Vr and takeoff trim

ajinla21

I replaced the plastic part that covers the flap handle and trim wheel on my Arrow II. I know generally where the white line for trim takeoff was, but I’m wondering if I’m off a bit. I say this because Vr is 65, and the plane is not rotating until well past that (75-80). Should I put in more trim a little at a time to see if I can get Vr where it should be? Or is it possible I’m not using enough back yoke pressure? I feel as though I’m using the same pressure. I guess I’m looking for the safest method. Or is there nothing wrong with Vr being that much more than the manual?

empannin

Hi, you should work with a shop to confirm the trim system is working fine. It is likely you are off a bit (too much down trim). In your case they probably will neutralized the stabilator and then adjust the marking in the cockpit for the trim so that it streamlines.
I would also have them check tensions, travel and freeplay. The tolerance on freeplay is tight (.06 inches) and you risk flutter if it is too large.

This is the procedure for a Seneca III. I imagine it is similar for your plane.

MikeJJ

Hi ajinla21,
Don’t get too focused on book values vs. what you are seeing in the airplane. They were determined on new equipment, in ideal conditions, and perfect technique. For example, if your nose strut is low and your mains are a bit high, your pitch pressures to rotate will be different as you attempt a normal takeoff. Crosswinds, density altitude, etc., also have an effect.

There are many different takeoff techniques depending on conditions. Next time out, try this….

Assuming your airspeed indicator is working properly and with a suitable length runway and no obstacles ahead, start with a trim neutral indication and leave it there. With full power, accelerate to Vr and HOLD a gentle pitch up takeoff attitude. Let the airplane fly itself off the runway. When you have established a positive rate of climb, reach down and trim off any control pressure to fly this speed. If it still needs trim, resist the urge to just tweak the trim wheel “hands off!” First, PUT the airplane at the pitch attitude needed to maintain your climb airspeed, THEN, trim off the control pressure. Look at the trim indicator now. The current position is a good starting point for a takeoff trim setting.

Keep making these normal takeoffs and tweak the starting trim until it feels most comfortable, but realize that takeoffs, just like landings, can require different techniques on any given day. The numbers and control pressures will not always be the exact same values.

Regards,

Mike

griff390

I learn something from every one of your posts Mike! Thanks for this tip, I'm going to use it next time I fly.