Different corrections possible
Although not required by regulations, from a safety point of view it is wise to make corrections to the approach speed in case of strong gusty wind conditions to avoid reductions in stall margins. The speed correction given by 1/2 headwind + gusts with a maximum of 20 kt. is often advised by aircraft manufactures such as Boeing, Fokker, and McDonald Douglas. However, it should be realised that it is not an official requirement. It is not part of the aircraft certification (unlike stated in one thread). It is left to the operator to use this or not. Also there are another corrections used. For instance Airbus advises the following wind corrections depending on the aircraft model:
· A320/A330/A340 series: 1/3 of the headwind component (excluding the gust), limited to 15 kt;
· A310/A300-600: 1/3 of the tower average wind or the gust increment, whichever is higher, limited to 15 kt;
Another method is the one recommended by Bombardier and Cessna which only adds half of the reported gust to the approach speed.