Notices
RC Radios, Transmitters, Receivers, Servos, gyros Discussion all about rc radios, transmitters, receivers, servos, etc.

Unexplained loss of control

Old 07-23-2012, 04:43 PM
  #1  
Scota4570
Senior Member
Thread Starter
 
Join Date: Jan 2009
Location: Salinas, CA
Posts: 841
Likes: 0
Received 0 Likes on 0 Posts
Default Unexplained loss of control

I lost control of a giant scale and crashed. Flew this plane half a dozen times with no gliches.

I am running futaba 2.4 faast. A 6ex TX and R617FS RX. Dual batteries, 5-cell 200mah nimh, dual switches to dual ports on the rx. The ignition is powered from a hobby king bec plugged into the rx power system. The servos are hi-tech. The ignition is RCEXL. All connections are secured with shrink tubing.

I am most suspicious of the BEC. I have flown several planes wired exactly the same way many-many times.

The plane survived with modest damage. After the crash I range checked it in power down mode to over 100-yards. I also tapped the tx while working the servos with no gliching.

I have two questions. First, should I send the RX to Futaba for a check out? Second, any ideas on what might have gone wrong?
Old 07-23-2012, 07:55 PM
  #2  
dirtybird
My Feedback: (5)
 
Join Date: Jan 2002
Location: San Tan Valley, AZ
Posts: 5,768
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Unexplained loss of control

What were the circumstances of the crash? Did the motor quit? Did the servos freeze? What was the attitude of the airplane if you just lost control?
If you range checked it and it passed, sending it in is a waste of time.
200ma batteries are very small. Do you mean 2000ma?
Old 07-23-2012, 08:28 PM
  #3  
Scota4570
Senior Member
Thread Starter
 
Join Date: Jan 2009
Location: Salinas, CA
Posts: 841
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Unexplained loss of control

Sorry, yes 2000 mah.

I made my take off run and at about 20' altitude I lost all control. It was as if the transmitter was turned off. The plane did a single roll and pancaked in. The motor quit upon impact.
Old 07-23-2012, 10:34 PM
  #4  
Silent-AV8R
 
Silent-AV8R's Avatar
 
Join Date: Mar 2004
Location: Orange County, CA
Posts: 5,312
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Unexplained loss of control

It does not sound like you had a failsafe set for the throttle. Also, the 6EX should hold last good command if it loses connection with the TX. How exactly is the BEC connected to the "power system"?
Old 07-24-2012, 12:39 AM
  #5  
4*60
My Feedback: (41)
 
Join Date: Mar 2002
Location: Shuswap, BC,
Posts: 1,753
Likes: 0
Received 1 Like on 1 Post
Default RE: Unexplained loss of control

Giant scale and 2000nimh don't go together really well. The NIMH can't always provide the current required because of internal resistance. I would go with A123 or at least hi capacity LIFEPO4. There are many LIFEPO4 packs that are 6.6 volts nominal, 2000mah if you wish and 20-30C discharge capable which would do what you need.
Several radio people indicate NIMH is not the way to go.
Old 07-24-2012, 02:48 AM
  #6  
proline8000
My Feedback: (12)
 
proline8000's Avatar
 
Join Date: Dec 2004
Location: Newburyport, MA
Posts: 256
Likes: 0
Received 1 Like on 1 Post
Default RE: Unexplained loss of control

I have seen what happened to you many times. Not only with 2.4 but 72 mhz also. There are so many things that could have happened. The reciever could have over heated ( what was the temp?) and was the reciever wraped in foam. It also could have been the battery, I have been seeing more battery problems in the last couple of years. It only takes one time to over charge a battery and it is fried. I would send the reciever back to Futaba, After a crash it is best to have your electronics checked. Hopfully they will test it on a vibration plate set to 3-5 g's. This should tell you if you had a problem from vibration. Cheep insurance for a big money plane,
Old 07-24-2012, 05:22 AM
  #7  
Silent-AV8R
 
Silent-AV8R's Avatar
 
Join Date: Mar 2004
Location: Orange County, CA
Posts: 5,312
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Unexplained loss of control

I agree about sending the RX in. I would also send the TX as well. As far as heat goes, the R617FS has proven to be extremely robust when it comes to heat. I do not recall hearing about any issues with it, especially heat related one. Low voltage is not a likely cause either. The 617 will work to down below 3 volts, the point at which many servos will not move. Given the dual packs, I'm not voting for voltage in this case.

