<P> Owners have reported that on the ground, it can be harder to clear snow and ice from wing surfaces with VGs than from a smooth wing, but VGs are not generally prone to inflight icing as they reside within the boundary layer of airflow . VGs may also have sharp edges which can tear the fabric of airframe covers and may thus require special covers to be made . </P> <P> For twin - engined aircraft, manufacturers claim that VGs reduce single - engine control speed (Vmca), increase zero fuel and gross weight, improve the effectiveness of ailerons and rudder, provide a smoother ride in turbulence and make the aircraft a more stable instrument platform </P> <P> Some VG kits available for light twin - engine airplanes may allow an increase in maximum takeoff weight . The maximum takeoff weight of a twin - engine airplane is determined by structural requirements and single - engine climb performance requirements (which are lower for a lower stall speed). For many light twin - engine airplanes, the single - engine climb performance requirements determine a lower maximum weight rather than the structural requirements . Consequently, anything that can be done to improve the single - engine - inoperative climb performance will bring about an increase in maximum takeoff weight . </P> <P> In the USA from 1945 until 1991, the one - engine - inoperative climb requirement for multi-engine airplanes with a maximum takeoff weight of 6,000 lb (2,700 kg) or less was as follows: </P>

Vortex generators on the upper side of the wing