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Mysterious Tic-Tacs (Might Have) Downed Mavic Platinum Pro

Conservative Nihilist

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After thousands of miles of Litchi waypoint missions flown without incident, the law of probabilities finally caught up with me and the result was a Mavic Pro Platinum engaging some high-tension electric cables in a life-and-death duel, with predictable results. I had been testing the newly released extended-range battery for the Mavic 1 Pro and Pro Platinum, and the drone was 3 miles from home after traversing the skies above a huge palm tree plantation and a couple of swamps when it sent me an RTH alert.
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DJI Mavic, Air & Mini Drone Community

In-depth review of Mavic Pro extended capacity battery (Hobbitec 6830mAh) -...

Всего 11 миль 23 km homemade 5200mAh battery. My flight is not to Litchi, but to GO4.


Other users of this battery had recommended disabling smart RTH prior to takeoff, yet I was reluctant to cut that safety tether, and so foolishly opted to cancel RTH on the fly, banking on the premise that the drone would then complete the 12-mile round trip waypoint sequence without incident after my initial RTH cancellation.

Unexpectedly signal loss occurred at the precise moment when I canceled RTH, and I now surmise that the 240-foot RTH altitude I’d pre-set was either not sufficient to clear the high-tension cables or was inexplicably ignored by the drone, such that it went into a dive at the worst possible moment. and flew backward into the cables, at which point gravity exerted its influence without mercy.

Hopped in the Jeep and sped to the crime scene as indicated on my Litchi map screen, and after a few minutes of stumbling about in a corn farm, located the Mavic Pro Platinum where it had landed in the soft grass. The massive after-market battery had been ejected on impact and showed clear signs of abrasion where it was scuffed by the power line, while the battery housing has a minor dent in it. Tested the battery and it does power up the drone normally.

After my official mourning period has been observed, I will conduct a test of this drone, whose rear panel now sports a significant structural crack which may or may not mean the drone has breathed its last. Amazingly the camera of the drone appears intact. The fact that the drone was flying backward at the moment of impact is the reason why that camera was spared any visible damage.

I’ll take a few post-mortem photographs later today and add them to this thread. If I were to cite a lesson learned from this debacle, it would be that anyone who has installed a larger-than-stock battery in their Mavic 1 Pro or Mavic Pro Platinum should just go ahead and cancel smart RTH before takeoff IF they are intent on exploring the new range envelope made possible by that larger battery. Better risk landing with 15% battery than risk the drone adopting unpredictable RTH altitudes.
 
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than risk the drone adopting unpredictable RTH altitudes.
I stuck with it through that entire post but I don't understand that part. How can you say 'unpredictable RTH altitudes' when you had canceled RTH? And I don't think any DJI drone would inexplicably adopt an unprogrammed RTH altitude. My MPP never has, nor the Phantoms before that...

BTW, what's a tic-tac?
 
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I now surmise that the 240-foot RTH altitude I’d pre-set was either not sufficient to clear the high-tension cables or was inexplicably ignored by the drone,
Occam's razor suggests that the former explanation is the more likely.

Better risk landing with 15% battery than risk the drone adopting unpredictable RTH altitudes.
There's little risk in landing with surplus battery capacity. The risk lies in habitually extending flights until the battery is nearly depleted.

The fact that the drone was flying backward at the moment of impact
Is there anything to suggest the drone was flying backward other than the marks on the exterior of the drone? Flight logs?
 
Occam's razor suggests that the former explanation is the more likely.


There's little risk in landing with surplus battery capacity. The risk lies in habitually extending flights until the battery is nearly depleted.


Is there anything to suggest the drone was flying backward other than the marks on the exterior of the drone? Flight logs?

I did puzzle over how the most serious chassis damage came to be at the rear of the drone, while the fragile camera assembly in the front escaped virtually unscathed. My understanding of RTH flight is that the drone flies nose-first at the pre-assigned RTH altitude, yet the crash damage seems to suggest otherwise.

With smart RTH evidently having commenced PRIOR to my hesitant attempt to cancel it, the inbound drone was soon back within stuttering video reception range during which the final few seconds of that video clip did, in fact, show the drone to be flying backward. It is entirely possible that the impact caused the drone to whip around in the horizontal plane and briefly point rearward before plunging to the ground.

For this fateful flight, I disabled all collision sensors in order to attain the 30 mph airspeed that was not possible on previous flights when I had left the collision sensors active. I now wonder whether the disabling of anti-collision sensors somehow deleted the 240-foot RTH altitude setting I have always used because in hindsight I now realize I did NOT crosscheck my RTH altitude prior to this flight.
 

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I conducted a flight test and to my utter amazement both the Mavic Pro Platinum and the new extra capacity battery I bought for it worked perfectly, flying a Litchi waypoint mission without a glitch. There is, however, one anomaly to report. The camera no longer remains in the usual 20 degrees downward tilt angle that I prefer for my flights unless I hold the thumb wheel in place constantly.

The instant I take my finger off the camera tilt wheel on my RC controller, the camera tilts upward to zero degrees. and remains there unless I hold the spring-loaded camera tilt wheel in place to keep the camera pointed down. I will run a camera calibration to see if I can cure this solitary flaw that emerged after that horrific crash, and will report my findings here just in case anyone else encounters a camera tilt issue either in the wake of a crash or out of the blue.

All told I am impressed at the resilience of this Mavic Pro Platinum. There is a horrendous crack in the rear panel of the drone, and right after the crash, I did note that one of the rear motors didn’t spin as freely as it should, though it did resume normalcy minutes later, with no evidence of lasting engine damage encountered during my post-crash test flight.
 