I am still very curious about exactly what happened. Did it just stop responding? Did it go into failsafe (low throttle)? And how was the BEC wired in?
Old 07-24-2012, 05:34 AM
  #8  
dirtybird
My Feedback: (5)
 
Join Date: Jan 2002
Location: San Tan Valley, AZ
Posts: 5,768
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Unexplained loss of control

If you were just on a climb out after takeoff you were not using the servos so it is not likely a battery problem. If the engine was running OK its not a problem with the BEC.
With redundant connections,the only thing left is a receiver problem. Send it in and include a copy of this thread.
Old 07-24-2012, 06:09 AM
  #9  
Silent-AV8R
 
Silent-AV8R's Avatar
 
Join Date: Mar 2004
Location: Orange County, CA
Posts: 5,312
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Unexplained loss of control

I disagree about the BEC. It is very possible that the BEC or ignition was causing an internally generated noise that would not result in a failsafe event. This has been documented before. Failsafe works if the RX loses contact with the TX. But internally generated noise from a BEC issue, ignition, bad servo, bad connections/switches are a very likely culprit in this case.
Old 07-24-2012, 09:43 AM
  #10  
rmh
Senior Member
 
rmh's Avatar
 
Join Date: Dec 2001
Location: , UT
Posts: 12,630
Likes: 0
Received 3 Likes on 3 Posts
Default RE: Unexplained loss of control

Most likely?
the power to the rx-
There is NO substite for a really good battery system with NO BEC

2000ma NIMH -in the AA size are probably -as a group - the worst power cells you can buy- there are some good ones but not many-
The last thing to fail?
the rx
It may quit but typically due to power availability or overload from servo setup (same thing).
Old 07-24-2012, 11:11 AM
  #11  
Silent-AV8R
 
Silent-AV8R's Avatar
 
Join Date: Mar 2004
Location: Orange County, CA
Posts: 5,312
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Unexplained loss of control

His BEC was to feed power to the ignition. He also had dual packs, so while I agree that the typical AA size NiMH cell is not a great match for most uses, with dual packs (half the load per pack) the possibility of low power is less likely.
Old 07-24-2012, 11:48 AM
  #12  
dirtybird
My Feedback: (5)
 
Join Date: Jan 2002
Location: San Tan Valley, AZ
Posts: 5,768
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Unexplained loss of control


ORIGINAL: Silent-AV8R

I disagree about the BEC. It is very possible that the BEC or ignition was causing an internally generated noise that would not result in a failsafe event. This has been documented before. Failsafe works if the RX loses contact with the TX. But internally generated noise from a BEC issue, ignition, bad servo, bad connections/switches are a very likely culprit in this case.
You really pinned it down didn't you?
Old 07-24-2012, 12:18 PM
  #13  
MX240
Senior Member
My Feedback: (4)
 
MX240's Avatar
 
Join Date: Nov 2003
Location: PoDunk City, NE
Posts: 1,032
Likes: 0
Received 1 Like on 1 Post
Default RE: Unexplained loss of control

Well with ol'dirtybirds post, there is no use of the rest of us trying
Old 07-24-2012, 03:26 PM
  #14  
dirtybird
My Feedback: (5)
 
Join Date: Jan 2002
Location: San Tan Valley, AZ
Posts: 5,768
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Unexplained loss of control


ORIGINAL: MX240

Well with ol'dirtybirds post, there is no use of the rest of us trying
Words of wisdom from podunk Nebraska.
Funny, I grew up in Nebraska and never heard of Podunk city.
BTW I see big red has finally found a way to beat Penn State.
Old 07-24-2012, 04:05 PM
  #15  
pilotpete2
 
pilotpete2's Avatar
 
Join Date: Oct 2002
Location: Lyndonville, VT
Posts: 3,305
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Unexplained loss of control

