Flayaway theory

Are flyaways like this reported on Naza V2 controllers?
 
wattage said:
Not too sure about this. Most of the flyaways I've seen on the web show a Phantom behaving erratically, flying at scarily steep angles of tilt or roll at abnormally fast speeds. A Phantom having an inaccurate home point it thinks is outside its limits and trying to return to home should exhibit a smooth controlled flight towards this fictional home point, not like the 'joyriding teenager' footage that accompanies most flyaways on YouTube.

I think it's something to do with the compass data getting corrupted or hit with interference. Didn't DJI upgrade the compass module recently by putting it inside an anti-static enclosure, without an explanation of why they deemed this necessary?

+1 They almost always go off at, at least a high speed and sometimes flying strangely. Agreed about the compass. DJI never explained flyaways except to talk about proper pre-flight setup. While I agree that 95%+ of "fly away" is caused by human error and improper setup, why suddenly and without explanation introduce a "shielded" compass? Which also begs the question of how shielded is the compass and from what? I haven't taken apart the new compass so I have no idea what's in there but would love to know, anyone had occasion to look at the insides?

This has the makings of a good conspiracy theory :twisted:
 
Quote from rcgroups (mind you this is not a Phantom, but Naza controlled)

While I respect Made in Austria's comments, I did quite a bit of testing. What I found was the EMI generated by the speed controller switching circuits, leads, and motors, would create enough noise that would interfere with the compass. Once the system looses the compass then the data generated by the GPS and the compass do not correlate and thus the fly away. I discovered it by using a cheap little compass and with the props off, firing up the motors to speed. As I held the compass close to the frame, I could watch the compass (hand held one) drift away from north. I then raised and lowered it to see the effects and to see what level the effects were diminished. I also played with power settings to see if I could "manually" effect it. Once I found that, I went back to the field (stock mast height), flew it and then tried the control inputs that effected the compass and sure enough it started to fly away. Switched to manual mode, brought it back and tried it several times. I actually got good enough if you want to call it that, so I could make it fly-away on command.

Next I lengthened the mast to the height I had determined with the compass test and never had one again, neither forced or accidental.

Now some of the things that can also determine if you do or do not have one. Larger diameter frames put the speed controller and motors farther out thus increasing the distance to the compass just as height would. Position of electronics around it, etc.

As I said though, I did some analysis and this is what I found

This could be why DJI updated the compass on the Phantom 2.5 and made a the anti-static (anti-ElectroMagneticInterference to be exact) cover for it, as mentioned earlier in this thread.
If true, they should have sent the new cover out to all Phantom owners!!!
 
Fyod said:
Quote from rcgroups (mind you this is not a Phantom, but Naza controlled)

While I respect Made in Austria's comments, I did quite a bit of testing. What I found was the EMI generated by the speed controller switching circuits, leads, and motors, would create enough noise that would interfere with the compass. Once the system looses the compass then the data generated by the GPS and the compass do not correlate and thus the fly away. I discovered it by using a cheap little compass and with the props off, firing up the motors to speed. As I held the compass close to the frame, I could watch the compass (hand held one) drift away from north. I then raised and lowered it to see the effects and to see what level the effects were diminished. I also played with power settings to see if I could "manually" effect it. Once I found that, I went back to the field (stock mast height), flew it and then tried the control inputs that effected the compass and sure enough it started to fly away. Switched to manual mode, brought it back and tried it several times. I actually got good enough if you want to call it that, so I could make it fly-away on command.

Next I lengthened the mast to the height I had determined with the compass test and never had one again, neither forced or accidental.

Now some of the things that can also determine if you do or do not have one. Larger diameter frames put the speed controller and motors farther out thus increasing the distance to the compass just as height would. Position of electronics around it, etc.

As I said though, I did some analysis and this is what I found

This could be why DJI updated the compass on the Phantom 2.5 and made a the anti-static (anti-ElectroMagneticInterference to be exact) cover for it, as mentioned earlier in this thread.
If true, they should have sent the new cover out to all Phantom owners!!!
The GPS does not know heading and has nothing to do with the compass.
The ECS and motors generate a magnetic field, not interference, which is why the compass module is away from them. The farther the better.
Third: "anti-ElectroMagneticInterference" LOL! :lol: The only magnetic shield is Mu Metal, but if the new compass has "anti-ElectroMagneticInterference" shielding, then wouldn't that also block the earth's magnetic field?
 
SteveMann said:
The GPS does not know heading and has nothing to do with the compass.

Correct. The GPS actually doesn't even do anything other than search satellites and send information to the controller. The controller is responsible for acquiring information from the GPS, compass and user input and deciding (computing) how to manage the motors based on that information.

