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Mini RTH - altitude question
487 22 2019-12-22
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dougjeff
lvl.2
Flight distance : 265033 ft
Canada
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I was wondering if anyone can describe how the MM RTH altitude works when the aircarft has been flying up the side of a mountain during its flight.

Scenario
-Launch at 100m above sea level at the base of a mountain
-Fly at 20-30m above ground level climbing about 300m and travelling horizontally about 900m

If I initiate RTH at this point and my RTH altitude is set to 50m, what will happen?
1) Climb an additional 50m then start towards the home point.
2) Descend into the ground attempting to reach an altitude of 50m above the home point

If you have tried this I would be grateful to hear your experience.

Thanks
Doug
2019-12-22
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Donsir_LTU
lvl.4
Flight distance : 325079 ft
Republic of Lithuania
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Very interesting question. Lets think...Technicaly MM altitude will be at about 300m and if you press RTH, the drone's first action is to reach 50m altitude. So I think he will use option 2. I will try to test it on weekend. Sorry for my english
2019-12-22
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Bjord
lvl.3
Flight distance : 1861880 ft
Canada
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It's neither, for two reasons. First, the drone only cares about its altitude relative to the initial home point. It doesn't care that it's 30m above ground level or 400m above sea level. Second, the drone will only ascend to the RTH altitude, never descend. If the drone is higher than the RTH altitude when RTH is initiated, it will stay at its current altitude as it begins the trip back.

In the specific circumstance that you described, the drone will maintain an altitude of 300m (relative to the home point) or 400m above sea level as it returns home.
2019-12-22
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Geebax
Captain
Australia
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When you initiate RTH, the aircraft will only climb if it is below the RTH level you set. If you are already at or above the RTH level, it will neither climb nor descend, it will simply fly home at the level it is currently at. BTW, the aircraft has no idea what sea level is, it simply regards the altitude you took off at as zero.
2019-12-22
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hallmark007
Captain
Flight distance : 4797602 ft
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Ireland
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The mini will always use the height ATO at take off so if you flying up the side of the mountain you hit Rth or failsafe Rth mini if above it ATO of 50m it will stay at it present height and Rth , you can while in Rth lower the altitude control orientation and speed but not direction .
2019-12-22
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dougjeff
lvl.2
Flight distance : 265033 ft
Canada
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Excellent feedback - Thanks to all.

Hope to find some good weather to try a mountain flight. Should be about 1.5km with around 300m of elevation gain.
2019-12-23
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djiuser_oGgD2R91705d
lvl.1

Australia
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dougjeff Posted at 12-23 23:09
Excellent feedback - Thanks to all.

Hope to find some good weather to try a mountain flight. Should be about 1.5km with around 300m of elevation gain.

This is puzzling for instance.

I take off with RTH at 50mtrs, then if i am at 200mtrs on side of mountain or hill it may lower its self. This would be a very intresting test case video, but hey I aint trying it first
2019-12-24
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Crummett
lvl.4
Flight distance : 29131 ft
United Kingdom
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it would never descend into the ground as it would detect the surface.
2019-12-24
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Ice_2k
Second Officer
Flight distance : 160007 ft
Romania
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djiuser_oGgD2R91705d Posted at 12-24 01:14
This is puzzling for instance.

I take off with RTH at 50mtrs, then if i am at 200mtrs on side of mountain or hill it may lower its self. This would be a very intresting test case video, but hey I aint trying it first

It will *never* descend before reaching the home point. Whatever altitude it's at when RTH is initiated, if that altitude is higher than the RTH altitude, it will maintain its current altitude. Think of the "RTH Altitude" settings in terms of "Minimum RTH Altitude", that's more accurate.
2019-12-24
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djiuser_fdoHvWj2O1EN
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Haiti
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Bjord Posted at 2019-12-22 23:42
It's neither, for two reasons. First, the drone only cares about its altitude relative to the initial home point. It doesn't care that it's 30m above ground level or 400m above sea level. Second, the drone will only ascend to the RTH altitude, never descend. If the drone is higher than the RTH altitude when RTH is initiated, it will stay at its current altitude as it begins the trip back.

In the specific circumstance that you described, the drone will maintain an altitude of 300m (relative to the home point) or 400m above sea level as it returns home.

Good morning, can I then safely assume that if my home point is on TOP of the mountain and I set up my RTH altitude at 100 m and fly DOWN the mountain (say 100 m down) and hit my RTH, my MM drone will ascend 200 m (100 + 100) and fly back to the home point ?
1-12 08:46
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TDZHDTV
lvl.4
Flight distance : 1469495 ft
United Kingdom
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djiuser_fdoHvWj2O1EN Posted at 1-12 08:46
Good morning, can I then safely assume that if my home point is on TOP of the mountain and I set up my RTH altitude at 100 m and fly DOWN the mountain (say 100 m down) and hit my RTH, my MM drone will ascend 200 m (100 + 100) and fly back to the home point ?

This is correct
1-12 08:58
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jonny007
Second Officer
Germany
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100 Points for the answer ;-) But keep aware, in most countries there is a limit of height. In your case it would mean, that you're breaking the law, better said the RTH of the drone lol.
1-12 09:02
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Dirty Bird
Captain
Flight distance : 6752684 ft
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United States
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The bird considers 0 altitude the point from which it recorded the Home point.  If you have RTH set for 50', & flew 300' up the side of a mountain, 50' is 250' below the bird's current altitude.  Thus, if RTH engages, it will not climb further.  You would have to manually factor this in & calculate the required clearance altitude in advance.