OK, here's my take. The ignition is being powered from the receiver bus using a BEC to drop down the voltage of the 5 cell packs to less than 6V for the ignition. While I'm a fan of running an IBEC for just this purpose, they're designed especially for this type of setup, they provide filtering and current limitation (in case the module takes a dump) between the ignition module and the receiver bus, which the BEC does not, in fact, since most BEC are switching types, they can feed their switching noise back noise to the current source, in this case the receiver bus! I would look into either a separate ignition battery, or an IBEC like the Wike between the ignition and receiver, but you will need an actual open channel to turn the ignition on/off from the radio for these units. Of course you're getting the added benefit of an ignition kill switch when you go this route.
Pete
Old 07-24-2012, 05:50 PM
  #16  
Scota4570
Senior Member
Thread Starter
 
Join Date: Jan 2009
Location: Salinas, CA
Posts: 841
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Unexplained loss of control

BTW is is a big chaos from bridi with an OPS 30 running gas.

I installed a CRRC Opto coupled BEC cut off unit for the ignition. All of the extensions and y-harnesses will be replaced. The RX is velcro mounted on a piece of lite ply which is mounted to the fuselage with a piece of foam in between. This makes a soft mount.

I ordered an 8FG super today.

I was playing with it today and the ailerons were not working properly. It was a programing problem. I had flown the plane several times before. I checked the control surfaces before flight. Maybe I missed the ailerons being reversed???? Gads I hope not, I am a bit young for such issues.

Thanks for all of the great suggestions.

Scot
Old 07-24-2012, 06:25 PM
  #17  
pmerritt
My Feedback: (118)
 
Join Date: Nov 2007
Location: Wylie, TX
Posts: 445
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Unexplained loss of control

FYI Penn beat themselves. NO help needed from anyone but the devil was used to get them where they are! Enough said.
Old 07-24-2012, 06:43 PM
  #18  
p39
My Feedback: (5)
 
Join Date: Oct 2002
Location: New Ulm, MN
Posts: 387
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Unexplained loss of control

One question that was answered was about sending the receiver in. Yes... Futaba will run some tests on it. I had one suspected of failing and losing an airplane. Of course, everything worked fine when I get the plane back to the pitts. Sent the receiver in and it failed a vibration test. They couldn't repair it, but offered a replacement receiver at less than a discounted price. So, now I know it was the receiver and got a new one for much less. Futaba rocks here.....
Old 07-24-2012, 07:07 PM
  #19  
Desertlakesflying
My Feedback: (28)
 
Join Date: Jul 2005
Location: Sun Valley, NV
Posts: 2,901
Received 62 Likes on 53 Posts
Default RE: Unexplained loss of control

I would never ever run an ignition off my receiver battery. I have 3 batteries in one of mine with a gasser. Smart fly, 2 7.2 lipos for the receiver and servos and a separate 7.2v lipo for the ignition.
Old 07-24-2012, 07:33 PM
  #20  
dirtybird
My Feedback: (5)
 
Join Date: Jan 2002
Location: San Tan Valley, AZ
Posts: 5,768
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Unexplained loss of control

ORIGINAL: Desertlakesflying

I would never ever run an ignition off my receiver battery. I have 3 batteries in one of mine with a gasser. Smart fly, 2 7.2 lipos for the receiver and servos and a separate 7.2v lipo for the ignition.
It is simply impossible for noise generated in a switching regulator to interfere with a 2.4 ghz spread system. In the first place the generated noise is way to low to get anywhere near 2.4ghz. Then its a spread spectrum system. This system has been developed specifically to reject interference. You have to generate enough noise to wipe out the entire band to prevent the message from getting through. Spend a little time to learn how it works.
I think the answer is in post 15. He had the ailerons hooked up backwards.
BTW I fly small gas models. I use one A123 battery supplying both the receiver and the ignition. I just drop the voltage a bit with diodes for the ignition.
Old 07-24-2012, 10:05 PM
  #21  
essyou35
My Feedback: (11)
 
