Minimum safe altitude - FAR 91.119

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Hepburn

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Pierre
Dear all,

I am having trouble understanding the minimum safe altitude FAR.

From my understanding, there are 2 types of area:
  • congested, 91.119 (b) with a 1000' v and 2000' h from aircraft minimums
  • other-than-congested, 91.119 (c) with a 500' AGL minimum

In the other-than-congested area, there is one exception for open water or sparsely populated, where the minimum is a 500' radius.

What I don't understand is this exception. If we just consider ground and not water, removing the sparsely populated area from the other-than-congested area leaves what ? I would say something like not-populated area at all.

This would lead to this behaviour: I fly in the desert, I have to be above 500' AGL because I consider myself in the other-than-congested-area but not in sparsely populated area. Then I fly over a sparsely populated area, I can fly lower as long as I am not in the 500' radius, then I leave the sparsely populated area and I have to fly above 500' AGL again.
In other words, more safety over desert, less safety over populated area.

I am sure I am getting this wrong as this clearly doesn't seem right.

Could you please explain to me what I am getting wrong ?

I've made a splendid paint drawing to illustrate this :idea:



Thanks a lot!
A student pilot
 
Hepburn,

From what I've seen here, the definition of a "congested area" is a flexible concept with the FAA when they pursue enforcement. While the yellow areas on Sectionals and TAC charts gives an idea of where they start to consider congested areas, it's not binding. As far as the desert is concerned, that would certainly comprise a sparsely populated area. An "other than congested area" would likely be rural areas where there are groupings of people and homes, but not enough to meet the definition of "congested", AKA city/suburbia. For "sparsely populated", think of homes in the middle of nowhere, or no homes at all.

Sparsely populated can also mean not populated. If you see any signs of life, stay 500'+ from it except during takeoff or landing.

Edit: Welcome to PoA! I see it's your first post here, and you made it a good one.
 
Welcome to POA - ! When I don't know, I often use the larger number. For example, I fly near San Francisco. Let's say the top of the Golden Gate Bridge towers is 800 feet. If there is only one car on the Bridge, is that congested? Who knows, so I add 1,000 and cross the Golden Gate Bridge at only 1800 and higher.
 
Hepburn said:
Dear all,

I am having trouble understanding the minimum safe altitude FAR.


From my understanding, there are 2 types of area:
  • congested, 91.119 (b) with a 1000' v and 2000' h from aircraft minimums
  • other-than-congested, 91.119 (c) with a 500' AGL minimum
In the other-than-congested area, there is one exception for open water or sparsely populated, where the minimum is a 500' radius.

What I don't understand is this exception. If we just consider ground and not water, removing the sparsely populated area from the other-than-congested area leaves what ? I would say something like not-populated area at all.

This would lead to this behaviour: I fly in the desert, I have to be above 500' AGL because I consider myself in the other-than-congested-area but not in sparsely populated area. Then I fly over a sparsely populated area, I can fly lower as long as I am not in the 500' radius, then I leave the sparsely populated area and I have to fly above 500' AGL again.
In other words, more safety over desert, less safety over populated area.

I am sure I am getting this wrong as this clearly doesn't seem right.

Could you please explain to me what I am getting wrong ?

I've made a splendid paint drawing to illustrate this :idea:



Thanks a lot!
A student pilot
Click to expand...


PS - I love that your drawing uses solid, black lines that are all very straight but for the water line you have used blue and made it uneven.
 
I'm with Mike -- if there are no signs of life, go as low as you feel safe as long as you stay 500 feet from any person, vessel, vehicle or structure.

Is a cattle fence a structure? Does a cow count? :dunno: But I can say for sure that cattle do tend to panic when an A-6 Intruder goes over them at 30 feet AGL and 450 mph.
 
Ron Levy said:
I'm with Mike -- if there are no signs of life, go as low as you feel safe as long as you stay 500 feet from any person, vessel, vehicle or structure.

Is a cattle fence a structure? :dunno:
Click to expand...

Only if you're a cow.

And to the OP, welcome to POA. At least I beat Tracey.
 
kimberlyanne546 said:
Welcome to POA - ! When I don't know, I often use the larger number. For example, I fly near San Francisco. Let's say the top of the Golden Gate Bridge towers is 800 feet. If there is only one car on the Bridge, is that congested? Who knows, so I add 1,000 and cross the Golden Gate Bridge at only 1800 and higher.
Click to expand...
As a general rule of thumb, I consider any yellow areas on the chart to be "congested." So something like that bridge would be considered a structure within a congested area, regardless of how many cars are on it. Then there's open water within such areas... I could legally fly exactly 501 feet above a boat in the middle of the Hudson south of the GW Bridge, or in the harbor, but I wouldn't try it, because there would be hell to pay if they got my number, regardless of the wording of the FARs. Even the tour helis don't fly that low there unless they are taking off or landing at the midtown pad on the riverbank.
If any other pilots want to test that assertion in NYC or any other big city that's mostly yellow on the chart, feel free, and good luck to you. :D

