Almost a very bad day, but just a bad day instead

[michael503]

Well, its spring, and today, like most flyers in the spring, I was fighting the wind with my 700E, and was winning, right up until I wasn't. I just finished executing a RH turn to level when everything went away. Motor went to idle and the heli began a long, slow, perfect auto towards the spectator area. As I watched the heli descend from 150ft in a long glide with zero control (or any idea at the time what had happened) I yelled "I ain't got it" several times. As the heli got within 10 ft of the ground, it suddenly spooled back up, but the tail blew out since the HS was maybe 500 RPM ( I swear I could count the blades ). At this point in time the heli was between the pilots sheds and the spectators fence, an enclosed area of about 10-12 ft. I hit TH and she went in sideways. Fortunately no one was hurt, but in retrospect, if I'd tried to save it, someone would have been because at this time I could barely see the heli through the shed.. Except for me, all of the pilots were at that shed, looking at photos, not watching me fly, and because the heli was over the shed by the time they looked up, they didn't know where it was. On the other side of the fence spectating, was a Mennonite family with 2 small children. Nobody ran!

This was close folks.

The cause of the crash, as best I can tell, was the AR6200 Main RX. Post crash testing indicated no link capability with the main unit, even after several reboots, although the satellite LED was lit, the main unit LED was not. Wiggling servo wires did nothing.Eventually, while poking and prodding, I vigorously tried the sat wire@ the main unit and it linked. Light wiggling with pliers did nothing.

This was not a brownout, it was a loss of signal. A brownout would cause both the Microbeast and the CC ESC to reset, and neither of these things happened. The main RX is on one side of the battery and the satellite is on the other. My best guess is that, when the main unit went south, the sat was shadowed by the pack. As the heli descended and clanged attitude in relation to me, the sat came into view and I regained control.. just too low and too late. The MB did a good job of keeping the heli level, right to the end.

When I rebuild, I'm getting a RX that supports more than one sat.

Damage is extremely limited, considering. Blades, main grips, Elevator arm, 1 link, and of course, the RX. I have to say that the blades, Rail 696s, took all of the grunt. Hell, I didn't even strip a servo, or scratch the canopy. If the heli had not spooled back up, it probably would have hit the chain link fence, causing even greater damage.

My problem now is that I cannot duplicate the fault, so there is a lurking fear in the back of my head that the TX is at fault, even though I flew another bird successfully right after the incident.

Anyone got something similar to share, or have any thoughts?

[McKrackin]

Glad no one was hurt.

What's up with the Mennonite family?

[michael503]

They were the only spectators. Very nice people.

[michael503]

Since I don't wish to double post, I thought I'd post a link

https://www.helifreak.com/showthread.php?t=406225

Thanks!

[desertstalker]

Originally Posted by michael503

The cause of the crash, as best I can tell, was the AR6200 Main RX. Post crash testing indicated no link capability with the main unit, even after several reboots, although the satellite LED was lit, the main unit LED was not. Wiggling servo wires did nothing.Eventually, while poking and prodding, I vigorously tried the sat wire@ the main unit and it linked.

That sounds like the sat cable failed. Does the AR6200 link if there is no sat? Quite a few Spek RXs will not.

[michael503]

Thanks for the input.

I thought that might be the case too, but no, it will not link if the cable is disconnected, but the link light will illuminate solid on the sat when it was connected, just the whole system would not link and the light on the main unit stayed off. In short, cable connected, sat lit, main unit off. Of course it works now.

I pulled each of the three wires from the link cable connector and checked the pin fit individually to the main unit and they are all 3 very tight. When testing right after the crash,I had to wiggle on the connector forcibly for at least 3 seconds before the main unit light came on. To do this I had to have my hand covering the antenna on the main unit. Either my hand attenuated the signal enough, or there is a physical defect in the main board.. or its just coincidence

I plan on replacing the RX with a JR 921 and add an extra satellite. Due to the battery size on the 700E, and my arrangement of the RX/sat, the system would not tolerate the failure of either the sat or the main without signal loss. Since I am stumped as to how to rearrange just 2 RX units so that it can fly on 1, I'll just get a 3/4 unit system and pray its not the TX

[Andyzboy]

Glad no one was hurt, I've almost been in a similar situation when I had a static hit. Luckily it was aimed away from the pits. Gaining trust in the machine again is always hard, send the reciever to horizon and see what they find

[michael503]

Originally Posted by Andyzboy

Glad no one was hurt, I've almost been in a similar situation when I had a static hit. Luckily it was aimed away from the pits. Gaining trust in the machine again is always hard, send the reciever to horizon and see what they find

Thanks, but I plan on sending it to the dumpster, or saving if for scrap.

Now if it happens to another heli, then I'll assume the 5 year old TX is bad.
I mostly fly smaller stuff. I rarely fly the 700.. the possibility of stuff like this is why

[sun_E]

I had the same thing happen with an AR6200. Luckily it revived before the heli hit the ground and was saved. My best guess was an intermittent fault in the sat cable. The Rx was previously on several other helis, but is now relegated to be only a bench tester.
I have a bunch of AR7000s and never had a fault with them.

