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Open Rotor on the Roster?

mgiles — Sun, 25 Oct 2009 02:41:46 +0000

Open Rotor

Recently a student asked me what an open Rotor was and I replied it was basically a turbo prop but with things being how they are a sexier name had to be invented so they came up with this. It got me to thinking; as we are progressively backed up against the wall by reality it is only a matter of time before the open rotor makes its reappearance and so it is timely to have a look at how accurate my glib explanation was. Basically the problem with propellers is that they suffer from severe efficiency losses as the speed of the propeller tips approaches the speed of sound and basically the advantage of them is that they have to accelerate the working fluid (the air they fly in) less because they accelerate a lot more of it. I.e. they have in effect a much greater by-pass ratio than Turbo fans. The big question is where is the best trade off for speed versus efficiency. Time will tell. the Russian Bear long range patrol aircraft with its huge counter rotating props has been with us for years and conferred enormous range advantages when compared with the turbo jets of the time albeit with a considerable disadvantage in reliability. The new A400 European Military lifter will set new standards of frugality and is forecast to cruise at 450 kts which is quite respectable. After the next round of geared fans it looks as it there is only one place to go and that is the Open Rotor. Look for it in the next new wave; maybe with a blended body conformation aircraft.
OPEN ROTOR: HOW DOES IT WORK?
An open rotor engine is essentially a turboprop with two rows of blades, or propellers, which can operate efficiently at higher speeds than a conventional turboprop. The blades of a turboprop tend to spin air out, rather than pushing it back. In an open rotor engine, the forward propeller pushes the air backwards, while the rear one sucks it. “You actually entrain the air in between the two sets of blades, and you can think of it as a virtual fan case,” says Nuttall. “It’s actually stopping the air going out, and the second one straightens up the air from the first one. Most of the air is doing just what it does in a turbofan, hence you can go a lot faster. You can’t go as fast as a turbofan. We think the most efficient speed is about 0.76 Mach.” This compares to around M0.845 for typical jet-powered airliners. A turboprop engine would also need blades twice the diameter of its open rotor equivalent to produce the same power. “There are only two efficiencies in an engine,” says Nuttall. “There’s thermal efficiency, which is how efficiently you get the energy out of the fuel and turn it into ‘turning’. And there’s propulsive efficiency, which is how efficiently you take that energy and turn it into ‘push’.” In a conventional turbofan, propulsive efficiency increases as cruise speed goes up. A single propeller can provide 90-92% propulsive efficiency, but this drops off with speed. “The trick is to try to get an efficiency of that nature, but at [a turbofan] sort of speed, and that’s why you put one [propeller] behind the other. That entrains the air and lets you actually drive the aircraft forward at a mach number of 0.75-0.8,” says Nuttall. In terms of lifecycle costs, an open rotor has no nacelle, thrust reverser, or fan case. “It’s an interesting debate at the moment,” says Nuttall. “When we’re asked this by customers our basic rule of thumb is that it should be about the same as today. You’ve deleted a lot, but you have added complexity at the back. The main complexity you’ve added is the gearbox, but the gearbox is half the power of the [P&W] geared turbofan. We accept that the gearbox is a significant thing that we’ve got to develop, and we’ve got plans for that.” An open rotor would operate at constant torque, with the pitch of its blades and speed of its rotors controlled by a full-authority digital engine control to provide the thrust demanded by the pilot.

Open Rotor Airliner proposal

See http://www.flightglobal.com/articles/2009/10/06/332991/open-rotor-how-does-it-work.html

