Autopilot/Ail Trim and first flight

RVG8tor · #1 08-10-2012, 10:34 PM

I am doing my final assembly and wonder if I should have the autopilot servos hooked up for the fist flight. I don't intend to use them, I do notice them on the ground but I hear you will not in the air.

Along the same lines, the springs on the aileron trim are fairly stiff, should this be disconnected for the first flight. My thought is yes to the aileron trim since the springs are so noticeable, I figure I really need to feel the flight controls to make judgements about how the plane handles for the first few flights.

Now that I think about it the autopilot might be nice to have until the rings seat since that will be a lot of circles at 75% power.

Cheers

kbehrent · #2 08-11-2012, 12:59 AM

I had mine hooked up for first flight and had no issue. The auto trim works great.

roee · #3 08-11-2012, 01:24 AM

I would fly the first few hours without the aileron trim springs. That way, if there is any aerodynamic "heavy wing" tendency, you can detect and evaluate it without having the spring bias trim mechanism masking or confounding the issue.

No such problem with the autopilot servos, as they contribute only a small amount of friction but no bias. I don't see a reason not to leave them connected.

MauiLvrs · #4 08-11-2012, 01:38 AM

On our first flight, I had the aileron trim disconnected and the AP servos hooked up but disabled (circuit breaker pulled).

Simply less to go wrong. Maybe on the third annual I'll get around to hooking up the aileron trim.

drill_and_buck · #5 08-11-2012, 03:40 AM

Hi Mike,

I had the servo connected, but pulled the fuse for the AP for the first few flights.

Regarding the aileron trim springs, I kept mine on. With the RV-8, with the trim in the neutral position, if you have a heavy wing, you will know it.

Prior to my first flight a hangar rash incident required me to replace my left aileron. The new one I built had a trailing edge radius that was slightly smaller than the right aileron, resulting in a heavy left wing. I flew the first 15 hours of my test plan with a heavy left wing. After double checking all rigging, a slight squeeze of the trailing edge of the right aileron, fixed the problem.

I found having the aileron trim springs installed during phase 1 testing to be beneficial.

Pat Stewart · #6 08-11-2012, 07:18 AM

I always remove the aileron springs for initial flight testing.

AltonD · #7 08-11-2012, 07:54 AM

I had a pretty heavy left wing. When I took off, the aileron trim was neutral. The trim was useful to correct for the heavy wing.
My first flight was a tad longer than most. I flew a box around the airport for two hours to seat the rings (worked great, I watched the oil and CHT temps fall at the end of hour one). the auto pilot really helped with the boxes and the heavy wing.

rv9av8tr · #8 08-11-2012, 08:11 PM

There is every reason to leave the aileron trim springs functional. Set the trim on the ground so the ailerons set neutral, if you have a heavy wing you will know, the trim springs will not hide that if preset to neutral. You'll also be hating having to hold aileron stick force for the entire flight without being able to trim it out. It's the same logic as why would you want to disconnect the elevator trim. It is there to use in case you need it.

The first few hrs you should be orbiting in a race track around the airport within gliding distance, the legs will only be a few minutes before you'll be turning around and around. Leave the auto pilot functions off so you really get to understand the feel of the plane. This first flight is important to get understand what you are dealing with, yet not have to "fight" the controls. Always stack the deck in your favor, don't create a situation that makes your flight all the more complicated to successfully complete.

roee · #9 08-11-2012, 09:34 PM

Quote:

Originally Posted by rv9av8tr

There is every reason to leave the aileron trim springs functional.
[...]
It's the same logic as why would you want to disconnect the elevator trim. It is there to use in case you need it.

No, it's not the same.

Elevator trim is an essential component of the airplane's stability characteristics, which -- by design -- must be adjusted in flight for changes in the desired flight condition: power setting, air speed, altitude, level/climb/descent rate.

Aileron trim is non-essential, but rather an optional nice-to-have intended only to compensate for slight lateral weight imbalances due to loading and fuel. Certainly nice to have for normal operation, but it's an unnecessary confounding variable for initial evaluation of aerodynamic characteristics of the airplane.

rv9av8tr · #10 08-11-2012, 10:31 PM

One thing about this forum is there are as many opinions as there are viewers. On this we will have to agree to disagree. Use of trim is NOT a confounding factor, it is a tool to use. Why take on a task intentionally without all your tools? I've done many first flights and complete flight test programs on numerous different aircraft types. I've "been there done that". Mine is not an opinion as much as real world experience. I don't just throw "stuff" on this forum, it is ALWAYS based on MY actual experience, not some elses or what I "think". If it is, I always preface it as such. Granted, others have different "experiences"... and your mileage may vary. I know my mileage and will contribute when asked.