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Spektrum AR7000 failure?

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Old 04-03-2010, 09:13 PM
  #1  
gmohr
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Default Spektrum AR7000 failure?

Hi all,

I lost a plane this weekend (TF 1/7th scale P-51), in rare and unusual fashion. Here's the summary:

After about the fourth flight of the day, full throttle low pass, suddenly she broke into a vertical climb. I had no radio control from this point onward. The plane climbed mostly straight vertical for about 500 feet, then began to pull over the top into a series of loops. These loops continued for the next 10 minutes, all the while climbing and blowing downwind into the wilderness. I tried cycling the transmitter (DX7) a few times but to no effect. At one point, we were all standing slack-jawed as we listened (couldn't see it anymore, too high/far) for the sound of the engine to finally run out of fuel, which it must have done. The plane was never recovered. Here's our analysis of the crash:

1) The receiver never entered fail safe (or it would have gone to low throttle (and yes I checked the bind point for low throttle)).
2) The receiver never lost power. I figure that an unpowered servo would have blown to neutral in those full throttle powerdives on the backside of each loop. Additionally, I recharged the flight pack (A123 1100mah) just before that flight and it was fully charged.

My closest analogy to this would be when your PC computer "freezes" or "locks up", and requires a reboot. This AR7000 was about 2 years old and had performed flawlessly in a prior airplane, and never took any kind of damage or abuse.

Has anyone experienced this sort of failure, on Spektrum 2.4 or any other system?

Regards,
George
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Old 04-04-2010, 12:04 AM
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bigedmustafa
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Default RE: Spektrum AR7000 failure?

I've seen a very similar crash that occurred when an Airtronics Stylus transmitter suffered a Tx battery failure. It was with a large Goldberg Sukhoi, and all we could do was watch the plane fly around by itself for about 3 minutes before it finally came spiraling down.

Obviously this wasn't the case with your crash, as you sound certain that the failsafe was properly set to cut the throttle.
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Old 04-04-2010, 03:54 PM
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Default RE: Spektrum AR7000 failure?

Have you tested the receiver since the crash to see if it's still acting up?
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Old 04-05-2010, 04:32 PM
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Default RE: Spektrum AR7000 failure?

You can't check a reciever that you don't have !!! The plane was never recovered.
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Old 04-05-2010, 06:06 PM
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Default RE: Spektrum AR7000 failure?

Oops, missed that. I guess there's no doubt then that the AR7000 was the cause.
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Old 04-05-2010, 06:54 PM
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Default RE: Spektrum AR7000 failure?


ORIGINAL: skipperwayne

Oops, missed that. I guess there's no doubt then that the AR7000 was the cause.
I love it
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Old 04-05-2010, 07:55 PM
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Default RE: Spektrum AR7000 failure?

Hi all,

I was pretty convinced it was the receiver, but the above stories make me question that. To me, the crux of this matter is, would a servo with no power maintain a substantial amount of "up" elevator, agains the pressure of the airflow and g's of full power loops, on an overpowered TF 1/7th P-51 with an OS 120AX. If the answer is "no", then its the receiver. If the answer is "maybe", then it could be the power system (batt, switch, etc).

Its a hard question to answer.

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Old 04-06-2010, 06:31 AM
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Default RE: Spektrum AR7000 failure?



I just purchased a Spektrum DX7 so I have been following these kinds of threads very closely.  Its a real shame that you did not recover the model.  Much could have been learned.  I read and re-read your account but still have a couple questions.

1 Fourth flight of the day... were these 10 to 15 minute flights? 

2 TF P-51 seems a pretty big Electric.  yet you say flight pack was A123 1100mah  pack.  That seems small.  And, why wouldn't you power the radio off the substantial motor power pack, if electric?  You allude to "run out of gas" so was this Nitro, electric or Gas? what engine?

