Here's an interesting RTH scenario and I'm not sure what would happen

[finity]

Let's say that I'm flying VLOS but past the other side of a tall large object (hill, mountain, etc). And for whatever reason I get into a RTH situation (battery low, interference, controller issue, etc).

I know that the drone will ascend or descend as needed to get to the RTH altitude and then execute the RTH flight.

If the large object is now between home and the drone what will the drone do? Will it try to fly around the object while trying to get back to home? Or will it try to go over the object even if the object is taller than the RTH altitude (but less than the altitude limit set in the controller)? or will it just give up and hover until the battery dies? I'm assuming the OA will still work and it won't just blindly fly into the side of the mountain.

What got me thinking of this scenario was on my current trip to Colorado I had pulled over onto a pull off and flew my drone around the mountains there. I had my altitude limit set pretty high so I could go over the mountains (but staying within 400'AGL of course). But since I didn't think about resetting my RTH altitude that got me into a situation where the RTH altitude was lower than the peak of the mountain between me and the drone.

Heck, I bet that my RTH altitude was below ground level at several points as I was flying around the mountains. So another question would be what happens if the drone tries to go to the RTH altitude but can't get there because the ground is in the way?

Here is a ridiculously quick and crude illustration:



Obviously everything worked out OK but I got to thinking about it later and I realized I could have gotten myself into a bit of a pickle if something went screwy.

 

[Yorkshire_Pud]

I know that the drone will ascend or descend as needed to get to the RTH altitude and then execute the RTH flight.

That depends on the model of drone, that I have read of, only one/certain 'new' model/s will descend to RTH height.
I think, settings and distance depending, some new models will not climb to RTH height.

This is why I think it is absolutely essential to thoroughly dissect and study the RTH behaviours especially with the newer models and then experiment with them in a safe place.

That said, I have yet to read of a drone that will break the max height setting ( unless it is malfunctioning ) but I think, note think, OA etc. could force a drone through the RTH height.

I also think not resetting the RTH and max height ceilings to suit the flight is a grave error, excessively high and you waste power and risk putting the drone up into wind, too low and it may get stuck.

 

[finity]

That depends on the model of drone

It's a Mini 3 Pro.

Sorry I should have been more specific.

 

[Sir Maxwell Greene]

I had a Mavic 2 Pro a while back, I did not realize at the time the RTH height was literally ~3 meters lower than the top of a building. I lost connection, feed etc on the wrong side.... I found the drone in pieces later that day. From the video recording it hovered against the glass building till the battery died then shut off. Expensive lesson learnt...

Not sure about the newer drones, but rather too high than too low is my margin of error now.

 

[mavic3usa]

I think you probably already know this but just to keep it clear, the drone doesn't have a set RTH absolute altitude rather it has a number which indicates how high above the take off point to "ascend" before returning but yes it is still the "altitude." The drone never descends to that level as part of the RTH function. This is with traditional RTH drones not the newer drones with smart RTH.

You said "I had my altitude limit set pretty high so I could go over the mountains (but staying within 400'AGL of course)." I never understood why this is a thing, why not set it to unlimited or no limit? When flying up to a 2000 ft mountain, this setting cannot keep you within 400 ft AGL and it's not meant to. I believe it is meant for something else. In your drawing, if that mountain has a peak of 2000 feet (or 2000 feet higher than your take off point) then you need to set your RTH to 2100 feet. Isn't that how it works? The drone will rise to 2100 feet above the take off point and then try to return....not add 2100 feet to it's current height, correct?

Otherwise, you will have crashes:

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Or something like this when similar to what is commonly experienced when you are very near your take off point and you lose connection:

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[Yorkshire_Pud]

I had a Mavic 2 Pro a while back, I did not realize at the time the RTH height was literally ~3 meters lower than the top of a building. I lost connection, feed etc on the wrong side.... I found the drone in pieces later that day. From the video recording it hovered against the glass building till the battery died then shut off. Expensive lesson learnt...

Not sure about the newer drones, but rather too high than too low is my margin of error now.

I suspect other things came into play in your case.
Once it got stuck I think "forced landing" would have eventually been activated, the percentage at which that happens depends on the drone's height.
Without input from the controller the drone would then descend in a controlled manner until it either caught something on the way down or landed or decided that the landing spot was not suitable.
If the latter happens the drone will hover and await authorisation to land.
This applies even if it reaches 10% and less i.e. the critical battery level phase.
I just tested this and let the drone hover until 7%.
What firmware version was the drone using and do you still have the log for the flight?

