In the United States, researchers of the National Aeronautics and Space Administration have been trying to solve the problem of wake vortices-the funnel-like patterns of air that swirl off the wings of planes as they speed along.

SYNOPSIS: Vortices cannot be seen unless smoke or dye pods are attached to wings of aircraft The larger the plane, the bigger the vortex and the resulting problem. At present traffic controllers avoid the problem by carefully spacing takeoffs and landing. If the vortices can be reduced or eliminated, it will cut down air traffic delays at many of the world's busy airport.

The tests are all part of a continuing effort by those involved with aviation to improve the safety and comfort of air travel. Using a model of a jumbo jet, the experts recently carried out a series of tests at the Dryden Flight Research Centre in Laurel, Maryland, USA, to look at the vortex problem from a different angle-underwater.

Testing an aircraft in water might seem strange, but water and air are both fluid mediums. The researchers, using a tank, mounted the vortex-generating model on the carriage. And this motor-driven carriage moves the model through the water channel. The following model, a small business jet, is mounted on a separate carriage downstream of the generating aircraft. As the test progresses, dye is let out of the wing tips of the generator aircraft. This dye ?wirls up in the vortex with the axial velocity, According to NASA. results of the wake vortices research are very encouraging.