The short field takeoff is emulating departure from a short airfield. Usually this procedure is also performed with an obstacle clearance procedure, considering a make believe or real 50+ foot obstacle.
The objective is clear: get off as soon as we can, and climb to clear the 50 foot obstacle.
Let’s break it down.
First, set your flaps to 10º. Now we go full power while holding the brakes. This prevents the aircraft from moving forward while we make sure full power is available, and all systems are normal. This should only take several seconds.
Now, having lined up at the very start up the runway, we release the brakes and begin rolling. Go through your normal takeoff checks at this point, once again checking engine instruments.
There will also be a big pull to the left as soon as you let go of the brakes. Counteract accordingly with right rudder pressure.
You’ll lift off the aircraft right at rotation speed. That’s usually about 55-60MPH, or less based on the equivalent in knots. (Considering also this is a 172, and it changes based on aircraft type).
At rotation, you’ll climb out at Vx. Vx is best ANGLE of climb, or best climb over distance. It’s the slower of the two climb airspeed. This airspeed will mean we gain the most altitude over the short distance we have remaining to that 50 foot obstacle up ahead.
Again, make sure you achieve best performance by having continued right rudder pressure, and therefore coordination, throughout this climb.
Once clear of the obstacle, you can accelerate to your Vy climb speed by reducing the angle of attack. When appropriate, move your flaps to the up position.
Do all this smoothly, with enough speed, and maintaining that climb performance. Everything from here on out is normal for the climb.
Now, go out there in the real world with an instructor and see a real short field. There’s nothing like staring at real trees at the end of the runway.
Do your performance numbers and be honest about your ability to execute the procedure well. Give yourself a big buffer on your distance, say 50% extra.