 

[Yorkshire_Pud]

why not set it to unlimited or no limit?

Because it leaves the door open to breaking the 400ft ceiling over the home point etc. etc. Obviously, since you can fly over descending ground and quickly break 400ft AGL, it's a somewhat flawed safety feature but it is a safety feature none the less.

It also leaves the door wide open to accidentally setting an illegal and risky ( wind if nothing else ) RTH height. Under normal circumstances the set RTH height can not be higher than the set maximum height.
With the Fly App which has those 'blooming' slider adjustments for limits which are all on one 'page' that is easily done, I can vouch for that.
Additionally, for most DJI drones, there is a 500m hard ceiling in the firmware I have yet to read of an unhacked DJI drone with an "unlimited" height setting or a "no-limit" height setting.
Yes I know firmware can, in some cases, be hacked to remove the 500m hard ceiling and that at least one drone (Mavic 3 ?) can be given a 1km ceiling.

 

[mavic3usa]

Because it leaves the door open to breaking the 400ft ceiling over the home point etc. etc. Obviously, since you can fly over descending ground and quickly break 400ft AGL, it's a somewhat flawed safety feature but it is a safety feature none the less.

Fine but that was my point, it's pretty useless. Instead it is likely more effective when you are flying in restricted airspace where the area in the grids are more confined and let's say you are in a 200 feet grid, you want to set your max height to 200 so you don't exceed the limit. Because 50 and 100 are so low, you reach them much sooner which makes it more likely you will exceed if you are not watching closely. Our drones are fast but not so fast that they blow thru 400 feet without you realizing.

We all fly drones weekly if not daily. Do we really need a hard stop at 400 feet? I rarely find myself even flirting with 300 or 400 feet, so I understand others are different and it's just me but do you set your max distance so you don't inadvertently go BVLOS? The PIC should keep control of his drone and that means both within VLOS and max height. Yet, I keep my max distance to unlimited, too.

If you routinely set your max height to 120m then no wonder DJI has plans to hardcode that limit into the Mini drones. Like others have mentioned, I believe it is the pilot's responsibility, not the sw.

Also the DJI FPV doesn't have a 120m/400 feet setting. All the settings are presets and one of them is below 400 feet and the other is above 400 feet; you cannot choose 120m. Because the FPV is super fast and agile, you could quickly find yourself shooting above that limit because you know....orientation and speed, etc.

 

[Yorkshire_Pud]

t, it's pretty useless.

we will have to disagree, I think it is sensible even if it doesn't work 'properly'.

With regards to within restricted airspace, never done that, never will so no idea.

I had a much more detailed response typed but I will abbreviate it because we are getting away from the OP's subject matter.

I think government's compelling manufactures to introduce hard limits on both range and height is the way things will go. If people insist on breaking the laws and posting there doing so all over social media then forcing the manufactures to introduce those limits is a very easy way for government to enforce the law.
I think the social media users who post videos of flights to 500ft+ AGL and x miles distance do the law abiding fliers a severe disservice.

 

[finity]

The drone never descends to that level as part of the RTH function.

Thanks. that was the part I was missing. I thought it would always go to that height and ascend or descend as needed.

It's good to know that as long as I'm high enough it will just fly home.

And I believe that second to last video kind of answered the question I had.

On RTH as it flew toward the building the drone OA kicked in, the drone ascended to above the top of the building and it continued the RTH.

Am I safe to assume that's the behavior of all the newer drones?

I never understood why this is a thing, why not set it to unlimited or no limit?

it's mostly so I don't screw up. Kind of a backup plan.

the area where I mostly fly is fairly flat (northeast Indiana) so setting it right below 400 ft doesn't really limit me in any way.

I know past 400' there is a warning that pops up on the controller warning me that I may be in violation of laws but by then it's too late. But before my trip I didn't know about that pop up since I never went above 400' above take off since I had my limit set to 395'. It actually surprised me when it popped up.

I think you probably already know this

Sure do but thanks for clarifying for others who might not.

The drone will rise to 2100 feet above the take off point and then try to return....not add 2100 feet to it's current height, correct?

I'm almost 100% sure that you are correct.

