Maximum Altitude in Mountains

[LaFrance]

Hi All, newb pilot here (working on my part 107 cert...)
I am trying to figure out: 400ft is max altitude, but from....? i.e.
if I am standing on/launching from the top of a mountain that is at 5000ft MSL, and there is a valley
below that reaches a depth of say, 3000ft MSL... can I fly out over the mountain horizontally? This
would of course put me at far above 400ft... so, I think I know the answer to this, but thought I'd ask anyway.
Thanks for any advice.

 

[Nightwolf]

Nope, you have to stay under 400' AGL

 

[LaFrance]

not to beat the point to death.. but...
so, If my drone has a constant altitude mode, and I set that to say, 300 ft, and it flies around the mountain staying always less than 300 ft
above the nearest point directly below it.. still not kosher?

 

[Nightwolf]

Trust me the point has already been beaten to death. Just do a search and you'll see this. You can maintain constant altitude if you stay within 400' feet horizontally from the mountain. so you could go out 300' feet and circle the mountain as long as you maintain line of sight. otherwise you lose connection. After you pass the horizontal 400' distance you should be under 400' off of the ground beneath the drone (AGL)

 

[LaFrance]

awesome, thanks for the info. I'll do a better search next time

 

[Meta4]

so, If my drone has a constant altitude mode, and I set that to say, 300 ft, and it flies around the mountain staying always less than 300 ft
above the nearest point directly below it.. still not kosher?

Constant altitude mode?
The Phantom will maintain a constant altitude at any time.
But the altitude is relative to the launch point.
The Phantom cannot maintain constant height relative to the ground below it.

 

[LaFrance]

thanks, point taken

 

[BigAl07]

Think of it like this... imagine the drone has a laser beam shooting straight down under the aircraft. The 400' altitude is the distance between the aircraft and the small parcel of land/object directly under the aircraft.. aka where the imaginary laser beam is hitting.

Unfortunately you can only "Guestimate" at best.

 

[LaFrance]

thanks all!

 

[daveisim]

You can maintain constant altitude if you stay within 400' feet horizontally from the mountain.

Are you implying that a mountain is a structure? Hmmm

 

[sar104]

Are you implying that a mountain is a structure? Hmmm

That's not explicitly written anywhere as far as I know, but it may be a reasonable assumption and is often mentioned in discussions. If not, then there is a clear hole in the guidance - how far out from the top of a hypothetical 1000 ft cliff can you fly?

 

[BigAl07]

You can maintain constant altitude if you stay within 400' feet horizontally from the mountain.

Are you implying that a mountain is a structure? Hmmm

I'm with @daveisim on this. A structure is something "constructed" ie man made. A mountain is an obstacle (which doesn't apply in this instance) but it's not a structure. I completely understand the rationale behind such a statement but the FAA does not consider mountains etc to be "structures".

With the above being said, you "should" still be ok if flying within 400' of the mountains surface because manned aircraft would need to be 500' away (or should be anyway) except in some strange circumstances. If you have an incident and it's not clearly spelled out in the FARs then you're leaving the interpretation up to the courts and odds are they won't rule in our favor.

 

[sar104]

I'm with @daveisim on this. A structure is something "constructed" ie man made. A mountain is an obstacle (which doesn't apply in this instance) but it's not a structure. I completely understand the rationale behind such a statement but the FAA does not consider mountains etc to be "structures".

With the above being said, you "should" still be ok if flying within 400' of the mountains surface because manned aircraft would need to be 500' away (or should be anyway) except in some strange circumstances. If you have an incident and it's not clearly spelled out in the FARs then you're leaving the interpretation up to the courts and odds are they won't rule in our favor.

I agree - a mountain is almost certainly not an FAA-defined structure. I look at it from the point of view of intent - the intent of the structure rule is to permit operations but deconflict with other aircraft, which should not be operating within 400 ft of a structure (with notable exceptions). It's not a requirement per se, but it is probably also a reasonable assumption (although maybe less certain) that aircraft will not be operating within 400 ft laterally of a mountainside or cliff.

 

[Wilbur]

Constant altitude mode?
The Phantom will maintain a constant altitude at any time.
But the altitude is relative to the launch point.
The Phantom cannot maintain constant height relative to the ground below it.

Can't some of the newer drones essentially do this? Maybe for a Follow Me mode or something like that? Just curious.

 

[Meta4]

Can't some of the newer drones essentially do this? Maybe for a Follow Me mode or something like that? Just curious.

Phantoms with VPS sensors can detect the ground below them ... but that only works within 10 metres of the ground.