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I now wonder whether the disabling of anti-collision sensors somehow deleted the 240-foot RTH altitude setting
Not possible. Post your flight log if you want to know what really really happened instead of endless conjecture
 
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The high-tension power lines can be seen towards the lower edge of this picture as a faint tilted line running from left to right and intersecting the point of impact that truncated the return leg of the flight. For my previous flights along this route, I'd always been very careful to briefly increase the drone's cruise altitude from 160 feet AGL to 220 feet AGL so as to ensure there was adequate clearance above those power lines. At the same time, my RTH altitude has ALWAYS been set to 240 feet AGL, which makes this drone's nose dive into the power lines during what started out as a routine smart RTH, all the more baffling.

In conclusion, therefore, I cannot entirely rule out tic-tac UFOS as possible suspects to be held accountable for this anomalous departure from controlled flight, even though none were captured on my drone's camera during this strange incident. Investigations continue. More details at ten.
 

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The .txt log is not in the drone's memory, it's in your flight device. Go to the crash and flyaway sub forum here, the instructions on how to retrieve the log are in a sticky at the top of that forum.
 
The .txt log is not in the drone's memory, it's in your flight device. Go to the crash and flyaway sub forum here, the instructions on how to retrieve the log are in a sticky at the top of that forum.
Ah, I see. I've got some homework to do. I am genuinely curious as to what happened since I do intend to fly this route again at some point. Checking into flight log retrieval information now.
 
Never did tell me what a Tic-Tac is...
 
I stuck with it through that entire post but I don't understand that part. How can you say 'unpredictable RTH altitudes' when you had canceled RTH? And I don't think any DJI drone would inexplicably adopt an unprogrammed RTH altitude. My MPP never has, nor the Phantoms before that...

BTW, what's a tic-tac?
I was attempting to inject a little humor into my account of this mini calamity starring my Mavic Pro Platinum. My reference to tic-tac UFOs relates to the 2004 encounter off the coast of San Diego between several US Navy F18 Hornets and a number of wingless cylinder-shaped aerial vehicles that exhibited flight characteristics far beyond the performance specs of any known man-made aircraft. The subject of UFOs in general has fascinated me for years, hence my shameless inclusion of that intriguing topic here.


As for the lower-than-usual RTH altitude that sent my MPP into those power lines, I am still at a loss as to what exactly happened there. My small collection of DJI drones has covered well over 3,000 miles all flown under the fully autonomous control of Lithi, and this is the very first time that a crash has occurred during a waypoint mission. I am determined to learn what happened so it never occurs again with any of my drones.
 
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FYI, the camera is not spring-loaded, it's Servo-driven
It is the thumb wheel that I referred to as being spring loaded, and I found it very difficult trying to hold that wheel on the RC controller steady to compensate for the MPP camera's refusal to remain at its normally assigned minus 20-degrees during my post-crash flight test. There ensued a seesaw up-and-down tilt of the camera which renders all footage worthless until I can resolve the camera tilt issue.
 
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It is the thumb wheel that I referred to as being spring loaded
Ahhh, I misread... sorry.

Did you try to figure out how to submit your .txt log to phantomhelp.com and post a link here? When perused by one of the expert analysts here that log will tell you the entire exact story of what happened.
 
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Holy smokes I've been watching youtube videos about disassembling the Mavic 1 Pro and I was shocked to learn that the GPS unit is housed in that rear panel right where the most crash damage occurred. The fact that the GPS works perfectly despite that massive crack in the chassis makes this almost perfect post-crash flight performance all the more remarkable. I've decided to replace the upper shell which costs only $20 and requires a minimum of open-drone surgery skills.
 
Wow! 3 miles away? I would never try that unless in the flat desert.
I stick with the FAA rule of not flying beyond line of sight. I like to see where it is at all times. Guess I'm old school.....well, I am old!
 
Wow! 3 miles away? I would never try that unless in the flat desert.
I stick with the FAA rule of not flying beyond line of sight. I like to see where it is at all times. Guess I'm old school.....well, I am old!
I must add a disclaimer that I reside way out in the boonies of a Third World backwater where FAA rules are but a distant curiosity. In my neck of the woods, drones are a relatively new arrival on the scene and are typically flown ten feet above party revelers to film social occasions. Long sorties that extend miles from home are a rarity.

As far as I know, I am the only drone flier that uses Litchi to send drones on meandering ten-mile-round-trip fully autonomous waypoint missions while I relax indoors with the RC controller powered off, awaiting the preset alarm that alerts me to the drone's imminent arrival. I can name so many aspects of SoCal life that I sorely miss out here in the jungle, but having the FAA breathing down my neck is prominent among the things I don't miss here.

One last bit of encouraging news for me is that the upper shell of a Mavic Pro Platinum costs a very affordable $22 on eBay, and luckily for me, the visible crash damage to this drone is restricted to that upper shell which only requires six screws removed, and the GPS plug to disconnect, as the replacement procedure.

Just checked your profile, Greg, and noticed you are a retired airline pilot AND a military aviator. Man, you must have some stories to tell. The jumpseat in a Boeing 737 is the closest I've ever been to the flight deck of an airliner, but due to my lifelong fascination for aviation, I've spent hundreds of hours in the virtual skies of Microsoft Flight Simulator, battling ferocious crosswinds as I crab in along the ILS feather on short finals at the helm of PMDG's ultra-realistic 737 and 747 jets, and the venerable Level D 767-300ER offering from Level D Simulations.

Watching all three autopilots lit up for a full CAT III ILS autoland is a thing of beauty to behold. My home simulator cockpit is replete with a CH flight yoke, Saitek rudder pedals, and a Flight Link throttle quadrant with thrust reverse levers and buttons configurable for auto-thrust and TOGA.Ten Mile Round Trip Litchi Mission.png
 
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