On a wing and a prayer
Air travel is a question of trust.
We trust the science which says that air pressure over the leading edge of a wing can support a giant passenger plane across thousands of miles of sky.
We trust that the design which shapes the plane matches the needs of this mysterious science.
We trust that the aircraft's manufacturer follows this meticulous design to the very letter.
And we trust that the official regulatory agencies have fulfilled their side of the bargain by monitoring and policing every step of that process - from drawing board to airport runway.
But what happens if that trust is shaken?
Every five seconds
For more than a year Al Jazeera has been investigating allegations - made in US Federal Court proceedings - that between 1996 and 2004 ill-fitting, illegal and dangerous parts were assembled on to many of the most commonly-used passenger planes in the world today.
The allegations concern the Boeing Company - the most respected name in international aviation and the world's second-largest commercial aircraft manufacturer. The claims were made by then employees of Boeing in Wichita, Kansas who were working on a radically new passenger plane - the 737 Next Generation (NG).
Boeing had produced 737s since the mid-1960s, and the 737 series is the world's most popular short and medium-haul passenger aircraft. It is estimated that, throughout the world, a 737 takes off or lands every five seconds.
But by the mid-1990s Boeing had begun to lose market share to its European rival, Airbus. To regain its pre-eminent position, Boeing decided to build an entirely new version of the 737 - the Next Generation.
Earlier models were built by hand: as a result the dimensions or accuracy of each individual part would often be marginally different, resulting in the need for assembly workers to pack out gaps with "shims" or fillers. These added to the overall weight of an aircraft, making it more expensive to fly.
Parts for the new 737NG plane were to be designed, manufactured and built by a revolutionary new computerised process called ATA. Not only would this ensure that each individual part was identical, but that each would be precise to within 3000ths of an inch.
According to leading aircraft engineer, Dr Michael Dreikorn: "This ATA was designed so that the tolerances on putting the aeroplane together would be so tight that the aircraft would have higher strength and reliability. And in response to that, this aeroplane was certified to have higher gross weight and be able to operate at higher altitudes."
Boeing through and through
Every new aircraft design has to be assessed and approved by a regulatory authority: for American manufacturers like Boeing, the regulator is the Federal Aviation Administration (FAA).
Boeing submitted all its engineering drawings and data to the FAA and, in 1996, the FAA gave Boeing the thumbs up. It issued what the industry calls a Type Design Certificate - essentially a licence to manufacture the aircraft provided to all the specifications laid out in the engineering data which had been submitted and approved.
Boeing planned to assemble the 737NG fuselages in Wichita. But it subcontracted the manufacture of some key parts to a company called AHF Ducommun, based in Gardena, California.
Gigi Prewitt was Boeing through and through. Her family had worked for Boeing in Wichita for three generations and she was excited when she was asked to look after buying key parts for the 737NG. But within a short space of time, she noticed something was wrong.
"The minute that I took the desk of buying 737NG parts I had shop personnel coming to me talking to me about the problems and the issues they were having with the parts not being manufactured accurately. [They reported] Shy-edge margins and were, out of contour, parts not fitting correctly ..." Prewitt says.
'Catastrophic failure'
The parts in question were some of the most crucial elements of an aircraft fuselage - parts known as "chords" and "bear-straps".
An aircraft fuselage is like a giant tube. That tube is made up of interlocking semi-circular pieces of metal - these are the "chords" and put together they form the 'frame' around which every other part of the airframe is built ... and on which the external 'skin' is assembled.
Exit doorways and cargo hatches are potential weak points in this fuselage: to strengthen them, huge re-enforcing sheets are assembled around the holes - these are the "bear-straps".
So vital are these parts to the safety of an aircraft, that Boeing's own #fb9d04; text-decoration: none; font-weight: bold;">737NG Structural Repair Manual - obtained by Al Jazeera in the course of its investigation - lists them as "Primary Structural Elements" and warns: "The failure of PSE's could result in the catastrophic failure of the airplane."
According to lawyer Bill Skepnek - who for the last six years has become intimately acquainted with almost every nook and cranny of the 737NG design - when Boeing talks of the potential for these parts to cause "catastrophic failure", it means exactly what it says.
"These are the parts of airplanes that, if they fail, we can have a decompression at altitude or we can have a rupture in the vessel, in the fuselage vessel of the aircraft. And as long as we can make that [fuselage] hold together we can keep the passengers safe."
But in Wichita, Gigi Prewitt was not the only Boeing employee coming across reports of ill-fitting and badly made parts. In another building on Boeing's vast factory site, Taylor Smith was getting very similar-sounding complaints.
"One of the shop managers sent me an email saying they were having problems with the fail-safe cords which are the long ribs that go all the way along the aircraft [...] They were telling me that from the beginning of the 1996 timeframe when they started manufacturing these parts, that they were coming in with shy edge margins, they were out of contour," Smith says.
Boeing's internal documents, which Al Jazeera obtained, give a snap-shot of the scale of the problem.
Part out of contour: quantity 1 … Part width – oversize: Quantity 4 … Material thin: Quantity 6… Part undercut: Quantity 26 … Hole mis-located: Quantity 17….
They also show the source of the problem: AHF Ducommun.
read more (source: Al Jazeera)
Reeding is hrd!
Pray that the airplanes are repaired properly, too...