Multi-copter un-commanded motor speed-up

I recently calibrated the compass and the ESC's on my hex, then did a no-props test to see if all of the motors (1) started at the same time, and (2) all revved up at the same time. Everything looked and sounded like they were working okay. Then took it out for a test flight.

(1) Five of the six motors started simultaneously. The 6th (motor #2) "stuttered" when I plugged in battery in, just like all the others did, but it would not start until I had advanced the throttle a couple of detents, and even then it did not spin up to the same speed as the others (even after I moved the aileron/elevator joystick around in a circle)

(2) During subsequent start-ups I noticed that sometimes it was the #2 motor that would not spin up, sometimes #1, or sometime one or two of the others - in other words, it was sort of random, but #2 seemed to be the one most often not starting up with the others.

(3) I could actually get the 'copter in the air with one (sometimes two) motor(s) not working - albeit the machine didn't want to fly particularly good! Lots of yaw spin, sometimes one motor would spin up much more than the others, even ending with the occasional flip-over (luckily I was keeping it only a couple of inches above the nice, soft grass!)

Note: This 'copter was involved in a rather severe crash. The frame was completely replaced but all electronic components (TX, RCVR, Flight Controller, ESC's, GPS, PDB) were re-used. Four of the six motors are brand new, the other two (#'s 1 and 2) have an unknown (to me) use history.

My major concern is the un-commanded motor speed-up issue. Any ideas?

=========

Frame: 550 hex

Radio: Turnigy TGY-9x (tx) / Turnigy 9x8c (rcvr)

APM: Arducopter 2.5 w/on-board compass

Motors: 4-each Turnigy Propdrive 28-26 1200 kV, 2-each Turnigy Propdrive 28-26s 1200 kV

ESC:s: Turnigy Plush 30 A

Battery: Turnigy 5000 mah

Jacek Jackiewicz said:

you might have problem with the motor or ESC for that motor. Easy way to check : swap motors ( for example 2 with 3 and then see it the problems happens again with number 2 or number 3 this way you can find out which part has the issue.

Thanks for the reply. I am inclined to believe the problem is in the Flight Computer (Arducopter APM 2.5). This hexacopter experienced a violent crash earlier this year (a prop tangled with the tether line which I had attached to the under-side of the machine, wrapping the line up around the prop shaft like a high-speed fishing reel.. Wham! into the ground it went - breaking three motor arms and tossing various bits and pieces here and there - and nearly taking my arm off in the process!) Since rebuilding the machine I have found, in addition to the problem noted above, it:

1. will arm the FC normally, but it won't disarm it using the radio transmitter (joysticks in left corner, or right corner, or left and right corner, or any combination thereof - nothing will dis-arm it) and

2. it reverses "east" and "west" when displaying the heading data on the Flight Data screen in Mission Planner., and

3. it reverses the roll angle depiction on the Flight Data screen (when you roll to the left the artificial horizon in the Flight Data screen shows you are rolling to the right, and

4. the internal compass heading is just a bit over 40-degrees off from the GPS heading.

I've got a new FC ordered - will report back when it comes in and I get things set up again.

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Jerald Thompson September 12, 2016 at 7:53pm

Jacek Jackiewicz said:

you might have problem with the motor or ESC for that motor. Easy way to check : swap motors ( for example 2 with 3 and then see it the problems happens again with number 2 or number 3 this way you can find out which part has the issue.

Thanks for the reply. I am inclined to believe the problem is in the Flight Computer (Arducopter APM 2.5). This hexacopter experienced a violent crash earlier this year (a prop tangled with the tether line which I had attached to the under-side of the machine, wrapping the line up around the prop shaft like a high-speed fishing reel.. Wham! into the ground it went - breaking three motor arms and tossing various bits and pieces here and there - and nearly taking my arm off in the process!) Since rebuilding the machine I have found, in addition to the problem noted above, it:

1. will arm the FC normally, but it won't disarm it using the radio transmitter (joysticks in left corner, or right corner, or left and right corner, or any combination thereof - nothing will dis-arm it) and

2. it reverses "east" and "west" when displaying the heading data on the Flight Data screen in Mission Planner., and

3. it reverses the roll angle depiction on the Flight Data screen (when you roll to the left the artificial horizon in the Flight Data screen shows you are rolling to the right, and

4. the internal compass heading is just a bit over 40-degrees off from the GPS heading.

I've got a new FC ordered - will report back when it comes in and I get things set up again.
Jacek Jackiewicz September 12, 2016 at 7:54am

you might have problem with the motor or ESC for that motor. Easy way to check : swap motors ( for example 2 with 3 and then see it the problems happens again with number 2 or number 3 this way you can find out which part has the issue.

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Multi-copter un-commanded motor speed-up

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