will simplify gun control and potentially increase the firing envelopes of other weapons.

The large area of cockpit glazing may create glint and specular reflection issues. One assumes that the crew will be equipped with helmet mounted displays and that the aircraft will be network-enabled and able to share target information (including identity / rules of engagement compliance data) with other ISTAR assets.

Without this capability, there may be a mismatch between weapon range and the ability of the on-board sensors to obtain positive identification of potential targets.”

Hush-Kit notes: Boeing hopes that their fly-by-wire experience with the Defiant and Comanche will overcome the kind of control issues suffered by the Cheyenne fifty three years ago. The compound helicopter, a helicopter equipped with an additional  propulsion system purely for forward flight, dates back to at least 1962 (the Lockheed XH-51 and Piasecki 16H Pathfinder being early examples) but as yet none have entered actual service.

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