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Weird crash - IPS muddled by regular patterns on ground?! Or interference from a 40 Mhz RC transmitter?

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Three days ago, I had a super-weird crash, and my Breeze almost hurt a four-year old boy at that incident...

This was during my vacation. The Breeze had been flying fine as always, with the last flight only two days ago, for several flights in the same area and after a proper calibration. On the last day, I wanted to shoot my son's new toy RC boat on the lake, and took off from the little wooden pier we was standing on. 6-8 meters behind us, under some trees, another family was gathering for a swim, with three small boys.

Directly upon take-off, maybe even before the Breeze had reached its start altitude of about 1 m (this happend too fast for me to be able to react, and also to remember all details), it accelerated horizontally to full speed over its left-rear arm, right in the direction of two of those little boys which I had believed to be in a safe distance. As the banks of the lake slope up a bit, it crashed into the ground only 50cm from his feet, at full speed. The poor guy was pretty shocked, and so was I. (I'll retrieve and post the flight log later - I was flying per phone control on that occasion, so there should be a log file.) In the end, nothing serious happened, not even his parents got angry with me, although I felt very guilty. But I had come to trust the Breeze quite a lot, after many flights without anything like this happening.

Anyways, even the Breeze incurred no major harm. The bottom cover popped off, with a few of the plastic notches broken, and two props are nicked and bent, and one motor housing is scratched. But today, home again, I tried flying it again in my garden, after a new calibration, as the vacation place was 500 km away. No problems whatsoever!

The big question of course is, what caused this crazy behavior? (I swear it was not user input.) I have two and a half ideas and would like to hear your opinions:

1. The IPS system got upset over one of two things: either the fact that I was starting close to the edge of the pier (like 20-30 cm from the edge, with the water 50 cm below), so it might have 'seen' something very uneven. I imagine that the infrared sensor got confused once the Breeze was airborne. Or it is the ground cam, which fell over the lined pattern of the pier surface: the planks had a regular pattern of 4 mm wide cuts in about 10 mm distance. This strange idea comes to one because I suddenly remembered that I had had a similar incident (without anyone being at risk, though) shortly after I bought the price - then, I had been flying over a very regular metal grid with about 8 mm wide rectangular holes, at about 150 cm altitude and at the moment the Breeze reached that grid, it shot back horizontally over its left rear arm and crashed into the wall. Luckily, that wall was only 40 cm away, so it had no time to really accelerate. Overall, these two crashes were the only ones I ever had with the Breeze!

2. The other alternative is that there was interference from the toy remote my son was using to control his boat. This is a very cheap 40 Mhz style remote (with good range for a toy, it runs from a 9V battery), and he was standing like 2 or 3 meters away from the Breeze (I know, too close for his safety - I was quite obviously over-confident). The hypothesis would be that it was causing direct eletronics errors on the Breeze flight controller, but somehow I cannot bring myself to believe that.

Any other ideas?

Thanks for your input!
 

DoomMeister

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For the first over the metal grid I would suspect a combination of magnetic interference and the repeating pattern confusing the optical flow camera (rear sensor).

How much metal was there on the pier where your latest incident took place? I suspect compass interference more than the IPS system in both cases as it usually is the cause of a high speed flyaway. The IPS usually just causes drift.
 
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Thanks for the response.
No visible metal in the pier, except for screws. It appeared to be an entirely wooden structure.
The metal grid in the other case was small, like 40 by 80 cm, and not so massive. Further, I am sure that I even flew with GPS off because I started that flight indoors.
 
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Hi,

I had similar accident with mine. But it was because of battery low level. It could not took off correctly and instead of drop down it accelerated to the left and passed some people over in maybe 1 meter.. So, Don't ever try to take off if battery lower then 10%.
p.s. it was my 2nd flight
 
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So here is the log file of that flight. The actual flight shows only two log events before the bird hits the ground, I think.
As you can see from some of the info, I was flying with the latest modded BreezeCam app version. But I am pretty sure that the mod had nothing to do with this. (Maybe it is causing the odd time stamp entries, however? Or is that because I am using an US firmware in Europe?)
The earlier flight/crash I mentioned was with the original BreezeCam app.
 

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Hi,

I had similar accident with mine. But it was because of battery low level. It could not took off correctly and instead of drop down it accelerated to the left and passed some people over in maybe 1 meter.. So, Don't ever try to take off if battery lower then 10%.
p.s. it was my 2nd flight
I didn't expect it would let you take off with less than 10% battery level, so it is good to know that you have to be wary about this. Mine starts an emergency landing at 9% battery or so - and it goes there dramatically fast, once it is below 20% battery level.
 
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I suspect that toy RC transmitter.
When close enough a harmonic on its signal could have confused the breeze.
In the past, any time you're close to a steel structure, magnetic interference is likely.
 
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DoomMeister

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So here is the log file of that flight. The actual flight shows only two log events before the bird hits the ground, I think.
As you can see from some of the info, I was flying with the latest modded BreezeCam app version. But I am pretty sure that the mod had nothing to do with this. (Maybe it is causing the odd time stamp entries, however? Or is that because I am using an US firmware in Europe?)
The earlier flight/crash I mentioned was with the original BreezeCam app.
I’ll look at the log later today. For some reason I never got an alert that you responded back. Rather odd this happened twice in the same manner.
 
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Hi @DoomMeister, did you notice anything of value in the log file?
Myself, I just see the pitch value going crazy right after Hoover altitude is achieved, and the motor emergency stop probably only occurs after the impact (but why only three motors?).
 

DoomMeister

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No chance to look yet. The wind was right this weekend to burn all of the deadfall from the trees and trim bushes and pull weeds. I then use the resulting ash as fertilizer for the lawn.

I’ll try to look today, sorry for the delay.
 
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No chance to look yet. The wind was right this weekend to burn all of the deadfall from the trees and trim bushes and pull weeds. I then use the resulting ash as fertilizer for the lawn.

I’ll try to look today, sorry for the delay.
No need to apologize! Life always has priority over forums...
 

DoomMeister

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I see nothing to give a precursor to this event. Right after liftoff it just made a sharp pitch and roll and sped into a crash with the ground. Is there a chance you powered the Breeze up, then walked it to the end of the pier before launching? looking at the kml file generated looks like that may have been the case.

Very odd behavior, since there were no error files until impact.
 
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I see nothing to give a precursor to this event. Right after liftoff it just made a sharp pitch and roll and sped into a crash with the ground. Is there a chance you powered the Breeze up, then walked it to the end of the pier before launching? looking at the kml file generated looks like that may have been the case.

Very odd behavior, since there were no error files until impact.
I don't recall how much I walked around on the pier after powering up, but it could well have been the case that I powered up while still on firm ground. Which would have been underneath trees, so no stable GPS lock to be expected there anyway.
 

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I could understand drift with the wind without a good GPS lock, but not quickly shooting away like it did.
 
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I could understand drift with the wind without a good GPS lock, but not quickly shooting away like it did.
When it took off, the Breeze DID have accetable GPS lock, as the log also shows. And yes, the speed at which it went into the ground was remarkable... I am still surprised that it didn't just explode into dozens of pieces. Somehow, the rear-left foldable leg must have buffered most of the impact, and the ground was mostly raw earth. But mainly, I am glad that none of the boys was harmed. The one standing next to the crash point was quite shaken, though.
Anyways, my lesson is to be more cautious around people, RC transmitters, and regular ground patterns.
 
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