Review - Pax tells his side of 787 Maiden Flt

[Kip Powick]

Hong Kong (CNN) -- I am something of a plane spotter. I can spend hours at an airport watching planes taking off. Yes, I know that sounds a little bit sad but when I was told about this assignment to cover the maiden 787 passenger flight from Tokyo to Hong Kong I got pretty excited.

With that it mind here are my thoughts on Boeing's claims for the 787 "passenger experience."

Larger windows

Boeing says: The larger windows allow for spacious views making every seat a window seat. Passengers can individually adjust their environment by electronically darkening or lightening with a push of a button, blocking the light but not the view.

Stevens: This is true. For me, it's perhaps the best thing about the 787.

The windows are about 30 percent bigger than the aircraft's predecessor, the 767. They are also much higher so you don't need to hunch over to see the view.

You really do get the feeling that you are seeing a lot more of the world passing by.

Dreamliner's first flight -- three years late

They also have a manually operated switch that can tint the glass to a darker shade which stops light getting in but still allows you to see out. It takes a little time for the full change in the color of the glass but preferable to the snap open/shut blinds.

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Stevens: Because the plane's wings and fuselage are made of composites -- basically a high-tech plastic reinforced with carbon fiber which is lighter than traditional aluminum -- humidity and cabin pressure can be increased, which makes the plane's environment closer to a ground-like environment.

It's pressurized to 6,000 feet rather than the normal 8,000 feet of other comparable size aircraft.

On our four-hour flight it didn't really make a difference to me. Long haul is where it will be noticeable, although some passengers on our flight said it felt fresher.

Cleaner air

Boeing: Cabin air is much cleaner than today's commercial airlines. Fresh air comes from scoops on the side of the fuselage rather than coming from the engines. Along with the standard filtration system the 787 has additional systems that together can help to reduce throat nose and eye irritation for passengers.

Stevens: I can only take their word for it. See above.

<A href="http://edition.cnn.com/2011/10/25/travel/dreamliner-features/index.html" target=_blank>Seven reasons the Dreamliner is special

Smoother ride

Boeing: Passengers benefit from smoother ride technology that senses turbulence and counteracts it. Travelers can enjoy a more comfortable flight with significantly less motion sickness.

Stevens: Interesting one. A passenger just in front of me for whom flying is his "passion" told me that the conditions were perfect for flying -- no turbulence.

But we did encounter some minor jolts coming in to land at Hong Kong.

ANA's first officer on our flight, who had been seconded to Boeing for four years, told a pre-flight news conference in Tokyo that the aircraft had weather/turbulence censors which activated changes in the wing shape to help combat any rough ride.

A Boeing spokesman told me the plane was able to flatten out extreme up and down movements caused by turbulence.

But because it was such a good day for flying, it apparently wasn't put to the test.

Architecture

Boeing: From welcoming entryways to larger windows to vaulted ceilings to blue-sky effects the plane's features ensure that passengers will be enjoying the flight. And since the plane was designed around the passenger there will finally be enough room, as the pilot says, to move about the cabin.

Stevens: In economy, where I was, it was still a struggle to get past anyone in the aisle and impossible if the drinks trolley was doing the rounds.

The seats appeared to be pretty standard economy class style. But one of the first things I noticed when I got on was that the ceiling of the fuselage was higher.

The effect was also enhanced by sophisticated lighting from the LED system and the fact that the overhead luggage bins were less obtrusive. So sitting down and looking up gave the impression of more space.

Larger bins

Boeing: With a unique cabin architecture and design passengers have ample room to easily stow at least one large roll aboard bag in an overhead compartment close to their seat.

Stevens: Yes. How long before more low-cost carriers start charging for those bags though?

LED lighting

Boeing: Adds variation and ambiance to the cabin. The lights can gently simulate a full flying day gradually changing through a spectrum from dawn to dusk, enhancing the flying experience.

Stevens: The lighting system has been designed to a dawn-to-dusk effect that helps maintain the circadian rhythms that tell our body when it's time to sleep.

Boeing has spent a lot of time on the lighting. The "blue-sky" lighting that greets you on a daytime flight is replaced by a softer yellow light when meals are served. It also does a mean rainbow effect but I'm not sure what that's for.

The 787 has been built as a medium-size long-haul aircraft where sleeping matters.

In conclusion

So all in all, an impressive flight. Is it the game-changer that Boeing says it is? Certainly there are enough new effects and engineering gadgets that make it a nicer experience.

At the end of the day, though, in economy a long-haul flight will always be a drag.

