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Emergency event during testing...

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Today's second test flight session of the season had some very interesting things going on in it...

1. Large greyhounds pursuing craft wherever it went in sky, making landing much more exciting than usual. Solved that.
2. Helicopter appearing over the treeline at 400 ft or so, and vectored directly at my craft. Solved that too.
3 Mysterious drop-from-sky type event just after take-off with 3rd pack, and it is that one I am documenting here...

It was the 3rd flight of the day, and the previous 2 had completed as normal, with impeccable behaviour from the H at every stage of the way.
I had loaded up with the 'red' battery pack, a Yuneec original, which is being used for the first time for its 3rd season after a slightly problematic charge with a balance charger that died in the process, and would balance charge to 4.2v on 3 out of 4 cells, then just as the final one crested 4.2, would reset it to 3.7, and then spent an hour trying to get back to balance. Having spotted this, the charger was retired, and a new B6 V2 charger was acquired, and plugged into that battery pack in order to try and rescue it. It balanced in 40 mins, and when checked with a separate voltage checker reported 4.17v across all cells, which gave me 16.7 total, which I thought was commensurate with the age and cycles on the pack.I expected about 8-9 mins flight down to 14.6v.

All pre-flights passed, we had 18 sats acquired, and launched perfectly. I climbed to 5 ft to clear the worst of ground effect, then paused to adjust some camera ISO settings. At this point, ready to do my planned video mission, I bumped her to 12 ft high, and dropped my right hand to raise the landing gear. As i did this I gave a firm increase in throttle to 'launch' out of hover with purpose. At this point, the craft began the ascent, then stopped, and pretty much fell out of the sky. I had not yet raised landing gear, so we came down on soft heath ground / sand, and the gear took the hit, protecting the camera from damage, and remaining unbroken itself luckily. However now I have a craft with all motors still spinning, bouncing up and down on the ground, and looking like tipping is imminent.

At this point I am heavily down-sticking (to try and keep it down and stop it bouncing) and simultaneously trying to red-button it, and what seems like a seriously protracted 5 second later motors stop, and we have a craft made safe and landed without damage.

So this has gone as well as I could hope events like this might end up, and I recorded what my screens were saying, powered down, examined the battery, and went over the craft looking for damage, which I didn't find. All motors continue to spin correctly when powered up (unlaunched) subsequently. Pack voltage was not doing anything unusual according to St-16.All motors slightly warm, but none hot. Battery emerges un-puffed, but hot.

After 15 mins rest and further inspections, I tried my remaining 2 packs, and commenced hovering at 1ft for an extended test period, then began a series of gently increasing ascents and descents, all of which were without further incident. For the last pack of the day, which was a virgin pack (also re-balanced by the new charger) I did go a little higher, but being very cautious kept her under 30 ft for nearly the full duration, and did some gentle circles to further test things. Everything was fine after 4 mins of that, so I risked a small climb to 60 ft just to grab the sunset, which was looking very attractive at the time.

I have not yet retrieved the telemetry, but obviously that is my next plan. I need to get the Telemetry reading app (forgive me I can never remember what it's called) installed on this new Win 10 machine, but will try that tomorrow. Am I right in thinking I have to run that in Win 7 compatibility mode, but that if I do so and use the Yuneec USB cable specifically, I am expecting that to work right ?

So anyway, there is my initial account before I forget it ! More to follow as investigations continue...

AJ

EDITED in light of new evidence so report remains accurate.
 
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@h-elsner makes "Q5002KML" available on git-hub. The English language version is at "h-elsner/Q500log2kml"

This is going to be an interesting read. It would be great if you uploaded a copy of the logs for the forum to review.
Already got it, but thx :) just trying to find the original yuneec cable now... will upload logs when I have them.
 
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OK, not sure what to make of this... anyone care to take a look ?

Many thanks for any insight...

J
 

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OK, not sure what to make of this... anyone care to take a look ?

Many thanks for any insight...
First looks are almost always off the mark, but first look this time says the altimeter failed. Unless the aircraft is still in the air. (If it is, I want to know what brand of battery you're using.)

We may need to see some additional flights to compare historical altimeter readings, and certainly the flights that were conducted right after this one.
You can use Attachment 56 (Typhoon H Flight Log Retrieval) of "Way To Fix Drones project" to download all logs. That will avoid making individual file copies, and it will be easier for the reviewers. Individual files have to be manually inserted into the correct file structure, one at a time, for the program to use them.

