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In flight glitch - please help diagnose

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Old 08-24-2005, 01:31 PM
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MTEXX_2
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Default In flight glitch - please help diagnose

Today I flew my 'corn during lunch. I know the setup can draw 30A+ on the bench so I usually run at about half throttle (which is 10A on bench).

After about 10 minutes, it got real squirelly and then spiraled in (which I managed a pancake landing in tall grass).
On the ground I noticed the starboard elevon was fully deflected up. The port elevon was jittering, and the motor was spazzing.
I took it inside still in this state for a closer look.
Nothing too hot.
Still spazzing.
I disconnected the batt for a moment and reconnected. The ESC beeped normally then kept spazzing.
I DC'd again for about a minute and reconnected. Things were back to normal.

So I flew...
Same thing yet it happened after about 2 minutes. Interestingly, the starboard elevon was drawn tight up, and the other one jittering. Motor spazzing the same way!!!

So it's a "reproducable" glitch.

Postmortem the batt is at 11.74V, which is fine??.
Heatsink was not too hot. ESC was warm but not hot.
Batt in fine condition, slightly warm.

What is going on???

Unicorn 48" wing
TP 2100, 10C discharge @ 3S2P = 11.1V, 42A
HiTec Electron6
Castle 45A ESC (don't recall what it's LVC is set for...)
Mega 16/15/3
Clamshell heatsink
Zagi 5x5 prop

Thanks a million,
MTEXX
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Old 08-24-2005, 08:48 PM
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Default RE: In flight glitch - please help diagnose

Hmmm. It happened again after work... I got about 8 minutes of good fly time in- real agressive stuff while coworkers watched.
PS- hadn't charged the LiPo yet as I knew it had charge.

Well, it went into seizure mode and landed thru a tree. No prob except I can't find a winglet.

Just now I hooked up the PhoenixLink (I love this thing!!!!!!!!!) and it says my LVC was 6.1V. It <should> be 9.0V.
However, that shouldn't screw up the RX enough to cause the servos to go into cardiac arrest...
Also, the servo which wasn't seized up moved normal speed in one direction but slow in the other. Who knows...

I'll definitely set my LVC to LiPo 3S (9V) and fly again tomorrow.

-MTEXX
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Old 08-25-2005, 10:10 AM
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Default RE: In flight glitch - please help diagnose

Bad servo can cause this. I would replace the one that's slow in one direction. Sounds suspicious. Make sure the ant. isn't near anything. Good range check. etc. I had a shorted out servo in the Zero. Locked up everything. Went in at full throttle from about a hundred ft. Popcorn
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Old 08-26-2005, 09:29 AM
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Default RE: In flight glitch - please help diagnose

Thanks for the input Flypaper.

Yesterday afternoon it happened again. Flying fine for a while then it gets real squirrelly then seized up. This time both servos seized up in a spiral configuration. THe ESC also went full blast. I ran to the site. No damage but the motor was going 100%. I had absolutely no control. I'll have to check the polarity of the servo, but I'm guessing the RX is sending 100% to all channels. Given the elevon configuration, that would put the control surfaces opposite eg hard right turn.

I tried to reproduce on the bench. This time I put all the radio EQ in the plane and closed the hatch. The idea is to see if heat soak is a factor. After about 10 minutes at half throttle, all channels bucked and surged for about 1 second then went full stroke. Right elevon skyward, left downward and motor at full-bore.

The batt was warm. The ESC was pretty hot but typical. The wires going to the ESC were very hot. The motor was rather hot but typical. The RX was slightly warm.

I unplugged the ESC from the RX and plugged in a regular glow-flight batt. The servos returned to nominal. Control from TX was again established.

My suspicion is now that the ESC is somehow fouling up the RX. I'm gonna try wnother RX this afternoon and perhaps hook up another ESC too. I also have another set of servos.

I am most fortunate that the last 4 crashes have narrowly missed roadways and parked cars. And that nothing more than a winglet has been damaged.
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Old 08-26-2005, 10:18 AM
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Default RE: In flight glitch - please help diagnose

Let us know what you find. Might help someone else with the same symptoms. Sounds like, after 10 mins. something is heating up and shorting out causing everything to go haywire.
Another thing you might try is, take the prop off so it isn't so dangerous first, Then get it to act up, then unplug each servo one after the other, to see if it straightens out with any particular one.
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Old 08-31-2005, 08:33 AM
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Default RE: In flight glitch - please help diagnose

I emailed Castle yesterday. Here is a response:

Hi Micah,

We talk with litterally thousands of hobbyists per week, and this is
something that looks like it may be starting to be a trend.

Apparently, when the electron 6 Rx voltage gets a bit low (strong current
going out to servos, and in your case, BEC power sagging a bit because of a
hot controller) it's reaction is to send all channels to 100% - as you've
observed. When it does so, in most applications, that travel is beyond the
"normal travel" you're using and the servo binds and stalls. A stalled servo
draws an excessive amount of current (more load on the BEC) and you can see
where this is headed - a downward spiral the Rx doesn't get out of, and any
ESC's BEC can't remedy the situation because it's maxxed out already.

A cooler running ESC would help keep the above loop from happening in the
first place (as would a different Rx) so having it in some cooling flow
would help yes.

I'd be happy to mail you a new peice of heat shrink if you'd like to send me
back your mailing address?

Thanks,
Shawn Palmer
Marketing/Support Dir.
support@castlecreations.com
785-883-4519
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Old 08-31-2005, 09:42 AM
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Default RE: In flight glitch - please help diagnose

test
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Old 08-31-2005, 09:54 AM
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Default RE: In flight glitch - please help diagnose

OK I hope I don't get sued copying for this, but it's very relevant. I AM GOING TO SOLVE THIS PROBLEM [>:]


[link=http://www.ezonemag.com/pages/faq/a506.shtml]RC Groups - Disadvantages of the BEC[/link]

Q. What are the disadvantages of a BEC?
A. Doug Ingraham, Lofty Pursuits

A BEC using a linear regulator has some very strict limits over which it can operate. Modern regulators only need about 0.25 volts more input voltage than output voltage. Therefore, a BEC that supplies 5 volts to the radio gear needs 5.25 volts from the battery. So a 6 cell pack operated at reasonable current levels (<30 amps) is the minimum needed to be safe in powering a radio from a BEC. Strange things happen when the input voltage drops below 5.25 volts. On the other end of the scale one shouldn't try to operate a linear regulator type BEC on more than 10 cells. At ten cells, the regulator may overheat and shut off. Of course when they turn off the radio is turned off and the plane generally crashes. I have seen a number of crashes that I am certain were caused by the BEC regulator chip overheating. The characteristic of this event will be that operation is fine for a couple of minutes into the flight and then radio loss is complete. It is most likely to occur on high cell counts (8+) with many servos (4 or more) and a fast airplane (the speed of the plane affects the amount of current that the regulator must provide to the servos). The pilot generally thinks he got interference and doesn't blame the real culprit. There are other types of regulators that don't have this problem but so far they are not in use because they are larger, weigh more than a small four cell receiver pack, and cost more as well.
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