Flight instructors rarely take over flight controls during a student's lesson. Normally, it's because there's no time for a student to react to a mistake. Here's when it can happen...

1) Dangerous Stall Recoveries / Inadvertent Spins

Using aileron to correct for wing-drop during stall practice is one way to get yourself into a spin, as this pilot found out. Notice how he lets go of the flight controls as his instructor takes over for the spin recovery:

2) No Flare On Landing

Fixation on a landing point is a leading cause of hard landings for student pilots. Instead of transitioning their eyes to the end of the runway, they fixate on hitting their pre-determined touchdown point. If aggravated enough, this can lead to a prop strike.

If a student fails to flare after roundout, an instructor will usually call for "back pressure." If no control response is given, the instructor probably will help by adding pressure themselves. When a student totally freezes, they might take full control or call for a go-around.

3) Not Reacting To A Go-Around Call

If you don't react to a go-around instruction, your instructor will take over flight controls. Maybe it was an unstable approach, or maybe another airplane just taxied onto your runway. When a go-around is called, don't hesitate. Follow these steps.

4) Low-Level Windshear

The worst place to encounter windshear is on short final. Low altitude means any loss of airspeed could cause you to touch down short of the runway. If strong windshear is encountered just above the ground, your instructor may not have time to analyze your reaction and instead might take the flight controls, say "my airplane," and initiate the go-around immediately.

5) Sudden Drift Or Crab Just Before Touchdown

Landing in strong crosswind conditions is challenging for even the most experienced pilots. It's critical to keep the longitudinal axis of your plane aligned with the runway's centerline so you don't land in a crab, or worse yet, go off the runway. This is how quickly things can go wrong...