Life in the 21st century looks set to be healthy for turboprop engine builders



Turboprop makers are getting used to paraphrasing author Mark Twain. Rumours of their death are premature, they say, and there is evidence that - if anything - they could be looking forward to a healthy life in the 21st century.

Without doubt, commercial turboprops have been hit hard as regional jets (RJs) continue their onslaught on the North American airline market in particular. According to Rolls-Royce, sales of turboprop-powered regional aircraft have plummeted by about 70% over the decade, with firm turboprop orders accounting for a little over 20% of total sales last year, compared with almost 90% in 1990. By contrast, firm orders for regional jets exploded from 10% over the first two years of the 1990s to almost 80% of annual sales by 1998.

As the regional jet business begins to mature in North America and new sales increase in former turboprop strongholds around the world, turboprop makers are refocusing efforts on new markets of their own, as well as on propping up established niches. ATR, the Franco-Italian manufacturer of the ATR42 and ATR72, for example, plans to build more than 300 of its Pratt & Whitney Canada-powered turboprops over the next 10 years, while Raytheon, which makes the 19-seat Beech 1900D, forecasts a requirement for "three to four dozen new 19-seat aircraft for the next five years, and possibly the next 10 years". Raytheon sold 45 new 1900Ds in 1998, a year in which most of the pundits had all but written off the 19-seat turboprop market altogether for new-build aircraft.

ATR marketing president Jean Daniel Leroy says the company's objective is "to be at 30-plus sales a year, and we plan to deliver 37 aircraft [in 1999]". ATR plans to win more than 50% of the large-turboprop market from Bombardier's Dash 8Q series, its major and sole surviving competitor in that class. It predicts a market for around 900 turboprops over the next 10 years, with the largest sector (360) in the 60/100-seat size. Independent forecasts by aerospace consultancy Walsh Aviation also indicate relatively strong demand continuing for turboprops in the 35/99-seat market between now and 2008. It predicts a demand for almost 1,500 turboprops over the period.

Major market

China, which all manufacturers continue to view as having unfulfilled potential, is seen as a major market for new and used turboprops, despite the old joke that the Chinese equivalent of a small regional aircraft is a Boeing 747. P&WC is among those hoping to benefit from the revival of indigenous aerospace groups AVIC I and AVIC II, each of which is developing upgraded versions of their dated turboprops. AVIC I is developing the MA 60, a derivative of the Y7-200A, fitted with P&W PW127Js, Hamilton Standard 247F-3 propellers and Rockwell Collins avionics. AVIC II is developing an improved version of its 14-passenger Y-8 turboprop. The first PW127J-powered Y7-200A is due to enter service this month with Changan Airlines of Xian, China.

Other PW127-series engines seeing new life include the PW127H, which powers a newly certificated version of the Ilyushin Il-114. The -100 version has been launched by Uzbekistan Airways, and is built by the Tashkent Aircraft Production Organisation. Another programme coming to fruition is the PW127G-powered CASA C295 utility aircraft, launched in 1997 and expected to enter service next year.

Another important entry into service for P&WC, and for Bombardier, is the Q400, due to make its commercial debut by the end of this year. Powered by the most powerful P&WC turboprop yet, the PW150A, the Q400 is set to enter service with initial customers Augsburg Airways, Changan Airlines, Horizon Air, Jersey European and SAS Commuter. Although firm orders for the long and fast turboprop are relatively slow, with just 29 announced by the end of this year, Bombardier is convinced that a market exists for as many as 3,560 new turboprops over the next 20 years. Most of these - more than 2,000 aircraft - will be needed to fulfil the 40/79-seat short-range market, Bombardier believes, where it claims the economics of the turboprop remain compelling, despite the rush to RJs - including its own. As a successful manufacturer of turboprop and jet-powered regionals, Bombardier is even more bullish about prospects for the RJ family. Its overall regional aircraft delivery forecast for the period to 2018 projects a need for more than 9,900 aircraft, two-thirds of them jets.

P&WC, for one, will hope the forecast comes true. With more ATR, 8Q Series 100, 200, 300 and 400 sales in the offing, it could look forward to continuing to build on its tally of over 53 million hours of operation. The PW100 family powers more than 1,920 aircraft in service with 277 operators in 92 countries.

