CASCINA COSTA, Italy --- Combining vertical take-off and landing with high transit speeds has always been the helicopter designer’s lodestar, but the technical limitations inherent to rotary wings limit the helicopter’s maximum speed to less than 200 knots – and, in fact, to about 150 knots in terms of operating speeds.
Designers have thus looked for alternatives to the basic helicopter design, and its main/tail rotor layouts. Each of the world’s three leading helicopter manufacturers has opted for distinct technical solutions: AgustaWestland for the tilt-rotor with the AW-609; Eurocopter for the hybrid X3 design, and Sikorsky with twin, counter-rotating main rotors for its X2.
None has yet proved its superiority over the others, but each manufacturer is certain it has found the ideal and most economical solution. If one of these solutions demonstrates its superiority, the payoff could be huge, as the helicopter industry has been waiting for decades for the magic formula that will allow it to overcome its speed and range limitations.
To look at how these competing designs shape up, we first traveled to AgustaWestland’s factory in this bucolic northern Italian town, just west of Milan’s international airport, to look at the AW609 tilt-rotor.
AgustaWestland Takes Over AW609 Program
After several years of dithering, AgustaWestland and Bell Helicopter in mid-2011 dissolved the partnership through which they had begun the development of the BA-609 (now designated AW609), Bell’s need for cash to invest in future programs having proved greater than its faith in the future of civil tiltrotors. Conveniently, the situation was diametrically opposite for AW, whose renewed product line was generating a strong cash flow and whose management strongly believed in the potential of tilt-rotor aircraft in the civil market.
AW’s faith in the civil tilt-rotor is supported by a poll of 60 civil operators, 57 of whom had signed purchase agreements for the AW609, that it queried during the first half of 2012. The survey found that range is the tilt-rotor’s most important competitive advantage (speed is a bonus). An AW609 taking off from a roof-top helipad in Milan, for example, can fly direct to London or Berlin in a single hop, crossing the Alps in the process thanks to its pressurized cabin.
The poll also found that, as oil rigs move further offshore to exploit new fields, the large helicopters serving this market, Eurocopter’s EC225 and Sikorsky’s S-92, fly with fewer passengers, says AW 609 program manager Clive Scott, with one Australian operator for example carrying on average just 5 passengers per flight. Thanks to its 4-hour range, the AW609 can fly the same mission as a conventional helicopter in half the time, or fly twice as far in the same time, depending on the mission requirements.
In fact, says Scott, the tilt-rotor should be thought of like a small turboprop transport capable of vertical take-offs and landings, rather than a helicopter with extra capabilities. This is its main difference with competing designs, which can improve some aspects of performance but which remain limited by their basic helicopter design, he says.
While it will expand the AW609 flight test fleet in 2013 and 2014 with the addition of a third and fourth prototype, AgustaWestland is already working on a larger follow-on design which will have greater payload, speed and range. These characteristics will provide a key competitive advantage when, thanks to next-generation avionics including satellite-based navigation allowing all-weather operations, the tilt-rotor will be able to fly autonomously without being dependent on air traffic management.
Additionally AgustaWestland has plans to introduce a new-generation, satellite-based navigation system and mission avionics to enable all weather operations and increase the tiltrotor’s operational capabilities.
Since closing the purchase of the AW609 program a year ago, in November 2011, AW has been concentrating on absorbing and assimilating program-related data and knowledge from the previous partnership and transferring it to its own Integrated Development Team based here. This process should be completed by late 2012.
AW also plans to maintain Bell Agusta Aerospace Company (BAAC), the joint venture which managed the BA-609, as a wholly-owned subsidiary, as it is the applicant for the new FAA type certificate.
About 120 people are currently working on the program at Cascina Costa, and another 85 at the US facility in Arlington, Texas, with another 60 hires expected here in the coming year.
Under the new arrangements, AW is assuming ownership of all the technologies involved in the AW609. Bell will continue its involvement in the design and certification of AW609 components, two of which it will in addition supply when the aircraft enters production: the rotor blades and their hubs, whose intellectual property Bell retains.
This transition is a complex process, as Bell was previously the program leader, and all sorts of intellectual property and other issues have to be resolved as they arise.
The digital Fly-By-Wire system was also a Bell contribution, and AW currently has a Bell license for the related software (i.e., the source codes), while the hardware is supplied by BAE Systems. This license allows AW full control of the system, which it can modify and amend at will.
AW and Bell are currently completing a review of the FBW software prior to the final transfer of Bell’s know-how to Agusta, and their agreement allows the final production software to include a percentage of software licensed from Bell.
The company’s two flight test prototypes, one of which is based in Cascina Costa and the other in Arlington, Va., have logged over 850 flight hours – 270 of which since November 2011 – and have explored almost 90% of the flight envelope, says Scott. The two other prototypes will be based at Cascina Costa: the third will fly in 2013 and be used for icing trials, while the fourth, due to fly in 2014, will be used for developing the new-generation avionics. As of early November, total operating time (flight and ground runs) for the two prototypes exceeded 1,080 hours.