3. High speed pass then straight vertical, followed by loops...  If I reconstruct this in my mind's eye, and try and mate what the stick inputs would have been, here's what I come up with....    holding slight forward stick pressure as plane descends, speed building up, throttle full forward, then across deck, slight pull back, just a tick, then another, but this one is a slip up, causing total pitch up, elevator goes back to neutral, but plane goes straight up...  (If full up elevator continued, it would have done one quick loop ending with a splat on the ground)..  Ok so now it's going straight up... (panic sets in throttle is chopped, does motor respond?) plane has to start slowing, unless it is extremely overpowered, but you say that at 500 feet (that's pretty high up) it starts looping...  I'm amazed that the loops were so consistant, with a low wing model, I would think that it should have started to roll off at least a little especially with the engine still full bore.  Hope you had your name and address along with AMA number inside, like the AMA rules state...  I know it must have seemed like an eternity, but in talking with others, how long did it take for the model to disappear?

4. Dual rate switches....   one thing I don't really like on the DX7 is all the switches.  There's lots of opportunity to really hose things up with just an unintentional bump of a switch..   Your story is a wake up call to me to go through all models and make certain I don't have one where the dual rate switch is set so low that when its on (I seldom use dual rates) it would seem that I have no control.

5. AR7000 receivers and 2 years old... did this receiver have the dual front ends?  I am still struggling to understand the Spektrum receiver line-up...  I'm queezy about the park range receivers, although I must say, I have never had so much of a hint of a glitch no matter what receiver I am using.



6. Had the plane ever seen any rough landings?  I know that the G forces are pretty tall when you first pull level after a prolonged dive.  It sure sounds like something broke.





Just some museings.  Please post any followup information.





Thanks





KKKKFL

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Old 04-06-2010, 07:21 AM
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Default RE: Spektrum AR7000 failure?

I thought the same thing about 4th flight then I read this...

Additionally, I recharged the flight pack (A123 1100mah) just before that flight and it was fully charged
Separate reciever packs isn't unusual.

As for the servo tough call, I would think "maybe"
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Old 04-06-2010, 05:13 PM
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Default RE: Spektrum AR7000 failure?

It was a glow powered plane (OS 120AX). The plane did have one hard landing the previous weekend due to a dead-stick, but performed well in the following few flights. It was indeed overpowered, and was able to climb vertically with no problem.
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Old 04-06-2010, 06:00 PM
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Default RE: Spektrum AR7000 failure?

Depends on the servos being used. A normal cored motor servo will generally stay where it was when it lost power. It may move a bit.

Coreless servos will not hold position without power unless the gear train locks up or something like that.
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Old 04-06-2010, 06:23 PM
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Default RE: Spektrum AR7000 failure?

Interesting... here's the servo on the elevator (Spektrum DS821). I'm not sure what motor type it is.

http://www.horizonhobby.com/Products...702#quickSpecs

What is it about coreless motors that have less tendancy to stay put than cored motors?

Thanks,
George
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Old 04-06-2010, 06:38 PM
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Default RE: Spektrum AR7000 failure?

there's less mass to the rotor in the motor - takes less externally applied torque to move it with no power applied.

The servo you linked to is not a coreless motor - it's a 3 pole ferrite (iron) core motor.

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Old 04-06-2010, 06:41 PM
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Default RE: Spektrum AR7000 failure?

Ok so based on that, you think it likely that the servo would have held in absence of power. And that means I'm back to square zero on knowing what happened Oh well, better no knowlege than false knowlege!

Regards,
George
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Old 04-07-2010, 06:05 AM
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Default RE: Spektrum AR7000 failure?

George,
You really have my curiosity piqued now...  I just looked at the OS120 AX  man that's a hunk of iron up there!  Was there no way to locate the airplane? 

And, now I am trying to envision an airplane that big transitioning from horizontal to vertical (servo musta moved somehow), then the servo returns to neutral, (or  near instant crash), now it is going vertical and my first instinct would have been CHOP Throttle, which I am assuming you did, but nothing happened.  If this is correct, I would conclude that you had no receiver/transmitter link, or at least no response from the receiver.. but no fail safe either which sounds like total battery failure.  I have not tried this test since I've gone to electrics, but  maybe someone could report, "What happens when, with throttle  open (Doesn't need to be full bore, just above idle) what does the AR7000 do when the transmitter is turned off? 

