Sky High

Well, I had two great flights again tonight but the third ended in a hard landing or a semi-controlled crash. I was showing the SAVS to a SWAT member and metro drug task force members and they were very interested in it's abilities. I flew two perfect flights showing how it could hover over structures and other hard to see inaccessable areas. Needless to say, they loved it!! The SWAT member had a handheld FLIR (Forward Looking Infrared) camera system that we were going to use to view the helo flying at night. Anyway, I had pulled out my laptop and set it on my hood after the second flight to show them some aerial video. After that, I wanted to see if he could see the heat signature from the motors. So, I prepared for the third flight.

I prepped as usual and right before I initiated a lift off, all of the sudden the helo shot up in the air like a rocket! [X(] I didn't know why that happened but thought that I had inadvertantly hit the throttle and didn't think much more of it. So, after I gained control and started to hover he observed the helo with the FLIR camera while I flew around different obstacles. Well, I decided to fly out over the field which turned out to be a good choice because what happened next was just nauseating! [:'(] All of the sudden the helo just lost control and began erratic behavior. Luckily I was only about 15-20 ft high and so I just let off the throttle to ensure it came down in the grass. Of course I panicked and didn't even want to go over to see what it looked like but I had to. [] I quickly ran over and was pleasantly surprised to find that only two landing struts had been broken with no other damage! I was still nauseated but very happy to see that was the only damage. The next question was what in the world caused this to happen? Is this area becoming the Bermuda Triangle? This was my second crash in the same area this week. [:@] However, I had 4 perfect flights and got some great AP on Wednesday.

Well, I went back to the truck and reset everything and took off again to see if it would fly. It did and with no issues. I only flew it for about one minute and just above my reach just to see if it would. I still could not figure out what could have caused this. The only thing that was different from the other two flights was that my laptop with a WiFi card was on my hood, powered up and only ten feet from me at any given time during that last flight as was the FLIR camera while pointed at the helo. The laptop and FLIR were also on during the short flight after the crash with no issues. [sm=confused.gif] That was such a short flight though, I probably didn't allow enough time for another incident. I thought if the FLIR did transmit a beam that it might have hit the Ti sensors and caused the helo to act that way. But from what I was told, it only detects available heat and does not transmit an IR beam. I am thinking now that either the laptop or electronic RF from the FLIR camera caused a glitch (possible loss of signal) to make my helo just rocket off in the air like that when I first took off and then eventually crash minutes later from another intermittent loss of signal.

When you think about it, I guess it could be possible. The internal wireless card is a transceiver so it is constantly pulsing while searching for a wireless network. However, after calling Gateway, they said that it operates on the 2.4 Ghz- 2.497 Ghz range. My DF operates on 72 Mhz. I asked if my wireless card could have possibly interfered with my DF transmitter and they said yes it was possible at that close proximity. I didn't think that two totally different bands, Ghz and Mhz, could interfere with each other though. If that's the case, why doesn't the 2.4 Ghz wireless video signal interfere with the DF receiver that is only 4 inches away from it? So that is my question. Is that even possible? I thought it would only interfere with the 2.4 Ghz video signal or only anything in that same band. If it is possible, then that is a whole new issue to worry about when flying in a congested area, but only in very close proximity because I know that I've flown in areas with Wifi without any issues but never with it as close to my transmitter as this time. I am going to perform a controlled test in a secluded area and try to replicate this to see if my laptop will interfere with my DF transmitter and/or receiver. My DF's rotors have twitched erratically before when my transmitter was lying close to other electronic gear and those were shielded and weren't even wireless devices. It immediately stopped when I moved my transmitter away and I didn't have any issues in flight. So maybe this is possible because my laptop is a wireless device or maybe that FLIR camera was putting out some serious RF, well see. So, be aware that this is a potential liability. Any further experience, info or advice on this issue would be most helpful.

Click here to hear about the FLIR camera results!
www.rcuniverse.com/forum/fb.asp?m=4109460

Hooch

Very possible, I haven't had any issues with the flying of the heli around my house with all my wifi, but I do know it causes havoc on my video, if I am in my office and turn on the camera it shuts my wifi down! But outside all is ok but video just isn't that clear. So very probably it could interfere with the heli transmission as well.

