Flying By Trim
"Some pilots are told by their instructors to fly by the trim. My instructor religiously says to trim after you find your appropriate angle of climb, descent, or cruise. Which is true, and which is false?" - Craig T.
"I agree with your Instructor. You should trim after setting power and after setting the aircraft attitude for climb, cruise or descent.
The idea is to trim off control pressures after power and attitude are set. Attempting to fly the aircraft with trim will result in a wide divergence of airspeed and trim before the proper setting is achieved.
Trim tabs are not a primary flight control. Remember that trim is both power and airspeed sensitive. Therefore trim can only be accurately set after the power and airspeed stabilize. This applies in climbs, cruise, and descents."