[michael503]

Thanks.

Due to the attitude of the heli in relation to me, both when it lost link and when it regained it, coupled with the main RX link issue, I feel it was the main unit rather than the sat, or the cable. By unplugging the sat after if has linked up, on the bench, control is still possible through the main unit. Presumably, the reverse is true, although I have no way to test that short of selectively damaging the main unit.

I have had this RX for over 4 years. It has not seen as much service as my AR7000, or the 6100 that I have, and neither of them has given me any issue. This is in fact the first issue I have had with a Spektrum product

[Santini]

Originally Posted by michael503

.. Since I am stumped as to how to rearrange just 2 RX units so that it can fly on 1, I'll just get a 3/4 unit system and pray its not the TX

Your stuff is kind of old at this point, so maybe consider buying new to be on the safe side. Maybe it would be a good time to look at futaba set up, like 8fghs and an s-bus 6203sb rx, and not worry about signal blocking and mutliple sats.. one wire s-bus set up is v nice, fast radio,etc. Good luck.

[Varc]

Can almost being a bad day count as being a good day? Nobody getting hurt would make it a good day.

[michael503]

Originally Posted by Varc

Can almost being a bad day count as being a good day? ---

Not at 300 bucks worth of damage.
Also, once word gets around, I'm sure I'm eventually gonna hear rumbling from the anti heli crowd at the field.

Originally Posted by Varc

Nobody getting hurt would make it a good day.

That is the only shining piece of joy in this whole event
Its kept me awake one night so far.

[kelseh]

You are always going to have the anti heli crowd but what funny is that some of those props scare the hell out of me. They spin so fast.

[Airworks]

ive seen more close calls and stupidity from plankers then ive ever seen in the heli world....thus far.

glad noone was hurt for sure.

[michael503]

I want to relate a few incidents, that just may be coincidence.. or something else

A fellow pilot with a profile foamy was flying on a DX6i and lost control for an unknown reason. said he had nothing. I did not investigate the reason for the crash since these planks are usually pretty shoddy and cheap. At the time he crashed I had been turning my DX7 on and off accessing the model select menu. I did it about half a dozen times in less than a minute.

Last week, one of the pilots lost a foam ARF powered glider, with I think an orange box RX. It flew away, but the distance was not that great, maybe 800-1000 ft. They still have not found it.

This past Saturday, I lost radio link with my 700E, for about 10-15 seconds and regained control about 10 feet off the ground. Just enough time to firmly crash it in the pit area.

Now in my case, the evidence points to a loss of signal to the AR6200 main RX, but the satellite was still linked, albeit shadowed by the huge pack these things run.. Evidence for this is somewhat circumstantial since I can no longer duplicate the fault. The other 2 could have been setup/QC issues.

No one else was flying at the time, so there were not butt loads of frequency's filling the air, at least from our field.

Now there are 2 possibilities. either there is some sort of interference going on, or we have 3 closely related coincidental loss of signal events in a very short time. We have had pretty much zero failures up until now.

can this be interference? and if so, from where?

[wanderer56]

I've read that wireless routers and any device transmitting on similar frequencies can cause interference on the 2.4 ghz frequency spectrum. Not sure what that list might include, but we are seeing more and more wireless devices coming onto the market. Most are low power, but can range from garage door openers activated from your cell phone to remote control lawn mowers! What's the world coming too!

I've heard rumors of high voltage power lines and signal jammers also.

The nice thing about DSMX is that it will find 2 more new frequencies and lock on to them in a heartbeat.

[aerocal]

Michael
There are several things about your post that dont quite make sense.
Without any other details its not really possible to start trying to make a diagnosis.
You say your "evidence" points to loss of main Rx but Remote was still linked.What evidence would make you think this?Are you meaning the main Rx was blinking? The 6200 doesnt provide any FlightLog data so theres not going to be any evidence there.
You say they were all working fine and then suddenly one day you had a control issue.

With a 700e Im assuming you did an adequate low power(range) test to check the signal in all orientations before you flew.

The important question.Are you running a BEC? Did you check to see that it is maintaining adequate power? Under load for an extended period of time? Specifically which BEC are you using and are you powering the 700e with one lead? Is it an FBL unit?Ive seen this issue so many times with generally the same symptoms.First thing that most seem to generally assume is that it is signal related.Of all the ones(dozens) I have personally diagnosed only 1 actually traced back to being a signal issue.It was a DX7 and the low power(range) button was apparently sticking On and the radio was staying in low power most of the time.There were signs before an actual crash that the guy ignored but they did kind of point me in the right direction figuring it out.Occasionally when the radio was powered up it attempted to bind without the button being pushed.It is possible it is a radio/signal issue.The huge majority of the rest were actually a power issue directly traced to a bad BEC.A few to bad leads or switches but those also fall into the power delivery column.

