AIM

8/15/19

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Potential Flight Hazards

at least 2,000 feet. Additionally, new towers may not
be on your current chart because the information was
not received prior to the printing of the chart.

c. Overhead Wires.

Overhead transmission and

utility lines often span approaches to runways,
natural flyways such as lakes, rivers, gorges, and
canyons, and cross other landmarks pilots frequently
follow such as highways, railroad tracks, etc. As with
antenna towers, these high voltage/power lines or the
supporting structures of these lines may not always be
readily visible and the wires may be virtually
impossible to see under certain conditions. In some
locations, the supporting structures of overhead
transmission lines are equipped with unique sequence
flashing white strobe light systems to indicate that
there are wires between the structures. However,
many power lines do not require notice to the FAA
and, therefore, are not marked and/or lighted. Many
of those that do require notice do not exceed 200 feet
AGL or meet the Obstruction Standard of 14 CFR
Part 77 and, therefore, are not marked and/or lighted.
All pilots are cautioned to remain extremely vigilant
for these power lines or their supporting structures
when following natural flyways or during the
approach and landing phase. This is particularly
important for seaplane and/or float equipped aircraft
when landing on, or departing from, unfamiliar lakes
or rivers.

d. Other Objects/Structures.

There are other

objects or structures that could adversely affect your
flight such as construction cranes near an airport,
newly constructed buildings, new towers, etc. Many
of these structures do not meet charting requirements
or may not yet be charted because of the charting
cycle. Some structures do not require obstruction
marking and/or lighting and some may not be marked
and lighted even though the FAA recommended it.

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4. Avoid Flight Beneath Unmanned

Balloons

a.

The majority of unmanned free balloons

currently being operated have, extending below
them, either a suspension device to which the payload
or instrument package is attached, or a trailing wire
antenna, or both. In many instances these balloon
subsystems may be invisible to the pilot until the
aircraft is close to the balloon, thereby creating a
potentially dangerous situation. Therefore, good
judgment on the part of the pilot dictates that aircraft

should remain well clear of all unmanned free
balloons and flight below them should be avoided at
all times.

b.

Pilots are urged to report any unmanned free

balloons sighted to the nearest FAA ground facility
with which communication is established. Such
information will assist FAA ATC facilities to identify
and flight follow unmanned free balloons operating
in the airspace.

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5. Unmanned Aircraft Systems

a.

Unmanned Aircraft Systems (UAS), formerly

referred to as “Unmanned Aerial Vehicles” (UAVs)
or “drones,” are having an increasing operational
presence in the NAS. Once the exclusive domain of
the military, UAS are now being operated by various
entities. Although these aircraft are “unmanned,”
UAS are flown by a remotely located pilot and crew.
Physical and performance characteristics of un-
manned aircraft (UA) vary greatly and unlike model
aircraft that typically operate lower than 400 feet
AGL, UA may be found operating at virtually any
altitude and any speed. Sizes of UA can be as small
as several pounds to as large as a commercial
transport aircraft. UAS come in various categories
including airplane, rotorcraft, powered

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lift (tilt

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rotor), and lighter

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than

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air. Propulsion systems of

UAS include a broad range of alternatives from
piston powered and turbojet engines to battery and
solar

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powered electric motors.

b.

To ensure segregation of UAS operations from

other aircraft, the military typically conducts UAS
operations within restricted or other special use
airspace. However, UAS operations are now being
approved in the NAS outside of special use airspace
through the use of FAA

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issued Certificates of Waiver

or Authorization (COA) or through the issuance of a
special airworthiness certificate. COA and special
airworthiness approvals authorize UAS flight
operations to be contained within specific geographic
boundaries and altitudes, usually require coordina-
tion with an ATC facility, and typically require the
issuance of a NOTAM describing the operation to be
conducted. UAS approvals also require observers to
provide “see

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and

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avoid” capability to the UAS crew

and to provide the necessary compliance with 14 CFR
Section 91.113. For UAS operations approved at or
above FL180, UAS operate under the same
requirements as that of manned aircraft (i.e., flights