SteveMann said:
The ECS and motors generate a magnetic field, not interference, which is why the compass module is away from them. The farther the better.
Third: "anti-ElectroMagneticInterference" LOL! :lol: The only magnetic shield is Mu Metal, but if the new compass has "anti-ElectroMagneticInterference" shielding, then wouldn't that also block the earth's magnetic field?

I don't know if you're being sarcastic or just ignorant. Electro-magnetic Interference and radiation is common in all of today's devices.

Typical materials used for electromagnetic shielding include sheet metal, metal screen, and metal foam. Any holes in the shield or mesh must be significantly smaller than the wavelength of the radiation that is being kept out, or the enclosure will not effectively approximate an unbroken conducting surface.

Another commonly used shielding method, especially with electronic goods housed in plastic enclosures, is to coat the inside of the enclosure with a metallic ink or similar material. The ink consists of a carrier material loaded with a suitable metal, typically copper or nickel, in the form of very small particulates. It is sprayed on to the enclosure and, once dry, produces a continuous conductive layer of metal, which can be electrically connected to the chassis ground of the equipment, thus providing effective shielding.

RF shielding enclosures filter a range of frequencies for specific conditions. Copper is used for radio frequency (RF) shielding because it absorbs radio and magnetic waves. Properly designed and constructed copper RF shielding enclosures satisfy most RF shielding needs, from computer and electrical switching rooms to hospital CAT-scan and MRI facilities.

And further from DJI wiki:

The compass is very sensitive to electromagnetic interference which causes abnormal compass data and leads to poor flight performance or even flight failure. Regular calibration of the compass enables the compass to perform at its optimal level.
 
SteveMann said:
Hughie said:
EDIT+1: This link https://www.youtube.com/watch?v=_ge3GuhEDRM
The whole theory is based on the homepoint not being set properly in the first place.

The author of this video doesn't understand how GPS works. If your home location is wrong when you start flying, it will immediately head to where it thinks the fence is located. There won't be an opportunity to fly around to "calibrate" the GPS.

My theory is based on the current position data being corrupted, but a corruption of the home point could so it also. widening the limit radius to a very high number would help reduce this type of flyaway.

I agree, he is confusing the way that cell phones work - which *want* to give the user some information fast even if it is rubbish to start with, on the basis that it gets incrementally more accurate; with how a DJI Phantom requires a minimum number of satellites to guarantee a certain level of triangulation accuracy.

However I found his video interesting for discussion if nothing else, particularly in relation to fences being part of the flyaway issue.
 
SteveMann said:
msinger said:
SteveMann said:
Or disable the horizontal limits. (Is this even possible?)
Wouldn't this be sufficient?
That is almost 19,000 miles, but I would worry that the firmware programmer didn't anticipate an unusually large number and you may overflow the data into another parameter. I wonder if zero would effectively turn off the radius limit?

Due to Microcontroller register sizes, the value is much more likely to be truncated than to overwrite other data.
 
SteveMann said:
Bad compass data wouldn't cause a fly-away. If you told your Phantom to go home and it flies in a straight line, then your compass is OK. If it flies in an arc to home, then your compass needs recalibrating. No compass data would still go home, but it would be a spiral route.

Bad compass data can and has caused flyaways.

Zinnware said:
His fly-away was caused by not following a good start-up procedure and not getting a good home lock before taking off.

What are you basing this conclusion on? "Not getting a good home lock" will not cause a flyaway.

msinger said:
What if you change locations and take off before the home point is marked in the new location? Would the Phantom still remember the previous home point?

The Phantom forgets the home location as soon as it is powered down. Before the home location is set, there is no home location.
 
Switch the Phantom on, Wait for the rapid green flashing lights (Home point set)

Calibrate the compass (360 spin and 360 spin when pointing down)

Phantom is now good to go right?

I set failsafe on my toggle switch and give it a try every flight to make sure it comes back to where the home point was set. If It didn't one day (Hope to god it always does) I would flick to ATTI mode ASAP.
 
rhysvins said:
Switch the Phantom on, Wait for the rapid green flashing lights (Home point set)

Not true if you are in IOC mode

rhysvins said:
Calibrate the compass (360 spin and 360 spin when pointing down)

I would do this rarely and when I do I would do it before setting home point. This can lose satellites as you tilt it for starters.
 
Hughie said:
rhysvins said:
Switch the Phantom on, Wait for the rapid green flashing lights (Home point set)

Not true if you are in IOC mode

rhysvins said:
Calibrate the compass (360 spin and 360 spin when pointing down)

I would do this rarely and when I do I would do it before setting home point. This can lose satellites as you tilt it for starters.