No matter how big the windows are or how effective the lighting and air quality is. But this is definitely a start.

[chockalicious]

Interesting report. I had heard that Boeing surveyed pilots about what they liked to see the most in flight and the overwhelming answer was the horizon. The windows in the cabin are more of an oval shape than circle so apparently 90% of the population will be able to see the horizon when in flight.

I have seen the LED lighting and it os pretty cool.

[boestar]

Fresh air comes from scoops on the side of the fuselage rather than coming from the engines.

A bit of a simplistic statement. Fresh air is brought in from the outside without going through the engine compressor but it is compressed by an electrically driven compressor. It is not just ram air keeping that pressure in the cabin.

[boestar]

Close

Massive 787 Electrical System Pressurizes Cabin

By Michael A. Dornheim

ELECTRIC CABIN

Boeing's 787 Dreamliner grabs attention for its composite structure, but its systems are just as radical.

The aircraft is a large step toward the all-electric airplane--one in which all systems are run by electricity. Bleed air from the engines has essentially been eliminated and while hydraulic actuators are still used, the majority of their power comes from electricity.

The most eye-popping change is that the cabin will be pressurized by electric motors, not by the bleed air used by almost every pressurized aircraft. Breaking with five decades of practice, Boeing claims that electric compressors are better suited for the cabin than engine bleed.

Related changes include:

*A pair of large generators on each engine will extract more than four times the normal amount of power. They total 500 kilovolt-amps (kva.) per engine, compared to a normal maximum of 120 kva. That large drag on the engine shaft may hurt compressor surge margins, and one manufacturer, Rolls-Royce, has made fundamental changes that it says improve surge margin (see p. 51).

*The generators are now large enough to be used backwards as engine starters, a task exclusively performed on large turbofans by much lighter pneumatic motors. The high torque required at low rpm. results in running the units beyond their rated current and the starting task is a bigger issue than the switch to electric cabin pressurization, says Michael J. Zolidis, chief engineer at Hamilton Sundstrand Electric Systems in Rockford.

*Anti-icing of the wing will be done with electric heat instead of bleed air. This is a large electrical load, roughly 100 kw., but much less than the nominal 700 hp. (522 kw.) that cabin pressurization takes. Engine inlet anti-icing is the only remaining bleed air function.

*Power density in the generator is 50% higher by weight and 2.5 times greater by volume than in today's units. To help accommodate that, output voltage of the three-phase device is double the norm, at 230 volts AC (VAC) instead of 115 VAC. Within the motor controllers an even higher level, 540 volts DC (VDC), is used.

*Liquid cooling has been introduced for the motor controllers, which handle hundreds of horsepower for the starters, cabin compressors and electric hydraulic pumps. While this is more efficient, it could be a maintenance problem. The propylene glycol cooling loop also is routed to galley refrigerators to take their heat.

*There is a much higher level of system integration at the supplier level. Hamilton Sundstrand has the contracts for the electrical system, cabin pressurization and environmental control system, auxiliary power unit (APU), generator drive gearbox for the Rolls-Royce Trent 1000 engine for the 787, ram air turbine, and several other systems. The scope is broad enough that the company is able to make design trades within each work package and across company divisions. And the design work reaches further into the aircraft, to things that Boeing might have done itself before.

Why did Boeing make the jump to electric pressurization? Some of the answers seem to be already fading in the mists of time and computer programs as the aircraft rapidly becomes more solid, and not everyone gives the same answers.

A top reason is that Boeing feels that power electronics, which are key to the all-electric airplane, are on a steep curve of performance and cost improvement, while pneumatic systems growth "tapped out" around 1995, says Michael K. Sinnett, Boeing chief engineer for 787 systems. At the moment, the performance of pneumatics and electrics is roughly similar, but electrics are poised for growth and pneumatics are not.

"This was a Boeing gut decision, and I think they made a good decision," says Clifton D. Jacobs, Hamilton Sundstrand Electrical Systems vice president and general manager. "If we get a high-temperature power transistor that needs less cooling, the system will be better later. I don't see much further improvement in bleed."

Along the same line, Boeing believes it should get its technology more from the broader industrial market, which has a large investment in better designs, rather than from what it calls the "boutique" aircraft business--and electrics have broader use than pneumatics. The billions of dollars being thrown at hybrid cars affects the motors and controllers that Boeing will use.

But do electrics burn less fuel? "When we decided on electric pressurization, it lowered aircraft empty weight 1,000-2,000 lb. and fuel burn was down several percent," Sinnett says. "But the numbers got muddied as the 787 got integrated. It's hard to say where the weight has gone."

