The program is intended to create a new generation of multipurpose tiltrotor vertical takeoff and landing aircraft to replace between 2,000-4,000 helicopters currently in the US Defense Department inventory.
Spirit’s fuselage was designed for the Bell helicopter entry in the program, the V-280 Valor. Spirit completed the project in the firm’s rapid prototyping facility in Wichita, from design to completion, in only 22 months. The unit will be shipped to Bell’s Amarillo Texas facility for final assembly.
Tiltrotors are quite new. Bell’s V-22 Osprey was the first in series production and endured a rocky start with multiple accidents and fatalities. Current technology, however, reduces weight through competence and adds advanced control of the engine and the complex tilt mechanism to improve in-flight stability.
So why replace helicopters? Speed.
Rotary wing aircraft have inherent limits to their forward speed. A major part of these limits is built into the nature of rotating wings. In forward flight, the advancing rotor blade experiences a faster relative airspeed than the retreating rotor blade, creating a lift imbalance.
Helicopters address this by twisting the individual rotor blades to change their angle of attack relative to airstream, thus balancing lift.
But, there’s a limit. Rotor blades are essentially aircraft wings and are subject to all of their limitations, including stall at high angles of attack. And that’s just one limitation to speed in forward flight.
The advantage of the tiltrotor concept is that the rotor blades become propellers in forward flight, handing over the lift duties to the relatively short, high aspect ratio wings the outrigger engines are attached to.
It’s like having the best of both worlds. Helicopter qualities for low-speed vertical flight, and turboprop aircraft qualities for high-speed, higher altitude flight.
Bell is the only company working on this concept. Agusta–Westland also has one and as the technology improves, larger and larger tiltrotors can be expected. Bell is proposing a quad tiltrotor that would allow heavy lift transport for the military and potentially for civilian use in the future.
Civilian Applications
From a manufacturing standpoint, the military applications will prove the concept, but civilian use is a lot more challenging.
If the economics work, we could be looking at intercity transportation that operates from the rooftops of downtown office buildings, completely eliminating the need for commuter airports. This could revolutionize aircraft manufacturing and potentially destroy the helicopter industry as we know it.
If it works, the potential demand could easily be in the tens of thousands of airframes, possibly hundreds of thousands as global fleets re-equip.
With the military project essentially funding the R&D effort, tiltrotor technology could evolve the same way jet airliners evolved in the 1950s: Boeing’s 707 actually started as the USAF’s KC-135 tanker. The result was a major boost to the fledgling jet airliner industry.
Let’s hope the JMR-TD program does the same.
The V-280 is scheduled to make its first flight in the second half of 2017. You can find more information about the V-280 at
