R O Ltd′s innovative Centre-Line Tiltrotor concept

Rotorcraft Operations Ltd is developing an innovative Centre-Line Tiltrotor concept to complement the formidable capabilities of a military tiltrotor, the Bell/Boeing V22.

The V22 is a medium lift transport tiltrotor capable of carrying 24 fully equipped troops. It’s a big success in expeditionary and similar roles where range and speed are critical. Over 200 are in service with more orders from the USMC, US Navy, USAF SOCOM and Japan. Eventual fleet size looks 400+.

Its range and speed completely outclasses all existing fleets of gunship helicopters and all utility support helicopters, leaving the V22 transport fleets totally without matching close air support and totally without matching utility support.

These 400+ tiltrotor V22 transports will need to be complemented by an equally capable support fleet of gunship and utility rotorcraft: the physics says that these will be tiltrotors to enable them to match the complete operational envelope of the V22s.

Bell Helicopter Textron Inc are the front runners in tiltrotor capability. Their advanced tiltrotor V-280 Valor technology demonstrator is already hovering, transitioning, flying and expanding its envelope. Bell are uniquely placed to exploit this V22 support fleet opportunity.

So how would a full size Centre-Line Tiltrotor (CLTR) compare with Bell’s V-280? Assume the CLTR is designed and manufactured to the same mission and same high standards as the V-280.

Imagine the CLTR and the V-280 Valor in the hanger of an aircraft carrier. Lets follow the pair through a simple mission to deliver stores and return personnel.

Bringing the pair from the hanger, the CLTR quickly unstows rotors and wings while the V-280 is slower: slewing its wings before unstowing rotors. The V-280 takes off from the V-22 spot, while the CLTR has a smaller footprint so takes off from one of the helicopter spots. Both take off and transition to cruise smoothly into the first leg of the mission, 50 nm over sea plus 50 nm inland to the landing zone, LZ.

Above the LZ both simulate close air support, CAS, by loitering in winged and in helicopter flight etc for 40 minutes, then land. With stores off-loaded and personnel safely on board, both execute 80° tilt, defensive, close to ground take off to high speed before climbing away for the final leg back to the carrier.

Approaching the carrier, its decks are busy, the V-280 has to wait for a V-22 spot to free and the CLTR has to wait for a helicopter spot to free. Once landed both unload and prepare to be taken into the hangers, again the CLTR is quicker as it wing fold and rotor stow process is simpler than slewing V-280 wings.

Finally, both got the job done identically, with the CLTR finishing with far more fuel left in the tank: it can take on much more fuel because it does the same job with a lower empty mass, it has no tail/empennage, wing fold is much lighter than slewing the complete V-280 wing, CLTR powerplant/transmission systems are more compact and lighter being integral with the fuselage, not stretched from V-280 wingtip to wingtip.

CLTR is a concept at present. The 10kg model flies well in helicopter and winged helicopter modes: see the video below.

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