Did you rule out a power issue before you started looking towards a signal issue? Im kind of confused about what evidence you used to come to this conclusion.This is reinforced when you say there are 2 possibilities for your issue.There are actually many many more.I think you may be overlooking something important.

add: It may be possible to have an interference problem that caused you to be "shot down" but it is exrtemely rare and not likely.Even with DSM2.Honestly all the incidents you described are exactly what happens when a BEC warms up after its had a load on it for part of a flight and the voltage starts dropping to a point where the system cant function anymore and/or it shuts off completely from thermal overload and after a number of seconds it cools down resets and starts to work again.So many times the conclusion is "when I got to the debris field everything was working so it couldnt be a power failure".Most of the time this is the wrong conclusion.Its very unlikely that out of the blue you are going to have an extended "hold" situation from loss of signal.Especially if your low power test didnt show a glaring problem with shadowing in any specific orientation.

[Ah Clem]

A couple of things come to mind...

1) The AR6200 is not really the best receiver to use in a 700 sized machine, as the traces supporting the power buss are fairly thin. Someone posted photographs on RR a few years ago showing them burned through on two different receivers.

It is a very good receiver on small machines, but not really appropriate, IMHO, for the big stuff. I have about six of them on 450 sized machines and foam airplanes and have never had one fail (of course, now that I type this, I will). Does your receiver work now (after the problem)?

The traces on the AR7000 and above are much more robust.

2) This statement by Aerocal is a very good one:

"With a 700e Im assuming you did an adequate low power(range) test to check the signal in all orientations before you flew."

I installed an AR6200 in a foam B-25. On the intended day of the maiden flight, I did a 360 degree range check (walking all the way around the ship with the button on the TX pressed down to (the low power Aerocal was referring to). At one point, while walking around the machine, it failed the range check. I did it again and it always failed in the same place (orientation). I took it home and moved the receiver away from the BEC and moved the satellite further forward (also away from the BEC) and it passed the range test. The BEC was very noisy, from an RF standpoint.

If I had flown it with the original electronics placement, I would have lost it.

3) I have been able to induce shadowing on one helicopter and one foam airplane causing lockouts (repeatable on the airplane). It is very important to make use of the antenna diversity available with the satellite receivers by mounting the satellite and the main receiver at opposite ends of the aircraft and in such a way that they are not both blocked by a large conductive structure, such as the motor, battery, or CF frame from the same orientation.

4) To follow up on Aerocal's point regarding BEC's. They must be adequate in terms of current capacity for the job. 10 amps is the minimum for a 700 sized machine and both plugs from the BEC should be used to power the on-board electronics as each plug is only capable of about 5 Amps. Both must be plugged into the receiver, servo buss, or FBL unit.

5) It is possible that you encountered actual interference, but pretty unlikely. Regarding the "orange receivers", I have used them in small planes, but the quality is unknown. I would not judge Spektrum performance/resistance to interference by these.

Most of the time, Spektrum issues will be caused by inadequate power to the receiver. A much, much, much, smaller part of the time, the cause will be shadowing causing signal loss, then actual receiver failure. People using transmitter trays with some of the early Spektrum equipment occasionally suffered failure due to the tray pressing on the "Bind" button.

6) Regarding Brown Outs. The original Spektrum receivers, if the power dropped below 3.5 volts, would begin the entire "boot-ups" sequence again. The receiver would scan all 80 of the frequencies used in order to locate the two that were transmitting the GUID of the transmitter they were bound to. The intervening 5-10 seconds before the receiver re-booted and found these to frequencies could be quite sporting.

Probably about a year into DSM2, Spektrum changed the firmware to "Quick Connect", which caused the receiver to come back on the two frequencies it had last been using, prior to the brown out. The reconnect, once power is restored, is essentially instantaneous.

[michael503]

There is a brief description of the event here

No, I do not do a range check every time I fly. I don't know anyone who does.

The heli has flown in this configuration without issue for 2 years. The power buss issue is moot because I share power to the servos via the MB and a splitter.

I do not run a BEC. Straight Lifep04 battery.
Evidence indicates that it was a loss of communication between the RX and TX. I did have time to glance at the TX while this was happening and it was still operational, although there is no way to determine how strong the transmission was. My first thought while I was watching the train wreck was that the RX pack was depleted, but it was only the second flight that day on a 3000ma pack, and subsequent inspection indicated an almost fully charged pack. Had this been a brownout, the heli would have pitch pumped when the Microbeast reset, and I would have had to send the throttle to zero to reinitialize the esc... which spooled up without me doing so as soon as I regained control.

I only mention the possibility of interference because of the 2 other pilots with issues, but once again, this could be coincidence. The bind button is protected by my TX tray, which has at least 0.75" clearance.


My personal opinion is that the main RX unit locked up, but the sat, which was shadowed, until the last minute, was not. It just occurred to me that their might be something more, and I thought I would ask