Even if PW100-series sales exceed P&WC's wildest dreams, it could never hope to achieve the records notched up by its smaller, and older, sister engine, the PT6 turboprop. With the 28,500th engine due to be delivered by the end of the century, the PT6 is easily the world's most popular engine in its class. Ranging in power from 410kW (550hp) to 1,230kW, the engine is operated in more than 160 countries on agricultural, corporate, military, training, utility and regional aircraft, and was fast approaching 209 million flying hours as Flight International's directory closed for press. The engine is perhaps best known for its outstanding reliability, a hallmark of turboprops in general but exemplified by the PT6, which has achieved a basic in-flight shut-down rate of one per 250,000 flight hours. The engine continues to attract new business and is expected to be certificated next year on the Piaggio Aero Industries twin-engined utility P166. The plan, which has been delayed for two years, is back on track thanks to new financing, and will see the aircraft's AlliedSignal LTP101-700s replaced with the PT6A-121.

The reliability of turbines is such that one company, Integrity Aircraft of New Zealand, is discussing with Britten-Norman the development of a single-engined, AlliedSignal TPE331-12 version of the Trislander. As its name implies, the Trislander was designed to be powered by three pistons, all of which would be replaced under the plan by the single, 745kW turboprop. The aircraft would have up to 450kg (205lb) in extra payload. The TPE331 is also being used to replace pistons, in this case the Pratt & Whitney R-1340 radial, in a re-engining of the de Havilland Otter by Texas Turbine Conversions. The -10 version offers a 220kW increase in power and a 180kg increase in useful load, plus improved performance for climb, take-off and landing.


Advances within the TPE331 family have also produced an active conversion programme for operators of -3, -5, -6 and -8 engines. Through AlliedSignal Service Centers, hundreds of Cessna Conquest 441s, Twin Commanders, Beech KingAir 100s, Dornier 228s and Mitsubishi Mu-2s have been converted to TPE331-10 configuration. The conversion comprises a new combustor system, turbine and stator hardware, a new static structure and fuel distribution system. The modifications improve climb performance, cruise speed and temperature margin for hot-day operations, as well as reducing cost of ownership.

An engine that shares some TPE331 heritage is the CTP800, a turboprop built and developed jointly by AlliedSignal and Rolls-Royce Allison. A derivative of the T800 developed for the Comanche RAH-66 helicopter, the CTP800 is in development to power the ungainly Ayres LM200 Loadmaster. Two engines will be strapped side by side and connected to a single propeller through a reduction combining gearbox to form the CTP800-4T power system. Rated at 2,010kW, the propulsion system has been designed to permit the Loadmaster to carry a 340kg payload over a range of up to 1,045km. The aircraft is aimed at FedEx, which has 250 on order and option.

One Western turboprop maker with hopes for market success in new territory is General Electric, which has penetrated the CIS and powers the newly built Sukhoi S-80 twin utility transport with its CT7-9. The 1,305kW turboprop is also used by the Czech-developed Let L-610G, sales and manufacturing of which will continue under the stewardship of new owner Ayres. Deliveries of the first production CT7-9C3 turboprops began at the start of this year to CASA for the upgraded CN-235-300.

The S-80, under construction at KNAAPO's plant in Komsomolsk-on-Amur, is vying with the MiG-110 to succeed the Antonov An-26. Powered by two 2,465kW Klimov (Izotov) TV7-117S turboprops, the MiG-110 is being constructed in mock-up form at the Mikoyan Engineering Center near Moscow. Other derivatives are planned, including a MiG-110M with Western engines and avionics. The -110A would be built under licence in Austria, along with two light tactical transports, the -110VT for the Russian air force and a search and rescue version, the -110PR. As usual with so many CIS projects, development of both the MiG and Sukhoi utility turboprops has fallen behind schedule because of lack of money, but key milestones for both are expected next year.

Another long-delayed effort looking for firm decisions next year is engine selection for the Airbus A400M medium transport. After dropping turbofans for turboprops, the choice between the Snecma/MTU M138 and rival Rolls-Royce GmbH BR700-TP was again put off, and is now promised for the first quarter of next year. However, with the total programme now not expected to amount to much more than 250-300 aircraft, both engine teams are questioning the development costs of a new turboprop which is unlikely to find any other applications.

