777-200LR ready to stretch its legs to the limit

Paris Air Show » 2005
December 12, 2006, 6:54 AM

As the second Boeing 777-200LR makes its public debut right here in Paris this week to show off its snazzy interior, prototype number-one continues to work hard back at the airframer’s facility in Everett, Washington, testing aerodynamic adjustments and stretching the type’s range capacity close to its limits. Scheduled for U.S. Federal Aviation Administration certification by October and first delivery to Pakistan International Airlines early next year, the 777-200LR by last month had flown roughly half of the 400 to 450 hours Boeing estimates it will need to win regulatory approval. Next, the company plans to take the first prototype on an 11,000-nm demo flight in an attempt to break the distance record.

The program’s focus now has turned mainly to evaluating tweaks to the airframe, such as adding vortex generators to the outboard part of the wing and reducing the size of the devices originally planned for the inboard section. Tests will show whether the smaller generators, about the size of those on a 737, can keep airflow attached to the wing. Of course, the shorter the vortex generators, the less drag and, hence, better fuel burn. Boeing plans to apply the changes to both the -200LR and its heavier sibling, the -300ER.

Another study centers on cutting the drag produced by the airplane’s air-conditioning system design. The 777 uses a system in which ram air travels through an inlet in the fairings below the wing-body connect point, enters a heat exchanger and cools the bleed air coming from the engines, thereby regulating the temperature of the cabin. Behind the inlets Boeing has fit computer-controlled louvers that adjust the amount of air intake needed depending on flight conditions. If the system needs less air intake, the louvers close to their optimum position, therefore cutting drag.

Other tests on the latest 777 have shown that the -200LR’s rudder moment would allow for an engine thrust increase from 110,000 pounds to 115,000 pounds, giving it better field performance and/or payload capacity. Now flying the -200LR with de-rated versions of the GE90-115Bs used on the 777-300ER, Boeing plans to offer a version of the -200LR powered by the 115,000-pound-thrust engines used on the bigger airplane.

“We studied whether the rudder was sufficient to handle 115,000 pounds of thrust like it can do on the -300ER, because that’s a longer airplane, and we’ve determined that, yes, it can,” Boeing 777 program manager Lars Andersen explained to Aviation International News. “But we won’t certify that until an airline buys that level of thrust.”

All told, Boeing hopes to cut fuel burn by another 2.25 percent over original estimates, including about 0.8 percent from engine improvements. The company claims the -200LR and the 365-passenger 777-300ER burn between 6- and 8-percent less fuel than their competition, the Airbus A340-500/600. Taking into consideration passenger capacity, Andersen said both fly 20- to 25-percent more efficiently per seat. In service now for more than a year, the -300ER has also shown impressive reliability by Boeing’s reckoning, registering a 99.2-percent dispatch rate–only 0.1 percent below the entire 777 family’s average.

“Reliability and fuel burn efficiency are just crucial, even more so than for the shorter range airplanes, because if you lose a couple of hours in dispatching airplanes you’re going to bust duty times because of the long flights,” said Andersen. “That hurts you as well with slot times at your destination.”

After this week’s Paris show Boeing plans to fly the second prototype on an around-the world demo tour. Andersen wouldn’t name the cities, citing “security reasons,” but a company spokesman said it would cover every region Boeing sees as a market for the airplane. Upon return to Everett, it will resume flight testing for interior type certification.

Boeing has outfitted the airplane on display here at Le Bourget with a first-class section devoid of center and side stowage bins to emphasize cabin roominess and highlight the interior’s contoured, gull-wing-shaped ceiling. The business-class section has side bins, but no center bins, again to show off the new ceiling design and create more overhead space.

Supplemental storage from an optional overhead stowage closet will allow airlines to fly the airplanes without center bins in first and business class, explained Andersen. Using an elevator-lift system similar to that in the DC-10 and MD-11, the closet can hold anything from garments to galley items.

The cavernous area between the cabin ceiling and the top of the 777 fuselage allows Boeing to include such features into the design. By redesigning some of the latticework and moving air-handling ductwork, hoses and wires away from the center of the overhead area, engineers freed enough space from the nose to the tail to place both flight crew and attendant rest areas above the ceiling rather than in the lower hold. The arrangement not only frees enough space on the main deck for another four business-class seats, it creates enough room below the floor to add another six LD-3 cargo containers.

The world’s longest range airliner, the 777-200LR will fly as far as 9,420 nm. Launch customer PIA plans to initiate service from Karachi to New York and Chicago, and eventually to Houston and Los Angeles. Airlines that work the airplane to its range limits will submit passengers to flight durations of 19 to 20 hours. Recognizing the potential for passenger resistance to such long flights, Boeing paid more attention to the interiors of the two latest 777s than to those of any of their predecessors.

Still, the question of whether or not passengers will tolerate 20-hour flights continues to stir debate, and critics point to that issue as one reason the -200LR until recently had drawn orders for only five airplanes. Over the last couple of months, however, Boeing’s longest range 777 has started gaining some sales momentum, drawing firm orders for eight airplanes from Air India and from Air Canada as part of a mix of eighteen 777-300ERs and-200LRs. It also for the first time proved its attractiveness as a cargo hauler, drawing orders for five 777-200LR Freighters from Air France and another pair from Air Canada.

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