Hardened Unit Load Device (HULD)

The Hardened Unit Load Device (HULD) is a high-strength, unibody container for widebody aircraft to confine the blast and suppress the fires caused by internal explosives. Prototype testing has demonstrated that the HULD can contain explosives significantly above the threshold of current detection technology. The device not only conforms to the IATA specifications for these containers, but also promises to provide greater durability due to its extraordinary strength. Combined with existing detection technology, comprehensive protection for airline passengers can be provided. This technology is ready to be put into service to gain operational and durability experience and to enhance passenger safety.

Aviation Security

Commercial aircraft represent vulnerable and attractive targets for terrorist bombing. This unfortunate reality has been dramatized by the downing of a number of commercial aircraft with the loss of all onboard. Faced with this threat, the Federal Aviation Administration (FAA) has invested in the development of various technologies to detect explosive materials and to mitigate the effect of an explosion should detection fail. As indicated in Figure 1, the optimal solution to the problem of aircraft bombing vulnerability involves a balance of structural hardening and detection. As the quantity of explosives to be detected diminishes, the cost of detection becomes unacceptable. Similarly, to harden against a large quantity of explosives is also economically unfeasible. A balance between the two approaches can provide a realistic solution that enhances the level of safety afforded to the traveling public, while minimizing the total security-related costs. The structural hardening of aircraft cargo containers, known as Unit Load Devices (ULDs), represents a practical means of achieving this balance.

Toward this end, the FAA contracted with Jaycor (now Titan) to determine the blast capacity of existing ULDs and evaluate various countermeasures to improve their resistance. These evaluations were performed using analytic models which embodied the essential characteristics of the transient blast loading from the explosive, the response of the ULD to this dynamic loading, and the failure models of the ULD. The evaluations and prototype testing indicated that the resistance of existing containers was minimal.

Figures 2 and 3 below compare the effects of internal explosions form bombs detonated inside ULDs. Figure 2 shows Titan's HULD after 2 explosions. Figure 3 shows a ULD, representative of the type used in widebody aircraft, after a small bomb was detonated in one of the suitcases. This bomb was actually below the limit of detection equipment currently in service. The externally propagated blast and fragmentation would have damaged the aircraft. Further, a menacing fire followed this blast, as in all our tests in which the explosion vented from the container.

Figure 2. Titan's HULD intact and functioning following two internal explosions from bombs above the current detection threshold.	Figure 3. Destruction of typical aluminum ULD caused by an internal explosion from a bomb below the current detection threshold.