Height regulations when flying over a cliff?

[eEridani]

From personal experience, I live near the Snake River and there are places where the canyon is a sheer cliff 450' or more down to the river below, but a few thousand feet wide. When I fly off those cliffs, I generally stay within a couple hundred feet of the canyon walls as I descend to a couple hundred feet above the river (-200 on the altimeter). At the same time, there are places where I launch from the river bank and fly up the cliffs or surrounding hills. Again, I stay within a couple hundred feet horizontal, and do my best to avoid being 400' AGL.

I don't think the rules are to keep you from flying in unusual places, but some common sense application is needed. Keep in mind "ground level" is pretty well defined. At the top of a cliff the ground is, well, the ground level. At the bottom of a cliff, again, the ground is the ground. Staying less than 400' above seems pretty easy except on the slope. And I doubt any FAA person is going to ding me if I incidentally exceed 400' as I descend from one ground reference to the other IF I am staying close to the slope - like within 400'.

 

[Desert Sands]

I largely use my drones for communications tower inspections.

Unless otherwise limited by restrictions. I could fly to the top of the tower... and up to 400 feet above the tower in a circle centered on the tower, with a DIAMETER of 800 feet (400 ft Radius). Typically I stay within 50 feet of the tower and... generally do not fly more than 20 feet above it.

There are instances where I fly at a radio tower of 1250 feet AGL and there is, adjacent to this tower a cliff that drops perhaps 200 feet. This cliff is within the 400 foot radius of the tower. Flying over that cliff would NOT be a violation, as I am within 400 feet of the tower.

So it begs the question, which would need to be asked of FAA, does the "obstruction Rule" which applies to towers, chimneys and buildings... apply to the Cliff scenario raised by the OP. I do NOT know the answer... I am just raising a question which needs to be clarified...or codified by the FAA in the U.S...or the corresponding agency CAA et al.

I have no dog in the fight as I know what my rules are. It would be interesting for a perhaps CBO or even a civilian Remote Pilot get a ruling on the "Cliff scenario".

I too like the OP have wondered how such a flight would be ruled. Technically, based on comments by others...the flight is a violation the moment the aircraft crosses the cliff line... and so merely crossing the line and dropping 100 ft (as in the OP scenario) would still technically be a violation.

The FAA rules such as this are designed to protect Pilots, Aircraft and the public as a whole, from harm. It is unlikely that a prudent pilot of a helicopter or fixed wing aircraft is going to dive over a cliff or, for that matter fly close to a cliff wall. A wing suit flyer or a hang glider might do it though.

If someone on here has a written response from FAA regarding this situation, I would love to know what the ruling was.

Fly Safe and courteously.

Joe

 

[B52-D]

I largely use my drones for communications tower inspections.

Unless otherwise limited by restrictions. I could fly to the top of the tower... and up to 400 feet above the tower in a circle centered on the tower, with a DIAMETER of 800 feet (400 ft Radius). Typically I stay within 50 feet of the tower and... generally do not fly more than 20 feet above it.

There are instances where I fly at a radio tower of 1250 feet AGL and there is, adjacent to this tower a cliff that drops perhaps 200 feet. This cliff is within the 400 foot radius of the tower. Flying over that cliff would NOT be a violation, as I am within 400 feet of the tower.

So it begs the question, which would need to be asked of FAA, does the "obstruction Rule" which applies to towers, chimneys and buildings... apply to the Cliff scenario raised by the OP. I do NOT know the answer... I am just raising a question which needs to be clarified...or codified by the FAA in the U.S...or the corresponding agency CAA et al.

I have no dog in the fight as I know what my rules are. It would be interesting for a perhaps CBO or even a civilian Remote Pilot get a ruling on the "Cliff scenario".

I too like the OP have wondered how such a flight would be ruled. Technically, based on comments by others...the flight is a violation the moment the aircraft crosses the cliff line... and so merely crossing the line and dropping 100 ft (as in the OP scenario) would still technically be a violation.

