When engine maker Pratt & Whitney opened its first machine shop in a tobacco warehouse in Hartford, Conn., 80 years ago last month, former Wright Aeronautical president Frederick Rentschler probably could not have imagined how popular, and ubiquitous, the company’s engines would become.
Rentschler established P&W, which is now part of United Technologies (UTC), in 1925 to develop a nine-cylinder air-cooled radial for the U.S. Navy. Obtaining $250,000 from Niles-Bement-Pond, he adopted the name of that company’s Pratt & Whitney Machine Tool division.
The design became the hugely successful 400-hp R-1340 Wasp, which remained in production (in modified form) until 1960. Boeing’s Model 40 mailplane used the engine, which soon powered Curtiss and Vought aircraft with impressive results. P&W’s next engine, the Hornet, was half the weight of the competing water-cooled Packard powerplant installed on the U.S. Navy’s T4M torpedo bomber.
In 1928 P&W joined Boeing and Vought to establish UTC forerunner United Aircraft and Transport, forming what later would sprout Pratt & Whitney Canada (P&WC), first to maintain local P&W engines and later to manufacture them.
A number of new engine designs followed. Sporting twin rows of seven cylinders, R-1830 Twin Wasps and R-1535 Twin Wasp Juniors followed, powering eight out of nine Bendix race winners and eight out of 11 Thompson Trophy victors in the 1930s. The heavier R-1535, which had lower installed drag and permitted better pilot vision than the Hornet, equipped the 1935 Hughes racer to a world landplane speed record.
The 1,000-hp R-1830 propelled 29,000 B-24 Liberators and C-47 transports. The R-2180 Twin Hornet produced 1,400 hp by 1935 but was overtaken by the 18-cylinder, 2,000-hp R-2800 Double Wasp, which pulled the Vought F4U Corsair along at more than 400 mph. It powered P-47 Thunderbolt and F6F Hellcat fighters and Convair 340 and Douglas DC-6 airliners.
The 20-cylinder, liquid-cooled 1,100-hp R-2060 was a disaster, before P&W successfully developed liquid-cooled, sleeve-valve engines of up to 3,000 hp.
With large British and French orders and U.S. government funds, P&W extended its World War II production capacity by 1 million sq ft and drafted companies such as Ford, Buick, Nash-Kelvinator, Continental and Jacobs to license- build its R-985s, R-1340s, R-1830s, R-2000 and R-2800s. P&W also produced the R-4360 Wasp Major, a monster 28-cylinder corncob radial rated at 3,500 hp. P&WC built Wasps before taking over all P&W piston-engine production.
Stepping Up Turboprop Production
By V-J Day, P&W had shipped more than 363,000 engines, but with orders slashed and competitors building jet engines (from which P&W had been barred), the problem was what to do next. The company had studied turboprops since 1939 and set about learning more: it built more than 100 J30 turbojets for Westinghouse and Rolls-Royce Nenes (J42s) for the U.S. Navy’s F9F fighter. P&W and Rolls-Royce also co-produced Tay/J48s.
P&W’s first home-grown turboprop was the 7,000-shp PT2/T34, then the 8,200-pound-thrust JT3 turbojet and a related (but unsuccessful) 10,000-shp military turboprop. The JT3 led to the 10,000-pound-thrust J57 for the B-52, F-100 Super Sabre and KC-135 tanker/transport. Of course, it also equipped Boeing 707 and Douglas DC-8 jetliners, as P&W built 15,000 examples (and Ford another 6,000). Then came the (cancelled) 15,000-shp T57 turboprop, while the JT4/J75 powered the F-102, F-105 and F-106 “Century-series” fighters and (later) the Lockheed TR-1, as well as more 707s and DC-8s.
In 1957 P&WC began building the 3,000-pound-thrust JT12/ J60, before developing a 500-shp design that became one of aviation’s most successful: the PT6, initially for the Hiller Ten99 helicopter. PT6s equipped an experimental de Havilland Canada Otter and a Beaver. Beech put PT6s on a Model 65 Queen Air, spawning the now ubiquitous King Air business twin.
P&W has built more than 33,500 examples of its reverse-flow configuration PT6. The engine has logged nearly 270 million hours on 13,250 aircraft in variants that offer between 475 and 2,000+ shp.
Work in the 1950s on the six-foot-diameter J91 (with heat provided by nuclear power) led to the JT9D commercial and related J58 military engines. Funded by defense budgets, the TF33/JT3D became the first “[relatively] big” turbofan, according to P&W. An extra low-pressure turbine stage and a fan bypass duct increased thrust, cut fuel burn and reduced noise; P&WC produced 8,600 copies of the engine.
