BACKGROUND OF THE INVENTION

This invention relates to stabilisation of aerodynamic bodies and is particularly applicable to bodies which are towed by an aircraft.

It has been found that bodies which are towed by aircraft are subject to disturbance from the wake turbulence of the aircraft. In severe cases, the ensuing pitching movements of the body can cause the tow line to break.

This invention aims to provide a means for reducing the oscillations of a towed body.

SUMMARY OF THE INVENTION

The invention therefore comprises an aerodynamic body of generally cylindrical form, said body being provided with front and rear tubular shrouds which are rotatable about the longitudinal axis of the body, and means for compelling the shrouds to rotate in opposite senses when the body is in motion.

The invention thus utilises the principle of gyroscopic inertia to stabilise the towed body when in flight.

The invention has the further advantages of being inexpensive and simple to manufacture and being maintenance free.

Because the body is provided with two shrouds rotating in opposite senses, gyroscopic precession effects due to each spinning shroud oppose one another. For complete cancellation, it is necessary for the two shrouds to rotate at the same speed.

In one embodiment, vanes are fitted to the walls of the shrouds and are inclined so that the shrouds rotate in opposite senses when the body is in motion.

Preferably, the vanes on the shroud mounted towards the front of the body are mounted on the internal wall of the shroud, and the vanes on the shroud mounted towards the rear of the body are mounted on the external wall of the shroud. This measure ensures that the rear shroud spins at a similar speed to the front shroud by using the free stream air rather than air that has already been de-energised after propelling the front shroud.

In an alternative embodiment the front and rear shrouds (each of which carries a set of vanes) are coupled by one or more wheels. The presence of the wheel(s) ensures that the shrouds rotate at the same speed, irrespective of the aerodynamic forces acting on them.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments of the invention will now be described, by way of example only, with reference to the drawings of which;

FIG. 1 and FIG. 2 show side views of alternative embodiments of a stabilised aerodynamic body in accordance with the invention,

FIG. 3 is a plan view of the embodiment of FIG. 2 and,

FIG. 4 is a cross-section on a line A--A' of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows an aerodynamic body 1 attachable to an aircraft (not shown) by means of a tow line 2. A front shroud 3 and rear shroud 4, both of tubular form, envelope part of the body 1. Each shroud 3, 4 is free to rotate about the longitudinal axis of the body 1. A set of vanes 5 is mounted on the interior wall of the front shroud 3. The exterior wall of the rear shroud 4 carries a further set of vanes 6. The vanes 5 and 6 are inclined so that when the body is in motion, the shrouds 3 and 4 rotate in opposite senses.

Referring now to FIGS. 2, 3 and 4 which show an alternative embodiment. FIGS. 2 and 3 show part of a towed body 7 connected to a towline 8 and carrying front and rear shrouds, 9, and 10 respectively. The shrouds 9, 10 rotate in bearings 11 and each carry a respective set of vanes 12, 13 on their interior walls.

Two wheels 14, 15 diametrically opposed across the towed body 7 couple the two shrouds 9, 10 together. The wheels ensure that if one of the shrouds is rotating, the other shroud would be forced to rotate at the same speed but in the opposite direction, irrespective of the aerodynamic forces acting on it.

In the case of either embodiment, when the towed body is disturbed by the towing aircraft's wake turbulence, the gyroscopic inertia created by the rapid spinning of the front and rear shrouds exerts a damping effect on any ensuing oscillatory motion of the towed body.