Boeing 787 Challenges


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Boeing 787 Challenges

Courtesy Aviation Week & Space Technology, a 2011 issue. This essay is loosely based on a 2011 letter to the editors entitled "Recipe for Disaster?" by Stephen Incledon of Glendora, California.
Edited by David Barth 14 June 2013.

In the early years when Boeing decided to build an evolutionary plane that would be lighter and therefore, more fuel efficient than the Airbus designs, it started with a "clean sheet" of paper, meaning that it wanted to use all possible ways to lighten the plane.

Fuel costs fluctuated, but in general, they were rising and costing the aviation industry a lot of money. The flying public in general, wanted lower fares. To achieve this, there were some possible solutions.

1) Make the airplane as light as possible.
2) Use very fuel-efficient engines.
3) With ever more powerful engines being designed by the engine manufacturers, the aircraft designers realized that fuel used by two more powerful engines was less than that used by three or four engines.

The second solution was easier because the problem was on the backs of the major power plant manufacturers such as General Electric, Pratt & Whitney, and Rolls Royce, the major players in large engine manufacture.

In the 1950s, a moderately-sized commercial airframe needed four engines because engine output was not great enough to get by with fewer. By the 1960s, it was found that three engines could do the job, and the result was odd-looking, three-engine aircraft such as the Boeing 727, the McDonnell-Douglas DC-10 and DC-11, and the Lockheed L1011.

In addition, if a future engine came along, it could usually be retrofitted to an existing airframe so that the airplane could enjoy the fuel efficiency of an engine that was not available when the airplane was originally built.

An example was the use of the high-bypass fan engines from CFM, a joint venture between GE and Snecma of France that replaced the older, low-bypass engines on the Douglas DC-8, Douglas' first entry in the commercial passenger plane market in the late 1950s which competed head-to-head with the Boeing 707.

Older aircraft are often retired when they have flown 40,000 hours because of wear and tear of the aluminum spar that carries the load. Favorably (or unfavorably) to Douglas, the DC-8 wing spar was overbuilt, and could withstand 60,000 hours. Spar condition could be measured by using high-tech techniques including magniflux that would show hairline cracks. Innocent through they were when small, as they slowly grew, the life of a spar could be estimated.

Some aircraft had "spar kits" developed to beef up the spar, but for commercial aircraft, that was not an economically viable choice. It was better to sell the old aircraft to third-world entities who would eke out the last remaining utility of the airframe and to buy new airplanes to replace them.

That is why, well into the 1980s, United Airlines and other carriers were still flying some variant of the original, four-engine DC-8 with its long-lasting spar, albeit, with updated, more efficient engines.

Back to our story. As Boeing began a "clean sheet" design for what would become known as the 787, it did its utmost to put the airframe on a diet to slim it down. There were several options including the use of a composite fuselage and flying surfaces.

One change that would be most noticeable by passengers was the larger windows. This change was long in coming because over the past 50 years, since the original window design was made for high-flying jets, people have become taller, and for some, the top of a window reaches to a person's nose, requiring a tall person to contort his or her neck to look out. Bigger windows should be in the design of every new commercial aircraft.

Perhaps one reason window design has not evolved during the past half-century relates to two de Havilland Comet 1 inflight breakups that occurred over the Mediterranean in 1954. The investigation found that the square window design was a contributor to the failures due to stress concentrations at the corners. As a result, airlines made sure that their windows were small, oval, and low enough for short people and children to use.

Fortunately for the flying public, Boeing has broken this chain of design and made larger windows from which tall people can look out.

Hydraulic actuators, such as those used in raising and lowering landing gear were heavy. Not only did they have to be beefy to contain the high-pressure fluid, but the high-pressure hydraulic pipes that ran to each actuator, including those in the wings and tail, were heavy, not to mention that the many gallons of fluid in those pipes weighed a considerable amount, too.

