Strong wind copter didn't move

[GekoCH]

Hy

Just flew my H in some "heavy" winds. Speeds were constat at 20km/h (12mph) with wind gust of up to 40km/h (25mph).
I had a really strange experience right after taking of with the typhoon. The H had a hard time keeping the position due to the wind and then suddenly I was not able to move the H backwards anymore. It was only possible to move it forward (away from me). Since I was flying on a small rock right next to the sea this was terrifying since I couldn't get the H back to land.
I think I can call me an experienced quad / hex flyer since many years so I immediately thought to disable the GPS and fly it manually. And it totally worked.
I switched the GPS off the copter got blew away by the wind but reacted immediately to my stick inputs.

I was very glad and flew four more batteries but this time with the GPS switched off before take off and had no troubles anymore.

Did someone else experienced such a weird behavior before?

Andy

 

[Rayray]

Totally weird, glad you were able to think quick and recover it. You did not start in Smart mode, right?
How close was it to you, Andy?

 

[Typhoon Charlie]

I have said this before, based on research and my experiences with GPS. Just because you have GPS lock with a number of satellites, it doesn't mean you have a low HDOP(Acronym for horizontal dilution of precision. A measure of the geometric quality of a GPS satellite configuration in the sky. HDOP is a factor in determining the relative accuracy of a horizontal position. The smaller the DOP number, the better the geometry. Satellite receivers often take as much as 15 min to settle in and get a good low HDOP. Specially if the GPS receiver has been off for some time.
.
The GPS Navigation Message consists of time-tagged data bits marking the time of transmission of each subframe at the time they are transmitted by the SV. A data bit frame consists of 1500 bits divided into five 300-bit subframes. A data frame is transmitted every thirty seconds. Three six-second subframes contain orbital and clock data. SV Clock corrections are sent in subframe one and precise SV orbital data sets (ephemeris data parameters) for the transmitting SV are sent in subframes two and three. Subframes four and five are used to transmit different pages of system data. An entire set of twenty-five frames (125 subframes) makes up the complete Navigation Message that is sent over a 12.5 minute period. These tables are updated every 2 hours, so if you dont fly for several days you will be very out of date abd the GPS need to update in order to be current and accurate.

If you just power your GPS receiver and fly, then the accuracy of the GPS may be way off. Always wait 10 to 15 min before flying the first time, after that you are good to go even if you power down to change batteries.

If you have an Android phone ,install this app and watch how long it takes for the accuracy to come down to a reasonable level.

 

[DroneClone]

Where you in Smart Mode? if so and less than 26' out, it won't fly back to you!

 

[Rayray]

Good information and good advice. Even if you fly in the same location, the GPS Sats overhead are not necessarily the same ones. Geomagnetic storms can also degrade signals coming from more distant Sats (the so-called Kp factor).

I'll admit I rarely wait more than 5 minutes after Sats start appearing, tho I do keep the H hovering in the air a couple minutes to make sure all is OK.
I'll check out the app you recommend, thanks for this post.

 

[Typhoon Charlie]

Here is another favorite. It will show magnetic flux and other cool data.

 

[abinder]

I wouldn't be surprised that you could fly back to yourself with the GPS mode off because the top speed of the H is much greater then. The winds very well of been higher than you thought. Also you may of been getting a 'rotor' effect coming off the rock and/or surrounding terrain.
(Just a thought though.)


Sent from my iPhone using Tapatalk

 

[GekoCH]

All was done in Angle mode. I havn't use smart mode yet since I'm more used to the angle mode form ym previous drones.
And come on, with my PIXHAWK drones I never waited for the HDOP to be as small as possible and had never a problem.
Ok maybee the yuneec drones are programmed this way but this would be bad since you can't asked the user to wait for 15min
before he can start flying. By then the sun would have set (in my case )

It totally could handle flying back with GPS on with the current wind speed, it did also a few seconds before it totally locked into position
and just would move forward.....

