Boeing Continues To Bolster 747-8’s Performance

Farnborough Air Show » 2012
Boeing 747-8 Lufthansa Frankfurt
The first 747-8 passenger airliner takes off from Frankfurt on its maiden revenue flight on June 1.
July 11, 2012, 2:30 PM

Lukewarm market reception and performance deficiencies that continue to fall short of the new 747-8’s original design specifications might have elicited a fair share of skepticism from various industry quarters, but they haven’t deterred Boeing from declaring that “prospects look quite good” for the stretched, re-engined and re-winged jumbo jet, now in passenger operation with Lufthansa Airlines and five cargo customers.

In fact, last month, 747 program vice president and chief project engineer Bruce Dickinson told reporters at a briefing at the company’s widebody factory in Everett, Washington, that the cargo airplane’s “real-world” fuel efficiency has proved 1 percent better than forecast estimates for this point in time, as engineers work toward meeting all performance guarantees in 2014.

“We’re not done; we’re never done,” said Dickinson. “Continuous improvements are all about what we’re doing…The improvements in aerodynamics and weights continue, they’re identified…”

A performance improvement package (PIP) for the airplane’s new General Electric GEnx-2B turbofans would account for most of the original 3-percent improvement needed to meet Boeing’s original promises. The PIP, including a new low-pressure turbine design, redesigned high-pressure compressor airfoils, as well as an “upgraded” combustor and improved high-pressure turbine aerodynamics, would gain certification in the second quarter of 2013, according to GE’s schedules.

Although not considered a major contributor to the airplane’s fuel-efficiency shortfall, the airplane’s flight management computer (FMC) from Honeywell had assumed a high priority for Boeing and its customers well before its entry into service with Cargolux last October. In fact, during last year’s pre-Paris Air Show briefings in Everett, program head Elizabeth Lund revealed that the FMC hadn’t performed up to expectations. Although Lund said it could do all that the prior FMC could do in the 747-400, it took close to another year before Boeing finally “rolled in” some improvements and new features about two months ago.

“Our third block point will include some capabilities around required navigational performance (RNP), and that allows for just a little more efficient approaches, a little more opportunity for operational advantages,” said Dickinson.

Finally, Boeing continues work toward a software solution to certify tail fuel tanks meant to hold another 3,300 gallons of jet-A in the Intercontinental. Computer simulation testing showed that the airplane would experience some minor structural flutter in the event of a failure of the R3 under-wing, mid-spar strut-to-wing fitting, one of six connecting the outboard engines to the wing, when the tanks held more than 15 percent of their capacity. As a result, Boeing had to decommission the fuel tanks to gain certification of the variant last December.

The tanks raise the 747-8’s total fuel capacity to 64,055 gallons, extending its range from roughly 7,650 to 8,000 nm. The 747-8 Freighter does not use the tanks.

Although Lufthansa doesn’t yet need all the extra range the tail tanks would deliver, the absence of fuel in the tail of the airplane does actually produce some fuel-burn penalty because the condition changes the airplane’s center of gravity. Once it certifies the tanks, it will, in fact, regain the resulting lost fuel efficiency. “We’re still working on all the details of what the solution will be,” said Dickinson, “but we’ve got it just about finished.”

Boeing plans to fit a single instrumented flight test airplane with the PIP, the FMC improvements and the tail tank reactivation for simultaneous certification by the end of next year, said Dickinson. The engine PIP alone should bring performance to within 1 percent of specification, while aerodynamic upgrades and weight reductions account for much of the balance. “We don’t have very far to go,” said Dickinson. “And we’re confident we’ll hit it because we have completely audited through all of our experts the numbers for the improvements that are coming.”

Designed to operate 15 percent more efficiently than its GE-powered predecessor, the 747-400, the 747-8 relies largely on a new supercritical wing for its performance benefits. The engine, meanwhile, represents fifth-generation technology and resists deterioration over time far better than its precursors, translating into better midlife performance and less cost for customers, said Dickinson.

As of mid-June twenty 747-8s had entered service–specifically, 16 freighters, three VIP airplanes and a single Intercontinental. Boeing had delivered 11 airplanes this year, and the first at a two-per-month rate since it announced an increase in production output from 1.5.

Boeing’s most recent corporate guidance specifies planned delivery of between 70 and 85 Dreamliners and 747-8s combined, split roughly evenly, suggesting a total of between 35 and 43 this year for each. Although some 747-8s scheduled for delivery remain in change incorporation in San Antonio, Texas, Boeing has already sent “a number of airplanes straight through the factory,” said Dickinson.

Meanwhile, the OEM has watched market interest gravitate toward the passenger model as cargo markets continue to experience weakness, according to Dickinson. Now holding firm orders for 106 airplanes, Boeing still counts among its list of customers only three passenger airlines, accounting for 27 airplanes. However, a deal with Air China for five awaits government approval, while Russia’s Transaero has yet to convert a memorandum of understanding for four and an unnamed airline’s commitment for 15 remains off the books.

“Part of it is, a number of airlines wait until the airplane gets out there,” said Dickinson. “So a lot of people are watching.”

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