Political correctness weakening national industrial base

mgiles — Tue, 01 Sep 2009 03:04:42 +0000

Industrial base of USA

WW 1 and to a lesser extent WW2 caught the US and Europe unprepared for conflict and with an industrial base of modest proportions. Despite many warning signs political decisions were it seems based on what government officials hope to be the case rather than what experts were warning to be the case. As the sage said those who do not learn the lessons of history are doomed to repeat them. There are some commentators who see a similar situation developing again. World War I caught the U.S. military unprepared, and although Congress was quick to order a massive buildup of guns, tanks and planes, with “virtually no defense industrial base … the war was over before U.S. industry could deliver any of them.” Today’s Pentagon budget cuts risk a return to the same situation. James Carafano a Washington Examiner comlumnist warns. “Washington has not seriously worried about the industrial base since the end of the Cold War,” and “production could virtually vanish” over the course of the next decade.
It isn’t easy to put U.S. defenses back on track after they’ve endured a season of neglect as Gen. William Snow found that out firsthand. Snow’s job, when he arrived in Washington in the World War I era, was to direct the buildup of artillery for the Allied Expeditionary Force. He thought his office should have stationery reflecting the importance of the task. His request was rejected. Rather than fund this extravagance, it was suggested the general purchase a rubber stamp to mark his correspondence.
Snow had joined a War Department completely unprepared to fight a war. The Army hadn’t been used to buying much of anything since the Civil War. It had forgotten how.
Nor was there much to buy. The United States had virtually no defense industrial base. When America entered the war, Congress handed out unprecedented contracts for artillery, tanks and planes. The war was over before U.S. industry could deliver any of them. Doughboys went into battle riding British tanks, piloting French planes and firing artillery made by their allies.
America in 2009 is returning to the 19th century, a world where America will be incapable of producing the instruments needed to defend America. Worse, Secretary of Defense Robert Gates’ defense policies are pumping steroids into the speed of that decline. Both houses of Congress have passed the defense authorization bill, giving their rubber stamp to dismantling the defense industrial base. Last week, President Barack Obama made a speech to the Veterans of Foreign Wars cheerleading the decision. The White House has couched many of these defense cuts in rhetoric that makes them sound like smart business decisions — axing unneeded weapons and killing costly programs. We’ve seen massive cuts to everything from missile defense to how many ships and planes America needs.
The truth is that the administration is more interested in budget slashing than smart buying. And its ill-advised cuts are endangering operations in Afghanistan and Iraq. The proof of this is simple. They are cutting programs and replacing them with … nothing. The Pentagon plan is to simply ignore future needs or else push the decision to buy new equipment far into the future, when paying for new planes, combat vehicles, missile defenses and ships will be somebody else’s problem.

What Washington has not explained is how it’s going to sustain a defense industrial base when it doesn’t buy anything. Today, defense purchases account for about 10 percent of the nation’s industrial output. In a decade, that production could virtually vanish.
In fairness, Obama did not invent this problem. Washington has not seriously worried about the industrial base since the end of the Cold War. While Gates’ cuts have been trumpeted from the Pentagon’s E-Ring, folks forget that his predecessor, Secretary Donald Rumsfeld, slashed about 100 procurement programs.
The problem is that neither administration really considered the effect of these decisions on the capacity of the American industrial base to support any future Pentagon strategy. A recent study by the Aerospace Industries Association found that some of our defense sectors were already on life support. Regardless of any strategy the Pentagon might pick, the industrial base for developing rotary-wing systems (like combat helicopters), long-range bombers and some space assets is now so crippled that companies would have a difficult time responding to new requirements, even if the military decided today that it wanted a lot more new stuff.
There is only one answer. The Pentagon should immediately start a sustained program of modernizing its military capabilities.
Otherwise, the defense industrial base is going to dry up and blow away. With it will go more than just high-paying jobs and technical innovation. We’ll be saying goodbye to America’s capacity to defend itself at a reasonable cost. And that’s simply unacceptable.
From http://www.washingtonexaminer.com/opinion/columns/jamescarafano/James-Jay-Carafano-Obama-Gates-are-gutting-Americas-defense-industry-56248742.html

Time for a Radical Change

mgiles — Sat, 20 Jun 2009 02:47:27 +0000

Blended body concept

Some years ago (maybe 30) I read in Flight that the time was coming when a latest generation Combat aircraft was going to take the entire GDP of a small nation. At the time I took it seriously and though it a bit of an exaggeration but as time has worn on it seems they were joking at the time using delightful British irony but that they had unwittingly hit the nail on the head. That day is here with the F22 that the US wont sell to any one because it cost them so dear and mega Airliners taking many Billions to create and 100s of millions to buy.

Blended body plan

As the financial crisis looms and doomsayers prattle away I wonder whether now is the time for a paradigm shift. Skip the A380 and A350 and B787 etc and go for a highly standardized no frills blended body well and truly subsonic alternatively powered (fuel cells and props?) solutions that will halve the cost per kg per kilometer (Note I use metric as I am talking of the future)
Anyone with the courage to do it should (?!) clean up.