Sky High

I still don't get how Ghz could interfere with Mhz. That's what two different bands are for. [sm=confused.gif]

TheHindmost

I think you're right, Sky High, that it's highly unlikely your WiFi card is the culprit. As you say, the bands are entirely different (by orders of magnitude). Now, it is the case that harmonics could be playing a role, but I tend to doubt it, and I think the best evidence against WiFi as the culprit is also something you cited: that camera is on the same basic frequency and it causes no issues. (So far, I've seen the camera interefere with the WiFi in my house, but not the other way around. And no issues with the DF yet in that department at all, knock on wood. My radio TX and RX have been rock solid since day 1, I'm happy to report!)

This glitch could have been caused by any number of random factors, including (seriously, actually) gamma rays. A question which needs to be asked is whether you're fairly certain the subsequent crash was also caused by interference, or could it have been due to the surprise of having the DF jet into the sky and wanting to get it back on the ground post haste? The terrain transition probably didn't help any...

You mentioned urban and populated areas in relation to WiFi...but it's also possible someone else has a 72 MHz radio they're using for RC or walkie talkie or whatever purpose. We don't own the band, so glitches are going to happen, especially with population around!

As for the FLIR camera, you'd think it should be an emission-free device, especially if it's military. A FLIR has no need to send out an infrared probing signal, it just looks at the incoming infrared. Beyond that, it should be shielded both against emitting and being affected by RF, assuming it's battle-hardened.

Will

Sky High

I think it's time to invest in a frequency checker. There's just too much to risk now. Remember, I had two flights with no issues and I fly here most of the time with no issues. The only difference this time was that the laptop and the FLIR camera were in close proximity. I am in that very cautious period right now and wary of flying again. You know that feeling. Oooooo.

TheHindmost

Oh yeah, absolutely...Like any pilot, you want to know what--exactly--caused the crash before you go back into the sky again. I'd feel the same way, and in fact did after my bad crash. Fortunately for me, this board had the answers I needed! Now we get to solve another issue...it won't be the last, and it's part of the fun!

But the other aspect is that we need very high reliability to make the DF effective for commercial AP work. Going nuts due to RF interference, or even turning off the transmitter by accident, just won't do. Better behavior is needed to protect the investment in the payload, if not the DF itself.

I wonder if a small ballistic recovery chute could be justified? It would depend on the payload's value, and of course, we need more weight carrying capacity in the DF to do it. (Speaking of which: Any DF X owners here? I'm sure that's been asked before, but I'll do it again... )

Will

targit

Hi, I would think that WiFi is unlikely to be the culprit, its way out of band and so low powered.
The fact that you were showing this to 2 "cops" who always seem to have a walkie talkie of some description seems a possible cause :P

The main thing to remember is that as soon as you get up in the sky you will have line of sight ( ie. best possible) reception for any signals in your area that could interfere with control.

I use my DF on 72 MHz here in Australia (not the approved band!) where it is officially the emergency service band, I left my scanner on for days listening to see if this band was actually in use, but the all is quiet ( I think they went digital a few years back ) and I have had no control problems. I usually get it down on the ground as soon as I hear any sirens though, just in case

coptercaper

SKY HIGH,

I have been flying helicopters for awhile (DF IV and Raptor 30). Prior to take off I use a frequency checker to ensure I have no competition for signal. I highly recommend it, VERY CHEAP insurance. I know that you generally don't fly at an organized club, so sources of possible radio interference are many. Could have been the FLIR camera, could have been the WIFI, could have been some kid playing with a toy, etc. Check it out:

http://www.towerhobbies.com/products.../hcap0340.html

GOOD LUCK!

Greasetattoo

My Feedback: (3)

http://www.brsparachutes.com/default.aspx

Here is a place not far from me...Matter of fact about 2 miles....
Think we could make a miniature one??
I used to own one, when I had my Ultralight about 20 years ago.

coptercaper

There is an entire RCU forum for Simple Parachute Activation Devices (S.P.A.D) with a wealth of knowledge located at:

http://www.rcuniverse.com/forum/foru...smode_1/tt.htm

Also refer to this link for RC ballastic recovery ideas:

http://www.rcuniverse.com/forum/m_90.../tm.htm#908291

Sky High

ajc3487, I will definitely be getting one of those frequency checkers. Thanks for the link!

