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Troublshooting Corsair's Uncommanded Roll

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Old 06-05-2014, 07:32 PM
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70 ragtop
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Default Troublshooting Corsair's Uncommanded Roll

This past weekend, was flying my Corsair, and much to my dismay, it started an uncommanded aileron roll on the second flight on the day...then it stopped. Couple seconds later, it did it again. Rolled at a rapid rate, and stopped again. Was able to level wings and land right away. This setup has many flights on it, never had any problems

I am wondering if there is a way to determine it this is a radio problem, or a servo hardover from the RX LED blinking? Radio is a JR9303 with a AR8000. Model has not been power up since incident, no data logger. Did not think to check RX for flashing LED when I landed.......what can I say

One servo for each aileron, and four servos on the flaps. I did feed in opposite aileron to correct, and also tried commanding aileron same way it was rolling, and noted no changes. This all happened so fast, and the plane was very low and fast, did not try any other commands. Nothing else changed, just a nice clean roll

Time for a datalogger, so Pros and cons of the various data loggers are welcome

Any help would be appreciated
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Old 06-05-2014, 08:31 PM
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I had the same thing happen a week ago. It was a bad aileron extension in my case.
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Old 06-05-2014, 11:04 PM
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Get a servo tester before the data logger - test extensions as well as servos in place

I've had bad extensions too and took some head scratching to discover, we all suspect servos / Rx / power before we think extensions can fail too
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Old 06-06-2014, 08:51 AM
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Thanks Guys

I solder all my extensions, but maybe where wings plug in....will check it out

Curious what a servo checker will show you that cycling them with the radio won't?
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Old 06-06-2014, 11:00 AM
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It will reveal / rule out Rx / extension issues

also on auto-cycle mode it will stress test the servos for 30' at various speeds
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Old 06-06-2014, 12:19 PM
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Did you rebind the model after setup? If not, Worst case scenario, the model was going in and out of failsafe and the servo was going back to its presetup position which induced the roll.

If you did rebind after setup it could be a bad extension or servo
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Old 06-07-2014, 05:50 AM
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I did rebind after setup, but that was a couple years ago. Plane has a few seasons on it with no troubles.
Sounds like its too late to get any info from RX LED flashing....which I sorta figured.

Will go thru it this weekend and see if I cant find something

Thanks for the help
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Old 06-11-2014, 05:37 AM
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As a follow up, took a look at the Corsair last night. Everything seemed to be OK with servos and leads, wasn't really finding anything obvious on that end. The only plugs are at wings and RX as everything else is soldered. Those connectors look bright and shinny, and seem tight.

At some point the satellite RX bind LED started flashing, and the AR8000's red LED was also flashing. Looking thru instructions, the red LED shows the number of "holds" since RX was last powered up. Further examination showed the satellite plug connection might not have been 100%. It looked plugged in, and when pushed in, did not move. Once I removed plug, inspected and reinstalled, both RX bind LEDs were solid, could not get RED led to flash

FYI,AR8000 RX is mounted to vertical to sidewall, antenna goes straight back, sat is mounted horizontal on a 45. Replaced shrink tubing on antenna leads with air tubing to keep them straighter.


This still does not explain what happened though. In failsafe, none of the servos move from their neutral positions. When the LEDs started flashing, nothing changed, nothing moved out of wack, and nothing stopped moving. I don't think root cause has been found yet

Still not getting what a servo tester does for you. Does it just drive the servos, or does it also give you some sort of diagnostics info?
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Old 06-11-2014, 10:36 AM
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The tiny remote Rx wires are prone to breaking at the plug. That can cause odd ball issues. I use a touch of hot glue or electronics grade silicone as a strain relief right where the wires go into the plugs on the remotes. The wires will look fine, but the copper will be broken inside the insulation.
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Old 06-11-2014, 02:25 PM
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Thanks Jeff

I could see that happening, will take a closer look tonight.
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Old 06-11-2014, 07:54 PM
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No diagnostics from a servo tester, its just a simple device that allows you to test each component individually: servo, servo & lead, Y-connectors, reversers, etc

Helps isolate a problem by elimination, but in your case it looks to be the Rx so the tester cannot help there. Its tough if you cant reproduce the glitch, you will wonder when it will happen next without warning
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Old 06-11-2014, 08:11 PM
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Its tough if you cant reproduce the glitch, you will wonder when it will happen next without warning[/QUOTE]

You're not kidding!

Thanks for the info
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Old 06-11-2014, 11:59 PM
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Just a thought ....

make sure the end of your radio aerial is not pointing at the model at any time threw the flight,, even if you turn your body to follow the model in flight..
this happened to me a while ago and the model went into fail-safe.. i thought i had a bad receiver and after doing a lot of testing like you are doing now with no result i changed the position i have the aerial pointing now and have had no more issue's.
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Old 06-12-2014, 05:59 AM
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Be carefull I had the same issue with my TFG P47 with ZDZ80 in it. Every once and a while it would roll a little, or level back out. I swaped out the servos, and then the next flight while 15ft off the runway I decied to do a complet roll to inverted and was heading my way towards me, (as war birds need elevator to stay level while inverted) I had to let it crash about 15feet next to me, as I could not safely save it.

Everything still checked out later, But I can only assuem it was my Y harness, as It rolled very very fast, faster than I could make it do while flying.
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Old 06-12-2014, 08:51 PM
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Originally Posted by mikes68charger View Post
Be carefull I had the same issue with my TFG P47 with ZDZ80 in it. Every once and a while it would roll a little, or level back out. I swaped out the servos, and then the next flight while 15ft off the runway I decied to do a complet roll to inverted and was heading my way towards me, (as war birds need elevator to stay level while inverted) I had to let it crash about 15feet next to me, as I could not safely save it.

Everything still checked out later, But I can only assuem it was my Y harness, as It rolled very very fast, faster than I could make it do while flying.
That sucks!
When it stared rolling, I just thought to myself, oh well, this one's gone...then it stopped. Did it again, thought the same thing. I couldn't get it on the ground fast enough as I half expected it to start rolling again as I tried to land, but it didn't. Was feeling pretty lucky once on the ground.

Thanks guys for the advise
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Old 06-13-2014, 03:51 AM
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I even sent in my AR9020 to Horzon and it checked out
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Old 06-13-2014, 09:49 AM
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Hey 70 Rag Top,

Sounds like you are right path with your testing. You may also check your servo arms. I had this happen a couple years ago and found I had bashed the aileron somewhere along the line and one of the servo arm splines got damaged. The plane (FW-190) would fly great... Then start to roll and need lots of trim as the arm jumped splines in the air !!! It finally did it enough that I could feel the slop/play and replace all my aileron arms. They acted solid till they got some sort of pressure on them then they jumped splines.

As always.... It was my fault as I bashed it somewhere along the way.

Keep us posted.

Joe
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