Unexpected RTH at Dusk Flight and Uncommanded Yaws

[Billie Nelson]

My Phantom 3 S had been on the shelf for a few weeks so I decided to send it on a couple of beyond-signal-range Litchi missions since such missions are perfectly legal in my remote Third World backwater. Reviewing the video footage from the first flight, I was alarmed to see a couple of instances when the drone yawed violently enough for the camera to pick up a glimpse of one of the front motor housings, which I have never seen happen in over 2,200 miles of Litchi flights.

I reviewed my pre-set camera orientations along the flight path, and there simply weren't any abrupt changes in my assigned camera directions that could account for those two uncommanded and drastic yawing motions. I would be grateful if anyone could shed some light on this drastic and uncommanded yaw that I have seen this Phantom3S perform for the first time ever today.

The second odd behavior that I observed occurred when I launched the drone on a 22-minute duration Litchi flight plan mission right as the sun was about to set, at twilight. Now I do realize that most of the footage filmed at dusk would have been too dark to be of much use, but I intended to edit out all footage that was recorded after sunset. The drone was still within signal range when Litchi announced that the mission was being terminated and an RTH was about to be triggered. The drone rose to the RTH height and sure enough headed right back to base without any input from me whatsoever.

Because I'd never in the past launched the drone quite that late in the day, it occurred to me that perhaps Phantom drones are hard-wired to RTH when light sensors indicate that lighting will be insufficient for filming by the time the drone reaches its destination, but this is mere speculation. I sure would be grateful for any opinions that can be offered as to why this unexpected RTH occurred on this particular flight. I haven't calibrated the GPS for a while now, so maybe that might be a factor.

 

[MapMaker53]

How low was the battery when the P3S decided to return home?

 

[Meta4]

Because I'd never in the past launched the drone quite that late in the day, it occurred to me that perhaps Phantom drones are hard-wired to RTH when light sensors indicate that lighting will be insufficient for filming by the time the drone reaches its destination, but this is mere speculation.

Phantoms fly normally, night or day

I sure would be grateful for any opinions that can be offered as to why this unexpected RTH occurred on this particular flight.

Without seeing flight data, nothing comes to mind.

I haven't calibrated the GPS for a while now, so maybe that might be a factor.

No-one has ever calibrated their GPS ... it's just not possible.
If you meant the compass or IMU, you would know if they had a problem.
If the drone flies and hovers normally, both are fine and recalibrating wouldn't improve anything.

 

[Billie Nelson]

How low was the battery when the P3S decided to return home?

I started the flight at 96% battery, but there'd been a mixup due to my losing track of how many of my six batteries had been topped up recently. This got me to thinking perhaps the drone had sensed that this particular battery was not recently topped up, and might discharge at an abnormally rapid rate such that its power might not suffice to make the entire round trip. I'll repeat the flight today with a battery I am certain has just been topped up, to eliminate battery issues as a possible factor in this unexpected RTH.

 

[Billie Nelson]

Phantoms fly normally, night or day


Without seeing flight data, nothing comes to mind.

No-one has ever calibrated their GPS ... it's just not possible.
If you meant the compass or IMU, you would know if they had a problem.
If the drone flies and hovers normally, both are fine and recalibrating wouldn't improve anything.

This correction is appreciated, Meta4. I did mean calibrate the compass. I've only carried out the procedure a couple of times, hence my forgetting the specifics of what it entailed and its purpose. The drone hovers fine, but I did note that odd yaw behavior a couple of times even as I landed the drone manually, which is something I've never encountered in the past. I'll be keeping a close watch on the drone today as I repeated this flight with a freshly charged battery.

After so many hours of uneventful flights with this Phantom3S, these abrupt changes in flight behavior caught my attention right away, as did the unexpected RTH.