Here's my conclusion,  Red lead (or internal pin) failure....  if the pin (internal to connector) is no longer seated, you can plug stuff together and as long as the hot lead is touching all will work ok...  Ok so now we are doing a high speed shallow dive, you pull up sharply, this causes a serious "G" load, servo responds correctly, but wires seperate just enough to momentarily break connections causing servo to glitch (here's your pitch up and back to center) and you loose link, now the receiver takes a few seconds to re-establish link but due to vertical position and breaking electrical connections all bets are off.  One more glitch and servo moves full throw causing loops, which further breaks electrical connection, and now you are DIW as far as control....


How does this scenario play with what you observed...  I don't have an AR7000 but if someone does, can you tell us what happens if you do not completely push the battery plug in all the way, in other words you have intermittent connection to power?


Thanks


KKKKFL
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Old 04-07-2010, 10:30 AM
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Default RE: Spektrum AR7000 failure?

Ok......now we're getting somewhere.

See if the top of the output gear on the servo gear is gone.

Those servos have some limitations posted on JR's web site but helicopter guys won't touch them because the output shaft shears off the top of the output gear in vibration prone situations. I for darn sure wouldn't be using them on anything that big.

Edit: Sorry I forgot you didn't get the plane back for a post-mortem. If I had to guess though....
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Old 04-07-2010, 04:56 PM
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Default RE: Spektrum AR7000 failure?

Not only that, but I had no channel control at all, so it wasnt the elevator servo. Anyways, they are published for up to 120 sized plans, and this was a .60 to .90 sized plane with a 1.20 in it, so should have been well withink spec.
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Old 04-08-2010, 05:33 AM
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Default RE: Spektrum AR7000 failure?

I forgot to test my AR6200 receiver that is currently on the bench last nite, but I want to know how the servos react when the hot lead is intermittant  ie. wiggle the connection then pull completely... 

I am betting I can create servo movement that will duplicate what you experienced at the field.  What I will be looking for is a glitch on elevator that goes in the up direction, then neutral, followed by another full up glitch, then with that and pulled power no control... (pitch up, climb straight up, then start and continue loops.)


KKKKFL
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Old 04-08-2010, 12:08 PM
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Default RE: Spektrum AR7000 failure?

Please do let us know! Thanks.
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Old 04-09-2010, 05:38 AM
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Default RE: Spektrum AR7000 failure?



Did exactly what I had expected...  but wasn't the center hot lead....  Here's what happened, and it was quite by accident:

Purchased a new E-flite 40 ESC...  took it home and plugged it into a 2 cell 7.2 LiPo...  (didn't read the instructions when I purchased it...  for those out there just getting into electric..  ESC's come in different varieties..  I should have read that it was a 3 Cell or 11.1 v ESC)

OK so I plug it in,  no tones  doesn't work cannot be programmed...  back I go to the store where the attendant has the same problem..
(he didn't know it was a 3 cell ESC either)  We finally see the instructions and put a good battery as in 3 Cell pack on the system.  Now it gives us the tones, but as he moves the stick, the servos are not responding...  he wiggles the wire and discovers that the outside lead, Not signal , is slightly cut..  This was a new item right out of the box.  As the connection is broken, I notice that the servo always runs the same direction, but returns to neutral as he wiggles the wire.

This really re-inforces my thought that you pulled up putting high g-load on everything, a broken or loose wire pulled apart just slightly, causing the up elevator twitch.  You may or may not have ever regained control momentarily, at some point a command got through driving full elevator, which in turn caused the G-load to pull the wire apart, only this time completely so , no control from this point on...


This all reads well, and of course if you had recovered the model, you still would not really know since the crash could have caused further damage masking the initial broken lead.   The above scenario was with a 5 channel receiver, and I still want to wiggle connectors on a 7 channel to see if it responds similarly...

KKKKFL

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Old 04-12-2010, 08:16 PM
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Default RE: Spektrum AR7000 failure?

