"I think the gimbal pot is faulty"

"Can you plug a servo into that ch on the rx and see if you get the expected travel? It has to be a radio issue, as APM will only report what it sees as the pwm range output from the channel."

"Wow. That seems to be a lot. My replies are getting muddled but.. did you try pulling the Elev wires from the RX to the APM, leaving the RX empty, and plugging a servo into the Elev output of the RX? Center stick should be center servo or at least…"

"Euan, Center of gravity is good...triple checked. It really seems to be the pitch trim...the APM is getting a command from the radio to pitch up, even after all is calibrated. Anyway, I think the sub trim will work...but still it bothers me that…"

"Bill, I can fly level if I use full pitch trim forward/down.  But I am wondering why I have to do that if the radio and MP are both calibrated.  And didn't I read somewhere in the MP documentation that I should be flying with the…"

"Doug, The horizon shows level, and the apm is mounted level. It's definitely (well, I think), a command input...in other words the APM is getting a "pitch up" command from the radio, even though I have calibrated the radio internally,…"

"Indeed - this looks like a levelling issue.   Less likely, but worth check is COG. Ie is it in the middle of the airframe, level as Doug says, and is the APM completely centred in the frame as well?"

"Other thoughts... Did you check the leveling calibration? In short, with the aircraft level in two axis, right side up, does the Mission Planner Flight Data screen horizon show level? It is unlikely but...is the APM mounted level to the airframe? A…"

"See http://www.hobbyking.com/hobbyking/forum/forum_posts.asp?TID=18880 for links to the original manuals. Have you tried to use the trim switch to move the center point back? Try with a new model setup, you did select Acro when you did it the…"

"Well...they are all at "000". What does "sub trim" do?  What does it mean? There is a setting for elevator...it's at "000". -- Thanks...Bill "

"Thanks for the thought Doug... I think it does.. I will check and report back."

"Ah- sorry Bill. Was reading in a goofy mobile view. Anyway, Doug may well have it. If all looks well, try resetting that model on the radio and setup fresh. "

"Does the radio have a subtrim setting? If so, it could be way off. I am not familiar with the 9x, flying Spektrum here. -=Doug"

"Thomas... As far as I know... It is an actual 3DR radio... But really, I can't be sure. The main issue is that there are supposed to be 5 wires going IN to the APM 2.5 from the radio (though only FOUR go into the APM 2.0...and this is why I…"

"John... Thanks for that suggestio... Good thought. However, check the pic... You can see that the pitch "range" is off center... Its biased toward the top of the pitch bar, which is pitch back, or nose up of course. So it apprears to be…"

"@Bill, Are you sure it is a 3DR radio and not a clone? I have the 3DR 900MHz telemetry radios and they do not have the type of connector (Hirose) that is visible in your picture. The 3DR radios use the 0.1 spaced berg style pins and…"