Mavic Air behavior on top of buildings or cliffs (and water)?

[Q24H]

Greetings,

So I've flown my Mavic Air a few times and got some pretty nice views, just a few quick questions regarding expected behavior for some specific flying conditions:

1. Say I wanted to launch from the roof of a car garage, assuming its 100ft tall building. what would happen if I lift off and move off of the building footprint, would the sensor notice height being off and drop it 100ft to maintain height or stay in place?

2. For the same situation, what if I climb to the max 400ft while I'm hovering above the building, then move to the side, what happens then? Would I be able hovering at 500ft, above the build-in limit (in US)?

3. Different question for flying above water. I've not yet flown over water, but it seems pretty straightforward, but the Mavic Air is loaded with sensors and detection, are there anything that should be turned off (i.e. downward sensors) for best result?


I've flown dumber drones in the past so my flying abilities are decent, but sometimes being too smart is not a good thing and I'm trying to figure out what the drone would do before I attempt those things. Of course if anyone else have insights on when to turning off which smart features, please share your knowledge as well. Thanks!

 

[FatherXmas]

From my experience, the MA's altitude is always relative to where you took off. I've flown off a cliff and went down into the valley. The altitude indication on the MA went to negative numbers.

 

[beachcombing]

Greetings,

So I've flown my Mavic Air a few times and got some pretty nice views, just a few quick questions regarding expected behavior for some specific flying conditions:

1. Say I wanted to launch from the roof of a car garage, assuming its 100ft tall building. what would happen if I lift off and move off of the building footprint, would the sensor notice height being off and drop it 100ft to maintain height or stay in place?

2. For the same situation, what if I climb to the max 400ft while I'm hovering above the building, then move to the side, what happens then? Would I be able hovering at 500ft, above the build-in limit (in US)?

3. Different question for flying above water. I've not yet flown over water, but it seems pretty straightforward, but the Mavic Air is loaded with sensors and detection, are there anything that should be turned off (i.e. downward sensors) for best result?


I've flown dumber drones in the past so my flying abilities are decent, but sometimes being too smart is not a good thing and I'm trying to figure out what the drone would do before I attempt those things. Of course if anyone else have insights on when to turning off which smart features, please share your knowledge as well. Thanks!

1. No. The drone doesn't know how far it is about the ground underneath it. It only knows its altitude relative to the take off point. It would not change altitude.

2. The regulations/guidelines for maximum altitude are in relationship to the ground directly below the drone. If you fly to 400 feet above your take off point and then move over, your altitude above your take off point would not change. If you fly to 500 feet above the ground (note that the building height doesn't matter), you would be flying outside of the guidelines.

3. Some people would argue that you should turn the downward sensors off if you are flying low over water because the sensors could have a hard time with the water surface. Others would argue that it doesn't matter.

 

[Prismatic]

I have had my bird 650' (200m) below my feet while it was 50' above the treetops down in a box canyon in Utah. The flight path--off a 700' cliff'--put me instantly above the FAA guidance, before I could hope to descend.

But it seemed unlikely to me that any manned aircraft would fly that seriously winding canyon, 400 yards wide and 700' deep (600m X 200m). Kudos to the pilot who dares, but from the cliff-top, it'd have to be a super-secret stealthy chopper (probably black) to remain unheard ... but there are **** few cows to mutilate in that area.

 

[Q24H]

2. The regulations/guidelines for maximum altitude are in relationship to the ground directly below the drone. If you fly to 400 feet above your take off point and then move over, your altitude above your take off point would not change. If you fly to 500 feet above the ground (note that the building height doesn't matter), you would be flying outside of the guidelines.

Just a follow up on the 2nd point, so technically I would be able to climb to 400ft from top of the building (and 500ft relative to ground), I'd just not be following the guidelines if I did.

In any case thanks for the explanations, sounds like its not that troublesome at all, I just want to make sure I'd have total control if those situations

 

[Thwyllo]

Just a follow up on the 2nd point, so technically I would be able to climb to 400ft from top of the building (and 500ft relative to ground), I'd just not be following the guidelines if I did.

In any case thanks for the explanations, sounds like its not that troublesome at all, I just want to make sure I'd have total control if those situations

You're opening up a can of worms again there. It's guidance only with no teeth it would appear. Even if it were actually regulation, the 'guidance' effectively means there's a 400' bubble above and around any 'structure', for which read 'object in the landscape'.

 

[beachcombing]

Just a follow up on the 2nd point, so technically I would be able to climb to 400ft from top of the building (and 500ft relative to ground), I'd just not be following the guidelines if I did.

In any case thanks for the explanations, sounds like its not that troublesome at all, I just want to make sure I'd have total control if those situations

You could climb to 2000 feet from the ground if you wanted. Again, the building doesn't matter.

And again, you would be outside the guidelines if you did so.

 

[MrRobville]

I'd worry more about the compass than its sensors when flying near buildings. Large metal objects tend to cause a lot of interference when within close proximity. So be careful with that. But rule of thumb regarding sensors is: If you think they might go nuts, just turn them off. They are not essential.