Turboshaft development

The growing demand for cheaper, larger, faster and more capable helicopters continues to drive turboshaft development at a rapid pace. Much of the search for cutting-edge turboshaft technology in the USA is conducted by the Defense Department-led Integrated High Performance Turbine Engine Technology (IHPTET) programme, which has goals of increasing the kilowatt/weight ratio by 120% relative to the late 1980s production standard. It also aims to cut specific fuel consumption by 40% and production and maintenance costs by 35%.

While turboshaft engines like the T800 are evidence of IHPTET's success to date, the final goals of the programme are about to be demonstrated on Joint Turbine Advanced Gas Generator (JTAGG) cores running at AlliedSignal and General Electric. Future JTAGGs will test multirole cores to be developed under the Versatile Affordable Turbo Engine programme (VATE), which has been proposed as a successor to IHPTET.

Some of the advanced performance, either being demonstrated or planned to be shown by the JTAGGs, is exactly what is called for by the US Army's common engine programme (CEP). This is an advanced common engine that the army wants to power the BoeingAH-64 and Sikorsky H-60-series helicopters within six years. An operational requirements document has been drafted for a re-engined UH-60X Black Hawk, and a similar document for a CEP-powered AH-64X is expected to follow within two years. The goals of the CEP include a 25-35% reduction in specific fuel consumption, a 60-80% improvement in power-to-weight ratio, and a 20% reduction in operating and support costs. The improved performance will allow the UH-60X to carry a 4,100kg external load over a distance of at least 135km, or an 11-man combat assault team at least 275km.

This sort of performance would require a 60% improvement in power-to-weight ratio over the existing T700-701C, hence the requirement for the CEP. If the programme goes ahead, the used T700-701Cs could find their way into almost 900 Bell UH-1 Hueys, which the US Army wants to upgrade for up to a further 25 years of service with Army National Guard and Reserve units. Another option under study is upgrading the helicopter's AlliedSignal T53 to the more recent -703 configuration.

In line with calls from military and commercial users to cut the operating and maintenance costs of their engines, AlliedSignal has made big strides to improve the performance of its LTS101 turboshaft. After overcoming early reliability problems, the company made major efforts to extend the inspection interval by 50%.

General Electric, meanwhile, continues to develop the T700/T6E and CT7-8 turboshafts in an integrated programme, with FiatAvio and Hamilton Standard providing the full authority digital electronic control system. The T700/ T6E, specifically designed for the NH90 which it powered for its first flight in March last year, will be built by GE, FiatAvio and MTU. T700/T6E qualification by the Italian Ministry of Defence is targeted for 2002, with first deliveries in 2003.

This year also saw the first flight of the CT7-6D-powered Sikorsky medium-lift S-92A Helibus at West Palm Beach, Florida. Engine certification by US and European authorities is due by the end of next year, and the helicopter is expected to enter service in 2002.

Pratt & Whitney Canada, meanwhile, continued its push into Eastern Europe and the CIS by helping to launch the PW127T/S-powered Mi-38. The engine, a derivative of the PW127 turboprop, will produce almost 2,500kW take-off power, with a maximum continuous ratingof 2,200kW. In the initial flight test phase,P&WC will simply modify PW127s for theMi-38 demonstrator. For the future, the manufacturer is also studying potential PW127T/Sdevelopments for tilt-rotors, possibly based on the PW150.

This would compete with the Rolls-Royce Allison T406 that powers the Bell Boeing V-22. The PT6C-67, P&WC's largest turboshaft, will power the Bell Agusta BA609 tilt-rotor and the joint venture's AB319 medium twin helicopter. The PT6C-67A is due to be certificated in December 2001.

Future turboshaft developments planned by P&WC could be driven by technology coming out of the PW6XX programme - an all-new engine family specifically designed for general aviation and small business aircraft. The PW6XX is aimed at small jets in the 4.45-9kN (1,000-2,000lb)-thrust range, as well as turboprop and turboshaft engines in the 450-670kW range, using the same core technology. R-R, which had similar plans to develop a low-cost industrial "World Engine" successor to the Allison 250, has shelved this because of problems with different qualification requirements of aerospace and industrial applications. Alternative plans are being pursued, says the company, which is adding the latest version - the 335kW "Super R" 250-C20R/S engine -to its family.

Source: Flight International