 

[Billie Nelson]

Regarding the flight data, I'll read up on how to go about retrieving it as I haven't had cause to delve into this record prior to these alarming glitches showing up. I am eager to understand what lead up to the abnormal yaw behavior in particular, as it was violent and extreme both times it happened both during fully autonomous Litchi flights, and then again after I had disengaged the autopilot to perform a manual landing.

 

[Billie Nelson]

Glad to report that the unexpected RTH that my Phantom3S embarked on at the start of yesterday's aborted twilight Litchi waypoint mission was most likely a battery failsafe response. With a fully charged battery plugged into the drone, I dispatched the P3S to the same destination this time via a 22-minute round trip scenic route that followed the course of a river on the way out.

This time RTH only kicked in as the drone was completing its fourth orbit around a building located a full country mile away from my launch point. This is normal and crucial RTH behavior, confirming that yesterday's abrupt RTH as the mission commenced was due to the battery not having been fully topped up shortly before the flight, as is preferable in order to hit that desired100% battery level as the flight kicks off each time.

Despite this lowly P3S being nearly a decade old, I still marvel at the complexity of those instantaneous battery life expectancy calculations this drone processes before and during each flight, which makes RTH such a reliable safety net so expertly designed to ensure that bird returns to roost despite any number of operator blunders before each mission's initial throttle-up.

Finally, I didn't see a repeat of yesterday's wild yaw swivels after looking over this morning's mission footage, so hopefully that anomaly has resolved itself without my having to think, which isn't always a good thing haha.

 

[ultimatetetoyman]

My Phantom 3 S had been on the shelf for a few weeks so I decided to send it on a couple of beyond-signal-range Litchi missions since such missions are perfectly legal in my remote Third World backwater. Reviewing the video footage from the first flight, I was alarmed to see a couple of instances when the drone yawed violently enough for the camera to pick up a glimpse of one of the front motor housings, which I have never seen happen in over 2,200 miles of Litchi flights.

I reviewed my pre-set camera orientations along the flight path, and there simply weren't any abrupt changes in my assigned camera directions that could account for those two uncommanded and drastic yawing motions. I would be grateful if anyone could shed some light on this drastic and uncommanded yaw that I have seen this Phantom3S perform for the first time ever today.

The second odd behavior that I observed occurred when I launched the drone on a 22-minute duration Litchi flight plan mission right as the sun was about to set, at twilight. Now I do realize that most of the footage filmed at dusk would have been too dark to be of much use, but I intended to edit out all footage that was recorded after sunset. The drone was still within signal range when Litchi announced that the mission was being terminated and an RTH was about to be triggered. The drone rose to the RTH height and sure enough headed right back to base without any input from me whatsoever.

Because I'd never in the past launched the drone quite that late in the day, it occurred to me that perhaps Phantom drones are hard-wired to RTH when light sensors indicate that lighting will be insufficient for filming by the time the drone reaches its destination, but this is mere speculation. I sure

Glad to report that the unexpected RTH that my Phantom3S embarked on at the start of yesterday's aborted twilight Litchi waypoint mission was most likely a battery failsafe response. With a fully charged battery plugged into the drone, I dispatched the P3S to the same destination this time via a 22-minute round trip scenic route that followed the course of a river on the way out.

This time RTH only kicked in as the drone was completing its fourth orbit around a building located a full country mile away from my launch point. This is normal and crucial RTH behavior, confirming that yesterday's abrupt RTH as the mission commenced was due to the battery not having been fully topped up shortly before the flight, as is preferable in order to hit that desired100% battery level as the flight kicks off each time.

Despite this lowly P3S being nearly a decade old, I still marvel at the complexity of those instantaneous battery life expectancy calculations this drone processes before and during each flight, which makes RTH such a reliable safety net so expertly designed to ensure that bird returns to roost despite any number of operator blunders before each mission's initial throttle-up.

Finally, I didn't see a repeat of yesterday's wild yaw swivels after looking over this morning's mission footage, so hopefully that anomaly has resolved itself without my having to think, which isn't always a good thing haha.

