What this relates to
Wind shear and gusts, optical illusions, thermal updrafts or incorrect estimation of the rate of descent during the landing phase can lead to abnormal contact with the runway. If the aircraft descends too quickly, the landing gear may be damaged during touchdown. Excessive speed ends in a runway overshoot.
Example
While landing, an aircraft with a tail wheel is caught in a gust of wind. The wind pushes the left wing and the tail upwards. The pilot successfully takes corrective action. However, while the flight instructor (sitting in the front) tries to pull the control stick back to bring the tail down, the student (in the back seat) pushes the stick forwards. Combined with excessive braking, this leads to the aircraft flipping over.