Complex sentence: A problem with the supply of the As 8 engine forced a re-design to use one engine, powering two rotors on a common co-axial shaft, with the engine driving one rotor directly and the other through gearing to overcome the torque effects.
Split into simpler sentences: A problem with the supply of the As 8 engine forced a re-design to use one engine. The two rotors were on common co-axial shaft with the engine driving one rotor directly and the other through gearing to overcome the torque effects.