Question about Power on Stall
 

I was used to do power on stall at full power during my private training and instrument but for commercial single in a 172RG, my instructor told me to do it at 21 manifold pressure instead of full throttle. Can someone tell me why I shouldn't do power on stall at full throttle? Thank you

I don't see why not. I did my commerical in a C172RG and we did it at full power and 2700rpm just like you were configured after takeoff because that is what it is simulating. I have heard of people doing it in the climb profile of 25mp and 2500 rpm as well. I thought I read somewhere that it has to be atleast 75% power, but don't quote me on that!

The idea behind the reduced power is to avoid a dangerously nose-high condition. Either the Pilot's Handbook of Aeronautical Knowledge or the Airplane Flying Handbook says you should attain no higher than 30 degrees nose up during the stall.

I personally used full power in the RG I used for commercial, but it was an old beater. Stay safe.

The only type of plane I dont do power on stall @ full power are multis... for obvious reasons.

When I flew C310's for a 135 outfit, we did the power-on stalls in the reduced setting for that reason. It makes it pretty aggressive, and really no reason when you're light-weight, etc... Under-powered Gutless's and Arrow's you can do full-power and not be too crazy, but it is definately nicer at 25-squared or less.

We did reduced power-on-stalls in the RG also. That airplane can get VERY nose high otherwise, and when it breaks it's like cracking a whip...the nose comes down fast and hard, and the tail surfaces make a loud banging noise. I'm not sure if it's bad for the airplane, but it is certainly disconcerting to the pilots.

It's just 'power on' versus power at idle. Doesn't have to be a takeoff/full throttle.

Hey b18onboost, next time you're with your instructor do a power on drop leaf and a power off drop leaf. you will see how erratic and hard to control the aircraft on the power-on drop leaf than on the power-off which is nothing. You will learn from this and they are fun to do...

I forgot what the exact number is, but there is a FAA statement that power-on stall has to be done with XX% of full-power at sea level. (I think its 75%)

I had this discussion with coworkers this week. I still do full power in the Seminole (counter-rotating props) but it can get a high nose attitude. Best technique I've seen is to always continue the pitch until you reach the stops or you stall, all while maintaining coordinated flight. Our Arrows and Diamond Stars come up quite a bit too, now that I think about it.