A quick look at flight 232:
Flight 232.jpg Elevation.jpg

P.S. If this picture is true, NASA wants to borrow your drone for the next Mars mission. Notice it still thinks it is going up.
NASA.jpg
 
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Steve Carr

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Certainly the barometer was giving strange readings. It was normal at motor start but jumped to 27 meters about 3sec after liftoff.
About 9 seconds after liftoff it appears it may have landed. Then about 1-2 seconds later the mode changed from Angle to Standby (motor kill).
About that same time the IMU Status changed from 229 to 101.

I see no relationship between the battery and the flight problems. It just appears to be a Flight Controller/barometer glitch.
As @WTFDproject indicates, the previous and later flight data might help reveal a trend.
 
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Thank you both very much for your input - most appreciated. I shall divert my attentions away from battery packs, and look into the barometer readings in a bit more detail.

I have to say, as soon as @WTFDproject mentioned barometer, bells were rung and I sighed to myself 'eurgh, not that again'. For indeed there is history here with those wretched readings, which have caused a number of smaller issues in the past, though never anything as drastic as yesterday's events.

That barometer has been misreporting for quite some time ! If you go back through my posts here over the years, you'll notice that barometer readings feature quite heavily in my reports and worries about the craft, and I have been holding that responsible for the occasional descent refusals that I experience, and on several occasions have provided video with telemetry overlay that shows the barometer largely doing its own thing and regularly being 35 ft wrong, irrespective of what is actually happening to the craft. And yet after 230 odd flights, it has not proved a serious problem - I know how to rescue it when it refuses to come down, and am watching for that behaviour, and sometimes I stop and restart motors before launch if I notice barometer moving wildly when they are first initiated, and that motor restart usually stabilises it.


But this is the first time anything as drastic as this has happened, so now I am wondering if the craft is safe to fly, and how likely I might be to get a repeat of this sessions behaviour, which would almost certainly unavoidably kill the craft if it happened under any less favourable circumstances.

Is it possible to swap out the barometer I wonder ?

Many thanks

J
 
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The barometer is located on the bottom side of the Flight Controller under a piece of foam to filter the air. I'm not confident that the barometer could cause the aircraft to simply drop since it's a rough measurement device. The FC places much more dependence on the accelerometers/gyro than the baro sensor. In your case, changing the FC might have merit.

Barometer-2.jpg
 

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Are you sure you don't have an H Plus?🤔
 
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The barometer is located on the bottom side of the Flight Controller under a piece of foam to filter the air. I'm not confident that the barometer could cause the aircraft to simply drop since it's a rough measurement device. The FC places much more dependence on the accelerometers/gyro than the baro sensor. In your case, changing the FC might have merit.
Hmmmf. Thanks Steve, that's definitely not what I wanna hear, though I fear you may be correct :( Not sure I am up to a full FC swap out, or the expense of getting another one. This might be the push I need to sell it for parts and jump to Autel, though I don't really have the cash to do that either at the moment ! Is there any way we can be sure that the FC is responsible, and would you consider the craft safe to fly in the meantime ? This is the first and only time the H has done this before or since. I might do another 4 pack in a safe empty field, just to see if it's going to do it again any time soon... good idea ? Or do you think I can mentally compartmentalise it as a 1-off type of glitch, and just carry on with normal flight schedule, merely keeping an extra eye on it etc etc ?
 
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would you consider the craft safe to fly in the meantime ?
First check the accelerometers by powering on the H on the ground. Do an accelerometer calibration. Reboot the H. After it's bound, lift the aircraft over your head and see how much the altitude reading changes. Those readings are not from the altimeter. They are from the accelerometers. So that will give you some insight if the accels are working. Start and stop the motors to see if the reading resets to zero.

If that test seems normal, remove the camera and do some flight testing but only over something soft to land on and I would go no higher than a few feet to watch the alt reading.
 
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Thanks Steve, will do. I had done an accelerometer calibration just the day before as part of getting the craft ready for the new season, and all seemed fine then, but can't hurt to do it again before the further tests. I think I did 2 additional packs immediately after the event in which I did exactly as you suggested and remained a foot off the floor for the first one, and then did some graded ascents with the second pack, all of which went through without the slightest issue. Here's a quick graph of flight 234, which shows how much my confidence had returned already toward the end of it !

1600510104822.png

Definitely good idea to stay over as soft stuff as possible for a little while too !

I will post back here should anything weird and similar reoccur. Thanks again everyone...

AJ
 

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It's entirely possible this was just a glitch when the aircraft was booting up. It's rare but it can happen. Simply rebooting fixes the problem. It's one of the reasons to do a thorough check while in hover right after the launch.
 
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