AIM

8/15/19

7

−

5

−

3

Potential Flight Hazards

are operated under instrument flight rules, are in
communication with ATC, and are appropriately
equipped).

c.

UAS operations may be approved at either

controlled or uncontrolled airports and are typically
disseminated by NOTAM. In all cases, approved
UAS operations must comply with all applicable
regulations and/or special provisions specified in the
COA or in the operating limitations of the special
airworthiness certificate. At uncontrolled airports,
UAS operations are advised to operate well clear of
all known manned aircraft operations. Pilots of
manned aircraft are advised to follow normal
operating procedures and are urged to monitor the
CTAF for any potential UAS activity. At controlled
airports, local ATC procedures may be in place to
handle UAS operations and should not require any
special procedures from manned aircraft entering or
departing the traffic pattern or operating in the
vicinity of the airport.

d.

In addition to approved UAS operations

described above, a recently approved agreement
between the FAA and the Department of Defense
authorizes small UAS operations wholly contained
within Class G airspace, and in no instance, greater
than 1200 feet AGL over military owned or leased
property. These operations do not require any special
authorization as long as the UA remains within the
lateral boundaries of the military installation as well
as other provisions including the issuance of a
NOTAM. Unlike special use airspace, these areas
may not be depicted on an aeronautical chart.

e.

There are several factors a pilot should consider

regarding UAS activity in an effort to reduce
potential flight hazards. Pilots are urged to exercise
increased vigilance when operating in the vicinity of
restricted or other special use airspace, military
operations areas, and any military installation. Areas
with a preponderance of UAS activity are typically
noted on sectional charts advising pilots of this
activity. Since the size of a UA can be very small, they
may be difficult to see and track. If a UA is
encountered during flight, as with manned aircraft,
never assume that the pilot or crew of the UAS can see
you, maintain increased vigilance with the UA and
always be prepared for evasive action if necessary.
Always check NOTAMs for potential UAS activity
along the intended route of flight and exercise
increased vigilance in areas specified in the NOTAM.

7

−

5

−

6. Mountain Flying

a.

Your first experience of flying over mountain-

ous terrain (particularly if most of your flight time has
been over the flatlands of the midwest) could be a

never-to-be-forgotten nightmare

 if proper planning is

not done and if you are not aware of the potential
hazards awaiting. Those familiar section lines are not
present in the mountains; those flat, level fields for
forced landings are practically nonexistent; abrupt
changes in wind direction and velocity occur; severe
updrafts and downdrafts are common, particularly
near or above abrupt changes of terrain such as cliffs
or rugged areas; even the clouds look different and
can build up with startling rapidity. Mountain flying
need not be hazardous if you follow the recommenda-
tions below.

b. File a Flight Plan.

Plan your route to avoid

topography which would prevent a safe forced
landing. The route should be over populated areas and
well known mountain passes. Sufficient altitude
should be maintained to permit gliding to a safe
landing in the event of engine failure.

c.

Don’t fly a light aircraft when the winds aloft, at

your proposed altitude, exceed 35 miles per hour.
Expect the winds to be of much greater velocity over
mountain passes than reported a few miles from them.
Approach mountain passes with as much altitude as
possible. Downdrafts of from 1,500 to 2,000 feet per
minute are not uncommon on the leeward side.

d.

Don’t fly near or above abrupt changes in

terrain. Severe turbulence can be expected, especially
in high wind conditions.

e. Understand Mountain Obscuration.

 The

term Mountain Obscuration (MTOS) is used to
describe a visibility condition that is distinguished
from IFR because ceilings, by definition, are
described as “above ground level” (AGL). In
mountainous terrain clouds can form at altitudes
significantly higher than the weather reporting
station and at the same time nearby mountaintops
may be obscured by low visibility. In these areas the
ground level can also vary greatly over a small area.
Beware if operating VFR

−

on

−

top. You could be

operating closer to the terrain than you think because
the tops of mountains are hidden in a cloud deck
below. MTOS areas are identified daily on The
Aviation Weather Center located at:

http://www.aviationweather.gov

.