Many people including myself struggled with airplanes violently pitching down when AP is first engaged during the initial climb. So I thought I would test out the reasons and provide a bit of a solution. In the video, you will see that the take off and climb is pretty smooth and no nose pitch when AP was engaged at 700AGL. Here’re the steps:
Set heading, flaps 5 and importantly trim 40 before you accelerate down the runway. Altitude is set at this point but NOT engaged.
Manual control of liftoff and keep an angle of 10 degrees
Set auto air speed at 200KIAS
(This is the important part) Gradually increase trim, so that to keep the 10 degree elevation, you gradually push down on the yoke until a neutral position is reached. When this is achieved, you engage auto-pilot and this will give you a smooth seamless transition (in the video, this happened at 700AGL).
Retract flaps (900AGL in the video), set final climb rate and sit back to enjoy the view.
I do NOT recomend setting a Heading before lift off, bere in mind that some runways are in between two numbers (i.e 275-276) so you can somtimes be stuck steering to the left or right of the Runway. The only thing I ever preset are the Flaps and Planned Altitude. (and no smoking and seatbelts and so on)
Takeoff with Flaps 10 at around 160-170kts Trim 5%. (On Most Aircraft) then activate A/P 500ft AGL/MSL - lifting slowly and consitantly to coenside with the A/P when activated at 500ft.
Accelerate to 250kts then trottle back and sit at 250
Lift the flaps to 5 and reset trim to 0 @ 3000ft
Lift the flaps to 0 @ 4500-5000ft
Climb to 10000 and Accelerate to 300kts
Climb to cruise alt @ 300kts
Cruise at or above FL300 (don’t always fly that high)
Wether this is correct or not, its how I usually do it.
Although honestly most times I don’t bother with trim.
This avoids the A/P bouncing the plane around.
Just my method.
I don’t have that nose dive problem - I simply set flaps, set desired altitude prior to takeoff.
Manual takeoff throttle and rotate, positive rate of climb and retract landing gear.
Around 500ft (and this is depending on aircraft and flap setting etc), retract first stage of flaps, still flying manually
Once I adjust pitch after the flap retraction, I continue on manual and (if need be, bank to required heading). I use manual throttle and (I fly 737 or 717) and hold a climb out speed of 210 to 220.
Once I level out, I ensure I have a steady rate of climb, and at this point, I activate AP. if you are holding a steady speed and rate of climb, once you activate autopilot, it automatically matches your rate of climb and heading. Then I adjust speed and set the autothrottke.
I’ve found if you’re climbing steadily the AP activates smoothly. Remember don’t preset rate of climb because if you’re climbing at 2000fpm and had it set to say 1500fpm, the nature of IF AP is that it reacts like a fighter jet and will nose dive you to reach 1500 from 2000 in less than a second. Also, if you’re not manually climbing steadily, the AP doesn’t seem to be able to adjust and hold your climb, it almost seems like it detects what rate of climb you would end up if you continued your current pitch and again, adjusts to that in less than a second.
Every aircraft has this problem. Just put your desired VS on the A/P before takeoff and, when you´re reaching it, activate it. You won´t have problems.