Why is this not true? My green lights flash rapidly after waiting for about 1 minute?

So you're saying it's best to try and beat the rapid green lights and set the compass first?
 
rhysvins said:
Hughie said:
rhysvins said:
Switch the Phantom on, Wait for the rapid green flashing lights (Home point set)

Not true if you are in IOC mode

rhysvins said:
Calibrate the compass (360 spin and 360 spin when pointing down)

I would do this rarely and when I do I would do it before setting home point. This can lose satellites as you tilt it for starters.

Why is this not true? My green lights flash rapidly after waiting for about 1 minute?
If you are in IOC mode you get TWO sets of green flashing lights. In IOC mode you need to wait for the second one, not the first one.
 
Ah I see, thank you.

I think sometimes I only get one... or maybe they are two sets but very fast after each other :/ Regardless, RTH mode still works after the one set of rapid green lights. (That is if it's not two flashing one after the other) ahhh so confusing
 
rhysvins said:
Ah I see, thank you.

I think sometimes I only get one... or maybe they are two sets but very fast after each other :/ Regardless, RTH mode still works after the one set of rapid green lights. (That is if it's not two flashing one after the other) ahhh so confusing

I know !
 
spudraleigh said:
msinger said:
SteveMann said:
Or disable the horizontal limits. (Is this even possible?)
Wouldn't this be sufficient?

Isn't the default 0 meters for both horizontal and vertical limits which translates to unlimited? Am I missing something?
I don't see anything in the DJI manual about setting those values to 0 for unlimited. Perhaps it'll work.

The manual does say the limits are ignored when in ATTI mode though.
 
Buk said:
Steve not sure if this impacts your theory for some flyaways, but being in Phantom mode versus Naza-M mode the Phantom responds differently to the limits. I'm not sure I'm using the manual you are, but in Phantom mode being in Ready To Fly (Non-GPS status) there is no horizontal limit. Quoting the the manual I'm reviewing it states only the height limit works, "In Ready to Fly status, height, distance limits works together to restrict the flight. In Ready to Fly (non-GPS) status, only height limit works and the flying height restricted to be not over 120m."

Question: When you fly outward and hit a horizontal limit, right and left flight is still possible. You just follow the circumference of the circle. If you are beyond the limit would you be able to fly right and left while being "pulled" towards home and travel in a spiral curve toward home??

When you hit the limit, it just stops and hovers,(like it hit a soft wall) after a while of no lateral movement, it RTH. Can't see why you'd be able to fly through the barrier in the first place? What's it's function if it doesn't stop us from flying into restricted air space?
 
Has anyone considered the possibility of GPS jamming causing a fly away?

A cheap and nasty jammer off ebay can total screw up a GPS position putting your GPS position way off course/force you to lose sat reception and cause a fly away.
Some cigar lighter plugin jammers spoof the signal and the GPS receiver's position will appear to jump around randomly anywhere on the planet... but you'll still have a GPS "lock" of sorts.

Just something to consider :-/
 
msinger said:
The manual does say the limits are ignored when in ATTI mode though.
Here's what the manual says:
If the aircraft is flying out of the max radius in Ready to Fly (non-GPS) status, it will fly back
within the limits range automatically if 6 or more GPS satellites have been found.

In the Special Limits chart:
Limits%20of%20Special%20Area.jpg


So, msinger is correct that the radius limits do not apply in ATTI mode according to the Special Limits table.

So, new thought - what if the problem is the Special Limits algorithm making a mistake, not the GPS? Or a combination of the two? What happens if the Phantom is in ATTI and it thinks it's in a Special Limits range? I was not a Phantom flyer before the Special Limits were added to the firmware, but is there any coincidence between this feature and flyaways?

So, back to my original thought - it looks like the only way to completely break connection with the GPS is to switch to manual mode.
 
I was not a Phantom flyer before the Special Limits were added to the firmware, but is there any coincidence between this feature and flyaways?

Good question, but I don't believe there is any high quality statistical information to analyze this concern. In my mind, the number of reported flyaways was more significant during the introduction of the Phantom 1. However this is also the time when there would be more inexperienced operators. Again, in my opinion, fewer flyaways have been reported with the introduction of the Phantom 2 and I don't feel limits increased the reported incidents. Keeping in mind my focus is the Non-Vision P2. The increase, or perceived increase, may be purely due to the increase in operators due to increased popularity of quads.

Very incidentally, the video done by Colin Guinn regarding flyaways, seemed like an ah-ha moment for some folks. DJI acknowledged what was noticed by some flyers.

Can loss of GPS be documented by reviewing iOSD recordings from flyaways? Or, is it so momentary it is not visible?
 

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