TheHindmost

Thanks both Grease and Ajc for the links! I guess I need to expand my forum subscriptions...

Will

Sky High

Well, I went and flew in the Triangle again this evening. [:'(] I had three perfect flights but held my breath for each one. I'm thinking last night's incident was because of an RF hit for sure. What really convinces me is because of that surprise full throttle take off that only happens when it loses the signal. I'm still getting a frequency sniffer too.

Sky High

This evening I flew at the same location of this incident and tried to replicate the supposed RF interference that caused it. I set up my laptop just as before and then armed the helo for flight. This time I kept the helo in my hand in case it decided to go wild. I put the transmitter antenna and the armed helo right next to the laptop and the WiFi port in every possible angle and nothing happened. I also met with the SWAT member again to shoot FLIR footage and see if his camera was the cause and nothing happened with it in close proximity either. I did these tests with both helos and nothing happened with either of them just inches from these devices, not even a twitching rotor. [sm=confused.gif] . After the tests, I flew both helos 3 flights each with no issues. So, I guess this case is closed and the only conclusion that I can come to is that I got hit with a stray RF signal.

targit

Or one of the other unknown failures that make them fall from the sky so regularly? mine fell from 6 feet up and 15 feet away from me tonight, then I reset it and off it went like nothing had happened :P

detroitdr

Sorry just catching up on this feed....

No way your wi-Fi card can mix with our DF. Even at extermely close distance.

I would be that someone around that area either has an old Motorolla talkie band, or a kid wanting to mess with your unit!

Phodel

I agree.........almost always have my laptop with the WiFi on capturing video and do not have troubles. I do however experience the unknown power cut out and drop but almost always recover.

Do most of you set the failure recovery system built into the DF Vti? I do and I attribute that to my recoveries where RF signal loss or interferance is likely. I would like to hear some feedback regarding this.

Phodel

targit

I don't use Ti or the recovery system, I dont dare fly high enough in case it drops out of the sky and smashes.
I think the fact that so many people suffer from unexplained "cut outs" points to a design flaw somewhere. At the price of these units I think this needs to be addressed. If I crash through my own stupidity then I accept responsibilty/expense, but if the DF falls from the sky for no good reason I'm gonna get a little annoyed if I have to pay out for a load of spares.

Sky High

I totally agree with you targit if that's why a DF crashes. It means there are conflicting frequencies in your area or there is something wrong with your circuit board. Remember [link=http://www.rcuniverse.com/forum/fb.asp?m=4095602]this issue[/link]? That was a bad circuit board probably due to loose crystal solder joints. It was resolved with a new board. But altitude is not the problem, it is RF hits if not obvious mechanical failure. Considering the countless hours of high and low altitude flight that I have now which is well over 100, this is the only light crash that I have had due to a possible loss of signal. That is a pretty good ratio. The two fatal crashes that I have had were due to structural failure, one from a frame strike resulting in a disintegrating rotor and the other from a glued motor mount which was my fault for not replacing it. All of these issues and experiences are why we need discussion boards, to share information so we can compare common issues or talk about successes and methods of DF operation.

targit

I dont think mine was an RF hit, I was standing too close to the unit, If you have your TX within 10 feet of your DF it would take a very strong signal from another transmitter on the same frequency to swamp the receiver, let alone on some other frequency.
This could well be a fault with the pcb, but my main suspect is the switch, experience tells me to go for the moving part first!
To check this i moved the power source for my LEDs to the switched power side, now i have to wait and see if it happens again............

Sky High

Okay, I think I mistook what you said. At first I thought you were attributing crashes partly from flying high. I guess what you are saying is that you don't fly high because of the unknown and if you do happen to crash the damage may not be as bad because of your low altitude. Well, that makes perfect sense, but you need to get over that and reach for the sky, you'll never look back!

Phodel

I think we need to start a thread which tracks the 'Cut out' phenom and point Mike with Spectrolutions to it. I think they are in slight denial. I have have had numerous conversations with him and he seems to belive it is RF loss or RF hits but I have been in the middle of a South Georgia field with nothing around (I mean nothing!!) and it happens so there goes that theory.

Has anyone had the 'Cut Out' phenom happen then your DF start flipping out uncontrollably?