The greatest challenge in this work came in 1968, with the failure of the Flll-C within hours of official 'acceptance' by the Australian government. Working closely with the United States Airforce and the manufacturers, General Dynamics, ARL was able to make a major contribution to the analysis and solution of the problem. As a result of its work, the design of several components was changed and the machining practice was radically modified. During the work fundamental contributions to the theory of aircraft structures, corrosion fatigue, crack propagation and the statistics of failure were made.[56]

Bomb Aerodynamics

The Aerodynamic Division of WRE had conducted research in aerodynamics using wind tunnels and free flight models. This was to be applied to operational procedures and to weapon development.

Instability in the flight of bombs immediately after release from aircraft had long been known as a major source of bombing inaccuracy. It became of greater significance as bomber speeds increased, and was recognised as a hazard to the aircraft as very low level bombing became a common tactic.

Theoretical and experimental studies resolved the basic instability factors which were due to the dynamic coupling of rolling or spinning with natural pitching or yawing motions which caused 'coning' action, with high drag consequences. Mathematical modelling techniques developed for guided weapon operational analysis, were now applied to bombs which could be instrumented to validate the models.

The United States Air Force had developed a retarded bomb (called Snakeye) to permit very low sorties without aircraft damage. Modifications were made to the retarding mechanism in the Australian project called BALLARA. These modifications were adopted by the RAAF and the USAF.

The European and Asian theatres had generated staff requirements for dispersal weapons to be used against 'soft-skinned' targets like aircraft and light buildings. (Conventional bombs produce an excessive amount of damage, overkill, in a very small area.) The concept now was to launch a canister of a very large number of quite small bomblets, and to disperse these in a predictable pattern.[57]

With remarkable ingenuity, the work of WRE in clarifying the cause of bomb instability was put to use in securing a stable bomblet attitude in flight so as to produce a continuous lift force to cause divergence from a general heading. This was achieved by a careful arrangement of bluff body shape, centre of gravity and fin configuration. A family of sub-munitions could thus be made to scatter over a considerable area. This aerodynamic solution was an Australian contribution to a collaborative investigation on bomblet scattering with the USA and the UK. It was utilised in the development of a weapon to meet a RAAF staff requirement. The project was known as KARINGA.

14 Karinga

Australian Academy of Technological Sciences and Engineering