A Passively Actuated Spoiler Using Sequential Interacting Instabilities

Gust load alleviation systems can reduce the peak stresses an airframe may experience during its lifetime, allowing for a more lightweight structural design. Consequently, many gust load alleviation systems have been proposed, but most are `active' in the sense that they rely on sensors and actuators in order to function. Such ancillary systems add weight, complexity and cost to an aircraft design, partly diluting any benefit from the load alleviation function. We therefore propose a fully `passive' gust load alleviation spoiler, whose only stimulus for deployment is the deformation of the wing into which it is integrated. The optimal structural response for such a device is outlined, and the concept of sequential, interacting instabilities is adopted to meet these requirements---this approach allows the spoiler to remain stowed until a critical strain in the wing is reached, after which the spoiler deploys rapidly. The working principle of the passive spoiler concept is introduced using a simple bar and spring model, and a physical prototype is detailed. An experimental setup is also presented to verify the structural performance of the spoiler under aerodynamic loading.