I just went thru the violent yaw movements. Mine happened in DJI go4 app and continued so I replaced the yaw motor and at same time ribbon cable and it corrected itself. This may not be the same issue but the yaw motors have been a problem it appears.

would be grateful for any opinions that can be offered as to why this unexpected RTH occurred on this particular flight. I haven't calibrated the GPS for a while now, so maybe that might be a factor.

 

[ArnoldLeVine]

Reviewing the video footage from the first flight, I was alarmed to see a couple of instances when the drone yawed violently enough for the camera to pick up a glimpse of one of the front motor housings, which I have never seen happen in over 2,200 miles of Litchi flights.

It wasn't the DRONE that yawed, it was the gimbal/camera. This sounds similar to an occurrence with Phantom 4 pro, when flying sideways into a strong wind, and the camera flips to vertical for a second, then returns. At first, you think the drone went vertical, then later realize it was the gimbal/camera. If I remember correctly, it had to do with the gimbal motor being overstressed by the high wind.
Any idea if what the wind speed/direction vs your flight orientation would have been at that moment?
This is pure specualtion, btw.

 

[Billie Nelson]

Despite my not seeing those abrupt yaw movements while reviewing the footage recorded during my last couple of Litchi flight plan missions, I sadly now note that the yaw response is not what it was during my manual landings because I now notice the yaw to be either under-responsive or excessively so, intermittently.

Hoping to wish away this yaw response inconsistency, I at first chalked the squirrely yaw response simply to my being out of practice after a period of hardly any drone flying, but my suspicion now is that something is in fact amiss that may get worse over time.

I can only hope this yaw problem doesn't get any worse since virtually all my flights are cinematic Litchi auto flights with deliberately slow and gradual panning camera sweeps that don't seem to trigger those sudden jarring swivels in the yaw axis. Replacing the yaw motor and ribbon is not the sort of surgery I would be able to pull off with the ease that you were able to handle such fixes because frankly, I've never had cause to replace anything on this workhorse P3S.

 

[Billie Nelson]

It wasn't the DRONE that yawed, it was the gimbal/camera. This sounds similar to an occurrence with Phantom 4 pro, when flying sideways into a strong wind, and the camera flips to vertical for a second, then returns. At first, you think the drone went vertical, then later realize it was the gimbal/camera. If I remember correctly, it had to do with the gimbal motor being overstressed by the high wind.
Any idea if what the wind speed/direction vs your flight orientation would have been at that moment?
This is pure specualtion, btw.

The wind was somewhat gusty when those sudden yaws occurred, now that you mention it, and I was alarmed to catch a brief glimpse of the motor mount during both of the sudden swivels that were evident in the video footage recorded. If the entire drone had been making the yaw motion, the motor mounts wouldn't have come into the picture frame like that, which does suggest that the camera swiveled on its mount, while the drone maintained its programmed heading.

ArnoldLeVine I do believe you have identified the nature of this anomaly. That problem did not replicate when I flew the same mission today under calm conditions. This might be good news, in that freak gusts of winds aloft may have been the culprit, rather than a developing defect in the yaw motor or ribbon, as suspected by Ultimatetoyman in his post above. As the total mileage that my P3S has flown approaches 2,300 miles, I was beginning to think there wasn't much that could baffle me about this platform, but I was wrong, yet again.

 

[Martin Healy]

It wasn't the DRONE that yawed, it was the gimbal/camera. This sounds similar to an occurrence with Phantom 4 pro, when flying sideways into a strong wind, and the camera flips to vertical for a second, then returns. At first, you think the drone went vertical, then later realize it was the gimbal/camera. If I remember correctly, it had to do with the gimbal motor being overstressed by the high wind.
Any idea if what the wind speed/direction vs your flight orientation would have been at that moment?
This is pure specualtion, btw.

