We are advised not to use full 40 degrees of flap in my group's c150. The reasoning is that, for the typical runways most PPLs would go into (probably no less than 500m), the benefits don't outweigh the disadvantages if the the flap motor fails in the fully down postion and you have to go around. You apparently also need quite severe nose down attitude with the full flap setting, and power on until late in the approach, or else a very steep final approach which could be tricky to judge.
65mph with 30 degrees seems to work well, even for the shortest fields. Much slower than that and you don't have enough energy to flare properly.
Last edited by taxistaxing; 14th January 2013 at 15:54.