Press Release

AN IMPOSSIBLE DREAM by Hans van der Zanden

A draft copy of the manuscript has been published ahead of the expected first test flight of the 787. Certain section are still in progress, for example lightning strike protection. The text is now being completely revised and edited for publication later this year.

Introducing a new construction material at this scale in airliners is a very dangerous undertaking. ‘An impossible dream’ deals with the development of all-composite aircraft from the materials’ perspective. The book is based on more than 3000 hours study, driven by safety concerns over the materials dating back to the Columbia Space Shuttle disaster in 2000.

When the date for the 787’s first test flight was firmed up, to occur at end of June of 2009, Mr. Van der Zanden became increasingly alarmed. The airplane was held together by a provisionally strengthened wing box and thousands of wrongly-placed fasteners. He knew that the engineering models could not be relied upon for accurate stress analysis, not even closely.  What’s more, there were more issues with the airplane that remained unresolved, such as the lack of a reliable and robust lightning protection system.  As a result, Mr. Van der Zanden decided to publish a draft copy of his manuscript in a desperate effort to get his message out, and put it on his website, lonelyscientist.com, on June 9, 2009.  It was quite a relief to him when, two weeks later, problems surfaced and the first test flight was delayed again.  It was a relief because the engineers at Boeing had finally found the courage to step forward and tell management that enough was enough.

Within a one month time frame Mr. Van der Zanden’s site has been visited more than 4,500 times, almost 20% of them first-time visits by Boeing employees.

Principal aims

With all composite aircraft the principal aims are to save on weight and hence on fuel, to make manufacturing easier and hence cheaper, to succeed with less inspection and less maintenance and hence lower operation costs and to improve on flying experience. Large-scale application proved to be much more complicated than expected. As engineers at Airbus and Boeing now know, demonstrating that composites are lighter and stronger is not the same as demonstrating that lighter civil aircraft can be built with composites.

Weight issue

Composites have low damage tolerance and special measures have to be taken to try to compensate for these shortcomings, such at the expense of considerable weight. Mr van der Zanden argues that with all composite aircraft in the end ‘similar safety means similar weight’ when compared with aluminum aircraft – but even at equal weight all-composite aircraft will never reach the safety standards achieved with traditional aluminum aircraft.

With the A380 development faced a 2 year delay, the plane is 5,500 kg (~12,125 lbs) overweight and ramping up is causing further delay – the A400M is delayed indefinitely and is 12,000 kg  (~26,450 lbs) overweight – the 787 is already delayed by more than two years and gained some 21.050 lbs (~9,550 kg) overweight since firm configuration in 2005 – the A350 is still at the drawing board but reported to be to be still 8,000 kg (~17,600 lbs) overweight. Total costs for development – for these planes originally estimated at some $50 billion – reached $75 billion plus by 2009 and the companies have to deal with some $65 billion late and lost revenues and this will only get worse.

Damage tolerance

Mr. Van der Zanden’s concerns about all-composite aircraft entail composites’ low damage tolerance involving some of the more specific issues as follows:

