text: the airplane lift may be considerable immedi- 
  ately after landing, retraction of flaps or ex- 
  tension of spoilers immediately after touch- 
  down will 
  reduce the wing lift and increase 
  the normal force on the landing gear. With 
  the retraction of flaps, the reduced drag is more 
  than compensated for by the increased braking 
  friction force afforded by the increased normal 
  force on the braking surfaces. 