Howdy.

I have hunted around for this topic but am struggling to find anything.



So I take off from a cliff which is 1000 ft above see level and fly out over the ocean, is my max altitude now 1400 ft ?

If i fly down to the ocean, say 20 ft above sea level is there a possibility I wont be able to recover the drone at the top of the 1000 ft cliff ?

Is this 400 ft rule set in the software or do I manually stay below that altitude ?

Maybe a stupid question but just trying to figure things out before I get into trouble/problems.

From the CAA website:
must not fly the aircraft:
at a height of more than 400 feet above the surface unless it is flying in
airspace described in sub-paragraph (a) or (b) and in accordance with the
requirements for that airspace.


Cheers

Nice drawing... I have being looking for this answer myself. Hopefully someone will know the answer or somebody could try and test it. But remember to look for thermal wind current  

So I take off from a cliff which is 1000 ft above see level and fly out over the ocean, is my max altitude now 1400 ft ?
NO.  Think of it like this.

Mavic Max altitude:
The Mavic records the Pressure Altitude where you turn it ON (not necessarily - take off) and sets this as its 0' reference point.   It will happily climb to 400' above this level at which point it stops and gives you a warning about regulations. You can swipe the warning away and continue climbing up to its firmware max hieght of 1640' (500m). But dont do this.     

Legal Max altutude to fly:
Depending on juristriction - generally 400' above terrain or water contour.  So to be legal you should descend to at or below 400" above the water beside the cliff.

You could in theory, turn your mavic on atop a hill beside your hypothetical cliff that is 2,000' above seal level. Then with it in your car and powered on, drive down to your cliff top. It should then allow you to climb up to 1640' above the height at which you powered on which is 3,640' above the water when you fly beyond your cliff.


If i fly down to the ocean, say 20 ft above sea level is there a possibility I wont be able to recover the drone at the top of the 1000 ft cliff ?
Anything is possible. Theoretically you should be fine except flying beside a cliff could well effect your GPS reception. If it has to do a RTH, the default height will be a minimum of 60" above the cliff top where you took off, so it will climb above this first.


Is this 400 ft rule set in the software or do I manually stay below that altitude ?
Yes there is a warning that appears in the software. You can swipe it away though if you choose and fly higher than 400'.
Oh and yes, beware the thermal winds ( Sorry a standing joke around here these days)

Logger Posted at 2016-11-28 06:24
So I take off from a cliff which is 1000 ft above see level and fly out over the ocean, is my max al ...

Thermal winds

It's zero from where you start, so if you go below that the altitude goes into negative. (If you go down 1000ft from take-off point it would say -1000ft and you would not be limited at all to come back up to zero)

Also it is useful (legally) to set the max altitude above 400ft in some situations - for example starting at the bottom of a hill or mountain, where you follow the terrain up yet don't actually exceed 400ft from the ground.

Logger Posted at 2016-11-27 17:24
So I take off from a cliff which is 1000 ft above see level and fly out over the ocean, is my max al ...

Good response Logger.

One last clarification:  In the US, the FAA allows you to violate the 400 feet above surface rule as long as you are within 400 feet of a structure (i.e. the cliff).  So, you can legally fly off the cliff and as much as 400 feet from it without descending.  This would also allow you to fly from the bottom of the cliff to the top (600 feet higher than your 400 foot limit) as long as you stayed within 400 feet of the cliff.  I'm sure you would have to acknowledge the 400 foot warning to continue.  This would also let you fly from the ground to the top of a 1500' tower, as long as you don't move more than 400 feet from the side of the tower and are doing everything else legally.

The whole intent is to keep you out of normal aircraft airspace, which is 500 feet above ground level and 500 from obstacles.  Hypothetically, no plane should be flying within your 400 foot allowance of the cliff, however you need to remember that YOU are required to give the right-of-way to the aircraft, not the other way around.  That's the reason for the visual observation requirement.  You never know when a hang-glider, paraglider or other human-occupied aircraft may violate that airspace where you are flying.

So, if an aircraft DOES come within that margin, you should do everything you can to get out of their way.  This is the "common sense" part where you put the human life of the pilot above the cost of the drone.