This is the noisy, stressful, confusing prelude to a power-on stall, and the almost universal question flight students ask is, “Why am I required to do this?”
It’s a good question with a straightforward answer. Pilots can become distracted or disoriented after takeoff and climb too steeply. The airplane slows, the wing angle of attack increases, and an unintentional stall (and potential spin) is the result. Pilots must recognize the lead-up to a power-on stall to avoid it, or recover from it.
The good news is that the recovery procedure is stone simple: Fly coordinated, and reduce the angle of attack. The stall horn will be quiet, the airplane will stop buffeting and accelerate, and it will stop trying to turn. You’ll typically lose little, if any, altitude during the recovery, and you should resume climbing at a predetermined airspeed as soon as the stall recovery is complete.