Beware low battery RTH

[miker570]

I had my first near disaster with my MA2 after many flights.

I normally always take off from the deck on my home, and RTH always brings it back home safely to nearly the exact spot it took off from. I have my RTH height set to about 100 feet to clear all the tall trees near my home.

The incident occurred after I returned from a 20 minute flight and my battery was about 25%. I had a friend taking photos and wanted to get a close shot of me and my MA2, so I walked down to where he was standing, flying my MA2 just next to me about 6 feet off the ground, directly under a very large tree. When I stopped to let him take the photo, the MA2 was just hovering above me and a few feet away. As I took my eye off the RC screen to look at my friends camera, the MA2 took off straight up crashing into tree branches. It tumbled around and crash landed upside down. I was a bit shocked and puzzled why it did this unexpected behavior. In replay of the crash, I see the MA2 decided to RTH because the battery was low, without any alert to cancel it. It tried to reach the 100 foot RTH height when it was just 6 feet off the ground and within 6 feet of the RC.

Fortunately it landed flat upside down and only the props had minor damage. The motors continued to run for several seconds while it was upside down on the ground, which was also very strange behavior.

I know now that you have to be very careful when the battery is low. There is no warning when it wants to go home.

 

[PhantomFandom]

I had my first near disaster with my MA2 after many flights.

I normally always take off from the deck on my home, and RTH always brings it back home safely to nearly the exact spot it took off from. I have my RTH height set to about 100 feet to clear all the tall trees near my home.

The incident occurred after I returned from a 20 minute flight and my battery was about 25%. I had a friend taking photos and wanted to get a close shot of me and my MA2, so I walked down to where he was standing, flying my MA2 just next to me about 6 feet off the ground, directly under a very large tree. When I stopped to let him take the photo, the MA2 was just hovering above me and a few feet away. As I took my eye off the RC screen to look at my friends camera, the MA2 took off straight up crashing into tree branches. It tumbled around and crash landed upside down. I was a bit shocked and puzzled why it did this unexpected behavior. In replay of the crash, I see the MA2 decided to RTH because the battery was low, without any alert to cancel it. It tried to reach the 100 foot RTH height when it was just 6 feet off the ground and within 6 feet of the RC.

Fortunately it landed flat upside down and only the props had minor damage. The motors continued to run for several seconds while it was upside down on the ground, which was also very strange behavior.

I know now that you have to be very careful when the battery is low. There is no warning when it wants to go home.

Perhaps there actually was a warning and you were just preoccupied with taking a picture?

Knowing the limits of the equipment and your flight environment is always important. Don't let the battery get low to start with. This forum is full of stories about batteries getting too low. If you always plan on being on the ground with 30% battery left, it will leave plenty of reserve for emergencies, and also leave the battery at a much better charge level for storage.

Generally it will make you a better pilot if you learn to fly the drone home by yourself instead of depending on RTH. It works...until it doesn't.

Also as to expected behavior, please read the section on RTH in the manual. It doesn't matter one bit that the drone was within 6 feet of the RC. The distance that determines the RTH is distance from the drone to the Home Point. The RC distance is irrelevant.

 

[miker570]

On replay there was a brief warning for the low battery RTH, but no option with the current Fly App to cancel it. The pilot should be given an option to land or RTH in this case.

I was just sharing my experience, so others might avoid the same result.

 

[Nonprophet]

IIRC, you choose the low battery options in the Fly App--at least up until the default emergency landing procedure at 10% battery. Also, you can avoid a problem like this by changing the Home Point once you moved away from the original take off point.

 

[miker570]

Circumstances can change after take off. You can see in the photo my HP is 2 feet away. The App should give you a choice of the action to take, if it can’t figure it out it should just land. Flying 100 feet blindly straight up with no top sensors was the wrong choice for automated flight. The older versions of the Fly app for the MM use to give you a prompt of the actions to take.