He says the main reason the electric cabin is more efficient is that modern engines compress and heat the air too much--that energy is thrown away in the precooler and excessive expansion. At current 30-psia. bleed pressures, the amount of wasted energy is about 30%. The electric compressor creates less pressure and less waste.

A Boeing engine management workshop attended by Hamilton Sundstrand officials stated that bleed pressures of 45-50 psia. are expected, making more waste. Engineers would like to lower pressure by moving bleed ports upstream as stage pressure ratios grow, but can't because of interference with variable stator mechanisms.

Rolls-Royce says that doesn't apply to it. If the Trent 1000 were supplying bleed air, it would be at the same pressure and temperature as the Trent 700, or 30 psia. and about 370F--the same as now, says Rolls-Royce marketing manager Andrew Booth. And the bleed is not near variable stators on the three-spool engine.

The comments may apply more to General Electric and Pratt & Whitney engines. The variable stators in their engines go much further up the compression chain. A General Electric official says bleed vs. electric "is a wash relative to the engine performance. It may have differing values to each airframer on how they do the installation and how much they need to extract from the engine." General Electric is selling the GEnx engine for both the 787 and the competing Airbus A350, which uses bleed air, and must be careful not to offend either customer's design.

Other reasons may be more important. Boeing wants to reduce 787 assembly time and wants good dispatch reliability. Sinnett believes an electrical system will take less time to install than the bleed air equivalent, and have fewer nuisance faults, such as overheated bleed ducts. Wires are less likely to overheat the 787 composite structure than a bleed duct because wire problems are easier to detect quickly.

"How the prime weights things changes the answer," says John VanHorne, the 787 systems integration manager at Hamilton Sundstrand. Zolidis adds, "Aircraft of identical specifications could have completely different systems." And that is the case of the A350 and 787.

Big electric motors weren't considered before because the power electronics of just 10 years ago were too large and heavy, Sinnett says. "Now we have the weight, cost, power and reliability that works on an aircraft."

There are four cabin compressors, two on each of the two air-conditioning packs in the wing-to-body fairing. They compress outside air to roughly 15 psia. and an outlet temperature around 200F. The 6,000-ft. cabin is at 11.8 psia. The compressor wheel is about one ft. in diameter and turns 42,000 rpm. on oilless foil air bearings, though the speed of the permanent magnet motor varies in practice. Each one can produce 90-100 hp. The ozone-removing catalyst normally operates around 350F entry temperature and engineers had to make sure it works at 200F.

The low compressor pressure biases the heat rejection task away from the turbine-compressor air cycle machine, because it uses pressure drop for cooling. Instead, the new pack requires a larger radiator to dump the heat to outside air, and that increases cooling drag compared to current practice.

"We minimize the pressure drop from the compressor to the cabin and make the pack larger," says Louis J. Bruno, the engineering manager at Hamilton Sundstrand Air Management Systems. He says a low-pressure pack takes less energy overall, though there is more drag. The mixer for cold and recirculated air is much smaller than before so it will fit within the pack instead of taking space in the cargo bay.

The cargo bay is electrically heated. The environmental control system (ECS) includes the liquid cooling loop for high-power motor controllers and galley refrigerators. "We got such a large work package that we could make trades within the package," such as whether to use liquid or air cooling, says Sunil Agrawal, chief engineer at Air Management Systems. And the electrical system is intimately tied to the high power requirements of the ECS, creating design trades across work packages.

But Boeing makes Hamilton Sundstrand pay for that large role. "Boeing didn't ask us to sacrifice but to go the extra mile," Jacobs says. "There is a huge investment to make it work. We went to the top of the corporation to get the green light."

The engine generators are variable frequency three-phase alternators, and the electrical system supplies 115 and 230 VAC with frequency varying from 360-800 Hz. For components that need the traditional constant frequency power, a small amount of 115 VAC at 400 Hz. will be synthesized. There will also be the usual 28 VDC for avionics.

The variable frequency helps achieve the high power density because a heavy and bulky constant-speed drive is not needed. The six-pole generators make the maximum 800 Hz. at 16,000 rpm. and weigh about 200 lb. each.

Unusually high voltage occurs inside the system, and that is 540 VDC (actually ±270 VDC), which is rectified from the generators, then synthesized into a controlled frequency to run the big motors. This confusing conversion of AC to DC back to AC is done because the most efficient way to control a large motor is with AC power synchronized to motor rpm., Sinnett says.

