DX7 glitch - saved by the AP2000?

[crewchief]

Here's a little Halloween story. I got the h*** scared out of me yesterday while shooting a routine real estate job in a fancy neighborhood. I lifted off and made a standard slow climbing turn to get the 600 behind me and nose in to shoot over my head at the property, flipping on the AP2000 at about 40 feet as usual. Halfway through the climbout and still very close, the heli started to drift sideways, like it does sometimes when the AP2000 sees a hot cul-de-sac or something - no big deal. I corrected for the drift and...no response. It just continued to slowly and lazily fly away from me, towards some very expensive real estate.

The first thing I tried to do was to get the nose around, while I could clearly see the orientation...no response. However, during this time apparently the AP2000 was still keeping it level. It was just very slowly floating away. After about 5 heart-stopping seconds, the tail jerked about 20 degrees, then it jerked a few more times, and then the nose was pointed in my general direction. I put the cyclic full forward, but it was still drifting. Suddenly it responded and the nose pointed straight at the ground. After some ugly corrections, it was on its way home to daddy.

Later that day I shot 4 more jobs, large farm properties, and I flew it nearly out of sight without any control issues at all. I purposely pushed the limits because if it was going to screw up, I wanted it to do it over a farm and not downtown. It performed flawlessly as usual. I've got well over 200 flights and 30+ hours on the system, and this was the first time I've had any control issues. Spektrum says that there have been a lot of things like this, but they attribute it to low receiver battery voltage that causes the Rx to reset. I did not recharge the Rx or Tx batteries for the whole afternoon of good flights, so that wasn't it.

Attached are two pics from the afternoon flights to show the control distance. In the first there's a blue roof, and inline with the ridge of the roof near the road are two specks - that was us. The piece of property in the second shot is about 80 acres. We were flying that off the top of the nearby foothills.

I think if the AP hadn't been active, it would have dipped the rotor and accelerated into a house. Luckily for me one of the Rx's last actions before it went off-line was to activate the AP.

Very scary. Anybody else had anything like this happen?

[Efliernz]

Hmmmm I start installing my AP2K tonight into my new T600 kit. While I anticpate I would only switch it on at over 100Ft while hovering, it does show the added value.

Good shots too :lolol

[MarkWebber]

A clear indicator of why you want to properly set up your failsafe to turn the AP2000i on incase of loss of signal.

It has saved my gasser following an rx failure. Only slight damage to the mount and fortunately, I can make new parts for that.:thumbup:

[bcook01]

You might want to look around (when doing AP in the city or residential areas) for signs of 2.5 ghz point to point ethernet bridges. They look similiar to sat dishes but are pointing lower on the horizon. These are used for wireless broadband internet connections. With a 24dbi dish they can overpower the receiver. The transmit with an approximate 6 deg beamwidth. Google "motorola canopy radios" or see link below. Keep an eye on low hanging microwave dishes as they can be a source of interference due to spectral energy.

This could very easily be the cause of the receiver not picking up your transmitter.

fyi

BC

http://www.wbmfg.com/Home

[bullaculla]

If your RX did shut down and reset, shouldn't your ESC shut down too? Or do you have your ESC set to keep spinning even without an RX signal? sounds like a receipe for a fly away. Too bad spektrums flight log only works with the 9ch RX.
I'm running a medusa BEC off my 10s packs. No shutdowns or restarts yet. Also, im using the rotorworks HFE frames with mini servos so they do draw less power. But I also have a ton of flights on my stock setup 600 with no problems either, but i'm using aligns 6amp regulator. are you using the stock 3 amp one? I have heard of shutdowns when those are used with a spektrum RX.
I dont get the failsafe for the AR7000. I binded mine with 20% gain on the AP2Ki, so when I turn it on, it goes to 20%, but if I turn off TX, the RX will hold last good servo position, and if the AP was off, it stays off. If it was on, it'll stay on. :dontknow:
I'll set mine up better once I get my X9303 in... if I ever get it. preordered it ages ago.:arggg:

[crewchief]

If your RX did shut down and reset, shouldn't your ESC shut down too? I know - I've been wondering about that. The only two things I know for certain are a) it was not responding to Tx commands and b) I didn't know it wasn't responding until I tried to correct - meaning there was a very high probability that the AP2000 was flying it. I have a tendency to not touch the throttle unless necessary, so I probably didn't in this case either since it was in a slow climb. It felt to me like maybe the Rx had gotten into a null off the tip of the Tx antenna. The timing of the scenario was about equivalent to the time it takes for the Rx to start/reset, but I can't explain why the rotor speed remained constant. I probably would not have gotten it back if it had started descending. I've got the 75A Align ESC set up standard 1, 2, 1, 2, 3 beeps.

BC -
Thanks, good to know!

Mark -
Saved my a**.

EflierNZ -
Nice pics on your web site!

[MarkWebber]

Since I know didly about the DX7 setup, I'll ask...does it have a f/s setting? I just got the XPS module for my 9c and they default to hold last. That may explain your lack of esc shutdown.

[mlkm18]

Bruce, good for you to have the system. First time ever I installed my AP 2000i, and first thing I tried very hard was to make sure the system comes on automatically in a F/S need; before I take the bird off the ground. Never test that out but I am sure that will work.

[Efliernz]

I have my DX7 to "hold last".
I don't want the heli to down-power/slow spool up from a glitch. It's a tough safety call though. Whats the chance of a flyaway due to an extended rf break? Like I said, tough call.

[MarkWebber]

The flyaway chance would be very good in the event of loss-of-signal.

Again with "hold last" on the cyclic, your rx has the potential to overcome the AP2000i's stabilization. You need to set the cyclic to "hold center".

[j_kookboy]

The timing of the scenario was about equivalent to the time it takes for the Rx to start/reset, but I can't explain why the rotor speed remained constant. I probably would not have gotten it back if it had started descending.

Almost wondering if it wasn't the DX7 tx/rx at all since your rotor speed remained constant.

Mark, does the ap2000i control throttle as well in failsafe mode ? Basically fly itself ?

If not, then I would start to look at the connections between Rx/AP2000i and any loose pins/connectors/solder points.

We've tried everything to shoot down an old Trex with a DX6 and DX7 ontop of a WAN/WLAN 2.4 bridge from one IBM building to another and never had any glitches at all.

So far, from all of the DX 'glitching' threads I have read through, 99% of them were other issues.

I'm not saying that it's impossible, but that it is more probable that it is something else.

Just a thought.

ps. Good recovery.

[crewchief]

So far, from all of the DX 'glitching' threads I have read through, 99% of them were other issues.I agree. And it's pretty darn hard to track down a problem that only occurs every couple of hundred flights! If I had to guess, my suspicion would be on the Tx, since I have seen it boot up with some corrupted characters on the display, although only once or twice. Actually one time it booted up with the all the correct information on the display, but the display was inverted! I don't know how that is even possible electronically, but I was able to absolutely confirm it happened. Again, though, out of the hundreds, maybe thousands of times I've turned on the DX7, I only saw this happen one time. There is nothing perfect in this world, and if a person demands absolute perfection, they will be continually disappointed. Or maybe I discovered an advanced feature designed for people who like to fly inverted!

[crewchief]

I ran some loss-of-signal tests at take-off RPM today with these results (I did some lower-RPM tests on the bench first to ensure it would not do something weird):

1) the motor consistently spooled down
2) the AP2000 went to 94% control, even if it had been off.

Mark, is this percentage a configurable item?

I still don't know why it would not spool down the motor, and yet not respond to the Tx. This says the Rx still had the signal, but was not processing commands.