The Lockerbie Bomb:
Detailed investigations showed that an explosive device detonated on board the aircraft, in an aluminium baggage container and near the hull. Its size has been established and this has been used to guide research for this and other programmes.
Court cases were held and Abdelbaset al-Megrahi, a Libyan intelligence officer was imprisoned and the Libyans claimed responsibility. There still remains doubt over the veracity of the process, evidence and the politics at play, but these will not be issues addressed here.
The Programmes:
As a result of the bombing taking place in British airspace, the UK Government funded a two pronged research effort into hardening commercial aircraft from such events in the future. The programme to examine options for narrow bodied aircraft, such as Boeing 737s was awarded to ‘DRA’ the Defence Research Agency, predecessor to DERA which itself became Qinetiq and DSTL.
The second programme was to look at wide bodied aircraft, such the Boeing 747 used by Pan Am and in which the hold baggage is held in ‘Unit Load Devices’ – the odd shaped metal boxes ubiquitous in airports worldwide. This programme was awarded to Royal Ordnance, which at that time came under the umbrella of British Aerospace. It is that programme that will be discussed here.
ULDs:
A concern at the outset of the programme was the additional weight we could add to each ULD. In the early 1990s this turned out to be less of a limiting factor than it used to be. Modern engine efficiency and power output meant that the extra weight of a blast resistant ULD would not an issue – up to a point of course.
It was important that the handling characteristics and features of this new ULD should mimic the existing characteristics wherever possible. This would avoid the need for specialist training and equipment being required at airports of various standards and capabilities worldwide.
Rabbit Hutches and Dog Kennels:
The run up to full scale testing was split into more manageable and cost effective stages. These consisted of panel tests and scale tests. The panel tests were carried out in the Royal Ordnance Chorley site’s ‘Fast Event Facility’ a specialist indoors concrete structure festooned with viewing ports and intense lighting for high speed filming of explosive tests. The FEF was more commonly used for the development of munitions, warheads and fuzes. The test panels were used in two different sizes, used on test rigs designated as the ‘rabbit hutch’ and ‘dog kennel’. The panels were given a chequered pattern to better observe and visually record the deformation of the panel face during the explosive event. These panels allowed the project team to sift through a variety of materials in different combinations to down-select for scaled container testing.
One of the more obvious differences seen with ULDs is that some have a folding solid door and some have a fabric door. To not prematurely write off the option of a fabric door, its possibilities were investigated. The resulting design featured solid anchor points on the corners with an internal web of high performance strapping and multiple layers of Kevlar fabric. The blast and fragmentation protective elements was then enclosed in cordura nylon for environmental and wear protection. The tests on the fabric door were satisfactory but the cost and suspected lifespan issues made the team focus more on the solid door options.
Scale Testing – the Dark Arts:
Anyone who has ever done it will know that scale testing of explosives is not without it is issues and scale testing of explosive containment system is even more so. There are many different factors at play and they all scale according to their own predilection. In the early nineties, FEA modelling of blast and the high strain rate behaviour of materials was an exotic beast and empirical testing to look and see was often quicker and more cost effective.
At this stage the fabric door option had been dismissed but there were still two main threads running. One was an all composite material solution, which would lighter and stiffer, but more expensive and perhaps less robust for the rough and tumble of a major airport and minimum wage staff armed with forklifts.
The other thread was to use an aluminium skinned option but with the aluminium in the form of trays that contained now better proven combinations of blast absorbing materials.
Full Scale Testing:
The first full scale test with the aluminium panel/tray assembly with a folding door was not quite the success we had hoped for but was annoyingly close. This design also provided us with more options to make changes and based on the observed damage.
The composite structure version was put aside (abandoned seems a bit harsh) and efforts were focused on the changes to the aluminium model.
A standard LD3 was used as a baseline for measurement and a very useful visual reminder of what had occurred on the flight itself.
The outcome was a success – a Lockerbie sized device did not cause the integrity of the ULD to be breached and none of the surrounding baggage penetrated the body of the structure. The pressure measurements taken were used to investigate the implications for the neighbouring aircraft hull and this all proved to be feasible.
Through the programme the project team had formed technical links with the ULD industry and they felt that the aluminium version had promise. Using it was not an issue and it provided the option to replace individual faces or panels in the event of gross handling damage. There would be an extra expense, yet to be determined for manufacture of large numbers but the specialist containers were always more expensive. The view was that the market was there and we the solution was ready.
Issue 1: Then, as now the airline business runs on very small margins. Certainly at that time there were multiple US airlines hopping in and out Chapter 11 Insolvency Protection. Royal Ordnance had calculated that the cost of a hold full of blast resistant baggage containers, amortised over their lifespan and the number of flight legs that would encompass, would result in an additional cost of a few cents per ticket. That having been said, no large scale commercial airline was going to adopt this unilaterally and suffer any form of competitive disadvantage in their respective market sectors. From their point of view, legislation would be required so that everyone ‘jumped together’ and the commercial status quo maintained.
Issue 2: Early in the programme, the comment had been made more than once that the insurance industry would provide commercial leverage to help sales. Surely the promise of reduced premiums would encourage the airlines into rapidly adopting the technology. High level discussion with the insurers brought to light a different way of looking at the world. The view was that, though unfortunate for those involved, the insurance industry was fine with making such large payouts periodically as it reminded everyone why they pay their insurance premiums. The maths did not support a reduction in premiums.
Issue 3: Was the Lockerbie incident an isolated event or the start of a wider problem? Was it really necessary to adopt the technology for something that might not happen again? A lot of parallel effort was going into better baggage screening to detect devices before they got near an aircraft – would this be enough to deal with the problem?
In July 1996 TWA800 crashed into the sea shortly after leaving JFK in New York, bound for Paris. The first impression was that it was an explosive device and could well be the catalyst the baggage container programme needed as legislation was sure to be expedited. Investigation however showed that no explosives were involved in TWA800.