The 787 will have six starter/generators--two 250-kva. units on each engine and two 225-kva. units on the APU. That makes total generating capacity 1,450 kva. The Airbus A380 with 2.5 times the maximum weight has only 840 kva.

Making an electric starter replace the proven pneumatic starter is a top concern. If the generators weren't so large, it wouldn't make sense to use them as starters, but as it is, their size is driven by both roles. The problem is accelerating the large inertia and drag of a big turbofan in a competitive time. The typical Trent pneumatic starter motor makes 200 hp., Booth said. Both electric motors turn the engine and for a quick start are driven at 1.2 times the current rated for continuous generating. "Before, overload [was] rare on aircraft. Here we do it every start," says Robert W. Guirl, the 787 program director in Rockford.

One motor is enough to start the engine under almost all conditions, but at a slower rate. And starters are often used for other tasks, such as motoring the engine for cleaning. Can an electric starter take this lengthy duty cycle?

Engineers are worried about cooling the starter at high torque and low rpm. The units are cooled by their own oil system. Cooling that oil with air or fuel is the job of the engine company, and may be an issue.

If the APU doesn't work, a 90-kva. ground cart doesn't supply enough electricity to start the engine. Two carts connected to different aircraft systems should work.

The primary power distribution system includes the motor controllers and is split among four large panels, two in the forward cargo bay and two in the aft bay. They weigh 1,000 lb. each and are liquid-cooled. Arcing is a greater concern with 540 VDC inside, but vulnerable items such as relays have been engineered. Hamilton Sundstrand is partnered with ECE Zodiac of France on this system.

The remote power distribution system takes electricity from main buses to utility loads. The technological change is that instead of having centralized switching boxes, the switches have migrated closer to the loads, resulting in fewer wires and less maintenance, says Luis Andrade, chief engineer for electronic products engineering in Rockford. The system uses convective instead of forced-air cooling, made possible by components that both reject less heat and can run hotter.

The 787 flight controls have some electrohydraulic actuators as well as three centrally powered 4,850-psi. systems. Those are also heavily electric--the left and right engine systems each have an electric motor pump (EMP) and engine-driven pump (EDP), and the central system has two EMPs. The same 27 gallons-per-minute (gpm.) pumps are used on both EDPs and EMPs, and that is four times more power than an electric pump previously would have had. "The EMPs would have been air-driven pumps before at Boeing," says Leslie L. Bevans, the emergency power principal engineer in Rockford.

The EMP is driven by a 100-kva., 88-hp. motor. The motor controller varies rpm. with load so less use is made of the pump's variable displacement controls.

The company is building a new 12,000-sq.-ft. Aircraft Power System Integration Facility (APSIF) in Rockford for the 787, to be ready for operation in May 2006. Starter/generator prototypes are now being tested in the adjacent Integrated Systems Laboratory (ISL) on a 500-hp. dynamometer. That simulates enough engine load to test one starter at full capacity, but can take two starters only to 70-80% capacity. It can run them in either the starter or generator role. The ISL will receive a 1,500-hp. dyno to run two units to full capacity, and another 500-hp. dyno to simulate a 787 APU.

In an integrated test, the dyno has driven generators connected to two motor controllers supplying power to cabin compressor and hydraulic pump motors.

The APSIF floor plan is roughly like a 787 and will have a pair of 1,500-hp. dynos to simulate the engines and a real APU in a container outside where the tail would be. A number of real components--such as power distribution panels, cabin compressors, electrically driven hydraulic pumps, fans and avionics--will be in the facility. They will be connected by cables of the proper length and location, and, to further simulate impedances, they will be placed adjacent to a representative of the current return framework Boeing will use inside the composite structure. This will test electrical system dynamics with real loads and sources. Since most high-power switching is done with solid-state devices instead of relays, the switching is less abrupt and there should be less oscillatory "ringing" in the system.

Copyright © 2011 Aviation Week, a division of The McGraw-Hill Companies.

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[Kip Powick]

This article, (above this post), is what...5 or 6 years old??

I will assume it is and I would imagine many changes to all systems have been made since.

[boestar]

I am sure there have been refinements to the systems as many of them were a complete departure from conventional systems. however the aircraft remains an electrical bird to the nth degree. Still a complete departure from conventional systems technology all meant to be more efficient and passenger friendly.

[conehead]

For sure, it will mean job security for an Avionics Tech.

[boestar]

And that is a road we have been headed down for some time in this business. As aircraft become more and more electronic and electrical in nature, the technicians need to learn that it may take more than a wrench to fix the plane. Get out your meter and have at her.

[DEFCON]

...and your cannon plug 'spray can'.