So, the designers opted for electric motors to replace the heavy, bulky hydraulic systems. The motors were lighter, and wires to power them were considerably lighter than the pipes and fluid.

The designers realized that they needed around three-times the battery power of a conventional airplane to run all of the electrics, so they opted for lithium-ion batteries which are much more efficient and lighter than the traditional lead-acid type. However, if overcharged or not handled correctly, the lithium-ion batteries could overheat and go into a thermal runaway phase, also called a violent exothermic reaction, generating temperatures exceeding 500 degrees F (260 degrees C) that could not be stopped. As they melted, they could melt through the walls of the adjacent cell, causing that cell to meltdown, too.

The batteries were kept beneath the main deck, in the storage area, near the rear of the aircraft. The hint of trouble for the pilots would be a temperature spike and battery warnings. The hint for the passengers would be the smell of smoke, not a happy event.

Worst case, the batteries would all stop working, leaving the "fly-by-wire" plane's computers and electric motors without power. Not a nice thing to not be able to work the controls of an aircraft, to talk on the radio, or view the electrically powered flight display panels.

However, Boeing engineers had thought ahead and designed backup battery power so that if one group of batteries failed, a backup group would be available to power the plane's systems.

Still, the U.S. Federal Aviation Administration (FAA) grounded the fleet and mandated that Boeing redesign the 787 battery system so that never again would a 787 passenger smell the smoke of a battery-related, violent exothermic reaction.

Following Boeing's fixes, Boeing believes that there is little need to worry about battery failure or thermal runaway. Systems are in place to manage a worst-case scenario.

Airbus sidestepped the battery issue by planning to use older, less efficient lead-acid battery design for its new offerings.

Below is a chart of the challenging issues that Mr. Incledon brought up in his letter that was published long before the 787s had to be grounded.
  • The airplane was designed to have performance not previously achieved.

  • Engine manufacturers had not yet designed an engine with the power/fuel usage ratio (called fuel specifics) needed by the Boeing designers.

  • Engines had never been built out of the lighter-weight materials mandated by Boeing.

  • No aircraft had been built with a completely plastic fuselage. Airbus claimed that their planes also had a composite fuselage. However, the fuselage consisted of an aluminum structure with composite plates bolted to it.

  • Boeing decided to use vendors who were not familiar with the material and designs.

  • The computer models for the design were not verified as shown by the wing-attachment point delamination that required redesign and a rework of planes already manufactured to solve the problem. Boeing outsourced nearly all work using vendors inexperienced with them and their construction processes.

  • The 787 design specified an electrical system having three times the power output of existing aircraft systems, a design using "the wild frequency technique not previously used operating at twice the voltage of previous airplanes" by a systems designer who hadn't previously designed such systems. In Boeing's defense, a plane like this had never been designed, much less built, and no one on earth had prior experience doing it.

  • The author goes on to say that Boeing's top-level management had never built an airplane or managed outsourcing.

  • He said the schedule for the suppliers had never been achieved on a conventional airplane.

  • Boeing planned to hold payment to the vendors until after the plane was delivered to a buyer.


The author of the letter is correct. The 787 design was mostly new and untried, and Boeing had to make adjustments and improvements along the way just as trail-breaking automobile manufacturers did in the early part of the twentieth century and NASA had to make during the moon landing project of the 1960s.

At the time of this writing, in mid-2013, United had followed other airlines by putting the 787 into service. In United's case, the 787 would fly non-stop, Denver to Tokyo, a feat few other commercial airliners could achieve.

It appears now that the 787 will be a successful aircraft pushing the state-of-the-art in aviation. Sure, Boeing had some challenges along the way, and the delivery schedule had to be pushed back by at least two years, but the outcome seems to be a winning design and the company should be a contender for aviation awards.

Boeing 787
Boeing 787.
This was a flyby at the 2010 biennial Farnborough International Air Show, UK. Photo courtesy of Boeing via Wikipedia, the free encyclopedia.