The Short, Happy Life of the Prop-fan
Meet the engine that became embroiled in round one of Boeing v. Airbus, a fight fueled by the cost of oil.
- By Bill Sweetman
- Air & Space magazine, September 2005
The Boeing Company
(Page 5 of 6)
The UDF demonstrator is in the engine collection of the Smithsonian’s National Air and Space Museum, and the Allison-P&W prototype is in a company training center in Indianapolis. But nobody involved in the prop-fan or UDF writes the experience off.
GE put the UDF’s blade technology directly into the GE90, its most powerful commercial engine. “We trained a lot of good guys,” Rowe says. One was Mike Benzakein, then the company’s leading technologist. GE is still looking at counter-rotating turbines and fans, and came close to proposing such an engine for Boeing’s new 7E7.
Colman Shattuck, the program’s leader at Hamilton Standard (now Hamilton Sundstrand), says that the project was “one of the best times of my career” and that it spurred today’s all-composite propeller technology. The firm’s French subsidiary, Ratier-Figeac, makes the multi-blade propeller for the Airbus A400M military transport.
For Allison, the benefit had little to do with technology. “We got involved publicly with Boeing and Douglas,” says Novick, “and it helped us tremendously in getting back into the commercial business.” Embraer picked an Allison turbofan, the AE 3007, for its EMB-145 regional jet, and Rolls-Royce, which acquired Allison in 1995, cranks turbofans out by the boatload.
Mulally and Condit became the leaders of the next major Boeing project, the 777. It had little resemblance to the 7J7, but the underlying technologies and disciplines—computer-aided design and manufacture, and integrated electronics—were similar. Mulally quotes Boeing chairman Thornton “T.” Wilson as saying that the 7J7 “was the best investment in aircraft development that Boeing ever made” and adds that “we could not have done the 777 without the 7J7.” Condit went on to head Boeing until he resigned in late 2003, accepting responsibility for ethical and performance problems.
At the 2001 Paris Air Show, Mulally whipped the covers off another radical, rear-engine airplane, the tail-first Sonic Cruiser. In an echo of 1985, Boeing promised vast improvements over anything the competition could do. Like the 7J7, the Sonic Cruiser failed to ignite customer interest, and Boeing is pushing the 7E7, now redesignated the 787. Both aircraft offer more comfort with a lower fuel burn, Mulally says. “The cool story about the 7J7,” Mulally says today, “is that it’s exactly the same [idea] as the 7E7, but at a smaller size.”
The Airbus A320 went on to become one of the most successful airliners in current production, second only to the 737 in total unit sales. Airbus’ Adam Brown also compares the 787 to the 7J7. “The issue is whether the advanced-technology combination can give you a big enough gain in efficiency to supersede what’s already on the market,” he says.
And once again, the key to the fortunes of both companies could be the price of a barrel of
oil.
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Comments (6)
So, if somebody proposes a novel, simple but very advanced diesel fueled piston engine, with a power/weight ratio competitive with a turbo-shaft power plant of equivalent power and promotes it in combination with either UDF or contra-rotating propellers, and predictions are that this combination will result in a reduction in fuel burn to about 30% of the turbo-shaft equivalent, do you think anybody would be interested?
Posted by Nigel Eric Rose on August 18,2008 | 02:52 PM
Dear Nigel,
I think the diesel would still have more moving parts than a turbojet or turbfan or turboprop. More things to look out for in servicing. That is why they like turboprops over pistons -- TBO's. Some can theoretically go near 10,000 hours between overhauls. Plus you would have to find something other than metal to make your diesel engine out of to cut the weight. The holy grail of engine design -- the ceramic ( plastic ) engine !!
Posted by John Fox on July 30,2009 | 04:56 AM
any one remember an engineer at hamilton during the early 1980's last name Reynolds. I think they called him Mr Prop Fan!?!?!? JUst curious!
Paul
Posted by paul damiano on November 19,2010 | 05:39 PM
The Metropolitan Vickers firm in Britain designed, built and ground tested a propfan engine in 1945. It also had a counter-rotating fan at the rear of the engine, driven directly by a turbine inside the hub of the fan blades. It produced a significant increase in thrust and a reduction in fuel consumption compared to the company's turbojet engine, but like GE's UDF it failed to find a market and was abandoned.
Posted by Kurt on July 1,2011 | 12:53 AM
Well folks I'm still here and fuel costs and related matters such as emissions, are still the biggest problem confronting civil aviation. Not long now 'til everybody gets to really face up to reality and all this, when the Carbon Tax comes into effect in Australia. Regards the observation about more moving parts in a diesel, the originla concept was based on the DDC 92 Series engines and in a direct comparison at the time, there were 108 fewer parts per cylnder than the parent form; never actually looked at it on the baiss of moving parts, but I'd be sutrprised if there are more than a dozen per cylinder.
Nigel Eric Rose
Posted by Nigel Eric Rose on April 24,2012 | 02:47 AM
I've been exposing NASA to an advanced variable cycle diesel engine patterned on old Junkers 207 but with APU T/C, bottoming turbine, re-heated exhaust and variable exhaust nozzle. Looks to be about 20-25% better fuel consumption than best N-3 prop fans for 2035 on HWB type airframes. They are coupled with best NASA high Mach C/R props.
Installed weight estimate is about 9000 pounds for engine/ancillary engine equipment/props and pylons for 8 M/W engine. Takes 2 per 120 PAX, 3 per 240 PAX and 6 for a 500K 6000 nm freighter. Meets climb to .8 M. and 31K and looks to be able to get to 45K initial cruise if needed. Engine hits about 60% thermal efficiency at top of climb and cruise.
Engine is 6 cylinder opposed piston layout and part count is probably about 10% or less of comparable turboprop engine. Suspect cost to be about 50% of 10000 SHP turboprop engine.
Posted by Richard Johnston on September 20,2012 | 07:03 PM