 

[Ken-Mav-Mtl]

I have attached a recent "Range Test" video of the Mini 4 Pro by someone in Canada who says that there is no legal limit to the range for a sub-250 gram drone.
According to Transport Canada's web page on sub-250 gram drones, found at:

Find your category of drone operation

Categories of operations for drones

tc.canada.ca

Micro-drones (under 250 g)​

Micro-drones are drones weighing less than 250 g. The weight of the remote control is not factored in to the weight calculation, but the weight of anything attached or carried, such as optional cameras or safety cages, will be considered part of the weight.

Pilots of micro drones don’t need to register their drone or get a drone pilot certificate to fly them. Pilots of micro drones are not bound by the same requirements as other drones. However, you must not operate your drone in a reckless or negligent manner as to endanger or be likely to endanger aviation safety or the safety of anyone.

While there are no prescriptive elements of the regulations, there is an expectation that the pilot of a micro drone to use good judgment, identify potential hazards, and take all necessary steps to avoid any risks associated with flying your drone.

As a good practice, you should always:

• maintain the drone in direct line of sight
• do not fly your drone above 400 feet in the air
• keep a safe lateral distance between your drone and any bystanders
• stay far away from aerodromes, airport, heliport and waterdrome
• avoid flying near critical infrastructure (utilities, communication towers, bridges, etc.)
• stay clear of aircrafts, at all time
• do a pre-flight inspection of your drone
• keep the drone close enough to maintain the connection with the remote controller
• avoid special aviation or advertised events

Follow these guidelines to avoid flying in a negligent or reckless manner and being subject to fines. Enjoy a safe flight and minimize the risk of incidents. Remember: if you feel that your flight is risky, don’t do it.

Drones are considered aircraft under the Aeronautics Act and Canadian Aviation Regulations and are therefore prohibited to enter the following zones without the proper authorizations:

• Class F Special Use Restricted Airspace
• Over a forest fire area or any area located within five nautical miles of a forest fire area, or in any airspace for which a NOTAM for Forest Fire Aircraft Operating Restrictions has been emitted
• Zones where a 5.1 of the Aeronautics Act restrict the use of airspace to all aircraft has been emitted

++++++++++++++++++++++++++++++
(I have highlighted the relevant provisions in italics for the viewer to take notice)

As you can see from the above-posted regulations from Transport Canada, the above requirements are deemed to be "good practices", not hard legal limits.

If a Mini 4 Pro pilot does a BVLOS range check in a wilderness area where there is very little possibility of other aircraft, there is apparently no violation of the rules.
The same could not be said if flying in a densely populated area where the likelihood of an incident is much greater.

I look forward to any comments on this issue of BVLOS with sub-250 gram drones in Canadian airspace.

 

[Zbip57]

I have attached a recent "Range Test" video of the Mini 4 Pro by someone in Canada who says that there is no legal limit to the range for a sub-250 gram drone.

You didn't attach the video link?

This is rather off-topic and unrelated to the discussion topic of RTH behaviour, but you are correct. Other than specific flight restriction zones applicable to all aircraft (including sub-250g!), like over our Parliament Buildings, Niagara Falls, National Parks, active fire-fighting areas, etc, the ONLY regulation for sub-250g drones is CARS 900.06, the "Don't be Stupid" rule.

Here's a link to the index of all the (CARS) Canadian Aviation Regulations.

Start with a quick look at 101.01 - Interpretation, the definitions, which include this critical one:

"small remotely piloted aircraft means a remotely piloted aircraft that has a maximum take-off weight of at least 250 g (0.55 pounds) but not more than 25 kg (55 pounds); (petit aéronef télépiloté)"​

Then jump all the way down the index to the 900 series regulations dealing with Remotely Piloted Aircraft Systems (RPAS). 900.06 - Reckless or Negligent Operation, applies to all RPAS, including sub-250g. But everything else from there on down applies to Small remotely piloted aircraft, (i.e. NOT applicable to sub-250g).

Ergo, there is no Cdn regulatory limit to the range of a sub-250g drone, provided you still comply with CARS 900.06, which says,

"900.06 No person shall operate a remotely piloted aircraft system in such a reckless or negligent manner as to endanger or be likely to endanger aviation safety or the safety of any person."​

 

[Zbip57]

I look forward to any comments on this issue of BVLOS with sub-250 gram drones in Canadian airspace.

There's another significant and interesting difference between the Cdn vs FAA regulations concerning VLOS and Visual Observers.

The FAA insists the visual observer must be co-located with the pilot. That's never made any sense to me. If the pilot can't see the drone when it flies out of visual sight behind a tree, behind a hill, or behind a building, what's the point of having a visual observer standing right beside you if he can't see the drone either?