Andy

 

[JohnL]

Great post by @Typhoon Charlie. Hey Andreas (@GekoCH), take a look at your telemetry logs and check for a couple of things: Error 32 (compass calibration warning) and "gps_acch." This second field (value) is believed to be Yuneec's way of logging HDOP errors. Once your vehicle is finished with "flight mode 16" (Initializing) your should start to see the number drop below 1. This number should ideally be WAY less than 1 WRT this condition (as Typhoon Charlie very eloquently pointed out).

I use a very nice little program from @h-elsner to read the values from the Telemetry logs. link: Meine private Homepage - Computer, Autos, Reisen
Go to his "downloads" section and look for a file called q500log2kml. Really helps to analyze and understand some of the active parameters of the TH.

Nice to see you're up and flying and not just "grinding away in the salt mines" (ie, fabricating battery adapters).

 

[GekoCH]

lol just forgot to look at the log files thx for the idea
And yes that's why I currently can't send any connectors out since I'm on holiday Need to fly this thing and not just look at it

will report back once I looked at the log file

Andy

 

[GekoCH]

ok now thats really strange... Apparently I was in F_mode 21 and this is "Smart mode - Follow me" right after the motor started...
My FMode Switch was definitely in the middle position for sure because thats one thing I always check before powering up the ST16.

By the way, the HDOP was always at 0.55 after the motors started.

Andy

 

[DroneClone]

ok now thats really strange... Apparently I was in F_mode 21 and this is "Smart mode - Follow me" right after the motor started...
My FMode Switch was definitely in the middle position for sure because thats one thing I always check before powering up the ST16.

By the way, the HDOP was always at 0.55 after the motors started.

Andy

I suspected Smart Mode, I believe the switch was in middle like you tell us, but did you notice the light color? Was it green or purple?

 

[GekoCH]

I can't remember the color of the led blinking at the back had enough to do to figure out how to get it back (my wife just told me it was purple... )
May bee switching the FMode back and forth etc before take off would be a good practice too...

Andy

 

[DroneClone]

I can't remember the color of the led blinking at the back had enough to do to figure out how to get it back (my wife just told me it was purple... )
May bee switching the FMode back and forth etc before take off would be a good practice too...

Andy

Maybe the rocks were very high iron content and threw the GPS off, where the rocks black or reddish? Just a though if you feel all your settings were correct ! Try again somewhere else over land/open field and see if it operates normal is all I can suggest!

 

[GekoCH]

since I studied geology a few years back I can say no, because those were leucocratic granit so they have a really low iron content

EDIT:
And the lighthouse I was filming was a good 50m away and so this shouldn't affect the H

Andy

 

[JohnL]

ok now thats really strange... Apparently I was in F_mode 21 and this is "Smart mode - Follow me" right after the motor started...
My FMode Switch was definitely in the middle position for sure because thats one thing I always check before powering up the ST16.

By the way, the HDOP was always at 0.55 after the motors started.

Andy

Well that seems to be the root of the problem. When you can sit down in your house with the St16 and (while nice and relaxed and all calm), check your switch positions and read outs with the Hardware monitor.

 

[GekoCH]

the switches work ok. As an additional safety feature, at least for me, I now disabled the smart and RTH mode (never used it before and might never use it in the future) on the FMode switch with the channel settings option on the ST16.

Andy

 

[JohnL]

the switches work ok. As an additional safety feature, at least for me, I now disabled the smart and RTH mode (never used it before and might never use it in the future) on the FMode switch with the channel settings option on the ST16.

Andy

Good for problem solving, but you may need that RTH function in a pinch someday. Please update this thread with your findings!

 

[GekoCH]

Thx everyone for the help.
For me its not a huge deal since I was able to operate the drone without GPS, so no deal breaker. However I will pay more attention in the future and maybe even record the ST16 screen with a wearable GoPro on my chest just to see whats going on.

And yes I already put the RTH function on the AUX button so as long as I press it, it will RTH once I release it ,it is back in Angle mode, for me perfect

Andy

 

[JohnL]

And yes I already put the RTH function on the AUX button so as long as I press it, it will RTH once I release it ,it is back in Angle mode, for me perfect
Andy

That's pretty clever. Good post!