URBAN AV OPS
Variety of V/STOL design concepts could herald age of urban aviation
As world population continues to rise, long runways and space to accommodate them are increasingly unavailable.
The DARPA-funded GBA Heliplane project was used to validate gyrodyne design scalability in terms of speed and payload potential.
Named the Heliplane by DARPA and priced at $6.4 million, this aircraft will exploit GBA's gyrodyne technology to take off and land vertically, reach a top speed of 400 mph, and carry a 1000-lb payload over a 1000-mile range without refueling. It will be the first rotary-wing aircraft with performance comparable to that of an airplane in terms of speed and efficiency.
In 2003, Bell/Agusta made aviation history with the inaugural test flight of the world's first civil tiltrotor, the BA609. Pricing in 2004 was $8–10 million, depending on year of delivery.
By 2005, concurrent certification (European and FAA) was expected in 2008 with deliveries of 60 orders to follow shortly thereafter. Although orders grew to 80, certification was pushed back to 2011. In Jun 2011, AgustaWestland took full ownership of the delayed program and renamed the aircraft the AW609.
It is designed as a multimission aircraft. As the first pressurized production rotorcraft, it will be capable of flying above adverse weather at speeds twice that typical of helicopters and with a range of 750 nm. It features an advanced glass cockpit and full fly-by-wire (FBW) digital controls—and it will be certified for dual-pilot IFR/flight into known icing conditions (FIKI)/ flight more than 50 nm over water.
The X3 is an experimental compound aircraft used to validate the concept of a high-speed helicopter which slows down the rotor speed to avoid drag from the advancing blade tip and which avoids retreating blade stall by unloading the rotor while a small wing takes up lift instead.
By 2020, Eurocopter expects to offer a slowed rotor/compound system carrying 12–19 passengers (which does not require a flight attendant) and later one that can carry 20–50 passengers. In May 2011, the X3 reached a speed of 232 kts in stabilized level flight.
The Sikorsky X2 is another experimental compound helicopter but with coaxial rotors and a pusher propeller (propulsor). In addition, the aircraft will be used as a "flying wind tunnel" to determine the main rotor to propulsor aerodynamic interaction, shaft angle optimization for performance, and blade tip clearance for a range of maneuvers.
The X2 uses an integrated FBW system allows the engine/rotor/ propulsor system to operate efficiently, with full control of rotor rpm throughout the flight envelope, high lift-to-drag rigid blades, low drag hub fairings, and active vibration control. In Sep 2010, the X2 reached a speed of 260 kts in a shallow dive.
The future of urban aviation
With the V/STOL aircraft population largely unpressurized, traffic density in lower airspace segments will increase dramatically, as will reliance on high-precision navigation (such as NextGen), 4D glass cockpit displays and automated flight control.
By 2015, advances in materials and nanotechnology will further improve weight, strength and fatigue properties.
By 2050, R&D into electromagnetic propulsion may begin to show promise of eliminating both external noise and rotor downwash.
The war-fighting environment of the past 10–15 years has driven helicopter production rates up and R&D funding down to balance. With reduced R&D funding, the engineering talent needed to advance the state of V/STOL has dwindled.
Advances in rotorcraft technology have been incremental rather than inspiring, excepting the 30-year development of the V22 Osprey. Given such limited commitment, the future of civil V/STOL lies in commercializing tiltrotor, slowed rotor/compound and gyrodyne configurations and introducing new concepts in propulsion. These will be key to ensuring that the needs of the urban community are met by urban aviation.
Don Van Dyke is an 18,000-hr TT pilot and instructor with extensive experience in charter, business and airline operations. A former IATA ops director, he has served on several ICAO expert panels and is a Fellow of the Royal Aeronautical Society.