This is the first in a three part series on the development of Boeing’s all-new jetliner. Part one examines market evaluations and the configuration and materials selection process. Tuesday’s Part Two will explore the aircraft’s systems, propulsion and performance and Wednesday’s Part Three will look at the future production system and business model of the new jet.
Until now, few answers about Boeing’s next aircraft have been available and while the majority of its attributes have yet to be determined – including its launch – the all-new jet will be one aircraft, not two, and whose configuration will match the familiar tube and wing that defines commercial air transport today.
In recent months, Boeing has been quietly polling the worlds most influential airlines, offering them a veritable “grab-bag” of technologies, say industry officials, with the goal of identifying their future needs for an all new jet that is intended to first see revenue service in 2019 or 2020.
The task Boeing is now preparing itself to undertake – the development of the airframer’s next generation narrowbody – is now in the early planning phases. By the Paris Air Show in June, Boeing will announce the direction its intends to advance, deciding between an all-new design or a re-engined 737.
If Boeing can replicate the design resiliency of the original 1967 737-100 and -200, then “getting it right” now means laying the groundwork for an aircraft that will evolve well into the latter half of the 21st century. Boeing has succeeded in evolving the 737, making incremental improvements to the aircraft over time, without having to make the multi-billion dollar investment to fully replace the narrowbody, all while maintaining its existing industrial footprint for ever increasing production.
Despite that longevity, what the market doesn’t appear to want, says Mike Bair, vice president of Advanced 737 Product Development, is a re-engined 737: “I kind of characterize it as more underwhelmed than overwhelmed and almost all of them want to know what more we can do with a new airplane, so that’s kind of where our focus is right now.”
Though standing in the path of the all-new aircraft are significant unanswered questions about the commercial success of the 787 and what technology from its long-range twin can be used in a smaller platform. In charge of this effort is Bair, who first must answer the question from which all other answers will be yielded: What does the market want?
Boeing’s focus, says Bair, who has been in this role since January 2010, is to “figure out the art of the possible” for the company’s next all-new jetliner, which he says is less of a 737 replacement and more of an aircraft meant to fill the marketplace spot below the 210 to 250-seat 787-8, suggesting an aircraft centered around a segment slightly larger than today’s narrowbody.
“I try not to say 737 replacement, because what we’re trying to understand is what does the world need in 2030? Because if the airplane goes into service in the back half of this decade it’s going to be in its prime, plus or minus. So we’ve got to look that far out and try and makes some calls about what the world’s going to want out there.”
Six-Abreast or Seven-Abreast?
Boeing’s first industry trial balloon, confirms airline and industry officials, contains two notional cross sections: a six-abreast single aisle and a seven-abreast twin-aisle with a container-sized lower cargo hold sized smaller than the 767.
“There’s a wide open area in terms of what could be the cross section and that’s clearly a big conversation we are having internally and also with the airlines,” say Bair without going into specifics.
However, despite two cross sections and two potential aircraft families, Bair quickly rules out two aircraft families making it off the drawing board, eliminating a repeat of the concurrent development of the all-new 757 and 767 in the early 1980s.
“We won’t do two cross sections, it will be one, but we don’t know yet what that will be and we’re showing a lot of options to airlines and at some point we’re going to have to make the call,” he says.
“Obviously the wider the cross section, it’s not free, you lose efficiency for making the airplane wider and we need to understand how much are the airlines willing to spend, basically, on a wider airplane.”
One part of that determination is a flying focus group that is taking place on the roughly three dozen 737′s delivered with the Boeing Sky Interior. The new design allows passengers to load and unload the overhead bins without having to step into the aisle, says Bair, who adds Boeing is “watching very carefully” if this ergonomic change can improve aircraft turn time without the need for adding a wider or even a second aisle and a seventh seat.
A Radical Departure?
As it works to develop the configuration of the new aircraft, Bair says his team has ruled out radical configurations such as a blended wing body for two “pragmatic problems”. The first, has to do with the window arrangement, or lack thereof.
“A lot of people just say ‘give them TV screens and stuff’,” he says, “But one of the things we clearly found during our ’87′ journey is that people really like to look out the window.” The second, he adds, is the extra-wide cross sections that have passengers “a long way away from the center of the airplane and when the airplane does a roll manuever you better have your seatbelt on.”
Additionally, an unducted fan engine, while providing significant fuel burn improvement, would require a 14 to 16ft diameter fan that makes it “hard to even conjure up a solution on what to do with blade out…and when you lose a blade all kinds of bad things happen and we have yet to figure out a solution for it. And quite frankly, can’t conjure up a solution for it.
The risk of losing a blade, adds Bair, is low enough that its acceptable however “every time a blade comes off a propeller airplane the airplane is lost and we just won’t do that. Having a single thread failure that can cause an airplane to be lost, we just won’t do it. So we just don’t see that as a solvable problem.”
Bair concedes “These are going to be conventional looking engines and they’re going to be conventional looking airplanes. Tube and wing has been around for a long time for lots of really good reasons. It’s very very efficient way to fly stuff around, especially people.”
What do you build it out of?
As the general configuration of the aircraft takes shape, Bair says the material decisions remain “up in the air” with an all-composite, all-metallic or some hybrid of the two being evaluated. Boeing selected a majority-composite design for the 787, with both the wing and fuselage made of carbon fiber.
“We want to try and take advantage of everything we’ve learned on the ’87′, but this is a different airplane, different market segment, different mission rules, different requirements than an ’87′, so we have to make sure we don’t jump to a conclusion to understand what the answer is.
“So the other thing that happened is since we picked the materials set on the ’87′, the aluminum folks did not go to sleep, so there are more choices now than when we made the decision on the ’87′, so we have to methodically go through that and what that might mean.”
One consideration Bair considers “overblown” is the impact of ramp rash – or accidental impacts from ground handling – on a composite airframe. Compared to a long-range jetliner, a narrowbody aircraft in a high cycle environment spends more time exposed on the ramp in the course of a day, increasing the chance of potential damage.
“People’s initial reaction to composites were based on their experience with things like flaps and composite movable edges which are honeycomb laminates and they’re delicate. They can get damaged and they’re difficult to repair, the built up laminates that we’ve done on the ’87′ are actually harder to damage than aluminum, and we have dropped stuff on these things more often than you can imagine. So they’re harder to damage than aluminum…in some ways they’re easier to repair than aluminum. “
Yet at the same time, Bair says, all the skin thicknesses on the 787 are sized to absorb an impact, either by hail or baggage carts: “Which means if that’s how thick it has to be on a big airplane it needs to be that thick on a little airplane. So there’s sort of diminishing returns in terms of efficiency.”