The bird never descends to RTH altitude.  If it is below, it will climb before heading home.  If it is at or above RTH altitude, it returns home at the current height.
1-12 10:40
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dougjeff
lvl.2
Flight distance : 265033 ft
Canada
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jonny007 Posted at 1-12 09:02
100 Points for the answer ;-) But keep aware, in most countries there is a limit of height. In your case it would mean, that you're breaking the law, better said the RTH of the drone lol.

You are correct that in most countries the altitude limit applies. Fortunately in Canada the Mini is exempt from that regulation!

In practice I think I would try to regain control in a RTH like this to try and follow the mountainside down to the home position. That would avoid breaking the 400' AGL limit.
1-12 10:54
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jonny007
Second Officer
Germany
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dougjeff Posted at 1-12 10:54
You are correct that in most countries the altitude limit applies. Fortunately in Canada the Mini is exempt from that regulation!

In practice I think I would try to regain control in a RTH like this to try and follow the mountainside down to the home position. That would avoid breaking the 400' AGL limit.

Really ? No height limit in Canada ? In Germany we have 100 meters, probably from July with the new EU regulation 120 meters. BUT ... it was more of a joke that you would break the law. We recently had a similar discussion about flying over a cliff. Let's say a 800 meter cliff and you shouldn't fly a single centimeter over the cliff, but I said I would probably do it anyway ... at least 2 -3 centimeters ;-)
1-12 11:24
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dougjeff
lvl.2
Flight distance : 265033 ft
Canada
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jonny007 Posted at 1-12 11:24
Really ? No height limit in Canada ? In Germany we have 100 meters, probably from July with the new EU regulation 120 meters. BUT ... it was more of a joke that you would break the law. We recently had a similar discussion about flying over a cliff. Let's say a 800 meter cliff and you shouldn't fly a single centimeter over the cliff, but I said I would probably do it anyway ... at least 2 -3 centimeters ;-)

In Canada we have a 400'AGL (~120m) limit in most cases. However the MM is under 250g, so this rule does not apply to it. You can also exceed this limit if you are granted a Special Flight Operation Certificate (SFOC)
1-12 12:35
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jonny007
Second Officer
Germany
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dougjeff Posted at 1-12 12:35
In Canada we have a 400'AGL (~120m) limit in most cases. However the MM is under 250g, so this rule does not apply to it. You can also exceed this limit if you are granted a Special Flight Operation Certificate (SFOC)

Under 250g ... no height limit, just that of the mini (500m), woaw.
1-12 13:26
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Labroides
Captain
Flight distance : 9991457 ft
Australia
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Flying a Mini to 500 metres because you think you are exempt from rules doesn't exempt you from having your Mini blown away by upper level winds.
1-12 13:51
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dougjeff
lvl.2
Flight distance : 265033 ft
Canada
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Labroides Posted at 1-12 13:51
Flying a Mini to 500 metres because you think you are exempt from rules doesn't exempt you from having your Mini blown away by upper level winds.

Of course!

Also just because it is legal doesn't mean that I have done it.
1-12 14:56
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Labroides
Captain
Flight distance : 9991457 ft
Australia
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dougjeff Posted at 1-12 12:35
In Canada we have a 400'AGL (~120m) limit in most cases. However the MM is under 250g, so this rule does not apply to it. You can also exceed this limit if you are granted a Special Flight Operation Certificate (SFOC)

In Canada we have a 400'AGL (~120m) limit in most cases. However the MM is under 250g, so this rule does not apply to it.
If you believe that, you really should check your Canadian rules again.
Flying a >250g drone exempts you from registration and the requirement for a drone pilot certificate.
But it doesn't exempt you from the flying rules.
1-12 18:02
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Bjord
lvl.3
Flight distance : 1861880 ft
Canada
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Labroides Posted at 1-12 18:02
In Canada we have a 400'AGL (~120m) limit in most cases. However the MM is under 250g, so this rule does not apply to it.
If you believe that, you really should check your Canadian rules again.
Flying a >250g drone exempts you from registration and the requirement for a drone pilot certificate.

My understanding of the rules is that it does.

Check out the rules here: https://laws-lois.justice.gc.ca/ ... lText.html#s-900.01

In Part IX — Remotely Piloted Aircraft Systems, every rule with exception of the first rule (900.06) is under Subpart 1 — Small Remotely Piloted Aircraft. This section only applies to "small remotely piloted aircraft." which they specifically describe as "a remotely piloted aircraft that has a maximum take-off weight of at least 250 g...".

So technically, the only rule that applies is the generic " 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.".

Unless there is something that I am missing, it seems pretty clear to me though.
1-12 20:33
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dougjeff
lvl.2
Flight distance : 265033 ft
Canada
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@Bjord - I agree with your statement. This is what I understand about the rules. A sub 250g drone is classed as a micro drone, not a small RPAS. As such the only rule that explicitly applies is 900.06
"Reckless or Negligent Operation
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."

Here is the Transport Canada reference to micro drones: https://www.tc.gc.ca/en/services ... n.html#micro-drones
1-12 22:37
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Bjord
lvl.3
Flight distance : 1861880 ft
Canada
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dougjeff Posted at 1-12 22:37
@Bjord - I agree with your statement. This is what I understand about the rules. A sub 250g drone is classed as a micro drone, not a small RPAS. As such the only rule that explicitly applies is 900.06
"Reckless or Negligent Operation
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."

I also found this post from another thread with screenshots of emails from Transport Canada which confirm this. Straight from the horse's mouth: "they are unregulated."

https://forum.dji.com/forum.php? ... 0&page=1#pid2024786
1-12 23:29
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