On 7/31/18 3:40 PM, kstover@ac0h.net wrote:
I read in the reg that if you have obstructions, trees, that are higher than
your planned tower you are exempt as long as you keep the tower lower than
the trees.
R. Kevin Stover AC0H
### what happens if you have a bunch of 100+ foot tall fir trees, or
any other type of trees on your property ?? Does any type of aircraft,
or helocopter actually fly below 100 ft ? We have seaplanes landing
here
locally downtown, yet the entire downtown, esp right on the water front is
ringed with tall condos. Local airport has a lot of 100 ft + fir trees
in close proximity
to the airport. Like hundreds of em.... but they are off to the sides.
Then we also have the helijet
terminal, located next to the cruise ship terminal...which is also right
across the street from more tall
condos.
## Once you get into the requirement for painting and lighting the tower,
then its an ongoing
maintenance issue..and also a legal liability issue. I would not be
surprised if they didnt
require UPS power to keep the lights on for short....or extended power
outages. You may
want to think this through very very carefully before you proceed with
anything.
The concern with towers vs trees (aside from trees always having less
regulation) is that trees come in groups, so are less of a "see and
avoid" collision hazard. A forest is hard to avoid seeing.
Towers, particularly guyed towers, are a real problem, because they
aren't as visible as a big tree. You probably don't have a 100 foot fir
tree that is 2 feet wide from the base. It's probably more like 20 feet
in diameter a good ways up from the ground.
On a hazy day, with the wrong sun angle, a tower can be almost
invisible, until it's too late to take evasive action.
Your basic visual acuity is about 1 arc minute (0.3 milliradian), in the
day time, with no haze or impairments
At 1 mile, a 18" wide tower is right about the limit of visual acuity. A
20 ft wide tree is easily visible. Guy wires are invisible.
If you're puttering along at 100 mi/hr in your plane, you cover that
mile in about 30-40 seconds. Even if you instantly rack the plane into a
45 degree bank (unlikely if you're low and slow, that's good way to
explore the stall/spin behavior of your plane), you're still going to
cover a lot of ground.
This is how people run into 500 ft high towers, even if they're painted.
It's also why strobes (esp the double flash) work so well. the first
flash attracts your attention, and you actually *see* the second flash,
from a long way away.
The blinking red light is fine at night, but worthless in the day time.
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