Engine design is crucial to larger turboprop aircraft, says regional manufacturer ATR as it seeks powerplants of the future
Engines will be "the real differentiator" for the next generation of turboprops, says Mario Formica, head of marketing at turboprop airframer ATR.
"We consider that in the next 10 years, the regional market needs step-change technology: evolutionary technology, not revolutionary technology," he says. The goal is a new generation of larger turboprops. "There are 200,000 monthly frequencies on sectors up to 400nm [740km], where regional jets with between 30 and 70 seats are operated today. These frequencies could be operated profitably by 50-, 70- or 90-seat turboprops."
Formica rules out a stretch of the ATR 72, which could not achieve the required 30-40% cut in operating costs on short-haul sectors (compared with regional jets of similar capacity). Turboprop engines need to maintain a gap of 20% in propulsive efficiency over a turbofan operating at 300kt (555km/h] at low altitude.
"We cannot wait until 2020 or 2025," he says. "We [have] specific requirements that we have clearly communicated to the engine manufacturers." These include a 20% reduction in specific fuel consumption, a higher power-to-weight ratio, better fuel flow, lower emissions, and noise levels that fall below International Civil Aviation Organisation Stage 4 limits by "good margins".
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© Pratt & Whitney CanadaP&WC engines power Bombardier Q Series turboprops as well as ATR aircraft |
Of paramount importance is integration between the engine and propeller manufacturers from an early stage. "This was not the case at the beginning of the ATR programme, where we had Pratt & Whitney on the engine and Hamilton Sundstrand on the propeller," says Formica, adding that integration can contribute to optimisation of the gearbox and nacelle, as well as reduced drag, weight and line-replaceable unit count.
POSITIVE THINKING
Some engine manufacturers have responded positively to the integrated propeller approach, he says. "Some of them have also provided the first proposal, with the lightweight advanced reduction gearbox. Improvement at the level of compressor and turbine are essential. The 90-seat aircraft will be heavier, and to respond to the requirement that we are proposing in terms of cruise speed, time to climb and good performance in hot and high environments, we need more power."
The ATR 42 and 72 turboprop families deploy Pratt & Whitney Canada PW100 series engines. In December 2006 P&WC revealed that it would invest $1.5 billion in R&D over five years. An additional $360 million investment was announced in October.
"We're always trying to push the frontiers on system architecture, engine architecture," says Andrew Tanner, vice-president business and regional aviation. "Greenness is front and centre with everything we do today: newer materials, attacking fuel consumption, new concepts in aerodynamics. Another area we're investing in heavily is low-emission combustion systems."
P&WC engines power Bombardier Q Series turboprops as well as ATR aircraft. "We work with all our customers, trying to be ahead of the curve of what the needs are in the future", adds Tanner. "In terms of a timeframe, a lot of it depends on the economy. [But] we work on demonstrator programmes ahead of time, so that when the time is appropriate to bring new technology to the table, we're there."
Source: Flight International