The FAA rules such as this are designed to protect Pilots, Aircraft and the public as a whole, from harm. It is unlikely that a prudent pilot of a helicopter or fixed wing aircraft is going to dive over a cliff or, for that matter fly close to a cliff wall. A wing suit flyer or a hang glider might do it though.

If someone on here has a written response from FAA regarding this situation, I would love to know what the ruling was.

Fly Safe and courteously.

Joe

B52-D

 

[Desert Sands]

View attachment 142942
B52-D
View attachment 142943

Operating limitations for small unmanned aircraft” and contains a set of limits associated with speed, altitude, and visibility. Pertaining to altitude, item B of the Section states that:

“The altitude of the small unmanned aircraft cannot be higher than 400 feet above ground level unless the small unmanned aircraft is (1) flown within a 400-foot radius of a structure, and (2) does not fly higher than 400 feet above the structure’s immediate uppermost limit.”

 

[Desert Sands]

Operating limitations for small unmanned aircraft” and contains a set of limits associated with speed, altitude, and visibility. Pertaining to altitude, item B of the Section states that:

“The altitude of the small unmanned aircraft cannot be higher than 400 feet above ground level unless the small unmanned aircraft is (1) flown within a 400-foot radius of a structure, and (2) does not fly higher than 400 feet above the structure’s immediate uppermost limit.”

 

[HoozierDroneDaddy]

As I mentioned above, the OP's scenario is not the norm where we are talking about 400' AGL and the 400' Radius around a structure.
He specifically stated he was under a LAANC authorization with a 100' AGL limitation. He wanted to know if going over the cliff would allow him to now maintain his height, so if the cliff dropped 200', could he maintain his current height of 300' (even if within 400' of the cliff edge. His LAANC authorization is for 100' AGL. With a WAA in the past, your authorized height could not deviate because of a structure, so the question is, "can his authorized height with a LAANC authorization change due to a structure, or a cliff drop, while flying in a controlled airspace?" If there is a 200' building in his flight path, it does not change his authorization to 300'. And if the cliff drops 200', his authorization is still 100' "AGL", not 300'
If I am wrong, someone please provide the correct answer and a reference.

 

[BigAl07]

As I mentioned above, the OP's scenario is not the norm where we are talking about 400' AGL and the 400' Radius around a structure.
He specifically stated he was under a LAANC authorization with a 100' AGL limitation. He wanted to know if going over the cliff would allow him to now maintain his height, so if the cliff dropped 200', could he maintain his current height of 300' (even if within 400' of the cliff edge. His LAANC authorization is for 100' AGL. With a WAA in the past, your authorized height could not deviate because of a structure, so the question is, "can his authorized height with a LAANC authorization change due to a structure, or a cliff drop, while flying in a controlled airspace?" If there is a 200' building in his flight path, it does not change his authorization to 300'. And if the cliff drops 200', his authorization is still 100' "AGL", not 300'
If I am wrong, someone please provide the correct answer and a reference.

^^^^^ Nailed it!!

Authorizations are ABSOLUTE AGL unless it's a dire emergency and then you'd need to report the violation immediately.

@Desert Sands a cliff, mountain etc are NOT structures. There is a list of structures etc somewhere in the FAA articles but I don't have them but I have seen "Structures" detailed by the FAA. The mere definition of a structure eliminates the Cliff/Mountain etc and those are defined as TERRAIN in by the FAA.

Essential Meaning of structure
1: the way that something is built, arranged, or organizedThey studied the compound's molecular structure.The film had a simple narrative structure.the structure of a plant
2: the way that a group of people are organizeda solid family structurethe social structure of a college campuschanges to the company's power structure
3: something (such as a house, tower, bridge, etc.) that is built by putting parts together and that usually stands on its owna brick/steel structureThe structure was damaged by fire.a 12-story structure

Definition of terrain​

1a(1): a geographic area
(2): a piece of land : GROUND
b: the physical features of a tract of land

 

[BigAl07]

It's also important to note that @kjonyou did not state if flying Recreationally (~44809) or Commercially (Part 107).

The "Structural Allowance" noted above ONLY applies to Part 107 operators and ONLY if the additional altitude does NOT exceed their LAANC Approval height.