If the battery is low and it needs to land immediately when it’s only 3 feet off the ground, and only 2 feet from the HP, why fly blindly to 100 feet RTH? Yes I know the answer, because that’s how it was configured before takeoff, but software can be improved to adapt the automated flight to the current situation.

 

[Nonprophet]

Circumstances can change after take off. You can see in the photo my HP is 2 feet away. The App should give you a choice of the action to take, if it can’t figure it out it should just land. Flying 100 feet blindly straight up with no top sensors was the wrong choice for automated flight. The older versions of the Fly app for the MM use to give you a prompt of the actions to take.

If the battery is low and it needs to land immediately when it’s only 3 feet off the ground, and only 2 feet from the HP, why fly blindly to 100 feet RTH? Yes I know the answer, because that’s how it was configured before takeoff, but software can be improved to adapt the automated flight to the current situation.

It didn't "fly blindly" to 100' RTH, it did exactly what you had told it to do via the settings you flew with. Not sure why you couldn't override the RTH, perhaos because it was below 15% battery and RTH was auto-triggered. Goes without saying that flying below 20% battery level is VERY risky no matter where you are flying. While adaptive/AI flight might sound appealing, in the end it's up to the operator to set the correct flight parameters and adapt them mid-flight as needed. These are basically flying computers--they can only do what we tell them to do.

 

[miker570]

It didn't "fly blindly" to 100' RTH, it did exactly what you had told it to do via the settings you flew with. Not sure why you couldn't override the RTH, perhaos because it was below 15% battery and RTH was auto-triggered. Goes without saying that flying below 20% battery level is VERY risky no matter where you are flying. While adaptive/AI flight might sound appealing, in the end it's up to the operator to set the correct flight parameters and adapt them mid-flight as needed. These are basically flying computers--they can only do what we tell them to do.

There is no specific setting for actions to take for low battery. There is one for lost signal.

My point is that it should prompt the pilot what to do in this case, and the current version of the Fly app does not ask, it will attempt to return to the home point which is only 2 feet away by going straight up 100 feet the over 2 feet and down again.. not the smartest route to the home point.

 

[Nonprophet]

"Low Battery RTH Low Battery RTH is triggered when the Intelligent Flight Battery is depleted to the point that the safe return of the aircraft may be affected. Return home or land the aircraft immediately when prompted. DJI Fly displays a warning when the battery level is low. The aircraft will automatically return to the Home Point if no action is taken after a 10 second countdown. The user can cancel RTH by pressing the RTH button or Flight Pause button on the remote controller. If RTH is cancelled following a low battery level warning, the Intelligent Flight Battery may not have enough power for the aircraft to land safely, which may lead to the aircraft crashing or being lost."

https://dl.djicdn.com/downloads/Mavic_Air_2/20200519/Mavic_Air_2_User_Manual_v1.0_en_.pdf

 

[miker570]

There was no count down prompt issued with the 1.1.5 fly app.

The software does not do what the documentation states.

 

[Nonprophet]

There was no count down prompt issued with the 1.1.5 fly app.

The software does not do what the documentation states.

It's worked for me. Perhaps you were distracted and missed the RTH countdown? Did you try to cancel the RTH as outlined above? I have done this several times and never had an issue......

 

[miker570]

I just tested the low battery RTH and it worked as documented. It did not attempt to climb to 100 feet this time, it flew directly back. There was an audible voice stating the battery was low and the count down appeared.
Once the count down ended to came directly back to the HP.

This did not happen in the incident I described above. I would have heard the voice if I missed the message on the screen. Neither happened in that incident.

Not sure why it behaved differently this time.

 

[PhantomFandom]

Flying 100 feet blindly straight up with no top sensors was the wrong choice for automated flight. The older versions of the Fly app for the MM use to give you a prompt of the actions to take.

It only does what is outlined in the manual. It gives you a change to cancel.

Good piloting means preparing for these situations and not leaving everything up to automation. The best course of action is to never get into the situation to start with.