The Canadian CARS 901.11 requires the pilot of a small RPA (250g-25kg) or a visual observer to have the drone in sight at all times, but doesn't require them to be co-located.

CARS 901.20 then specifies the following;

"901.20 (1) No pilot shall operate a remotely piloted aircraft system if visual observers [note plural] are used to assist the pilot in the provision of detect and avoid functions unless reliable and timely communication is maintained between the pilot and each visual observer during the operation."​

That implies that you can have multiple visual observers strung out in a daisy chain as long as always at least one observer has the drone in sight and is in reliable communication via radio with the pilot.

 

[Ken-Mav-Mtl]

There's another significant and interesting difference between the Cdn vs FAA regulations concerning VLOS and Visual Observers.

The FAA insists the visual observer must be co-located with the pilot. That's never made any sense to me. If the pilot can't see the drone when it flies out of visual sight behind a tree, behind a hill, or behind a building, what's the point of having a visual observer standing right beside you if he can't see the drone either?

The Canadian CARS 901.11 requires the pilot of a small RPA (250g-25kg) or a visual observer to have the drone in sight at all times, but doesn't require them to be co-located.

CARS 901.20 then specifies the following;

"901.20 (1) No pilot shall operate a remotely piloted aircraft system if visual observers [note plural] are used to assist the pilot in the provision of detect and avoid functions unless reliable and timely communication is maintained between the pilot and each visual observer during the operation."​

That implies that you can have multiple visual observers strung out in a daisy chain as long as always at least one observer has the drone in sight and is in reliable communication via radio with the pilot.

I have attempted to attach the file a 2nd time. It's a VLC media file 152 MB. But it won't attach. Where can I send it to be viewed?

 

[Ken-Mav-Mtl]

I found the video clip by Shawn from Air Photography, at this link:

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[Zbip57]

I found the video clip...

I think those kinds of "range tests" are pointless and stupid.

He claims it's not dangerous, as in there's nothing out there. And, in case of failure, the worst that can happen is he loses his drone into the water. But why risk that?

Rather than sending the drone straight out over the lake, wouldn't it make more sense to fly it along the shoreline? That way, if he discovers there's not enough battery remaining to bring it home, he could at least set it down somewhere on land to retrieve it later.

 

[Mrprop365]

Because it leaves the door open to breaking the 400ft ceiling over the home point etc. etc. Obviously, since you can fly over descending ground and quickly break 400ft AGL, it's a somewhat flawed safety feature but it is a safety feature none the less.

if its avoiding an obstacle at 400ft then you arent 400ft agl anymore so its not a legal problem.

 

[mavic3usa]

if its avoiding an obstacle at 400ft then you arent 400ft agl anymore so its not a legal problem.

Unfortunately that isn't necessarily true. 400 feet AGL means above the ground level and it doesn't mean above the building level or above the obstacle. If your drone has to ascend 20 feet go over the top of a 400 foot building, I'm ok with rising to 420 feet AGL temporarily; however, the law may not necessarily agree with you. This is always true for recreational pilots and sometimes true for all other pilots, for example part 107 pilots in non-restricted airspace.

 

[DARKSeifer]

Always set the RTH a few meters higher than the highest obstacle that you think is going to be between you and your drone, and it will always come back no matter what.

For example, if I want to go over a mountain that is 250 meters high and then probably descend a bit over the top of the mountain (so the chances that I loose connection are high), I'd set the RTH to 300 meters, that way it will climb, and I'll regain connection, so I could cancel RTH and fly normally again.

If you have advanced RTH enabled, it will ignore your RTH altitude preset and use its own depending on the situation, so it will be prone to crash. Always use the standard RTH, not the advanced. And also, always set your OA to brake, not bypass. Brake will never make your drone crash, bypass can crash your drone, will make the flight trajectory unpredictable and will affect flying performance even at high altitude.

Whenever your drone loses connection, before climbing, it moves backwards 50 meters to try to regain connection, if it doesn't regain connection, then it engages RTH. That also could lead to a crash in certain situations.

 

[Yorkshire_Pud]

if its avoiding an obstacle at 400ft then you arent 400ft agl anymore so its not a legal problem.

Uum wind turbines, radio & TV masts, buildings, all can reach 400ft+ AGL. So do some cliffs and sea stacks, Old Man of Hoy comes to mind.

What does OA have to do with the section of my post that you quoted?