Hi Arnold and Billie, Some years ago this happened to me. The P4 was orbiting a building when I was alarmed by the very sudden change in the video feed and I thought the P4 was crashing. But it continued on the Litchi mission only for it to happen a couple more times before I cancelled the mission and took manual control to return to launch point. I put these erratic movements down to the plastic lens hood I had fitted to the camera. Although the hood was very light, only a few grams, it acts like a sail to catch the wind gusts as so overwhelmed the gimbal motors. When processing the video it was evident that the P4 came to a near halt briefly during the violent camera movements showing just how powerful the gusts were 200ft up. The moral of this story is beware of the loading on the gimbal motors when adding filters and lens hoods.

 

[ultimatetetoyman]

It wasn't the DRONE that yawed, it was the gimbal/camera. This sounds similar to an occurrence with Phantom 4 pro, when flying sideways into a strong wind, and the camera flips to vertical for a second, then returns. At first, you think the drone went vertical, then later realize it was the gimbal/camera. If I remember correctly, it had to do with the gimbal motor being overstressed by the high wind.
Any idea if what the wind speed/direction vs your flight orientation would have been at that moment?
This is pure specualtion, btw.

Yes mine was the camera humble yaw motor that seemed to go funny. It was a bit windy up higher that day. But funny it did it that day in the wind then did not do it another day with less wind. Then I took it out when it was windy again and it seemed the yaw motor was causing fumble overload. And it then got a bit worse. So I changed the motor and ribbon cable and perfect so far after 6-7 flights. If when you start up the drone you might hear a grinding type noise for a minute. If so it's probably the yaw motor just starting to go. Don't forget that if you replace the yaw motor you have to use the old drum cover of the motor as it is apparently calibrated at factory and it has to be the same or camera does not line up straight. I have found that so far on both my p4p the yaw motor acted up and needed replacements. They may be faulty or just get overstressed with the newer design setup.

 

[Pygar70]

I've experienced a temporary camera tilt on many occasions. It appears on-screen as a sudden roll, rather than a yaw. That said, it's never happened while flying forward. Were you orbiting or moving sideways at the time? If there were unusually high winds, it could well have caused your battery to drain more quickly than expected.

 

[Billie Nelson]

The drone was orbiting sidelong in a circular flight path while focused on a building I'd marked as a point of interest when the unexpected camera yaw occurred, It is odd that you've seen uncommanded camera tilt, but not yaw, during gusty wind conditions. On just one occasion, the camera on my P3S tilted fully down uncommanded during a flight that got caught in a light drizzle a while back. Unexpected camera tilt never occurred again besides that one occasion.

Speaking of camera yaw, I had until yesterday's incident assumed that the camera was only capable of tilting in the vertical axis and that panning the camera in the horizontal axis could only be accomplished by yawing the drone either manually if the drone is within signal range, or by assigned Litchi camera directions that are pre-set for each waypoint of a flight plan. Now I can see that the camera can get buffeted enough to yaw independently of the drone, meaning it does a degree of play in the horizontal axis that can be seen in gusty conditions.

 

[Billie Nelson]

I can now say with absolute certainty that there is something seriously amiss with the yaw control of this drone. I just sent it on another 22-minute Litchi waypoint mission on a dead calm day here, and when I switched over from F-mode to GPS mode for my usual glide slope approach to land, the drone went haywire, lurching left and right like a drunk driver on the freeway. I had to make constant yaw corrections to maintain a semblance of stability on the approach, and I darn near lost control twice before I finally landed the drone.

I do not look forward to the prospect of performing any repairs on this drone given my lack of expertise in that area of delicate surgery, so I will most likely fly autonomous missions for as long as the drone retains enough control authority to land without crashing. I love these old Phantom3 Standards, for their battery longevity, their light weight, and their simplicity, so it will be a sad day indeed when the fat lady finally sings for this current workhorse that has served me so well for over 2,250 miles and counting.