And there also are precedents for "congested" being applied outside of such yellow areas; again, the FAA can adjust the definition to fit, as they see fit. If you crash exactly 501 feet from a bunch of people or a school, from an altitude below 500 feet AGL, that will be held against you by the media, the police, and the feds, even more so than if you didn't file a plan. :D

Assuming no mishap occurs, it all really depends on whether or not you scare somebody... it may be legal, for example, to fly at 3 ft. AGL over a highway in the middle of the desert, staying exactly 501 feet behind some lone vehicle, but if they call in your N-number, you may find it's not so legal. :rolleyes2:
 
Didn't someone post a link to a decision by the FAA Chief Counsel a while back that considered even just one human made it a "congested" area?

I didn't save the link to that one...
 
Ron Levy said:
I'm with Mike -- if there are no signs of life, go as low as you feel safe as long as you stay 500 feet from any person, vessel, vehicle or structure.

Is a cattle fence a structure? Does a cow count? :dunno: But I can say for sure that cattle do tend to panic when an A-6 Intruder goes over them at 30 feet AGL and 450 mph.
Click to expand...
One day at Pot holes camp ground one of you guys did that, and I don't believe there was a camp table standing after the event.

So I don't blame the cows for panicking, because the language used by the campers that day had never been heard by the ladies before.

funny as hell.
 
kimberlyanne546 said:
Welcome to POA - ! When I don't know, I often use the larger number. For example, I fly near San Francisco. Let's say the top of the Golden Gate Bridge towers is 800 feet. If there is only one car on the Bridge, is that congested? Who knows, so I add 1,000 and cross the Golden Gate Bridge at only 1800 and higher.
Click to expand...

How do you get through the GG when there are 1200' ceilings?
 
rottydaddy said:
I could legally fly exactly 501 feet above a boat in the middle of the Hudson south of the GW Bridge, or in the harbor, but I wouldn't try it, because there would be hell to pay if they got my number
Click to expand...

I've done just that.... but it was pre-arranged and NYPD Av + FDNY was aware and coordinating :) . And of course 91.119 applies differently to helicopters (91.119(d)).
Screen_Shot_2012_03_29_at_7_42_02_PM.png

Screen_Shot_2012_03_29_at_7_40_23_PM.png


I tech'ed this shoot onboard the helicopter, but was not the photographer.

Back on track...here's a good read about 91.119: http://blog.globalair.com/post/Identification-of-a-Congested-Area-Under-FAR-sect3b91119.aspx .
Unfortunately, neither the FAA nor the NTSB has ever provided airmen with a precise definition of what constitutes a "congested area." Rather, a "congested area" is determined on a case-by-case basis. According to the Board, "the determination must take into consideration all circumstances, not only the size of an area and the number of homes or structures, but, for example, whether the buildings are occupied or people are otherwise present, such as on roads."
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It details the ruling in Administrator v Folk
 
And then there's the line about having enough altitude to make a safe landing if power is lost thing...

I used it when an instructor wanted me to fly low over some rough terrain. It was cold for Arizona and the instructor didn't want to go higher or use the heater. I just laughed at him and climbed.
 
pericynthion said:
Fly under it, of course.
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You would still be within 500' of the cars, though. :)

WHAT IS THE ELEVATION RISE OF THE BRIDGE ROADWAY?

At midspan, the height of the top of the roadway surface is +270.9 feet Mean Lower Low Water, which is the average of the lower low water height of each tidal day observed over the National Tidal Datum Epoch. At the south abutment of the Bridge, the height of the top of roadway surface is +186.5 feet. The difference, equalling the rise in elevation as you travel across the Bridge roadway, is +84.4 feet. These data are from the most recent survey done in 1992.
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http://goldengatebridge.org/research/facts.php#Ashes
 
Henning said:
Right, but you have to wait until there aren't any ships underneath or you'll bust 500'...
Click to expand...

...not to mention the fact that the Golden Gate Bridge is most definitely a STRUCTURE.
 
Welcome to POA....:yesnod:

The line that will hang you every time is the "able to make a safe landing".

Unless you are on a short final to a runway they can say you are too low.
 
Nice job with the graphic. My recollection from surveying NTSB rulings last time this came up the definition of a congested area could be distilled down to "at least two people annoyed about being buzzed". It seems some common sense applies.

I've never looked at interpretations of the "An altitude allowing, if a power unit fails, an emergency landing without undue hazard to persons or property on the surface" part.
 
N801BH said:
The line that will hang you every time is the "able to make a safe landing".
Click to expand...
You don't have to be "able to make a safe landing," just "an emergency landing without undue hazard to persons or property on the surface." What happens to you and your aircraft is irrelevant for this purpose.
 
Ron Levy said:
You don't have to be "able to make a safe landing," just "an emergency landing without undue hazard to persons or property on the surface." What happens to you and your aircraft is irrelevant for this purpose.
Click to expand...

