Type Certification in Hand, Maintainer-friendly PurePower® PW800 Begins Airframe Integration

Now that Pratt & Whitney Canada’s (P&WC) PurePower® PW800 series powerplants have gotten their type certification from Transport Canada, airframe integration tests are underway with the engines’ launch airframe customer: bizjet-builder Gulfstream Aerospace.

The 15,144-pound thrust PW814GA and 15,680-pound thrust  PW815GA will power, respectively, Gulfstream’s G500 and G600. The G500 flies 5,000 nautical miles at Mach .85; the G600 6,200 nm at Mach .85. The range of both is more restrained at Mach .90. By the time the PW800 engine is projected to enter service the PurePower engine family is expected to have accumulated more than 1.5 million hours.

Gulfstream Aerospace Vice President Technical Marketing and Communication Steve Cass says the G500 will certify in 2017, with customer deliveries slated one year later. The G600 is set to certify in 2018, with deliveries scheduled for 2019.

As of late March 2015, “We’re currently up around 3,500 hours [of engine testing] in the PW800 program as a whole,” says Scott McElvaine, Pratt & Whitney Canada’s director of marketing and customer service. That encompasses “work … we’ve done in our test cell, work that we do on our own flying test-bed, which is a Boeing 747SP that we’ve modified specifically for flight tests.”

What’s been the result of all the trials? “So far the program has been very successful for us,” he says. “Everything is exactly where we hoped it would be, and – in a lot of cases – more so. As usual you find small stuff. But it’s not anything that’s caused us a headache.”

In the meantime Gulfstream is working to ensure powerplant and airframe have a successful marriage. “There’s been tons of work done on making sure that the engine/airframe integration is [right],” says Cass. “We do a lot of computational fluid dynamics analysis.” So far, the OEM has completed more than 2,400 hours of wind tunnel testing.

Other analyses are looking at thrust-reverser design to make sure, when it’s deployed, the reverser’s exhaust plume “doesn’t impinge on the tail or cause any damage.”

Bleed-air and power extraction requirements are particularly important with these particular airframes/engine combinations. Cass says that’s because the G500 and G600 “have a very low cabin altitudes.” They vary from 3,000 feet at an actual altitude of 41,000 feet to about 4,800 feet at an actual altitude of 51,000 feet.

The edge

High-flying performance characteristics were critical in driving Gulfstream to mate the PW800 series with its new airplanes. Four different engine OEMs submitted proposals. The airframer looked at the powerplants’ specific fuel consumption, and environmental friendliness – especially when it comes to nitrogen-oxide emissions. P&W Canada says the PW800 series, “Delivers ultra-low levels of unburned hydrocarbons and smoke through its unique TALON™ X combustor.” Noise regulation compliance – not just Stage 4, but the possibility of Stage 5 – also played an important role in Gulfstream’s decision.

Maintenance marvels

Engine maintainability and customer support were critical. Gulfstream has implemented a 10,000-hour on-condition plan for the powerplant. “A typical business jet operator would use about 500 hours per year,” says Cass. P&WC says operators can expect a long time on wing compared to today’s powerplants.

The PW814GA and PW815GA promise to be among the most easily accessible powerplants flying. “We’ve spent a lot of effort making sure that performing maintenance on the engine is rapid,” says McElvaine. Take the cowl doors. They’re “a clam-shell type configuration that are very easy to open and close.” The doors self-latch. That means when they’re pushed to closure the latches hook, supporting the door weight while the maintainer locks the latches closed.

Then there are the access panels to the core through the bypass. They’re huge. “This gives you fabulous access to the core,” says McElvaine. That’s where important scheduled inspection work takes place. You want the working environment to be both safe and comfortable, to afford maintainers “access to everything they need.”

To that end, “We’ve put steps in the cowl doors so they don’t have to fiddle around with mats and ladders and things like that,” says McElvaine. The cowl door is designed to take the weight of two technicians and a significant load of their tools.

Pratt & Whitney Canada engineered the PW800’s accessory suite so technicians can remove and replace almost all accessories – such as FADEC – in 30 minutes or less.

Such is the micro-look for maintainers. The 35,000-foot view, says McElvaine, combines inspections, aligning maintenance intervals so technicians only have to open up the engine once to perform two tasks, as opposed to opening it twice.  “We’ve eliminated fundamentally 40 percent of the scheduled maintenance,” he says. That number encompasses 20 percent less actual inspection.

One key innovation is the fan. In the PW814GA and PW815GA it consists of a solid, single piece of titanium. “It’s a single piece of metal,” says McElvaine, “as opposed to a hub with blades stuck on.” That's good from both maintenance and operational standpoints.

With traditional fan assemblies comes aerodynamic loss. Simply put, part of the structure is dedicated to holding the assembly together. When engineers don’t have to worry about that they can design the full length of the fan blade for maximum aerodynamic efficiency. “That’s one thing less for maintainers to worry about,” says the P&W Canada marketing and customer service director, “rubbing between blades and blade roots.”

Common core architecture

Although the phrase “common core” engenders all sorts of controversy when it comes to education, there’s little dissension in aviation ranks.

The PW800 series shares a common core architecture with the PW1000 Geared Turbo Fan, a powerplant selected as the exclusive engine for a trio of regional jets – the Bombardier C Series, Mitsubishi Regional Jet, and Embraer’s second-generation E-Jets.

McElvaine says the PW1000 is ideally suited for the regional jet mission, where comparatively low-altitude, short-haul flights prevail. At those lower flight levels “Having an optimized fan and optimized fan speed” is important, he says. Many business jet aircraft, in contrast, operate at far higher altitudes, precincts in the neighborhood of FL410 to 510. 

Problem is, “When you take that gear box and much bigger fan up to the higher altitudes, where business jets fly, it just becomes a lot of weight and you’re not going to get as much thrust out of it.”

But it doesn’t mean you can’t take advantage of the PW1000’s core technology – the high-pressure compressor, the combustor, and the high-pressure turbine. That’s precisely what Pratt & Whitney Canada did when it collaborated with its Hartford-based parent/partner and the two began collaborating on the PW800 in 2008. McElvaine says as far back as the early 2000s the two were “looking at an alternative architecture to really bring a game change to the marketplace.”

To support the effort, P&WC says, “Definition of a new service plan designed specifically for the PurePower PW800 … is underway.” That service plan is set to launch around the end of 2015. The OEM says its hallmarks are “speed, simplicity, and performance.”

Pratt & Whitney Canada’s service network is extensive, with 30 owned or designated repair and overhaul facilities across the planet. In addition, there are eight parts centers and 100 field support reps. Mobile repair teams are primed for dispatch when needed.

These assets stand ready to support a market for the PW800 series, a market that could be formidable. McElvaine says long-range and ultra-long-range aircraft comprise about half the business jet deliveries over the next 15 to 20 years. “That’s our target market.”

Jerome Greer Chandler is a two-time winner in the Aerospace Journalist of the Year competition's Best Maintenance Submission category; he won in 2000 and 2008. His best-seller 'Fire and Rain' chronicles the wind shear crash of Delta Flight 191 at DFW. Chandler's passion for aviation safety is more than professional. It's personal. Two of his relatives have perished on commercial airliners, one of them in the infamous Braniff Electra crash of 1959.