Air Transport essential to Society

mgiles — Tue, 16 Jun 2009 01:04:26 +0000

An Airbus-commissioned report warns of danger to global employment if air transport’s long-term growth is limited
A single percentage point fall in air traffic growth over the next 20 years could eliminate 6 million jobs worldwide, according to a new report “Aviation: the real world wide web”. The report sets out to counterbalance the long-running debate about the impact of aviation on the environment. It was compiled by analysts Oxford Economics, and commissioned by Airbus, with the support of British Airways and EasyJet.

It puts the aviation industry’s contribution to global social and economic development into bold numbers and re-examines some potential myths about aviation and the environment. It lays out the facts for “well-meaning individuals” who, says BA chief executive Willie Walsh, believe that supporting aviation-related industries by buying imported produce, for example, is bad for the environment.

It also examines the benefits “eco-tourists” who travel by air bring to poorer countries through opening trade routes and increasing awareness of environmental preservation.

“The general view is that travel and tourism is bad for the third world, but you can come up with statistics and facts that prove the opposite,” says Airbus chief executive Tom Enders at the report’s launch in London on last Friday.

The 124-page report establishes that 35% of all trade by value ($3.5 billion) in manufactured goods carried by air. The air transport industry directly employs more than 5.5 million people and contributes $425 billion to global gross domestic product. It estimates that when combined with supply chain and dependent industries such as tourism, aviation supports more than 33 million jobs worldwide and contributes $1.5 trillion to GDP.

Based on the latest long-term market forecast from Airbus, Oxford Economics calculates that by 2026 the industry’s direct and indirect contribution will support 50 million jobs and $3.6 trillion of the world’s GDP. But the analysts warn: “Should passenger and cargo traffic growth be one percentage point lower than currently forecast for the 2007-26 period, the number of jobs supported would be reduced by 6 million to 44 million, and the contribution by $600 billion.”

While the report acknowledges that aviation has had an impact on aviation, it promotes a “sensible balance” between the industry’s positive contribution to the world, and the impact of future growth. “Stopping or reducing air transport would not automatically lower emissions,” says Oxford Economics, as a number of factors are at play: for example, the level of emissions released by replacement transport modes and the replacement activity, as well as their supply chains.
From http://www.flightglobal.com/articles/2009/06/15/327864/paris-air-show-airbus-commissioned-report-warns-of-danger-to-global-employment-if-air-transports.html

Worst is over for aviation but recovery not imminent

mgiles — Fri, 29 May 2009 01:37:51 +0000

Airliners of the world

The worst might be over for the aviation industry as the latest international traffic data for April 2009 has shown passenger demand fall only 3.1 percent compared to an 11.1 percent fall in March.

April figures were released by the International Air Transport Association (IATA) on Wednesday, showing the average passenger load factor was 74.4% compared to 72.1% in March.

Despite the improved figures, IATA’s chief executive Giovanni Bisignani stressed that the industry was “not out of the woods yet.”

“The demand improvements that we saw in April are welcome. But the 3.1% decline in passenger demand still outstripped the 2.5% cutback in capacity.

“There is no improvement in revenues as yields continue to fall. And freight remains at shockingly low levels”

Bisignani was referring to the international cargo demand figures which fell 21.7 percent, the fifth consecutive month figures have been in the negative 20 percent range.

The strongest cargo performers were Middle Eastern carriers (-11%) whilst European, North American, Asia-Pacific and African carriers were similar with -23.3%, -22.4%, -22.3% and –18.8% respectively.

“The worst may be over. However, we have not yet seen any signs that recovery is imminent”

As per his previous arguments put forward before, Bisignani stressed again the importance of flexibility and change in order to weather the economic storm.

“Airlines remain constrained by old rules that restrict basic commercial freedoms such as access to markets and capital. Much of the cost base remains out of our control—from volatile fuel prices to monopoly infrastructure charges.

“Many governments simply don’t understand the need for urgent change…to manage through this ongoing crisis, every
player in the air transport value chain must be prepared to drive change”

From:http://www.etravelblackboardasia.com/article.asp?id=62147&nav=109