Mavic 4 Pro, RC Pro2, Fly App Question on landing

[Paul2660]

I am new to the Mavic 4 Pro, Fly app and PC Pro2 having flown it now for only couple of months. I am coming from 6 years of flying either a Mavic Pro, Mavic 2 Pro (5 years) and Phantom 4.

I have had flights with other drones where some fog rolled in during the flight. When this has occurred in the past with the Go 4 app, I can just drop back down through the clouds and land. I prefer to do this with the gimbal pointed straight down.

Today after a good flight, I realized the fog was moving in so I attempted to land the Mavic 4, and all went well until I hit the low fog (Gimbal was pointed straight down). As soon as I hit the fog I saw the drone shadow that the fly app puts on the screen as you get low to the ground. And immediately after that I received a message the drone was starting to land. Now it was still over 100 feet in the air, and I assumed that since the message gave me a 3 foot warning with the shadow of the drone (what the fly app puts on the screen as you get close to landing) the drone would try to land in the next 3 feet and shut off the props, even though the app showed I was still 100 feet off the ground.

I immediately cancelled this auto landing, went up out of the clouds and tried again, same thing. Note, I had already turned off obstacle avoidance for this flight.

The only way I could get the drone, not to start an auto landing 100 feet above the ground was to return the gimbal to the horizon, and then start the landing. Now I was able to drop through the fog and when I saw the ground, return the gimbal to straight down, and complete the landing.

I have never had this issue with earlier Mavic Pro, or Mavic 2 Pro and the Go app.

I was getting down to 20 percent of remaining battery, so I did panic a bit as I thought at first there was no way I could get the drone to land. I always do a manual landing and what was the most startling about this was as soon as I hit the fog, the drone started the auto landing process thinking it was now 3 feet above the ground. (looking straight down). Not sure why having the gimbal out to the horizon made a difference, but that was the only way I was able to get around the forced landing at 100 feet.

Any thoughts on this to avoid it in the future would be appreciated.

I am running the latest firmware both drone and controller.

Paul C

 

[Cafguy]

Your drone got confused by all the water that makes up those clouds and fog. The only thing you can really do is fly with caution in those situations....When you are flying in this enviroment, Can you see the Drone?...at all times.

 

[Meta4]

Today after a good flight, I attempted to land the Mavic 4, and all went well until I hit the clouds (Gimbal was pointed straight down).

What happened had nothing to do with the gimbal position.
The clouds you tried to descend through were dense enough for the downward facing sensors to perceive them as solid ground.
When you have the left stick pulled down and your drone "thinks" it is just a few feet above the ground, it is programmed to initiate autolanding.
The way to deal with this situation is to disable the downward facing sensors or better yet, avoid the practice of descending through cloud or fog.

I immediately cancelled this auto landing, went up out of the clouds and tried again, same thing. Note, I had already turned off obstacle avoidance for this flight.

The only way I could get the drone, not to start an auto landing 100 feet above the ground was to return the gimbal to the horizon, and then start the landing

Obstacle avoidance wasn't your issue.
It was the VPS (downward facing sensors) which is a different system.

Gimbal position had nothing to do with helping the drone to land.
That was just a coincidence and you must have been descending through thinner cloud that the VPS didn't recognise as solid.

If you post your flight data, that will confirm what I've explained.

 

[Paul2660]

Thanks for the replies. I will look into disabling the downward sensors in the future.

Paul

 

[MS Coast]

I agree that the VPS system "seeing" the fog or cloud was the issue.

Here's an interesting question about that sort of situation. What happens if you hold the left stick full back and allow the drone to enter the landing mode and descend into the fog/cloud?

I suspect that it would continue to descend through the fog/cloud at the normal landing descent rate. I'm assuming that the motor shutdown is initiated by some a VPS signal that the "ground" is near and, more importantly, the descent rate reached and stayed at zero. With the descent rate not going to zero, I'd expect the drone to continue descending through the fog. It may be that the drone would suspend the auto-landing once the VPS sensors became aware of the height over the ground, as long as the fog/cloud didn't extend to the ground. If the drone did not, the pilot could take control.

Any thoughts? Anyone know about the control logic for shutting off the motors on landing?

 

[PINEBARON]

Thanks for the replies. I will look into disabling the downward sensors in the future.

Paul

Thats what you'd also do if you plan to skim low over water, a lake or the ocean.

 

[Paul2660]

Ok. Where is a setting besides disabling the Obstacle avoidance setting that turns off VPS? I
had gone to safety- then lined down to obstacle avoidance and turned it off. I believe there are three settings. Off being the farthest to the right. Obstacle avoidance Icon was red on main screen. However the drone would not come through the fog. I can’t find a way to turn off the VPS sensors only. It’s not something I want to do often but in relation to this type of flight I would want to turn VPS off.

Thanks

 

[PINEBARON]

How about turning Sports Mode on while decending through the fog then turn it back to Normal when its decended below the fog.

 

[Paul2660]

That’s a good idea. Didn’t think about sports mode.


Paul

 

[YorksPhotos]

That’s a good idea. Didn’t think about sports mode.


Paul

Sport mode will not disable the bottom sensor, only horizontal. To disable all sensing go to Settings-Safety-Advanced Safety Setting, at the bottom turn off Vision Positioning and Obstacle Sensing. Read warning explaining what it does and press OK. When it is off while descending it will not stop before landing sequence, it will immediately land/crash. You can test this by hovering with sensing on and putting your hand under the bottom sensor, it will gain altitude. With the sensing off it will stay in place and hover. I do this when I hand catch.
This option will reset to on after powering off and on.

 

[wdfly]

you may want to look at the regulations regarding clouds, while it sounds cool, there are rules and those rules may get you in trouble.

 

[YorksPhotos]

I agree that the VPS system "seeing" the fog or cloud was the issue.

Here's an interesting question about that sort of situation. What happens if you hold the left stick full back and allow the drone to enter the landing mode and descend into the fog/cloud?



Any thoughts? Anyone know about the control logic for shutting off the motors on landing?

It would descend at landing speed until it detects no further negative elevation change, then it would shut the motors down

 

[SkyeHigh]

Any thoughts? Anyone know about the control logic for shutting off the motors on landing?

A ‘normal’ landing uses the downward VPS sensors in combination with the IR sensors. With VPS off the flight controller uses the IR sensors to triangulate the height above ground during landing for the last 25ft or so. IR can pass through light cloud and moisture. Because it passes through, and the ground is more than 25ft below, the flight controller won’t be receiving a ground proximity reading and will continue to allow the drone to descend through light cloud with the VPS sensors disabled.

 

[FLDave]

A ‘normal’ landing uses the downward VPS sensors in combination with the IR sensors. With VPS off the flight controller uses the IR sensors to triangulate the height above ground during landing for the last 25ft or so. IR can pass through light cloud and moisture. Because it passes through, and the ground is more than 25ft below, the flight controller won’t be receiving a ground proximity reading and will continue to allow the drone to descend through light cloud with the VPS sensors disabled.

When did IR beams start to triangulate distance between 2 points rather then echo response times to calculate distance? The IR beam must pass through any obstruction on the way out and also on the reflection return.