Ian Sheppard/LONDON Guy Norris/LOS ANGELES
Supporters of turboprops should take heart. If history is anything to go by, it is possible that the surge of development work on new small turbofans with thrust ratings of below 35kN (8,000lb) may spawn new turboprop and turboshaft versions. Complementing their technical advances, these products could be pitched at attractively low prices, creating a new dynamic for the future of the engine type.
Until the regional jet honeymoon period is over and the true market potential revealed, however, the development of turboprop versions is sure to lag. Already, some manufacturers have declared their long term faith in the turboprop market. ATR, for example, caught the pundits off guard at the recent US Regional Airline Association meeting when it predicted a resurgence rather than a fight to the death. The Franco-Italian consortium believes some airlines will prefer to replenish fleets with more modern turboprops and predicts sales of up to 200 ATR 42-500s. At the same time, however, ATR is keeping an eye on regional jets and is keen to rejuvenate the former Airjet programme.
A watershed development has been Fairchild's Dornier re-engineing of its 328, replacing the Pratt & Whitney Canada PW119B turboprops with PW306B turbofans. In this case, the engine manufacturer is in a no-lose situation, and has provided P&WC with a springboard on to the larger 428JET. The Canadian company's success also prompted it to hold together the SPW14 project with Snecma, despite the cancellation of the Airjet, in the hope of gaining more work with Fairchild Dornier on its larger proposed family members.
While uncertainty dogs the passenger side of the business, the traditional turboprop markets of military trainers, utility aircraft and cargo transports continue to flourish. A recent development, with potentially large implications for the future of "dual-pac" (two engines-one propeller) applications is the adaptation of LHTEC's CTS800 for the Ayres Loadmaster. Originally developed for the Boeing Comanche attack helicopter, the turboshaft is being converted into the CTP800 turboprop for the ungainly transport. As well as being a new application for the T800 family for LHTEC, it also reverses the normal trend in which turboprops evolve turboshaft variants.
Another project closer to fruition in a similar vein is the Soloy Pathfinder 21 conversion of the Cessna 208B Grand Caravan. The large utility aircraft is fitted with two P&WC PT6D-114As powering a single propeller through a Soloy Dual Pac gearbox. This is due to be certificated at the end of the year. As if to underscore the continued popularity of turboprops in this area, another utility aircraft, CASA's C212-100, may well be the last aircraft to be fitted with upgraded AlliedSignal TPE331-10 turboshafts in a programme that now covers more than 13 aircraft types and versions and has produced more than 4,000 engines.
Meanwhile, the latest exploitation of a successful gas turbine core is the BMW Rolls-Royce BR700-TP, proposed for the Airbus Military Company's Future Large Aircraft. The BR710 turbofan already powers the Gulfstream V and Bombardier Global Express business jets and, as the BR715, will power the Boeing 717. The only new turboprop engine coming close to this high power level is P&WC's PW150 for the Bombardier Dash 8Q-400 with a thermodynamic rating of 4,980kW (6,680shp). At the same time, Snecma is still proposing a turboprop version, designated M138, of its M88 turbofan, which powers the Dassault Rafale.
In the pure-turboshaft arena, one of the most crucial developments for the long term future and pricing of turboshafts is Allison's "World Engine" project. Unveiled in February, the initiative is aimed at producing a low cost successor to the popular Allison 250 family. Based on industrial gas turbine technology to keep the cost down, the first core is expected to make its initial run by the end of this year. Allison hopes the World Engine will give birth to a family of turboshafts (and later turboprops) in the 220-820kW power range.
The Rolls-Royce/Turboméca RTM322 turboshaft, meanwhile, is being adapted for the UK version of the Boeing AH-64 Apache, while the MTU MTR390, which powers the Eurocopter Tiger, could be offered as an alternative to the General Electric T700-701.
One area where turboprops are unlikely to be usurped by turbofans for some time is the powered lift category, namely the Allison T406-powered Bell Boeing V-22 and the PT6-powered Bell 609 civil tiltrotor derivative. Some observers have predicted heavy demand for tiltrotors, as they each can replace two helicopters, which has prompted Eurocopter to revive its own plans for such an aircraft.
Source: Flight International