• Modeling: It is clear by now that the mathematical models that Boeing has relied upon don’t work and probably won’t work for the foreseeable future. Composites are far too complicated for modeling with currently available engineering analysis tools and their behavior is not well understood when applied to the harsh conditions that commercial aircraft operate under. Moreover, validation of these models with physical results is often not possible because of a lack of practical testing methods. This includes not only stress behavior, but also damage tolerance, in particular impact response; toxic flammability; and lighting protection.
• Impact resistance: Composites have famously low impact resistance and there is not much that can be done to change this inherent characteristic.  Indeed, with all-composite aircraft the glazing on the passenger windows provides far better impact response than the composite skin itself. A photograph of hail damage can be found on his blog dated July 19; just try to imagine how this would look like with an all-composite structure. (Mr. Van der Zanden is working on a simple test method for physical simulation of realistic hail impact of a full-scale nose section).
• Fire behavior: Thermoset composites were banned from application in aircraft interiors by the FAA a long time ago because of their highly toxic nature and high flammability, and have been replaced by thermoplast composites.  Ironically, though, the passengers on these new airplanes will be surrounded by skin that is similar to the very thermoset composites that were banned by the FAA for use on the interior of passenger planes.  The resin used in the manufacture of these composites not only add an additional source of fuel to a fire, but they also release extremely toxic smoke while the carbon fibres disintegrate to release respirable fibrils.  (According to studies, respirable contaminated carbon fibrils most probably include damage to tissues, lungs, and other organs, possibly leading to cancer.)
• Lightning strike protection: Even more worrisome is the lightning protection system – or the lack thereof – on these new planes. The composite structure is turned into a quasi Faraday cage through metallization; that is a metal wire mesh that is incorporated between the outer layers of the composite and provides a superficial conducting layer. Lighting protection through the ‘Mesh Method’ is successfully applied with grounded structures, normally in combination with a lighting or Franklin rod, but this method is based on long-term experience and does not involve any theoretical background. One can therefore question the effectiveness of the mesh method when applied to all-composite aircraft.
• Impractical: Boeing has worked for a number of years on a method to provide the 787 with lightning protection similar to that found on traditional aluminum aircraft, only to find out that it is not possible. Boeing now argues that their original approach was “impractical”, and the FAA agreed by relaxing the rules in a significant way: Aluminum aircraft will no longer be used as the benchmark for establishing lightning protection standards for commercial aircraft.
• A ‘more electric plane: The 787 is a first so-called “more electrical” airplane described recently by ‘Aviation Week’ as having three times the power of existing aircraft systems, designed using the wild frequency technique not previously used, operating at twice the voltage of previous airplanes. It has yet to be seen whether an all-composite structure can safely protect all of the electrical circuits and electronic components from damage and possible interference, and be shielded form lightning strike currents and electromagnetic fields, which might pose an even greater risk than the fuel tanks themselves. Mind that such shielding requires mass that is provided by the metal structure of which only some 20% is left. The composite structure offers no shielding and the protection that is obtained with the inserted mesh wire is uncertain.
• Safety margin: For certification, traditional aluminium aircraft have nowadays during static testing to sustain 150% of the design load that the aircraft will ever experience in service, for example when the wing is bended until it fails. Such test is performed under idealised circumstances and the 50% safety margin compensates for damage and ageing that weaken the structure during its lifetime. However, this threshold has gradually come down over the years from 200% when the engineer gained more experience and the safety of these aircraft slowly improved. Somehow, this 150% threshold is now also adapted for all composite aircraft and that is where it went wrong with the 787 during testing in May 2009, when the wing failed below 120%. But even when the structure can be strengthened to obtain 150%, it can be seriously questioned whether this provides a safety level similar to that of aluminium aircraft. Almost certainly not. All composite aircraft are new and have a far lower damage tolerance than aluminium aircraft, as was indicated before. This has to be compensated and it can be argued that a much higher threshold should be applied with all composite aircraft at these early stage of development, probably 200%!

All of this is only a small part of the whole story. A reader might wonder how all this can be happening.  But the fallout in the financial markets after so many billions of dollars have been spent would be far too great to bear, and so now the unthinkable has become normal practice.

Note on composed aircraft

In stead of all composite aircraft Mr. van der Zanden argues to concentrate on  composed aircraft. The A380, one of the most amazing developments in aviation history, has set the trend for composed civil aircraft that will further develop – the next generation of aircraft – with hybrid structures composed partly out of traditional and modern metal alloys and partly out of composites. In particular aluminium reinforced composites that are already successfully applied for the roof of the fuselage of the A380 and presents a superior alternative for plain composites and monolithic aluminum. Aluminum reinforced composites combine the advantages of aluminium and glass fibre composites and cancel out the disadvantages experienced with plain composites – and provide unique properties that cannot be obtained with the materials on their own, including very good damage tolerance. Boeing and Airbus are urged to join forces and focus their last recourses on composed aircraft – others are waiting in the sidelines.