Join Date: Dec 2009
Location: Central Midwest
Posts: 1,946
Received 25 Likes on 22 Posts
Default RE: Unexplained loss of control

Didnt read thread, but never use a BEC. Get a LIFE pack. BEC should be outlawed by AMA.
Old 07-24-2012, 10:06 PM
  #22  
Silent-AV8R
 
Silent-AV8R's Avatar
 
Join Date: Mar 2004
Location: Orange County, CA
Posts: 5,312
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Unexplained loss of control

You are correct about interference, but 2.4 receivers are still able to have problems from noise from the system in the plane, like an ignition, bad switch, bad plugs, servo going bad, etc. Every single one of those things has been documented. In the pre 2.4 days we just called it getting hit, but now we know that is not the case. External noise from metal to metal, outside interference, etc. generally have no effect. But the stuff on the other side of the RF deck can cause issues. You will not get a lockout since the RX is still seeing a valid signal. You get things like un-commanded surface movement, erratic behavior (i.e. "glitching") and so on.
Old 07-25-2012, 03:18 AM
  #23  
TimBle
Senior Member
 
Join Date: Apr 2010
Location: Cape Town, SOUTH AFRICA
Posts: 2,744
Likes: 0
Received 1 Like on 1 Post
Default RE: Unexplained loss of control

why would you get uncommanded surface movement etc from internal noise? How does he noise manage to mimic the PWM signal carrying a ID code and a command that matches the binary sequesnce used by the 2.4GHz radio system?

I'm curious because I figured this internal noise was only possible with non PWM systems
Old 07-25-2012, 03:28 AM
  #24  
Luchnia
My Feedback: (21)
 
Luchnia's Avatar
 
Join Date: May 2009
Location: Amelia, VA
Posts: 2,079
Likes: 0
Received 1 Like on 1 Post
Default RE: Unexplained loss of control


ORIGINAL: Scota4570

I lost control of a giant scale and crashed. Flew this plane half a dozen times with no gliches.

I am running futaba 2.4 faast. A 6ex TX and R617FS RX. Dual batteries, 5-cell 200mah nimh, dual switches to dual ports on the rx. The ignition is powered from a hobby king bec plugged into the rx power system. The servos are hi-tech. The ignition is RCEXL. All connections are secured with shrink tubing.

I am most suspicious of the BEC. I have flown several planes wired exactly the same way many-many times.

The plane survived with modest damage. After the crash I range checked it in power down mode to over 100-yards. I also tapped the tx while working the servos with no gliching.

I have two questions. First, should I send the RX to Futaba for a check out? Second, any ideas on what might have gone wrong?
I almost lost one just this past weekend. After all was said and done I found out it was a battery. I could hook a voltmeter to the battery and it was jumping up and down from around 4 volts up to almost 6. Never saw one do quite like that. You could sit there and just watch the voltmeter jump up and down randomly and sort of cycle through voltages.

Of course with your setup it can be a number of things, just make sure you are thorough in checking everything out. One other thing that I had happen once was strange. I kept losing control to a plane and I finally found it to be an aileron connection that was coming loose during flight! I would have never thought it would make the plane go crazy as far as radio connection - once fixed no more issues.
Old 07-25-2012, 03:36 AM
  #25  
OliverJacob
My Feedback: (12)
 
Join Date: Jul 2011
Location: Reedsburg, WI
Posts: 700
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Unexplained loss of control

What you looking at is the way the radio transfers signals between tx and rx. After the rx decodes the signal, interference can feed through a servo or battery wire into the receiver if the source is near it.
This happens after the signal is being decoded into a standard analog servo signal, just like the old 72 MHz systems.
Newer receivers do have better filters, but still - noise can happen.
In this case it looks like the power was completely lost. Interference normally causes some servo jitter, seldom total loss of control.
Now a lot of things are involved, something like a locked servo may have drained the voltage, but it could be any part of the electrical system.

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service -

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.