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AIM

10/12/17

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.