But it seemed unlikely to me that any manned aircraft would fly that seriously winding canyon, 400 yards wide and 700' deep (600m X 200m). Kudos to the pilot who dares, but from the cliff-top, it'd have to be a super-secret stealthy chopper (probably black) to remain unheard ... but there are **** few cows to mutilate in that area.

Heh, just imagine some advanced pilot doing all kinds of difficult maneuvers around a canyon successfully, only to hit a drone and crash regardless. That would ruin his day somewhat.

 

[WayneMHK]

I have taken off from a hill above a lake and flown down and it makes the AC height read negative. Just an FYI, intelligent flight modes may require you to be at positive heights before they'll work. I ran into that when I wanted to start a POI circle around the lake's outlet tower and I was at negative height.

In the US, you are allowed a certain radius buffer around taller objects. For instance, if you are headed up to examine the top of a 500' building (meaning you could technically fly up to 900'), as long as you are within a certain radius (200', I think) you are allowed to go above the 400' AGL limit to get there. No other AC are allowed within that radius anyway (as long as the roof isn't a helipad), so you're OK.

 

[beachcombing]

In the US, you are allowed a certain radius buffer around taller objects. For instance, if you are headed up to examine the top of a 500' building (meaning you could technically fly up to 900'), as long as you are within a certain radius (200', I think) you are allowed to go above the 400' AGL limit to get there. No other AC are allowed within that radius anyway (as long as the roof isn't a helipad), so you're OK.

This doesn't apply to hobby/recreation flights.

 

[charlas]

In the US does it hard limit the altitude? I've flown 400M above ground and that's well beyond 400ft! in the UK the ceiling only applies to heavier drones than the Air. Although technically VLOS is lost, so......

But one of my videos (the drone footage one) where I fly up the field to the tower by the opencast mine my 'altitude' is 475M above takeoff height (1500ft ish) so there's certainly no hard limit on my drone (even in FCC mode)

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[lisadoc]

In the US, you are allowed a certain radius buffer around taller objects. For instance, if you are headed up to examine the top of a 500' building (meaning you could technically fly up to 900'), as long as you are within a certain radius (200', I think) you are allowed to go above the 400' AGL limit to get there.

Again, as others have noted, this is only a guideline for recreation fliers, not a rule or law.

And for commercial operators (under Part 107), the 400' limit is in all directions from a structure, so your 200' radius is incorrect.

 

[charlas]

The Mavic Air falls under the light drone rules in the UK, so VLOS is lost a long time before you break any 'real' laws. Sure it's the same in the USA. Just remember when flying over things/people to make sure you have the right permissions / insurance if it's needed and your being as safe as you can. Pretty much everything else is fair game.

 

[Thwyllo]

Again, as others have noted, this is only a guideline for recreation fliers, not a rule or law.

And for commercial operators (under Part 107), the 400' limit is in all directions from a structure, so your 200' radius is incorrect.

Correct. The "guidance" in the US is a 400ft deep 'bubble' around an object (described as a 'structure' but omits the phrase 'man-made' so common sense dictates this means any landscape feature).

 

[lisadoc]

(described as a 'structure' but omits the phrase 'man-made' so common sense dictates this means any landscape feature).

Maybe... as I described here:
How does law measure the height above ground?

 

[Quadratic]

Regarding flying above water - I know it was a problem on phantom 4's for a while. We lost a phantom 4 pro into a stream as a consequence. They may have addressed the problem since and with all the extra smarts. Problem is when flying less than 30' altitude the drone switches to visual sensors. The visual sensors struggle with featureless surfaces such as water (and water appears pitch black to IR sensors). Also, the moving surface problem. Some youtube videos demonstrating the drone "floating" downstream as it attempts to keep stationary relative to the moving water surface. If you stay more than 30' above water, then it should switch to using the barometer for altitude, which is not affected by water. So that would be my advice - stay more than 30' above water.

 

[dwallersv]

1. No. The drone doesn't know how far it is about the ground underneath it.

Well actually, it does. Up to about 30-40', the VPS sensors have a fairly accurate measure of the distance to any hard surface below.

However, there is a barometric altimeter, and GPS elevation data, all of which are used in combination with the VPS height to control flight. And abrupt dropout of the VPS height, while the baro and gps altitudes don't change and are consistent is properly treated by the flight controller as a change in topography rather than an actual change in altitude.

 

[Gr8fulTed]

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[beachcombing]

Well actually, it does. Up to about 30-40', the VPS sensors have a fairly accurate measure of the distance to any hard surface below.

However, there is a barometric altimeter, and GPS elevation data, all of which are used in combination with the VPS height to control flight. And abrupt dropout of the VPS height, while the baro and gps altitudes don't change and are consistent is properly treated by the flight controller as a change in topography rather than an actual change in altitude.

That's not what the OP is talking about, though.

 

[Drgnfli]

From my experience, the MA's altitude is always relative to where you took off. I've flown off a cliff and went down into the valley. The altitude indication on the MA went to negative numbers.

Yes, me too! I find that very disconcerting in the least. I fly in AZ with a bazillion steep valleys & deep canyons to explore. With all the techy abilities the MP has you'd think it could 'ping' your correct altitude or obtain it from GPS.