May - 2013 ISSUE

Force Magazine
Into the Future - June 2012
Next generation hybrid helicopters will fly twice as fast and twice as high
By Atul Chandra

What will helicopters of the future be like? While fifth generation fighter aircraft are already flying and many sixth generation designs are in the pipeline, helicopters have evolved at a slower pace. Today’s helicopters offer a quantum leap in terms of capability but the basic designs have remained the same or have evolved from designs of the Seventies and Eighties. The first of a new generation of helicopters now offer unconventional designs while delivering performance far beyond what can be achieved by conventional helicopter designs.

Eurocopter’s X3 hybrid helicopter demonstrator is a five-ton class helicopter, offering a cabin size for up to 11 passengers. The X3 makes use of the Dauphin helicopter airframe equipped with two turboshaft engines powering a five-blade main rotor system and two propellers, installed on short-span fixed wings. Eurocopter calls the X3’s hybrid configuration an ‘advanced transportation system’ offering the speed of a turboprop-powered aircraft and full hover flight capabilities of a helicopter. Eurocopter has a long history of tailoring its commercial helicopters for military applications and not surprisingly has said that the X3 could well be used for Special Forces operations, troop transport, combat SAR and medical evacuation. These would benefit from the hybrid aircraft’s combination of higher cruise speeds and excellent vertical takeoff/landing performance. The X3 reached a performance milestone in May, last year when in level flight, it maintained a true airspeed of 430 kmph for several minutes, using less than 80 per cent of its available power.

According to Eurocopter test pilots, the X3 handled extremely well. The Flight testing of the X3 is being performed from the DGA Flight Test Centre in Istres, France. The flight test programme will continue throughout 2011 to explore the hybrid helicopter’s full flight envelope and evaluate all the possibilities offered by this new technology. It has demonstrated remarkable stability at high speed – even with the autopilot off. The X3 has demonstrated its performance at full engine power, including impressive climb and descent rates, as well as excellent manoeuvrability, while also confirming the hybrid propulsion system’s outstanding capabilities for acceleration and deceleration. In addition, it has low vibration levels despite not having the use of passive or active anti-vibration systems, providing flight characteristics comparable to those of the best traditional design helicopters currently in service. The American Helicopter Society (AHS) International last month awarded its annual recognition for helicopter technology improvement to the Eurocopter’s team, that developed the X3 and for its successful validation of the helicopter hybrid concept.

The radical Sikorsky X2 Technology has already achieved its goal of flying at speeds in excess of 450 kmph, more than twice the top speed that can be achieved by a conventional helicopter. The company will now build and develop 2 more X2 Technology aircraft. One will be offered to the US military for flight test and evaluation with both prototypes designated to become the first of an all new class of tactical helicopters. This will be the Sikorsky S-97, designated as the ‘Raider’ designed to meet the US Army’s Armed Aerial Scout requirement.

The ‘Raider’ will feature active elevator and rudders, load alleviating FBW controls, rigid co-axial rotor system and a composite fuselage. The S-97 will demonstrate low acoustic signature, exceptional hover capability, high cruise speed (200 kts) and range (600km) with agility for close air support. The X2 Technology demonstrator aircraft showcases new technology such as an integrated Fly-by-Wire system that 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. The X2 was used by Sikorsky as a ‘flying wind tunnel’ to determine the main rotor to propulsor aerodynamic interaction and blade tip clearance for a range of manoeuvres. These technologies have successfully been demonstrated in flight tests and will allow Sikorsky to move the technology ahead for future products.

The AgustaWestland AW609 is a tiltrotor with FBW technology and at this year’s Paris Air Show; AgustaWestland announced that it had taken full ownership of the BA609 tiltrotor programme. The new company will be totally owned by AgustaWestland and the BA609 tiltrotor has been rebranded as the AW609. The AW609 began life as the Bell XV-15, developed by Bell/Boeing in 1996. After Boeing pulled out, Agusta came onboard and hence the designation BA609. The flight test programme will continue with AW609 aircraft No. 1, based in Arlington. AW609 No. 2 will be based at AgustaWestland’s Cascina Costa facility. AW 609 No. 3 and No. 4 will be assembled at Cascina Costa with aircraft No. 3 being used for icing certification testing. FAA/EASA certification is planned for 2015 with deliveries following immediately afterwards.

Bell Helicopter will remain involved in the design and certification of AW609 components and will be the supplier when the aircraft reaches the production phase. The AW609 is designed to meet the most stringent Transport Category specific standards in both FAA and EASA certification environments and this makes it ideal for “Commercial Off-the-Shelf” possibilities and the tiltrotor can be configured for passenger transport, search and rescue, law enforcement, maritime surveillance, training and government applications. The AW609 features a composite fuselage and has been flown up to 616 kmph and can cruise at speeds up to 509 kmph at altitudes up to 25,000 ft. It is capable of performing long range missions with up to nine passengers two crew and a full fuel load. The 2 powerful PT6C-67A (1,447 kW) engines deliver Cat A Class 1 performance at MTOW of 7,620 kg. Taking off and landing vertically, the AW609 can fly above adverse weather conditions with up to nine people in comfort in a pressurised cabin at twice the speed and range typical of helicopters.


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