In cases where take off is obstacle limited,(mountain at end of runway for instance) less flap will improve climb performance and use the available runway length to achieve this with a higher speed at rotation.On some aircraft in our fleet, e.g A310 flap 0 is often the optimum setting on take off.
Where for example runway length is the most limiting factor , more flap is used to get the aircraft rotated at a lower speed in less distance, in which case flap 20 might be relevant, but a degraded climb performance will result.
Last edited by Frosty Hoar; 3rd May 2003 at 11:19.