AIM

4/3/14

7−5−13

Potential Flight Hazards

4.

Protect your aircraft while on the ground, if

possible, from sleet and freezing rain by taking

advantage of aircraft hangars.

5.

Take full advantage of the opportunities

available at airports for deicing. Do not refuse deicing

services simply because of cost.

6.

Always consider canceling or delaying a

flight if weather conditions do not support a safe

operation.

c.

If you haven’t already developed a set of

Standard Operating Procedures for cold weather

operations, they should include:

1.

Procedures based on information that is

applicable to the aircraft operated, such as AFM

limitations and procedures;

2.

Concise and easy to understand guidance that

outlines best operational practices;

3.

A systematic procedure for recognizing,

evaluating and addressing the associated icing risk,

and offer clear guidance to mitigate this risk;

4.

An aid (such as a checklist or reference cards)

that is readily available during normal day−to−day

aircraft operations.

d.

There are several sources for guidance relating

to airframe icing, including:

1.

http://aircrafticing.grc.nasa.gov/index.html

2.

http://www.ibac.org/is

−bao/isbao.htm

3.

http://www.natasafety1st.org/bus_deice.htm

4.

Advisory Circular (AC) 91−74, Pilot Guide,

Flight in Icing Conditions.

5.

AC 135−17, Pilot Guide Small Aircraft

Ground Deicing.

6.

AC 135−9, FAR Part 135 Icing Limitations.

7.

AC 120−60, Ground Deicing and Anti−icing

Program.

8.

AC 135−16, Ground Deicing and Anti−icing

Training and Checking.

The FAA Approved Deicing Program Updates is

published annually as a Flight Standards Information

Bulletin for Air Transportation and contains detailed

information on deicing and anti−icing procedures and

holdover times. It may be accessed at the following

web site by selecting the current year’s information

bulletins:

http://www.faa.gov/library/manuals/examiners_inspe
ctors/8400/fsat

7

−

5

−

15. Avoid Flight in the Vicinity of

Thermal Plumes (Smoke Stacks and
Cooling Towers)

a. Flight Hazards Exist Around Thermal

Plumes.

Thermal plumes are defined as visible or

invisible emissions from power plants, industrial

production facilities, or other industrial systems that

release large amounts of vertically directed unstable

gases. High temperature exhaust plumes may cause

significant air disturbances such as turbulence and

vertical shear. Other identified potential hazards

include, but are not necessarily limited to, reduced

visibility, oxygen depletion, engine particulate

contamination, exposure to gaseous oxides, and/or

icing. Results of encountering a plume may include

airframe damage, aircraft upset, and/or engine

damage/failure. These hazards are most critical

during low altitude flight, especially during takeoff

and landing.

b. When able, a pilot should fly upwind of

possible thermal plumes.

When a plume is visible

via smoke or a condensation cloud, remain clear and

realize a plume may have both visible and invisible

characteristics. Exhaust stacks without visible

plumes may still be in full operation, and airspace in

the vicinity should be treated with caution. As with

mountain wave turbulence or clear air turbulence, an

invisible plume may be encountered unexpectedly.

Cooling towers, power plant stacks, exhaust fans, and

other similar structures are depicted in FIG 7−5−2.

Whether plumes are visible or invisible, the total

extent of their unstable air is difficult to ascertain.

FAA studies are underway to further characterize the

effects of thermal plumes as exhaust effluents. Until

the results of these studies are known and possible

changes to rules and policy are identified and/or

published, pilots are encouraged to exercise caution

when flying in the vicinity of thermal plumes. Pilots

are encouraged to reference the Airport/Facility

Directory where amplifying notes may caution pilots

and identify the location of structure(s) emitting

thermal plumes.