During their latest 250 flight hours, the two prototypes have concentrated on High Rate of Descent testing, low speed handling, high speed handling maneuvres, STOL testing (including at increased MAUW), various performance tests, etc. as well as flight testing of new inertial reference platform.
Certification and Deliveries in 2016
Certification will be to the FAA’s combined FAR 25 and FAR 29 with tilt-rotor specifics, within a new Powered Lift category. The aircraft will initially have dual-pilot IFR, allowing flight in known icing conditions (including more than 50 miles over water), and will be fitted with emergency flotation equipment. However, single-pilot IFR is planned for the short-term future.
AW is working to a schedule that will allow the AW609 to receive its FAA type certificate in early 2016, rather than late 2015 as previously planned, and since it will begin production as the certification cycle nears its end, initial production deliveries will follow shortly thereafter. “Ours is not a technology demonstrator, it is a real aircraft, a real product,” notes a company official, implying that its competitors cannot make the same claim.
In parallel, AW is also looking to optimize the AW609’s performance, even though it has amassed all sorts of marketing and historical data that tends to prove that, even in its current form, the aircraft is capable of carrying out the great majority of real-world missions.
Clive Scott, for example, cites a study carried out by the UK Ministry of Defence, and which found that 90% of military helicopter missions are flown at a range of 100 nautical miles or less. The same study found that over 80% of helicopter Search And Rescue missions involved rescuing one or two people; the AW609 would be able to comfortably carry out both categories of missions much faster than conventional helicopters.
The tiltrotor’s speed is a major factor in its competitiveness. Although its direct operating costs are admittedly much higher than for a conventional helicopter, its high speed means missions are far shorter in duration, so the same aircraft can fly more missions in a given time.
For SAR, one the primary civil roles envisioned for the AW609, the aircraft can carry 2,500 lbs of fuel in its wing tanks, and a further 500 lbs is an internal fuel tank, making it possible for it to rescue two people at a range of 500 nautical miles, and hover for 30 minutes while doing it.
AW clearly thinks the AW609 is a winner. Triple-redundant critical systems mean that the probability of a catastrophic failure is reduced to 10-9, and a number of flight tests have still to be carried out, for example at high rates of descent, to determine flight parameters that will avoid the vortex ring phenomenon that proved catastrophic for the V-22 Osprey. The low-speed flight envelope also remains to be explored, although 85% to 90% of the flight domain has already been cleared.
What price speed and range?
Costs obviously remain an issue. AW officials are tight-lipped about the AW609’s estimated price and operating costs, but they say the tiltrotor will cost about 1.5 times the price of the similarly-sized AW169. However, as all production work is reorganized and rationalized under AW’s own roof, and as contracts are renegotiated with suppliers and subcontractors, the price tag can be expected to fluctuate somewhat.
During the summer, AW signed several new supplier agreements for the AW609. Pratt & Whitney Canada will now provide the final production version of its uprated PT6C-67A turboshaft, while Rockwell Collins will supply a variant of its Pro Line Fusion embedded display system (EDS) which will allow single-pilot IFR. BAE Systems will supply an upgraded flight control computer which will integrate AW’s own control laws and flight control software. Other agreements are expected to follow.
One of the arguments frequently leveled against the tiltrotor is the inordinately high engine power it requires compared to its payload. The V-22 Osprey, for example, requires over 12,000 shp of engine power to carry 24 passengers, while a conventional helicopter of similar payload and vintage, like an AS332 Super Puma, requires less than 4,000 shp, or one-third the engine power, to carry the same number of passengers. It is this difference that makes some operators skeptical about the cost-effectiveness of the tiltrotor for civil missions.
But while this is also true of the AW609, the differential is much smaller. With two engines rated at a total of about 4,000 shp, it can carry a useful load of 5,500 lbs., about the same as the AW169 which has half the engine power (2,000 shp).
However, in this case the trade-off is more attractive since the tiltrotor’s payload is delivered at twice the speed and over twice the range, both of which are major game-changers for civil operators.
And the tiltrotor also offers great operational flexibility, notes Clive Scott: for example, it can handily beat helicopters in many revenue missions because, just by using a short (300-meter) rolling take-off, with the rotors tilted at an angle of 70°, its MTOW increases by 1,000 lbs.
Bigger and better in the pipeline
AW envisions development of a larger second-generation variant of the AW609 which will have greater range and payload – an all-up weight of around 10 tonnes, and capable of carrying about 20 passengers. Perhaps even more importantly, this future large tiltrotor will have the capability to fly outside regular air traffic routes, which will make the most of its performance. This will be made possible by new air traffic management procedures enabled by satellite-based monitoring and a future generation of avionics that will focus on flying the aircraft autonomously, outside of the current restrictions imposed by ground-based infrastructure.
AW executives are convinced that bigger tiltrotors will be developed, as future vertical lift needs will inevitably be driven by requirements that only tiltrotor can provide: increased performance, new operating areas, increasing airspace restrictions as civil traffic increases, and environmental regulation.
If they are right, they will have won a head-start of such magnitude that competitors will find it difficult to catch up.