UM T-28 Trojan - Motor stuck on full throttle - RC Groups
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Aug 09, 2011, 02:58 PM
Ron Lauser
PACubFlyer103's Avatar

UM T-28 Trojan - Motor stuck on full throttle

This is a repost from another discussion group.

I took my recently purchased (not new) T-28 Ultra Micro out for a few flights before work this morning. After a crash which knocked the battery free of the plane, I plugged the battery back in and the motor jumed to full speed without any input from the transmitter. Moving the throttle stick has no effect motor continues to run at full speed. The other controls (rudder, etc)still respond to the transmitter sticks. Turning off the transmitter has no effect. Motor runs at full until I disconnect the battery.

I really didn't think the crash was hard enough to break anything.

I taken the fuselage apart. Connections to the motor look OK and the receiver/esc board looks undamaged.

Has anyone ever seen this problem? Do you think I have a bad receiver/esc?

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Aug 09, 2011, 03:34 PM
Registered User
ausf's Avatar
I once disconnected the motor to change fuselages and reconnected on the wrong pins and that happened.

I'm assuming you have the Tx on before you plug in the battery?

I'd try a rebind first.
Aug 09, 2011, 03:46 PM
Ron Lauser
PACubFlyer103's Avatar
Yes. I had the Tx on before plugging in the battery and I did try a rebind.

The motor runs on full even when the Rx is in bind mode.
Aug 09, 2011, 04:18 PM
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ICU's Avatar
To me it sounds like the board changed the motor output setting. The AR6400 has the ability to run an external esc. I would try changing this option.

Copied directly form the manual:

To Change the Brushed Motor to Operate an Optional Brushless Motor ESC or Brushless to Brushed Motor Control
The AR6400 is capable of operating brushless motors with the use of an optional brushless ESC, please see the illustration below for instructions.
Sticks must be held in this position while the transmitter is on and the receiver is off.
1. Ensure a successful bind was completed
2. Turn transmitter on
3. Move THRO stick to full throttle position (see illustration)
4. Move Control sticks to the corresponding position to change between the available options (see illustration)
5. While holding this position, plug the battery into the receiver, power receiver
6. The LED on the receiver will go solid and within 5 seconds the LED will flash 3 times quickly,
indicating the option is now changed
7. Disconnect battery from receiver
8. Turn transmitter off

***The image show to use FULL THROTTLE and FULL LEFT RUDDER**

Aug 09, 2011, 04:19 PM
The lunatic is on the grass
ridgewalker's Avatar
Maybe for some strange reason the crash happened to somehow switch the brick to brushless mode.

I have used the AR6400 with a brushless motor and forgot to set it back to brushed....when the brick is in brushless mode and you plug in the brushed motor it runs full blast constant.

I know that may sound crazy that a crash could have made it switch to brushless mode...but you never know.

You could try and switch the brick to brushed mode.


Below is the manual.
Aug 09, 2011, 04:56 PM
Ron Lauser
PACubFlyer103's Avatar
Thanks ICU and ridgewalker.

I followed the procedure listed above and that fixed the problem. I can now get back to flying my T-28.

You guys are great.


Ron L from Southeastern PA.
Aug 09, 2011, 05:07 PM
The lunatic is on the grass
ridgewalker's Avatar
Originally Posted by PACubFlyer103
Thanks ICU and ridgewalker.

I followed the procedure listed above and that fixed the problem. I can now get back to flying my T-28.

You guys are great.


Ron L from Southeastern PA.

Glad you got it figured out.

That is kind of strange how it changed profiles from a crash...,oh well you got it working and you can get back to flying that's what matters, have fun!!!

Nov 15, 2012, 03:42 PM
Registered User
I have the same with the AR6400 receiver of my PZ Sukhoi 26XP.

After a mild crash, throttle was always on, full power, as soon as I plugged the battery in. I found this thread and some other discussion where they recommended to use a new profile on the TX and rebind. I followed the instructions, and I am now able to switch the AR6400 in brushless mode and back with my DX7s. However, all this gives me is either always full throttle, or no throttle at all, no matter in what position I have the throttle stick.

I tried with a new default acro profile, but throttle stick just doesn't have any impact at all.

Does anybody have any idea on how to fix that?
Nov 15, 2012, 04:55 PM
Have fun
airpower's Avatar
You might have to open the plane up and play with different ways of plugging in the motor to the 3-pin connector, try that.
Nov 17, 2012, 09:19 AM
Registered User
I did that and changed the pins, but that didn't work, either. I never changed them before, so they should be wired correctly.

I'm still able to switch the AR6400 from brushed to brushless mode, and back, but I never get to control throttle. It's either full on (brushless mode) or no trottle (brushed). I do not have throttle cut, no mixes, and zero trim on my TX (empty default profile). The monitor on my DX7s shows an outgoing throttle signal corresponding to my throttle stick position.
Feb 17, 2013, 08:34 PM
Registered User
I'm having the same problem with my UM F4U Corsair, in brushless mode it is full throttle forward or reverse depending on which plugs I plug it into, in brushed mode it is full throttle reverse on the left pins, and no throttle on the right two pins (which should be the correct position. any help would be great.
Feb 21, 2013, 04:34 PM
Registered User
I wrote to Parkzone/Horizonhobby detailing my problem, the response was:

It sounds like the brushed ESC has been damaged, the board will need to be replaced in this case.
Looks like I now have some spare parts I'll never need... :-(
Feb 23, 2013, 12:32 AM
miatamama's Avatar
Mark, I will bid 5.00 for the brick.
Feb 23, 2013, 03:06 PM
Registered User
Guess I may be forced to upgrade to brushless

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