If the battery is low and it needs to land immediately when it’s only 3 feet off the ground, and only 2 feet from the HP, why fly blindly to 100 feet RTH? Yes I know the answer, because that’s how it was configured before takeoff, but software can be improved to adapt the automated flight to the current situation.

Perhaps if you supply the flight logs, it will tell everyone (including yourself) what actually happened.

There was no count down prompt issued with the 1.1.5 fly app.

The software does not do what the documentation states.

Initially you also said that there was no warning on the screen. It seems that you were distracted with other things when this incident occurred.

 

[DavidT_ NZ]

I had my first near disaster with my MA2 after many flights.

I normally always take off from the deck on my home, and RTH always brings it back home safely to nearly the exact spot it took off from. I have my RTH height set to about 100 feet to clear all the tall trees near my home.

The incident occurred after I returned from a 20 minute flight and my battery was about 25%. I had a friend taking photos and wanted to get a close shot of me and my MA2, so I walked down to where he was standing, flying my MA2 just next to me about 6 feet off the ground, directly under a very large tree. When I stopped to let him take the photo, the MA2 was just hovering above me and a few feet away. As I took my eye off the RC screen to look at my friends camera, the MA2 took off straight up crashing into tree branches. It tumbled around and crash landed upside down. I was a bit shocked and puzzled why it did this unexpected behavior. In replay of the crash, I see the MA2 decided to RTH because the battery was low, without any alert to cancel it. It tried to reach the 100 foot RTH height when it was just 6 feet off the ground and within 6 feet of the RC.

Fortunately it landed flat upside down and only the props had minor damage. The motors continued to run for several seconds while it was upside down on the ground, which was also very strange behavior.

I know now that you have to be very careful when the battery is low. There is no warning when it wants to go home.

I fly off a deck also and enjoy watching the auto RTH unfold with my Air 2. It is good to check its performance, also. But I sometimes flip to Tripod Mode and control the pad landing. Also, turn the gimbal down with a Fn#1 preset and crosshair on, with LED on using Fn#2, and bring it home on screen. Controls are slowed down nicely. You get the best of both worlds, then! And flying up into the tree was just following your preset. That height is great but you have to be in clear air to activate it! Personally, if the battery gets down to 30%, I would be looking for clear air; much below that and I would be ready to RTH - or get set to put down in a known recoverable location. Batteries can be fickle. Never trust them completely. ??

 

[hiflyer201]

Batteries can be fickle. Never trust them completely. ??

Brother..you got that right!

 

[amstel78]

I can't seem to find the RTH battery threshold indicator in the app. Does the MA2 set that autonomously depending on current flight characteristics and distance traveled from home point?

 

[DanMan32]

Yep. It would have to. Your point of no return would be at a much higher SoC at 5000ft than if you were only 200ft.

You can however set when it warns of a low battery, but that's just a warning.

With the P3, you could also set the critical battery threshold with a minimum of 10%, but that too is dynamic depending on altitude. Usually 10% though.

If DJI hadn't gotten rid of the battery status timeline in Fly that exists in Go, many would understand it better.

 

[DanMan32]

You also must have been way further than a few feet from HP, since RTH will instead land if within 5m or about 15ft. There's also a range that it will RTH but at current altitude. Latest FW has that at 50m from HP. I believe it was 20m.

Unless the above only applies to manual RTH.

 

[amstel78]

Yep. It would have to. Your point of no return would be at a much higher SoC at 5000ft than if you were only 200ft.

You can however set when it warns of a low battery, but that's just a warning.

With the P3, you could also set the critical battery threshold with a minimum of 10%, but that too is dynamic depending on altitude. Usually 10% though.

If DJI hadn't gotten rid of the battery status timeline in Fly that exists in Go, many would understand it better.

Thanks. Where do you set the low battery warning? I've looked at every menu and don't see anything regarding battery warnings. I'm using Fly 1.2.2 and firmware 511.