I know,,, but I am concerned about what happens to me and my plane..:yesnod:.

And if you read into it further they can say "you dug ruts in the dirt during your emergency landing", thus you created a hazard on the property on the surface...
 
Henning said:
How do you get through the GG when there are 1200' ceilings?
Click to expand...

Hopefully I would not be flying that day. I only go near the GGB on a Bay Tour. Or on a coastal flight. And I wouldn't be doing that with 1200 foot ceilings - well, I hope not.

But to answer you directly - I'd go around. I think there are other airspace restrictions nearby though, for Alcatraz, where I have to be even higher than 1800.
 
N801BH said:
I know,,, but I am concerned about what happens to me and my plane..:yesnod:.
Click to expand...
From a safety perspective, I suppose that's a good thing, but it is beyond the scope of that paragraph of that regulation.

And if you read into it further they can say "you dug ruts in the dirt during your emergency landing", thus you created a hazard on the property on the surface...
Click to expand...
I don't think so. It says "persons or propery on the surface," not the surface itself.
 
Ron Levy said:
.....
I don't think so. It says "persons or propery on the surface," not the surface itself.
Click to expand...
..

Good point....... Altho I get to live right next to, and fly out of Grand Teton National Park and if you happen to pull off the road and leave tire tracks on the dirt you will pay a multi thousand dollar fine and possible jail time for destroying park resources..:yesnod::yesnod::hairraise:.. This is unique though and does not apply anywhere there is common sense..:nonod:
 
Property could certainly be the surface itself, no? Land on a golf course and destroy a green...tht is the "surface", you might be more than 500' from persons, an it could e in a sparsely populated area.
 
kimberlyanne546 said:
Hopefully I would not be flying that day. I only go near the GGB on a Bay Tour. Or on a coastal flight. And I wouldn't be doing that with 1200 foot ceilings - well, I hope not.

But to answer you directly - I'd go around. I think there are other airspace restrictions nearby though, for Alcatraz, where I have to be even higher than 1800.
Click to expand...

Well hell, some days it's the only way to get out to Half Moon Bay, you have to go out the Gate to get to the beach...;)
 
Link

§ 91.119 Minimum safe altitudes: General.
Except when necessary for takeoff or
landing, no person may operate an aircraft
below the following altitudes:
(a) Anywhere. An altitude allowing, if
a power unit fails, an emergency landing
without undue hazard to persons or
property on the surface.
(b) Over congested areas. Over any
congested area of a city, town, or settlement,
or over any open air assembly
of persons, an altitude of 1,000 feet
above the highest obstacle within a
horizontal radius of 2,000 feet of the
aircraft.
(c) Over other than congested areas. An
altitude of 500 feet above the surface,
except over open water or sparsely populated
areas. In those cases, the aircraft
may not be operated closer than
500 feet to any person, vessel, vehicle,
or structure.
Click to expand...

If you are practicing emergency landings over a field, how low can you fly?


:idea:





(My answer: you can brush the blades of grass with your wheels if you care to...)
 
dmccormack said:
If you are practicing emergency landings over a field, how low can you fly?
Click to expand...
Exactly what it says in that reg.
(My answer: you can brush the blades of grass with your wheels if you care to...)
Click to expand...
Only of the grass is a runway or in a sparsely-populated area. There is no exception in the reg for practice or simulated emergencies.

I know where the grass airports in the local practice area are, so I often pull my engine-outs over them, but otherwise, the 500-foot rule applies.
 
Ron Levy said:
Exactly what it says in that reg.
Only of the grass is a runway or in a sparsely-populated area. There is no exception in the reg for practice or simulated emergencies.

I know where the grass airports in the local practice area are, so I often pull my engine-outs over them, but otherwise, the 500-foot rule applies.
Click to expand...


Soooo...:idea: I can simulate ditching along slide a ship that is going under the Golden Gate bridge and end the simulation just short of ditching and it's all good.:yesnod:
 
denverpilot said:
Didn't someone post a link to a decision by the FAA Chief Counsel a while back that considered even just one human made it a "congested" area?

I didn't save the link to that one...
Click to expand...

I don't think one person would qualify, but two or more could be "an open air assembly"!
 
Ron Levy said:
Exactly what it says in that reg.
Only of the grass is a runway or in a sparsely-populated area. There is no exception in the reg for practice or simulated emergencies.

I know where the grass airports in the local practice area are, so I often pull my engine-outs over them, but otherwise, the 500-foot rule applies.
Click to expand...

How many "fields" do you fly over that are "populated?"

:confused:
 
Henning said:
Well hell, some days it's the only way to get out to Half Moon Bay, you have to go out the Gate to get to the beach...;)
Click to expand...

Dude, I can drive to the beaches up here quicker than I can fly to Half Moon Bay (Bodega Bay, Stinson, etc)
 
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