It is conceivable that the materials used to construct parts of the Airbus 330 might have been a factor in the loss of Air France 447. While we may never know for sure whether structural issues contributed to the plane’s plunge into the Atlantic, the crash raises urgent questions that reach beyond even the untimely deaths of 228 people: Composite aircraft parts figure more and more in the future of commerical aviation, with the two biggest manufacturers preparing to roll out high-composite-content jets next year.
These carbon-fiber composites–basically, a form of plastic–are lighter than the aluminum they replace, which stands to cut down signficantly on fuel costs. But any weaknesses in parts built of composite may be impossible to detect during routine ground inspections–at least without costly testing methods that the manufacturers insist are unnecessary.
If critics of the new high-composite-content aircraft are right about their risks, then we may once again be facing a situation where the corporate profits of the aerospace and airline industries are placed before public safety, while the government declines to intervene.
This is not the stuff of conspiracy theories. Warnings about the possible safety risks of composite materials in aircraft construction have been issued by a number of engineers and experts, and by no less reliable a source than the Canadian Transportation Safety Board (CTSB). A 2007 article in the New Scientist discusses a report by the CTSB that reveals problems with composite materials used in the Airbus, and their role in a 2005 midair crisis. Most troubling is the report’s conclusion that such structural problems often remain undetected using current methods of safety testing.
Standard test used to assess the safety of carbon-fibre composite airliners can be dangerously ineffective, according to air-safety investigators in Canada. In a report published on 22 November, the Canadian Transportation Safety Board (TSB) says an aircraft can pass the “tap test”, even though its composites actually have small flaws.
Tap tests are part of routine servicing. A ground engineer listens for a change of pitch as they tap a composite surface like a tailplane or rudder. This is supposed to reveal gaps where layers of composite have come apart, but the TSB says small gaps can go undetected and later grow.
These gaps can suddenly grow in size and potentially endanger an aircraft, the board says. It is working with the aviation industry’s global International Maintenance Review Board to review the current maintenance procedures.
This report followed a two year investigation into a 300-series Airbus (Air Transat Airbus A310) that had lost most of its rudder on a flight from Varadero, Cuba, to Quebec City in March 2005. The New Scientist describes the harrowing situation on the flight from Cuba:
Following a loud bang that reverberated through the aircraft, the plane was immediately pitched into a “Dutch roll”, in which it repeatedly rolled its wings up and down while simultaneously swinging its tail side to side. By losing altitude, the pilots managed to bring the roll under control and land safely back in Varadero, with the whole episode only causing a minor back injury to one person.
The weather conditions during this flight were not unusual, so external forces didn’t appear to have been a factor. In trying to figure out what had happened, CTSB investigators focused on structural problems that might have cause the rudder to break apart–and how they could have been missed during pre-takeoff inspections of the aircraft.
They took already damaged composite specimens–some from other A310 rudders--and placed them in a vacuum chamber. The samples experienced pressure changes simulating changing altitude during many simulated flights.
“The areas of the damage almost doubled instantly,” the report says. “The rapid propagation event was explosively loud and violent.” The explosion even damaged their test chamber. The TSB say this explains the loud bang heard by the crew.
The Airbus A310 was the second version of the Airbus to be produced at Toulouse by the French. There have been 548 fatalities in the life of the plane. Accidents suffered by another model, the A300, include devastating crashes in Indonesia and China in the 1990s, and the 2001 crash of an American Airlines jet shortly after takeoff from JFK Airpot on its way to the Domician Republic, which killed all 260 people on board and five on the ground. That crash happened after the plane's composite tail broke off--but federal investigators concluded that pilot actions, rather than the plane's materials, triggered that crash. The A330 had no fatablities until this week, though it’s safety record was not flawless.
The implications of such findings are far-reaching, since composite materials are slated to make up a greater portion of some big jets. At around the same time the CTSB report was released, Boeing was touting plans–and taking numerous advance orders–for its new 787 Dreamliner, which is made up of about 50 percent composite materials by weight. As of last month, the Dreamliner was being prepared final testing, with an eye toward release in 2010. The Airbus 380, made up of 25 percent composite, is under constructin as well.
In 2007, as construction of the Dreamliner got underway, a Boeing aerospace engineer claimed he was fired after he went public with warning that the composite materials rendered the aircraft unsafe. (Boeing’s records gave other reasons for his dismissal.) According to a report in the Seattle Post Intelligencer:
Forty-six-year veteran Vince Weldon contends that in a crash landing that would be survivable in a metal airplane, the new jet’s innovative composite plastic materials will shatter too easily and burn with toxic fumes. He backs up his views with e-mails from engineering colleagues at Boeing and claims the company isn’t doing enough to test the plane’s crashworthiness.
