Help! Eflite Aero Commander crashed on me

[Yaw Morant]

Good morning all,

I just recently bought a used UMX Aero Commander that needed extensive repairs. I swapped the fuse, tail, and all electronics into a new one using reference pictures. Bound to my transmitter and everything worked perfectly. On the maiden (for me at least) it flew great until I pulled off a loop. Shortly after leveling, the plane spun straight down.

Now… when I recovered the plane I noticed the rudder was locked at full left and I couldn’t move it with the controls. Popped the canopy and got it working again, but I’m convinced something got loose when the plane went inverted and caused it to fall out of the sky on me.

Keep in mind, I know my fair share about these little things but I am by no means an experienced pilot. Just trying to understand the cause of this and increase my flight time vs my “hangar” time.

Thanks for reading and for your replies!

 

[Tench745]

A quick Google found this YouTube video of someone else's rudder servo failing.

I have had trouble on other builds where these linear servos can lock up if they travel to full deflection. Also worth noting, Spektrum transmitters have different endpoints than some other brands, so if you're not using a Spektrum transmitter, you need to limit your throws in the radio to avoid over-driving the servos.

 

[Yaw Morant]

It’s funny…I watched that video and thought to myself that maybe it was the servo. Lo and behold, the motor shaft is bent and the gear for the screw turns freely.

What’s interesting is I’m using a DX6e, so I figured I wouldn’t have to mess with any settings other than trimming out the plane. I will look into the endpoint settings when installing them into the new fuse.

 

[Tench745]

It’s funny…I watched that video and thought to myself that maybe it was the servo. Lo and behold, the motor shaft is bent and the gear for the screw turns freely.

What’s interesting is I’m using a DX6e, so I figured I wouldn’t have to mess with any settings other than trimming out the plane. I will look into the endpoint settings when installing them into the new fuse.

The DX6e shouldn't have the endpoint problem because it's a Spektrum radio, but turning things down just a hair won't hurt.

 

[Thomas B]

Common practice among experienced uMX aircraft owners is to reduce servo travel in the the TX to no more than 97% of full travel. This can prevent a servo jamming at full travel. Sometimes the conductive paint on the servo board is inconsistent at the very ends of the pot.

Once in a while a micro sized bit of grit will get in the gear train and cause it to lock up. This is not typically the cause of a jam at full travel, though.

It is also a good idea to use the electronic treatment Deoxit on the linear pot on the servo when the servo is new and once in a while thereafter.