A byproduct was the 7,500- to 11,200-pound-thrust J52/JT8, which led to the 14,000- to 21,000- pound-thrust JT8D. That engine powered every Boeing 727, 737-100/200 and McDonnell Douglas DC-9-80.
Mid-1950s work on liquid-hydrogen technology later contributed to the U.S. space program. P&W collaborated with Lockheed on the JP7-fueled JT11B/J58 for the Mach 3+ A-12/SR-71. Six large pipes carried compressor bypass air and the afterburner featured chemical-reaction ignition.
Boeing and P&W, losers in the USAF C-5 transport competition, collaborated on the very-high-bypass-ratio JT9D turbofan for the 747. The design involved improved fan and compressor, enhanced combustors, new materials and cooling systems, but early operations suffered engine-casing “ovaling,” necessitating a “thrust-frame” yoke that the company later replaced with a new mounting.
JT9Ds eventually offered 45,000 to 58,000 pounds of thrust and powered Airbus A300, A310 and Boeing 767 twin-aisle twinjets and McDonnell Douglas DC-10-40 trijets.
Targeting Corporate Aviation
In 1966 P&WC and Cessna perceived demand for 400-mph corporate aircraft. The engine company scaled down the JT9D fan to obtain 2,000 pounds of thrust and the JT15D-powered Citation was born.
The company’s JT25D was the result of early 1970s 5,000- to 7,000-pound-thrust studies. The decade also saw certification of P&WC’s PT6T turboshaft engine for light helicopters.
Interface problems on P&W’s 25,000-pound-thrust JTF10/TF30 for the F-14 led to a redesigned inlet, but compressor-burst troubles saw GE replace P&W. Specified long service life for the JTF22/F100 for F-15 and F-16 fighters stimulated introduction of high-nickel alloy and titanium. P&W then studied a 23,000- to 29,000-pound-thrust JT10D before addressing the 25,000- to 35,000-pound range with various fans and high-pressure compressors and turbines.
In 1979 P&WC launched the PT7 to power new post-deregulation regional airliners as a 2,000- to 4,000-shp successor to the Rolls-Royce Dart. It was renamed the PW100.
Further JT9D evolution produced the PW2037 (a 37,000-pound-thrust PW2000), which equipped Boeing 757s and offered the first commercial-aviation electronic engine control. The PW3000 designation defines 4,000- to 8,000-shp shaft-drive studies aimed at replacing AlliedSignal (Honeywell) T55 and Allison (R-R) T56 engines.
During the 1980s engine manufacturers flirted with very-high-bypass-ratio fans, and P&W was no exception. The company studied large contra-rotating units driven via a gearbox from a small multi-stage turbine; exploration continues today, with geared fans seen as a future technology to power 150-seat-class airliners.
In 1983 P&WC launched the PW200 for the Bell TwinRanger and MBB BO105 helicopters to be assembled in Canada. P&WC also considered growth versions of medium-size business jets that would need, say, 1,000 pounds of thrust at 40,000 feet/Mach 0.80, and produced the PW300.
For new large airliners, P&W developed the PW4000 with three fan sizes, beginning with the 94-inch fan on 52,000- to 62,000-pound engines for the Airbus A310-300 and A300-600, Boeing 747-400 and 767-200/300, and McDonnell Douglas MD-11. A 100-inch-fan, 64,000- to 68,000-pound-thrust derivative for the A330 became the first engine to receive approval for 90-minute extended-range overwater twin-engine operations (Etops) before service. The 112-inch-diameter-fan, 86,760-pound-thrust PW4084 for the Boeing 777 was the first cleared for 207-minute Etops. The PW4098 powers the 777-200ER and 777-300.
Engine Technology for the Future
The 21st century finds P&W equipping the Lockheed Martin F-35 with the F135 and the F/A-22 with the F119. Having lost the battle to power competing Boeing 787 and Airbus A350 designs, the company remains confident that the PW-EXX “all-electric” engine could yet see the light of day, while its 18,000- to 24,000-pound-thrust PW6000 for the Airbus A318 is close to receiving European approval.
P&WC is working on an engine for Bombardier’s proposed 110/130-seat C Series jetliner. The new PW600 family includes the 1,615-pound-thrust PW617F and 3,200-pound-thrust PW535E for Embraer’s very light jet (VLJ) and light jet, while the PW610F powers the Eclipse 500.
Continuing research includes an advanced fan integrator, based on P&WC’s PW308 engine. P&W swept-fan and advanced gear-drive technologies are being introduced on the 70,000-pound- thrust GP7000 for the A380.