Boeing vigorously denies Weldon’s assertions, saying the questions he raised internally were addressed to the satisfaction of its technical experts….Weldon thinks that without years of further research, Boeing shouldn’t build the Dreamliner and that the Federal Aviation Administration (FAA) shouldn’t certify the jet to fly.
In letters to the Federal Aviation Administration, which Weldon discussed on an interview on Dan Rather’s cable show, he raised several possible risks, including what might happen in a lightening storm. (Lightening is being discussed as one possible reason for the crash of AF 447.) According to the Post-Intelligencer, Weldon warned that:
The conductive metal mesh embedded in the 787’s fuselage surface to conduct away lightning is too light and vulnerable to hail damage, and is little better than a “Band-Aid.” Though aluminum airplanes are safe to fly through lightning storms, Weldon wrote, “I do not have even close to the same level of confidence” for the 787.
Weldon's letters to the FAA advocated a more vigorous testing protocol for the 787. Among other things, he urded the government agency to test the plane itself, rather than relying on tests run by Boeing. According to a follow-up piece in the Post-Intelligencer:
The Federal Aviation Administration (FAA) has rejected suggestions from a former Boeing engineer that it change the testing and certification process proposed to prove the 787 Dreamliner is as safe in a crash landing as current airplanes....
The FAA response said: "We consider it more effective to establish the standards and encourage [Boeing] to develop the most effective method of compliance."
In addition to demanding testing prior to certification, the FAA could, if it wished, require different kinds of routine ground testing depending on an aircraft's structural makeup. Reporting on the issue of how composite-built aircraft should be safety-tested, a 2007 piece in the Chicago Tribune discussed the alternatives to “tap test,” which include ultrasounds and other advanced–but costly–technologies. Unsurprisingly, the manufacturers and airlines have resisted instituting these kinds of tests.
There’s growing debate over how aviation maintenance should keep pace withsuch materials. Federal guidelines for inspecting composites remain vague, inpart because high-tech tools for detecting damage are rapidly evolving, and there isn’t yet consensus among researchers or regulators on what should become standard practice, experts say.
Planemakers insist that visual inspections are sufficient for the composites that account for more than 50 percent of the materials, by weight, on Boeing’s new 787 Dreamliner and 25 percent of Airbus’ hulking A380 superjumbo jet....
But while Boeing is "confident that visual inspections will besufficient for the 787 throughout its lifetime," the Tribune reports, it is nonetheless "advising its customers to use ultrasounds and other advanced imaging to check for hidden damage when a 787 suffers bumps and bruises typical in airport operations--a wrench dropped on a wing, forexample, or ground equipment nudging a plane’s fuselage."
In other words, Boeing is confident that their plastic plane is safe for a 5,000-mile flight, even though a wrench dropped on the wing neccessitates more sophisticated testing for hidden damage. The apparent backstory here, some critics suggest, is that the better testing methods are also very expensive, and might dissuade some airlines from investing in the Dreamliner and other high-composite-content planes. As the Tribune piece reports:
“Our concern is that competition [between manufacturers] might be driving amore aggressive attitude on operational issues,” said Todd Wissing, an American Airlines pilot who flies Airbus A300-600s, the same model as theplane that crashed shortly after taking off from New York’s Kennedy International Airport in 2001....
“As the price comes down and the equipment becomes more robust, that’s when aircraft manufacturers will be including [advanced testing] in theirspecifications for aircraft and recommending [it] for customers,” predicted John Newman, president of Laser Technology Inc., a Pennsylvania company whose technology is used by the U.S. military and NASA to find flaws in composites.
So far, the FAA has declined to heed any calls for new testing procedures to be mandated, and other new safety regulations be put into effect before the composite-heavy planes start flying. As of a month ago today, Boeing reported that it had 886 orders from 57 customers for the half-plastic 787 Dreamliner.
Notes: Thanks to chromodynamix, whose comment on my Unsilent Generation blog yesterday alerted me to the New Scientist article and the issue of composite materials in aircraft construction.
The Seattle Post-Intelligencer, with its eye on local corporate giant Boeing, has long provided some of the most complete reporting on the aerospace industry. Let's hope the staff layoffs and the demise of the paper's print edition don't change that.