Threads like this are what get rumors going. There are way to many variables to even suggest a 2.4 failure, not to mention a AR7000 failure. You had a way over powered plane with inadequate servo's (and yes I use DS821's, but never in anything with more than a .75 2C nad with small controll surfaces). I would be willing to bet that you had a battery failure, since this was also your 4th flight, even though you stated you charged it.
With that out I can state that I have never ever seen a failure with a AR7000 reciever. I have (3) AR7000's, and (2) AR6200's and the reliability has been rock solid. I have only ever seen a one plane crash that was blamed on a DX7 W/AR7000 reciever, and it was determined while looking through the crash damage on the table that the Guy had used the stock (4 cell) 1100 Mah pack in the Old 30% Weeks Special Bi-plane. I totally understand why that plane in particular crashed. I don't remeber exactly, but I think it had (4) aileron servo's, (2) elevator servo's, (1) rudder, and (1) throttle, and this guy could not understand what had happened.
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Old 04-12-2010, 08:37 PM
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Default RE: Spektrum AR7000 failure?

ORIGINAL: MOTORMAN37

There are way to many variables to even suggest a 2.4 failure, not to mention a AR7000 failure.
There are three possible components that could have caused this crash, and one of them is the AR7000 (battery and switch represent the other two). I'd say one in three warrants "suggestion".

I would be willing to bet that you had a battery failure, since this was also your 4th flight, even though you stated you charged it.
I didn't "state" I charged it, I charged it. And voltage checked it. And yes, perhaps it failed anyway.

You had a way over powered plane with inadequate servo's...
It was overpowered, but the servos were not inadequate. JR's specs explicitly state that the 821 is good up to 1.20 size airplanes. This was a .90 sized airplane with a 1.20 in it, so.. yeah. Anyway, thats a straw man, because it was not servo failure. I had no channels of control.

With that out I can state that I have never ever seen a failure with a AR7000 reciever...
Neither have I, at least and perhaps up to this incident. Either way, our combined experience is "anecdotal" at best.

Threads like this are what get rumors going...
Some might call it "discussion". If multi-billion dollar spacecraft and multi-million dollar airliners can fail, surely a 79 dollar consumer electronic gadget made in China can also.

Regards,
George
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Old 04-12-2010, 09:16 PM
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Default RE: Spektrum AR7000 failure?

ORIGINAL: gmohr

ORIGINAL: MOTORMAN37

There are way to many variables to even suggest a 2.4 failure, not to mention a AR7000 failure.
There are three possible components that could have caused this crash, and one of them is the AR7000 (battery and switch represent the other two). I'd say one in three warrants ''suggestion''.

I would be willing to bet that you had a battery failure, since this was also your 4th flight, even though you stated you charged it.
I didn't ''state'' I charged it, I charged it. And voltage checked it. And yes, perhaps it failed anyway.

You had a way over powered plane with inadequate servo's...
It was overpowered, but the servos were not inadequate. JR's specs explicitly state that the 821 is good up to 1.20 size airplanes. This was a .90 sized airplane with a 1.20 in it, so.. yeah. Anyway, thats a straw man, because it was not servo failure. I had no channels of control.

With that out I can state that I have never ever seen a failure with a AR7000 reciever...
Neither have I, at least and perhaps up to this incident. Either way, our combined experience is ''anecdotal'' at best.

Threads like this are what get rumors going...
Some might call it ''discussion''. If multi-billion dollar spacecraft and multi-million dollar airliners can fail, surely a 79 dollar consumer electronic gadget made in China can also.

Regards,
George

I still am willing to bet that you had a Battery or switch failure, since they are the most prone to fail. Just take a switch apart once. Some of the switch's, like the Cermark one with Led's, look like a little kid soldered them, since the one I took apart was all cold solder joints. I fly with nothing but JR Heavy duty switchs, and arming switchs that I make myself.
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Old 04-12-2010, 09:22 PM
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Default RE: Spektrum AR7000 failure?

This was the switch installed in this plane.

http://www.jrradios.com/Products/Def...ProdID=JRPA004

Regards,
George
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Old 04-13-2010, 05:55 AM
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Default RE: Spektrum AR7000 failure?

Lets agree on the basics, Based on your initial flight description :

Shallow dive(slight down elevator) to level across flight line(neutral elevator), then instantaneous nose up(full up for half second then back to neutral elevator) vertical climb for a period -500feet-  then full up elevator and continuous looping off across the horizon....

Something electrical broke....

KKKKFL
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